现在的ViewPager主要是横向的滑动实现，现在公司的业务需要实现竖直方向ViewPager，通过大量的寻找资料终于实现了
废话不说 直接上代码：
一：自定义viewPager
package com.example.test;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import android.content.Context;
import android.content.res.Resources;
import android.content.res.TypedArray;
import android.database.DataSetObserver;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.os.Build;
import android.os.Bundle;
import android.os.Parcel;
import android.os.Parcelable;
import android.os.SystemClock;
import android.support.v4.os.ParcelableCompat;
import android.support.v4.os.ParcelableCompatCreatorCallbacks;
import android.support.v4.view.AccessibilityDelegateCompat;
import android.support.v4.view.KeyEventCompat;
import android.support.v4.view.MotionEventCompat;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.VelocityTrackerCompat;
import android.support.v4.view.ViewCompat;
import android.support.v4.view.ViewConfigurationCompat;
import android.support.v4.view.ViewPager;
import android.support.v4.view.accessibility.AccessibilityEventCompat;
import android.support.v4.view.accessibility.AccessibilityNodeInfoCompat;
import android.support.v4.view.accessibility.AccessibilityRecordCompat;
import android.support.v4.widget.EdgeEffectCompat;
import android.util.AttributeSet;
import android.util.Log;
import android.view.FocusFinder;
import android.view.Gravity;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.SoundEffectConstants;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.view.ViewParent;
import android.view.accessibility.AccessibilityEvent;
import android.view.animation.Interpolator;
import android.widget.Scroller;
public class VerticalViewPager extends ViewGroup {
private static final String TAG = "ViewPager";
private static final boolean DEBUG = false;
private static final boolean USE_CACHE = false;
private static final int DEFAULT_OFFSCREEN_PAGES = 1;
private static final int MAX_SETTLE_DURATION = 600; // ms
private static final int MIN_DISTANCE_FOR_FLING = 25; // dips
private static final int DEFAULT_GUTTER_SIZE = 16; // dips
private static final int MIN_FLING_VELOCITY = 400; // dips
private static final int[] LAYOUT_ATTRS = new int[] { android.R.attr.layout_gravity };
/**
* Used to track what the expected number of items in the adapter should be.
* If the app changes this when we don‘t expect it, we‘ll throw a big
* obnoxious exception.
*/
private int mExpectedAdapterCount;
static class ItemInfo {
Object object;
int position;
boolean scrolling;
float heightFactor;
float offset;
}
private static final Comparator<ItemInfo> COMPARATOR = new Comparator<ItemInfo>() {
@Override
public int compare(ItemInfo lhs, ItemInfo rhs) {
return lhs.position - rhs.position;
}
};
private static final Interpolator sInterpolator = new Interpolator() {
public float getInterpolation(float t) {
t -= 1.0f;
return t * t * t * t * t + 1.0f;
}
};
private final ArrayList<ItemInfo> mItems = new ArrayList<ItemInfo>();
private final ItemInfo mTempItem = new ItemInfo();
private final Rect mTempRect = new Rect();
private PagerAdapter mAdapter;
private int mCurItem; // Index of currently displayed page.
private int mRestoredCurItem = -1;
private Parcelable mRestoredAdapterState = null;
private ClassLoader mRestoredClassLoader = null;
private Scroller mScroller;
private PagerObserver mObserver;
private int mPageMargin;
private Drawable mMarginDrawable;
private int mLeftPageBounds;
private int mRightPageBounds;
// Offsets of the first and last items, if known.
// Set during population, used to determine if we are at the beginning
// or end of the pager data set during touch scrolling.
private float mFirstOffset = -Float.MAX_VALUE;
private float mLastOffset = Float.MAX_VALUE;
private int mChildWidthMeasureSpec;
private int mChildHeightMeasureSpec;
private boolean mInLayout;
private boolean mScrollingCacheEnabled;
private boolean mPopulatePending;
private int mOffscreenPageLimit = DEFAULT_OFFSCREEN_PAGES;
private boolean mIsBeingDragged;
private boolean mIsUnableToDrag;
private boolean mIgnoreGutter;
private int mDefaultGutterSize;
private int mGutterSize;
private int mTouchSlop;
/**
* Position of the last motion event.
*/
private float mLastMotionX;
private float mLastMotionY;
private float mInitialMotionX;
private float mInitialMotionY;
/**
* ID of the active pointer. This is used to retain consistency during
* drags/flings if multiple pointers are used.
*/
private int mActivePointerId = INVALID_POINTER;
/**
* Sentinel value for no current active pointer. Used by
* {@link #mActivePointerId}.
*/
private static final int INVALID_POINTER = -1;
/**
* Determines speed during touch scrolling
*/
private VelocityTracker mVelocityTracker;
private int mMinimumVelocity;
private int mMaximumVelocity;
private int mFlingDistance;
private int mCloseEnough;
// If the pager is at least this close to its final position, complete the
// scroll
// on touch down and let the user interact with the content inside instead
// of
// "catching" the flinging pager.
private static final int CLOSE_ENOUGH = 2; // dp
private boolean mFakeDragging;
private long mFakeDragBeginTime;
private EdgeEffectCompat mTopEdge;
private EdgeEffectCompat mBottomEdge;
private boolean mFirstLayout = true;
private boolean mNeedCalculatePageOffsets = false;
private boolean mCalledSuper;
private int mDecorChildCount;
private ViewPager.OnPageChangeListener mOnPageChangeListener;
private ViewPager.OnPageChangeListener mInternalPageChangeListener;
private OnAdapterChangeListener mAdapterChangeListener;
private ViewPager.PageTransformer mPageTransformer;
private Method mSetChildrenDrawingOrderEnabled;
private static final int DRAW_ORDER_DEFAULT = 0;
private static final int DRAW_ORDER_FORWARD = 1;
private static final int DRAW_ORDER_REVERSE = 2;
private int mDrawingOrder;
private ArrayList<View> mDrawingOrderedChildren;
private static final ViewPositionComparator sPositionComparator = new ViewPositionComparator();
/**
* Indicates that the pager is in an idle, settled state. The current page
* is fully in view and no animation is in progress.
*/
public static final int SCROLL_STATE_IDLE = 0;
/**
* Indicates that the pager is currently being dragged by the user.
*/
public static final int SCROLL_STATE_DRAGGING = 1;
/**
* Indicates that the pager is in the process of settling to a final
* position.
*/
public static final int SCROLL_STATE_SETTLING = 2;
private final Runnable mEndScrollRunnable = new Runnable() {
public void run() {
setScrollState(SCROLL_STATE_IDLE);
populate();
}
};
private int mScrollState = SCROLL_STATE_IDLE;
/**
* Used internally to monitor when adapters are switched.
*/
interface OnAdapterChangeListener {
public void onAdapterChanged(PagerAdapter oldAdapter, PagerAdapter newAdapter);
}
/**
* Used internally to tag special types of child views that should be added
* as pager decorations by default.
*/
interface Decor {
}
public VerticalViewPager(Context context) {
super(context);
initViewPager();
}
public VerticalViewPager(Context context, AttributeSet attrs) {
super(context, attrs);
initViewPager();
}
void initViewPager() {
setWillNotDraw(false);
setDescendantFocusability(FOCUS_AFTER_DESCENDANTS);
setFocusable(true);
final Context context = getContext();
mScroller = new Scroller(context, sInterpolator);
final ViewConfiguration configuration = ViewConfiguration.get(context);
final float density = context.getResources().getDisplayMetrics().density;
mTouchSlop = ViewConfigurationCompat.getScaledPagingTouchSlop(configuration);
mMinimumVelocity = (int) (MIN_FLING_VELOCITY * density);
mMaximumVelocity = configuration.getScaledMaximumFlingVelocity();
mTopEdge = new EdgeEffectCompat(context);
mBottomEdge = new EdgeEffectCompat(context);
mFlingDistance = (int) (MIN_DISTANCE_FOR_FLING * density);
mCloseEnough = (int) (CLOSE_ENOUGH * density);
mDefaultGutterSize = (int) (DEFAULT_GUTTER_SIZE * density);
ViewCompat.setAccessibilityDelegate(this, new MyAccessibilityDelegate());
if (ViewCompat.getImportantForAccessibility(this) == ViewCompat.IMPORTANT_FOR_ACCESSIBILITY_AUTO) {
ViewCompat.setImportantForAccessibility(this, ViewCompat.IMPORTANT_FOR_ACCESSIBILITY_YES);
}
}
@Override
protected void onDetachedFromWindow() {
removeCallbacks(mEndScrollRunnable);
super.onDetachedFromWindow();
}
private void setScrollState(int newState) {
if (mScrollState == newState) {
return;
}
mScrollState = newState;
if (mPageTransformer != null) {
// PageTransformers can do complex things that benefit from hardware
// layers.
enableLayers(newState != SCROLL_STATE_IDLE);
}
if (mOnPageChangeListener != null) {
mOnPageChangeListener.onPageScrollStateChanged(newState);
}
}
/**
* Set a PagerAdapter that will supply views for this pager as needed.
*
* @param adapter
* Adapter to use
*/
public void setAdapter(PagerAdapter adapter) {
if (mAdapter != null) {
mAdapter.unregisterDataSetObserver(mObserver);
mAdapter.startUpdate(this);
for (int i = 0; i < mItems.size(); i++) {
final ItemInfo ii = mItems.get(i);
mAdapter.destroyItem(this, ii.position, ii.object);
}
mAdapter.finishUpdate(this);
mItems.clear();
removeNonDecorViews();
mCurItem = 0;
scrollTo(0, 0);
}
final PagerAdapter oldAdapter = mAdapter;
mAdapter = adapter;
mExpectedAdapterCount = 0;
if (mAdapter != null) {
if (mObserver == null) {
mObserver = new PagerObserver();
}
mAdapter.registerDataSetObserver(mObserver);
mPopulatePending = false;
final boolean wasFirstLayout = mFirstLayout;
mFirstLayout = true;
mExpectedAdapterCount = mAdapter.getCount();
if (mRestoredCurItem >= 0) {
mAdapter.restoreState(mRestoredAdapterState, mRestoredClassLoader);
setCurrentItemInternal(mRestoredCurItem, false, true);
mRestoredCurItem = -1;
mRestoredAdapterState = null;
mRestoredClassLoader = null;
} else if (!wasFirstLayout) {
populate();
} else {
requestLayout();
}
}
if (mAdapterChangeListener != null && oldAdapter != adapter) {
mAdapterChangeListener.onAdapterChanged(oldAdapter, adapter);
}
}
private void removeNonDecorViews() {
for (int i = 0; i < getChildCount(); i++) {
final View child = getChildAt(i);
final LayoutParams lp = (LayoutParams) child.getLayoutParams();
if (!lp.isDecor) {
removeViewAt(i);
i--;
}
}
}
/**
* Retrieve the current adapter supplying pages.
*
* @return The currently registered PagerAdapter
*/
public PagerAdapter getAdapter() {
return mAdapter;
}
void setOnAdapterChangeListener(OnAdapterChangeListener listener) {
mAdapterChangeListener = listener;
}
// private int getClientWidth() {
// return getMeasuredWidth() - getPaddingLeft() - getPaddingRight();
// }
private int getClientHeight() {
return getMeasuredHeight() - getPaddingTop() - getPaddingBottom();
}
/**
* Set the currently selected page. If the ViewPager has already been
* through its first layout with its current adapter there will be a smooth
* animated transition between the current item and the specified item.
*
* @param item
* Item index to select
*/
public void setCurrentItem(int item) {
mPopulatePending = false;
setCurrentItemInternal(item, !mFirstLayout, false);
}
/**
* Set the currently selected page.
*
* @param item
* Item index to select
* @param smoothScroll
* True to smoothly scroll to the new item, false to transition
* immediately
*/
public void setCurrentItem(int item, boolean smoothScroll) {
mPopulatePending = false;
setCurrentItemInternal(item, smoothScroll, false);
}
public int getCurrentItem() {
return mCurItem;
}
void setCurrentItemInternal(int item, boolean smoothScroll, boolean always) {
setCurrentItemInternal(item, smoothScroll, always, 0);
}
void setCurrentItemInternal(int item, boolean smoothScroll, boolean always, int velocity) {
if (mAdapter == null || mAdapter.getCount() <= 0) {
setScrollingCacheEnabled(false);
return;
}
if (!always && mCurItem == item && mItems.size() != 0) {
setScrollingCacheEnabled(false);
return;
}
if (item < 0) {
item = 0;
} else if (item >= mAdapter.getCount()) {
item = mAdapter.getCount() - 1;
}
final int pageLimit = mOffscreenPageLimit;
if (item > (mCurItem + pageLimit) || item < (mCurItem - pageLimit)) {
// We are doing a jump by more than one page. To avoid
// glitches, we want to keep all current pages in the view
// until the scroll ends.
for (int i = 0; i < mItems.size(); i++) {
mItems.get(i).scrolling = true;
}
}
final boolean dispatchSelected = mCurItem != item;
if (mFirstLayout) {
// We don‘t have any idea how big we are yet and shouldn‘t have any
// pages either.
// Just set things up and let the pending layout handle things.
mCurItem = item;
if (dispatchSelected && mOnPageChangeListener != null) {
mOnPageChangeListener.onPageSelected(item);
}
if (dispatchSelected && mInternalPageChangeListener != null) {
mInternalPageChangeListener.onPageSelected(item);
}
requestLayout();
} else {
populate(item);
scrollToItem(item, smoothScroll, velocity, dispatchSelected);
}
}
private void scrollToItem(int item, boolean smoothScroll, int velocity, boolean dispatchSelected) {
final ItemInfo curInfo = infoForPosition(item);
int destY = 0;
if (curInfo != null) {
final int height = getClientHeight();
destY = (int) (height * Math.max(mFirstOffset, Math.min(curInfo.offset, mLastOffset)));
}
if (smoothScroll) {
smoothScrollTo(0, destY, velocity);
if (dispatchSelected && mOnPageChangeListener != null) {
mOnPageChangeListener.onPageSelected(item);
}
if (dispatchSelected && mInternalPageChangeListener != null) {
mInternalPageChangeListener.onPageSelected(item);
}
} else {
if (dispatchSelected && mOnPageChangeListener != null) {
mOnPageChangeListener.onPageSelected(item);
}
if (dispatchSelected && mInternalPageChangeListener != null) {
mInternalPageChangeListener.onPageSelected(item);
}
completeScroll(false);
scrollTo(0, destY);
pageScrolled(destY);
}
}
/**
* Set a listener that will be invoked whenever the page changes or is
* incrementally scrolled. See
* {@link android.support.v4.view.ViewPager.OnPageChangeListener}.
*
* @param listener
* Listener to set
*/
public void setOnPageChangeListener(ViewPager.OnPageChangeListener listener) {
mOnPageChangeListener = listener;
}
/**
* Set a {@link android.support.v4.view.ViewPager.PageTransformer} that will
* be called for each attached page whenever the scroll position is changed.
* This allows the application to apply custom property transformations to
* each page, overriding the default sliding look and feel.
* <p/>
* <p>
* <em>Note:</em> Prior to Android 3.0 the property animation APIs did not
* exist. As a result, setting a PageTransformer prior to Android 3.0 (API
* 11) will have no effect.
* </p>
*
* @param reverseDrawingOrder
* true if the supplied PageTransformer requires page views to be
* drawn from last to first instead of first to last.
* @param transformer
* PageTransformer that will modify each page‘s animation
* properties
*/
public void setPageTransformer(boolean reverseDrawingOrder, ViewPager.PageTransformer transformer) {
if (Build.VERSION.SDK_INT >= 11) {
final boolean hasTransformer = transformer != null;
final boolean needsPopulate = hasTransformer != (mPageTransformer != null);
mPageTransformer = transformer;
setChildrenDrawingOrderEnabledCompat(hasTransformer);
if (hasTransformer) {
mDrawingOrder = reverseDrawingOrder ? DRAW_ORDER_REVERSE : DRAW_ORDER_FORWARD;
} else {
mDrawingOrder = DRAW_ORDER_DEFAULT;
}
if (needsPopulate)
populate();
}
}
void setChildrenDrawingOrderEnabledCompat(boolean enable) {
if (Build.VERSION.SDK_INT >= 7) {
if (mSetChildrenDrawingOrderEnabled == null) {
try {
mSetChildrenDrawingOrderEnabled = ViewGroup.class.getDeclaredMethod("setChildrenDrawingOrderEnabled", new Class[] { Boolean.TYPE });
} catch (NoSuchMethodException e) {
Log.e(TAG, "Can‘t find setChildrenDrawingOrderEnabled", e);
}
}
try {
mSetChildrenDrawingOrderEnabled.invoke(this, enable);
} catch (Exception e) {
Log.e(TAG, "Error changing children drawing order", e);
}
}
}
@Override
protected int getChildDrawingOrder(int childCount, int i) {
final int index = mDrawingOrder == DRAW_ORDER_REVERSE ? childCount - 1 - i : i;
final int result = ((LayoutParams) mDrawingOrderedChildren.get(index).getLayoutParams()).childIndex;
return result;
}
/**
* Set a separate OnPageChangeListener for internal use by the support
* library.
*
* @param listener
* Listener to set
* @return The old listener that was set, if any.
*/
ViewPager.OnPageChangeListener setInternalPageChangeListener(ViewPager.OnPageChangeListener listener) {
ViewPager.OnPageChangeListener oldListener = mInternalPageChangeListener;
mInternalPageChangeListener = listener;
return oldListener;
}
/**
* Returns the number of pages that will be retained to either side of the
* current page in the view hierarchy in an idle state. Defaults to 1.
*
* @return How many pages will be kept offscreen on either side
* @see #setOffscreenPageLimit(int)
*/
public int getOffscreenPageLimit() {
return mOffscreenPageLimit;
}
/**
* Set the number of pages that should be retained to either side of the
* current page in the view hierarchy in an idle state. Pages beyond this
* limit will be recreated from the adapter when needed.
* <p/>
* <p>
* This is offered as an optimization. If you know in advance the number of
* pages you will need to support or have lazy-loading mechanisms in place
* on your pages, tweaking this setting can have benefits in perceived
* smoothness of paging animations and interaction. If you have a small
* number of pages (3-4) that you can keep active all at once, less time
* will be spent in layout for newly created view subtrees as the user pages
* back and forth.
* </p>
* <p/>
* <p>
* You should keep this limit low, especially if your pages have complex
* layouts. This setting defaults to 1.
* </p>
*
* @param limit
* How many pages will be kept offscreen in an idle state.
*/
public void setOffscreenPageLimit(int limit) {
if (limit < DEFAULT_OFFSCREEN_PAGES) {
Log.w(TAG, "Requested offscreen page limit " + limit + " too small; defaulting to " + DEFAULT_OFFSCREEN_PAGES);
limit = DEFAULT_OFFSCREEN_PAGES;
}
if (limit != mOffscreenPageLimit) {
mOffscreenPageLimit = limit;
populate();
}
}
/**
* Set the margin between pages.
*
* @param marginPixels
* Distance between adjacent pages in pixels
* @see #getPageMargin()
* @see #setPageMarginDrawable(Drawable)
* @see #setPageMarginDrawable(int)
*/
public void setPageMargin(int marginPixels) {
final int oldMargin = mPageMargin;
mPageMargin = marginPixels;
final int height = getHeight();
recomputeScrollPosition(height, height, marginPixels, oldMargin);
requestLayout();
}
/**
* Return the margin between pages.
*
* @return The size of the margin in pixels
*/
public int getPageMargin() {
return mPageMargin;
}
/**
* Set a drawable that will be used to fill the margin between pages.
*
* @param d
* Drawable to display between pages
*/
public void setPageMarginDrawable(Drawable d) {
mMarginDrawable = d;
if (d != null)
refreshDrawableState();
setWillNotDraw(d == null);
invalidate();
}
/**
* Set a drawable that will be used to fill the margin between pages.
*
* @param resId
* Resource ID of a drawable to display between pages
*/
public void setPageMarginDrawable(int resId) {
setPageMarginDrawable(getContext().getResources().getDrawable(resId));
}
@Override
protected boolean verifyDrawable(Drawable who) {
return super.verifyDrawable(who) || who == mMarginDrawable;
}
@Override
protected void drawableStateChanged() {
super.drawableStateChanged();
final Drawable d = mMarginDrawable;
if (d != null && d.isStateful()) {
d.setState(getDrawableState());
}
}
// We want the duration of the page snap animation to be influenced by the
// distance that
// the screen has to travel, however, we don‘t want this duration to be
// effected in a
// purely linear fashion. Instead, we use this method to moderate the effect
// that the distance
// of travel has on the overall snap duration.
float distanceInfluenceForSnapDuration(float f) {
f -= 0.5f; // center the values about 0.
f *= 0.3f * Math.PI / 2.0f;
return (float) Math.sin(f);
}
/**
* Like {@link View#scrollBy}, but scroll smoothly instead of immediately.
*
* @param x
* the number of pixels to scroll by on the X axis
* @param y
* the number of pixels to scroll by on the Y axis
*/
void smoothScrollTo(int x, int y) {
smoothScrollTo(x, y, 0);
}
/**
* Like {@link View#scrollBy}, but scroll smoothly instead of immediately.
*
* @param x
* the number of pixels to scroll by on the X axis
* @param y
* the number of pixels to scroll by on the Y axis
* @param velocity
* the velocity associated with a fling, if applicable. (0
* otherwise)
*/
void smoothScrollTo(int x, int y, int velocity) {
if (getChildCount() == 0) {
// Nothing to do.
setScrollingCacheEnabled(false);
return;
}
int sx = getScrollX();
int sy = getScrollY();
int dx = x - sx;
int dy = y - sy;
if (dx == 0 && dy == 0) {
completeScroll(false);
populate();
setScrollState(SCROLL_STATE_IDLE);
return;
}
setScrollingCacheEnabled(true);
setScrollState(SCROLL_STATE_SETTLING);
final int height = getClientHeight();
final int halfHeight = height / 2;
final float distanceRatio = Math.min(1f, 1.0f * Math.abs(dx) / height);
final float distance = halfHeight + halfHeight * distanceInfluenceForSnapDuration(distanceRatio);
int duration = 0;
velocity = Math.abs(velocity);
if (velocity > 0) {
duration = 4 * Math.round(1000 * Math.abs(distance / velocity));
} else {
final float pageHeight = height * mAdapter.getPageWidth(mCurItem);
final float pageDelta = (float) Math.abs(dx) / (pageHeight + mPageMargin);
duration = (int) ((pageDelta + 1) * 100);
}
duration = Math.min(duration, MAX_SETTLE_DURATION);
mScroller.startScroll(sx, sy, dx, dy, duration);
ViewCompat.postInvalidateOnAnimation(this);
}
ItemInfo addNewItem(int position, int index) {
ItemInfo ii = new ItemInfo();
ii.position = position;
ii.object = mAdapter.instantiateItem(this, position);
ii.heightFactor = mAdapter.getPageWidth(position);
if (index < 0 || index >= mItems.size()) {
mItems.add(ii);
} else {
mItems.add(index, ii);
}
return ii;
}
void dataSetChanged() {
// This method only gets called if our observer is attached, so mAdapter
// is non-null.
final int adapterCount = mAdapter.getCount();
mExpectedAdapterCount = adapterCount;
boolean needPopulate = mItems.size() < mOffscreenPageLimit * 2 + 1 && mItems.size() < adapterCount;
int newCurrItem = mCurItem;
boolean isUpdating = false;
for (int i = 0; i < mItems.size(); i++) {
final ItemInfo ii = mItems.get(i);
final int newPos = mAdapter.getItemPosition(ii.object);
if (newPos == PagerAdapter.POSITION_UNCHANGED) {
continue;
}
if (newPos == PagerAdapter.POSITION_NONE) {
mItems.remove(i);
i--;
if (!isUpdating) {
mAdapter.startUpdate(this);
isUpdating = true;
}
mAdapter.destroyItem(this, ii.position, ii.object);
needPopulate = true;
if (mCurItem == ii.position) {
// Keep the current item in the valid range
newCurrItem = Math.max(0, Math.min(mCurItem, adapterCount - 1));
needPopulate = true;
}
continue;
}
if (ii.position != newPos) {
if (ii.position == mCurItem) {
// Our current item changed position. Follow it.
newCurrItem = newPos;
}
ii.position = newPos;
needPopulate = true;
}
}
if (isUpdating) {
mAdapter.finishUpdate(this);
}
Collections.sort(mItems, COMPARATOR);
if (needPopulate) {
// Reset our known page widths; populate will recompute them.
final int childCount = getChildCount();
for (int i = 0; i < childCount; i++) {
final View child = getChildAt(i);
final LayoutParams lp = (LayoutParams) child.getLayoutParams();
if (!lp.isDecor) {
lp.heightFactor = 0.f;
}
}
setCurrentItemInternal(newCurrItem, false, true);
requestLayout();
}
}
void populate() {
populate(mCurItem);
}
void populate(int newCurrentItem) {
ItemInfo oldCurInfo = null;
int focusDirection = View.FOCUS_FORWARD;
if (mCurItem != newCurrentItem) {
focusDirection = mCurItem < newCurrentItem ? View.FOCUS_DOWN : View.FOCUS_UP;
oldCurInfo = infoForPosition(mCurItem);
mCurItem = newCurrentItem;
}
if (mAdapter == null) {
sortChildDrawingOrder();
return;
}
// Bail now if we are waiting to populate. This is to hold off
// on creating views from the time the user releases their finger to
// fling to a new position until we have finished the scroll to
// that position, avoiding glitches from happening at that point.
if (mPopulatePending) {
if (DEBUG)
Log.i(TAG, "populate is pending, skipping for now...");
sortChildDrawingOrder();
return;
}
// Also, don‘t populate until we are attached to a window. This is to
// avoid trying to populate before we have restored our view hierarchy
// state and conflicting with what is restored.
if (getWindowToken() == null) {
return;
}
mAdapter.startUpdate(this);
final int pageLimit = mOffscreenPageLimit;
final int startPos = Math.max(0, mCurItem - pageLimit);
final int N = mAdapter.getCount();
final int endPos = Math.min(N - 1, mCurItem + pageLimit);
if (N != mExpectedAdapterCount) {
String resName;
try {
resName = getResources().getResourceName(getId());
} catch (Resources.NotFoundException e) {
resName = Integer.toHexString(getId());
}
throw new IllegalStateException("The application‘s PagerAdapter changed the adapter‘s" + " contents without calling PagerAdapter#notifyDataSetChanged!" + " Expected adapter item count: " + mExpectedAdapterCount + ", found: " + N + " Pager id: " + resName + " Pager class: " + getClass() + " Problematic adapter: " + mAdapter.getClass());
}
// Locate the currently focused item or add it if needed.
int curIndex = -1;
ItemInfo curItem = null;
for (curIndex = 0; curIndex < mItems.size(); curIndex++) {
final ItemInfo ii = mItems.get(curIndex);
if (ii.position >= mCurItem) {
if (ii.position == mCurItem)
curItem = ii;
break;
}
}
if (curItem == null && N > 0) {
curItem = addNewItem(mCurItem, curIndex);
}
// Fill 3x the available width or up to the number of offscreen
// pages requested to either side, whichever is larger.
// If we have no current item we have no work to do.
if (curItem != null) {
float extraHeightTop = 0.f;
int itemIndex = curIndex - 1;
ItemInfo ii = itemIndex >= 0 ? mItems.get(itemIndex) : null;
final int clientHeight = getClientHeight();
final float topHeightNeeded = clientHeight <= 0 ? 0 : 2.f - curItem.heightFactor + (float) getPaddingLeft() / (float) clientHeight;
for (int pos = mCurItem - 1; pos >= 0; pos--) {
if (extraHeightTop >= topHeightNeeded && pos < startPos) {
if (ii == null) {
break;
}
if (pos == ii.position && !ii.scrolling) {
mItems.remove(itemIndex);
mAdapter.destroyItem(this, pos, ii.object);
if (DEBUG) {
Log.i(TAG, "populate() - destroyItem() with pos: " + pos + " view: " + ((View) ii.object));
}
itemIndex--;
curIndex--;
ii = itemIndex >= 0 ? mItems.get(itemIndex) : null;
}
} else if (ii != null && pos == ii.position) {
extraHeightTop += ii.heightFactor;
itemIndex--;
ii = itemIndex >= 0 ? mItems.get(itemIndex) : null;
} else {
ii = addNewItem(pos, itemIndex + 1);
extraHeightTop += ii.heightFactor;
curIndex++;
ii = itemIndex >= 0 ? mItems.get(itemIndex) : null;
}
}
float extraHeightBottom = curItem.heightFactor;
itemIndex = curIndex + 1;
if (extraHeightBottom < 2.f) {
ii = itemIndex < mItems.size() ? mItems.get(itemIndex) : null;
final float bottomHeightNeeded = clientHeight <= 0 ? 0 : (float) getPaddingRight() / (float) clientHeight + 2.f;
for (int pos = mCurItem + 1; pos < N; pos++) {
if (extraHeightBottom >= bottomHeightNeeded && pos > endPos) {
if (ii == null) {
break;
}
if (pos == ii.position && !ii.scrolling) {
mItems.remove(itemIndex);
mAdapter.destroyItem(this, pos, ii.object);
if (DEBUG) {
Log.i(TAG, "populate() - destroyItem() with pos: " + pos + " view: " + ((View) ii.object));
}
ii = itemIndex < mItems.size() ? mItems.get(itemIndex) : null;
}
} else if (ii != null && pos == ii.position) {
extraHeightBottom += ii.heightFactor;
itemIndex++;
ii = itemIndex < mItems.size() ? mItems.get(itemIndex) : null;
} else {
ii = addNewItem(pos, itemIndex);
itemIndex++;
extraHeightBottom += ii.heightFactor;
ii = itemIndex < mItems.size() ? mItems.get(itemIndex) : null;
}
}
}
calculatePageOffsets(curItem, curIndex, oldCurInfo);
}
if (DEBUG) {
Log.i(TAG, "Current page list:");
for (int i = 0; i < mItems.size(); i++) {
Log.i(TAG, "#" + i + ": page " + mItems.get(i).position);
}
}
mAdapter.setPrimaryItem(this, mCurItem, curItem != null ? curItem.object : null);
mAdapter.finishUpdate(this);
// Check width measurement of current pages and drawing sort order.
// Update LayoutParams as needed.
final int childCount = getChildCount();
for (int i = 0; i < childCount; i++) {
final View child = getChildAt(i);
final LayoutParams lp = (LayoutParams) child.getLayoutParams();
lp.childIndex = i;
if (!lp.isDecor && lp.heightFactor == 0.f) {
// 0 means requery the adapter for this, it doesn‘t have a valid
// width.
final ItemInfo ii = infoForChild(child);
if (ii != null) {
lp.heightFactor = ii.heightFactor;
lp.position = ii.position;
}
}
}
sortChildDrawingOrder();
if (hasFocus()) {
View currentFocused = findFocus();
ItemInfo ii = currentFocused != null ? infoForAnyChild(currentFocused) : null;
if (ii == null || ii.position != mCurItem) {
for (int i = 0; i < getChildCount(); i++) {
View child = getChildAt(i);
ii = infoForChild(child);
if (ii != null && ii.position == mCurItem) {
if (child.requestFocus(focusDirection)) {
break;
}
}
}
}
}
}
private void sortChildDrawingOrder() {
if (mDrawingOrder != DRAW_ORDER_DEFAULT) {
if (mDrawingOrderedChildren == null) {
mDrawingOrderedChildren = new ArrayList<View>();
} else {
mDrawingOrderedChildren.clear();
}
final int childCount = getChildCount();
for (int i = 0; i < childCount; i++) {
final View child = getChildAt(i);
mDrawingOrderedChildren.add(child);
}
Collections.sort(mDrawingOrderedChildren, sPositionComparator);
}
}
private void calculatePageOffsets(ItemInfo curItem, int curIndex, ItemInfo oldCurInfo) {
final int N = mAdapter.getCount();
final int height = getClientHeight();
final float marginOffset = height > 0 ? (float) mPageMargin / height : 0;
// Fix up offsets for later layout.
if (oldCurInfo != null) {
final int oldCurPosition = oldCurInfo.position;
// Base offsets off of oldCurInfo.
if (oldCurPosition < curItem.position) {
int itemIndex = 0;
ItemInfo ii = null;
float offset = oldCurInfo.offset + oldCurInfo.heightFactor + marginOffset;
for (int pos = oldCurPosition + 1; pos <= curItem.position && itemIndex < mItems.size(); pos++) {
ii = mItems.get(itemIndex);
while (pos > ii.position && itemIndex < mItems.size() - 1) {
itemIndex++;
ii = mItems.get(itemIndex);
}
while (pos < ii.position) {
// We don‘t have an item populated for this,
// ask the adapter for an offset.
offset += mAdapter.getPageWidth(pos) + marginOffset;
pos++;
}
ii.offset = offset;
offset += ii.heightFactor + marginOffset;
}
} else if (oldCurPosition > curItem.position) {
int itemIndex = mItems.size() - 1;
ItemInfo ii = null;
float offset = oldCurInfo.offset;
for (int pos = oldCurPosition - 1; pos >= curItem.position && itemIndex >= 0; pos--) {
ii = mItems.get(itemIndex);
while (pos < ii.position && itemIndex > 0) {
itemIndex--;
ii = mItems.get(itemIndex);
}
while (pos > ii.position) {
// We don‘t have an item populated for this,
// ask the adapter for an offset.
offset -= mAdapter.getPageWidth(pos) + marginOffset;
pos--;
}
offset -= ii.heightFactor + marginOffset;
ii.offset = offset;
}
}
}
// Base all offsets off of curItem.
final int itemCount = mItems.size();
float offset = curItem.offset;
int pos = curItem.position - 1;
mFirstOffset = curItem.position == 0 ? curItem.offset : -Float.MAX_VALUE;
mLastOffset = curItem.position == N - 1 ? curItem.offset + curItem.heightFactor - 1 : Float.MAX_VALUE;
// Previous pages
for (int i = curIndex - 1; i >= 0; i--, pos--) {
final ItemInfo ii = mItems.get(i);
while (pos > ii.position) {
offset -= mAdapter.getPageWidth(pos--) + marginOffset;
}
offset -= ii.heightFactor + marginOffset;
ii.offset = offset;
if (ii.position == 0)
mFirstOffset = offset;
}
offset = curItem.offset + curItem.heightFactor + marginOffset;
pos = curItem.position + 1;
// Next pages
for (int i = curIndex + 1; i < itemCount; i++, pos++) {
final ItemInfo ii = mItems.get(i);
while (pos < ii.position) {
offset += mAdapter.getPageWidth(pos++) + marginOffset;
}
if (ii.position == N - 1) {
mLastOffset = offset + ii.heightFactor - 1;
}
ii.offset = offset;
offset += ii.heightFactor + marginOffset;
}
mNeedCalculatePageOffsets = false;
}
/**
* This is the persistent state that is saved by ViewPager. Only needed if
* you are creating a sublass of ViewPager that must save its own state, in
* which case it should implement a subclass of this which contains that
* state.
*/
public static class SavedState extends BaseSavedState {
int position;
Parcelable adapterState;
ClassLoader loader;
public SavedState(Parcelable superState) {
super(superState);
}
@Override
public void writeToParcel(Parcel out, int flags) {
super.writeToParcel(out, flags);
out.writeInt(position);
out.writeParcelable(adapterState, flags);
}
@Override
public String toString() {
return "FragmentPager.SavedState{" + Integer.toHexString(System.identityHashCode(this)) + " position=" + position + "}";
}
public static final Parcelable.Creator<SavedState> CREATOR = ParcelableCompat.newCreator(new ParcelableCompatCreatorCallbacks<SavedState>() {
@Override
public SavedState createFromParcel(Parcel in, ClassLoader loader) {
return new SavedState(in, loader);
}
@Override
public SavedState[] newArray(int size) {
return new SavedState[size];
}
});
SavedState(Parcel in, ClassLoader loader) {
super(in);
if (loader == null) {
loader = getClass().getClassLoader();
}
position = in.readInt();
adapterState = in.readParcelable(loader);
this.loader = loader;
}
}
@Override
public Parcelable onSaveInstanceState() {
Parcelable superState = super.onSaveInstanceState();
SavedState ss = new SavedState(superState);
ss.position = mCurItem;
if (mAdapter != null) {
ss.adapterState = mAdapter.saveState();
}
return ss;
}
@Override
public void onRestoreInstanceState(Parcelable state) {
if (!(state instanceof SavedState)) {
super.onRestoreInstanceState(state);
return;
}
SavedState ss = (SavedState) state;
super.onRestoreInstanceState(ss.getSuperState());
if (mAdapter != null) {
mAdapter.restoreState(ss.adapterState, ss.loader);
setCurrentItemInternal(ss.position, false, true);
} else {
mRestoredCurItem = ss.position;
mRestoredAdapterState = ss.adapterState;
mRestoredClassLoader = ss.loader;
}
}
@Override
public void addView(View child, int index, ViewGroup.LayoutParams params) {
if (!checkLayoutParams(params)) {
params = generateLayoutParams(params);
}
final LayoutParams lp = (LayoutParams) params;
lp.isDecor |= child instanceof Decor;
if (mInLayout) {
if (lp != null && lp.isDecor) {
throw new IllegalStateException("Cannot add pager decor view during layout");
}
lp.needsMeasure = true;
addViewInLayout(child, index, params);
} else {
super.addView(child, index, params);
}
if (USE_CACHE) {
if (child.getVisibility() != GONE) {
child.setDrawingCacheEnabled(mScrollingCacheEnabled);
} else {
child.setDrawingCacheEnabled(false);
}
}
}
@Override
public void removeView(View view) {
if (mInLayout) {
removeViewInLayout(view);
} else {
super.removeView(view);
}
}
ItemInfo infoForChild(View child) {
for (int i = 0; i < mItems.size(); i++) {
ItemInfo ii = mItems.get(i);
if (mAdapter.isViewFromObject(child, ii.object)) {
return ii;
}
}
return null;
}
ItemInfo infoForAnyChild(View child) {
ViewParent parent;
while ((parent = child.getParent()) != this) {
if (parent == null || !(parent instanceof View)) {
return null;
}
child = (View) parent;
}
return infoForChild(child);
}
ItemInfo infoForPosition(int position) {
for (int i = 0; i < mItems.size(); i++) {
ItemInfo ii = mItems.get(i);
if (ii.position == position) {
return ii;
}
}
return null;
}
@Override
protected void onAttachedToWindow() {
super.onAttachedToWindow();
mFirstLayout = true;
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
// For simple implementation, our internal size is always 0.
// We depend on the container to specify the layout size of
// our view. We can‘t really know what it is since we will be
// adding and removing different arbitrary views and do not
// want the layout to change as this happens.
setMeasuredDimension(getDefaultSize(0, widthMeasureSpec), getDefaultSize(0, heightMeasureSpec));
final int measuredHeight = getMeasuredHeight();
final int maxGutterSize = measuredHeight / 10;
mGutterSize = Math.min(maxGutterSize, mDefaultGutterSize);
// Children are just made to fill our space.
int childWidthSize = getMeasuredWidth() - getPaddingLeft() - getPaddingRight();
int childHeightSize = measuredHeight - getPaddingTop() - getPaddingBottom();
/*
* Make sure all children have been properly measured. Decor views
* first. Right now we cheat and make this less complicated by assuming
* decor views won‘t intersect. We will pin to edges based on gravity.
*/
int size = getChildCount();
for (int i = 0; i < size; ++i) {
final View child = getChildAt(i);
if (child.getVisibility() != GONE) {
final LayoutParams lp = (LayoutParams) child.getLayoutParams();
if (lp != null && lp.isDecor) {
final int hgrav = lp.gravity & Gravity.HORIZONTAL_GRAVITY_MASK;
final int vgrav = lp.gravity & Gravity.VERTICAL_GRAVITY_MASK;
int widthMode = MeasureSpec.AT_MOST;
int heightMode = MeasureSpec.AT_MOST;
boolean consumeVertical = vgrav == Gravity.TOP || vgrav == Gravity.BOTTOM;
boolean consumeHorizontal = hgrav == Gravity.LEFT || hgrav == Gravity.RIGHT;
if (consumeVertical) {
widthMode = MeasureSpec.EXACTLY;
} else if (consumeHorizontal) {
heightMode = MeasureSpec.EXACTLY;
}
int widthSize = childWidthSize;
int heightSize = childHeightSize;
if (lp.width != LayoutParams.WRAP_CONTENT) {
widthMode = MeasureSpec.EXACTLY;
if (lp.width != LayoutParams.FILL_PARENT) {
widthSize = lp.width;
}
}
if (lp.height != LayoutParams.WRAP_CONTENT) {
heightMode = MeasureSpec.EXACTLY;
if (lp.height != LayoutParams.FILL_PARENT) {
heightSize = lp.height;
}
}
final int widthSpec = MeasureSpec.makeMeasureSpec(widthSize, widthMode);
final int heightSpec = MeasureSpec.makeMeasureSpec(heightSize, heightMode);
child.measure(widthSpec, heightSpec);
if (consumeVertical) {
childHeightSize -= child.getMeasuredHeight();
} else if (consumeHorizontal) {
childWidthSize -= child.getMeasuredWidth();
}
}
}
}
mChildWidthMeasureSpec = MeasureSpec.makeMeasureSpec(childWidthSize, MeasureSpec.EXACTLY);
mChildHeightMeasureSpec = MeasureSpec.makeMeasureSpec(childHeightSize, MeasureSpec.EXACTLY);
// Make sure we have created all fragments that we need to have shown.
mInLayout = true;
populate();
mInLayout = false;
// Page views next.
size = getChildCount();
for (int i = 0; i < size; ++i) {
final View child = getChildAt(i);
if (child.getVisibility() != GONE) {
if (DEBUG)
Log.v(TAG, "Measuring #" + i + " " + child + ": " + mChildWidthMeasureSpec);
final LayoutParams lp = (LayoutParams) child.getLayoutParams();
if (lp == null || !lp.isDecor) {
final int heightSpec = MeasureSpec.makeMeasureSpec((int) (childHeightSize * lp.heightFactor), MeasureSpec.EXACTLY);
child.measure(mChildWidthMeasureSpec, heightSpec);
}
}
}
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
// Make sure scroll position is set correctly.
if (h != oldh) {
recomputeScrollPosition(h, oldh, mPageMargin, mPageMargin);
}
}
private void recomputeScrollPosition(int height, int oldHeight, int margin, int oldMargin) {
if (oldHeight > 0 && !mItems.isEmpty()) {
final int heightWithMargin = height - getPaddingTop() - getPaddingBottom() + margin;
final int oldHeightWithMargin = oldHeight - getPaddingTop() - getPaddingBottom() + oldMargin;
final int ypos = getScrollY();
final float pageOffset = (float) ypos / oldHeightWithMargin;
final int newOffsetPixels = (int) (pageOffset * heightWithMargin);
scrollTo(getScrollX(), newOffsetPixels);
if (!mScroller.isFinished()) {
// We now return to your regularly scheduled scroll, already in
// progress.
final int newDuration = mScroller.getDuration() - mScroller.timePassed();
ItemInfo targetInfo = infoForPosition(mCurItem);
mScroller.startScroll(0, newOffsetPixels, 0, (int) (targetInfo.offset * height), newDuration);
}
} else {
final ItemInfo ii = infoForPosition(mCurItem);
final float scrollOffset = ii != null ? Math.min(ii.offset, mLastOffset) : 0;
final int scrollPos = (int) (scrollOffset * (height - getPaddingTop() - getPaddingBottom()));
if (scrollPos != getScrollY()) {
completeScroll(false);
scrollTo(getScrollX(), scrollPos);
}
}
}
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
final int count = getChildCount();
int width = r - l;
int height = b - t;
int paddingLeft = getPaddingLeft();
int paddingTop = getPaddingTop();
int paddingRight = getPaddingRight();
int paddingBottom = getPaddingBottom();
final int scrollY = getScrollY();
int decorCount = 0;
// First pass - decor views. We need to do this in two passes so that
// we have the proper offsets for non-decor views later.
for (int i = 0; i < count; i++) {
final View child = getChildAt(i);
if (child.getVisibility() != GONE) {
final LayoutParams lp = (LayoutParams) child.getLayoutParams();
int childLeft = 0;
int childTop = 0;
if (lp.isDecor) {
final int hgrav = lp.gravity & Gravity.HORIZONTAL_GRAVITY_MASK;
final int vgrav = lp.gravity & Gravity.VERTICAL_GRAVITY_MASK;
switch (hgrav) {
default:
childLeft = paddingLeft;
break;
case Gravity.LEFT:
childLeft = paddingLeft;
paddingLeft += child.getMeasuredWidth();
break;
case Gravity.CENTER_HORIZONTAL:
childLeft = Math.max((width - child.getMeasuredWidth()) / 2, paddingLeft);
break;
case Gravity.RIGHT:
childLeft = width - paddingRight - child.getMeasuredWidth();
paddingRight += child.getMeasuredWidth();
break;
}
switch (vgrav) {
default:
childTop = paddingTop;
break;
case Gravity.TOP:
childTop = paddingTop;
paddingTop += child.getMeasuredHeight();
break;
case Gravity.CENTER_VERTICAL:
childTop = Math.max((height - child.getMeasuredHeight()) / 2, paddingTop);
break;
case Gravity.BOTTOM:
childTop = height - paddingBottom - child.getMeasuredHeight();
paddingBottom += child.getMeasuredHeight();
break;
}
childTop += scrollY;
child.layout(childLeft, childTop, childLeft + child.getMeasuredWidth(), childTop + child.getMeasuredHeight());
decorCount++;
}
}
}
final int childHeight = height - paddingTop - paddingBottom;
// Page views. Do this once we have the right padding offsets from
// above.
for (int i = 0; i < count; i++) {
final View child = getChildAt(i);
if (child.getVisibility() != GONE) {
final LayoutParams lp = (LayoutParams) child.getLayoutParams();
ItemInfo ii;
if (!lp.isDecor && (ii = infoForChild(child)) != null) {
int toff = (int) (childHeight * ii.offset);
int childLeft = paddingLeft;
int childTop = paddingTop + toff;
if (lp.needsMeasure) {
// This was added during layout and needs measurement.
// Do it now that we know what we‘re working with.
lp.needsMeasure = false;
final int widthSpec = MeasureSpec.makeMeasureSpec((int) (width - paddingLeft - paddingRight), MeasureSpec.EXACTLY);
final int heightSpec = MeasureSpec.makeMeasureSpec((int) (childHeight * lp.heightFactor), MeasureSpec.EXACTLY);
child.measure(widthSpec, heightSpec);
}
if (DEBUG)
Log.v(TAG, "Positioning #" + i + " " + child + " f=" + ii.object + ":" + childLeft + "," + childTop + " " + child.getMeasuredWidth() + "x" + child.getMeasuredHeight());
child.layout(childLeft, childTop, childLeft + child.getMeasuredWidth(), childTop + child.getMeasuredHeight());
}
}
}
mLeftPageBounds = paddingLeft;
mRightPageBounds = width - paddingRight;
mDecorChildCount = decorCount;
if (mFirstLayout) {
scrollToItem(mCurItem, false, 0, false);
}
mFirstLayout = false;
}
@Override
public void computeScroll() {
if (!mScroller.isFinished() && mScroller.computeScrollOffset()) {
int oldX = getScrollX();
int oldY = getScrollY();
int x = mScroller.getCurrX();
int y = mScroller.getCurrY();
if (oldX != x || oldY != y) {
scrollTo(x, y);
if (!pageScrolled(y)) {
mScroller.abortAnimation();
scrollTo(x, 0);
}
}
// Keep on drawing until the animation has finished.
ViewCompat.postInvalidateOnAnimation(this);
return;
}
// Done with scroll, clean up state.
completeScroll(true);
}
private boolean pageScrolled(int ypos) {
if (mItems.size() == 0) {
mCalledSuper = false;
onPageScrolled(0, 0, 0);
if (!mCalledSuper) {
throw new IllegalStateException("onPageScrolled did not call superclass implementation");
}
return false;
}
final ItemInfo ii = infoForCurrentScrollPosition();
final int height = getClientHeight();
final int heightWithMargin = height + mPageMargin;
final float marginOffset = (float) mPageMargin / height;
final int currentPage = ii.position;
final float pageOffset = (((float) ypos / height) - ii.offset) / (ii.heightFactor + marginOffset);
final int offsetPixels = (int) (pageOffset * heightWithMargin);
mCalledSuper = false;
onPageScrolled(currentPage, pageOffset, offsetPixels);
if (!mCalledSuper) {
throw new IllegalStateException("onPageScrolled did not call superclass implementation");
}
return true;
}
/**
* This method will be invoked when the current page is scrolled, either as
* part of a programmatically initiated smooth scroll or a user initiated
* touch scroll. If you override this method you must call through to the
* superclass implementation (e.g. super.onPageScrolled(position, offset,
* offsetPixels)) before onPageScrolled returns.
*
* @param position
* Position index of the first page currently being displayed.
* Page position+1 will be visible if positionOffset is nonzero.
* @param offset
* Value from [0, 1) indicating the offset from the page at
* position.
* @param offsetPixels
* Value in pixels indicating the offset from position.
*/
protected void onPageScrolled(int position, float offset, int offsetPixels) {
// Offset any decor views if needed - keep them on-screen at all times.
if (mDecorChildCount > 0) {
final int scrollY = getScrollY();
int paddingTop = getPaddingTop();
int paddingBottom = getPaddingBottom();
final int height = getHeight();
final int childCount = getChildCount();
for (int i = 0; i < childCount; i++) {
final View child = getChildAt(i);
final LayoutParams lp = (LayoutParams) child.getLayoutParams();
if (!lp.isDecor)
continue;
final int vgrav = lp.gravity & Gravity.VERTICAL_GRAVITY_MASK;
int childTop = 0;
switch (vgrav) {
default:
childTop = paddingTop;
break;
case Gravity.TOP:
childTop = paddingTop;
paddingTop += child.getHeight();
break;
case Gravity.CENTER_VERTICAL:
childTop = Math.max((height - child.getMeasuredHeight()) / 2, paddingTop);
break;
case Gravity.BOTTOM:
childTop = height - paddingBottom - child.getMeasuredHeight();
paddingBottom += child.getMeasuredHeight();
break;
}
childTop += scrollY;
final int childOffset = childTop - child.getTop();
if (childOffset != 0) {
child.offsetTopAndBottom(childOffset);
}
}
}
if (mOnPageChangeListener != null) {
mOnPageChangeListener.onPageScrolled(position, offset, offsetPixels);
}
if (mInternalPageChangeListener != null) {
mInternalPageChangeListener.onPageScrolled(position, offset, offsetPixels);
}
if (mPageTransformer != null) {
final int scrollY = getScrollY();
final int childCount = getChildCount();
for (int i = 0; i < childCount; i++) {
final View child = getChildAt(i);
final LayoutParams lp = (LayoutParams) child.getLayoutParams();
if (lp.isDecor)
continue;
final float transformPos = (float) (child.getTop() - scrollY) / getClientHeight();
mPageTransformer.transformPage(child, transformPos);
}
}
mCalledSuper = true;
}
private void completeScroll(boolean postEvents) {
boolean needPopulate = mScrollState == SCROLL_STATE_SETTLING;
if (needPopulate) {
// Done with scroll, no longer want to cache view drawing.
setScrollingCacheEnabled(false);
mScroller.abortAnimation();
int oldX = getScrollX();
int oldY = getScrollY();
int x = mScroller.getCurrX();
int y = mScroller.getCurrY();
if (oldX != x || oldY != y) {
scrollTo(x, y);
}
}
mPopulatePending = false;
for (int i = 0; i < mItems.size(); i++) {
ItemInfo ii = mItems.get(i);
if (ii.scrolling) {
needPopulate = true;
ii.scrolling = false;
}
}
if (needPopulate) {
if (postEvents) {
ViewCompat.postOnAnimation(this, mEndScrollRunnable);
} else {
mEndScrollRunnable.run();
}
}
}
private boolean isGutterDrag(float y, float dy) {
return (y < mGutterSize && dy > 0) || (y > getHeight() - mGutterSize && dy < 0);
}
private void enableLayers(boolean enable) {
final int childCount = getChildCount();
for (int i = 0; i < childCount; i++) {
final int layerType = enable ? ViewCompat.LAYER_TYPE_HARDWARE : ViewCompat.LAYER_TYPE_NONE;
ViewCompat.setLayerType(getChildAt(i), layerType, null);
}
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
/*
* This method JUST determines whether we want to intercept the motion.
* If we return true, onMotionEvent will be called and we do the actual
* scrolling there.
*/
final int action = ev.getAction() & MotionEventCompat.ACTION_MASK;
// Always take care of the touch gesture being complete.
if (action == MotionEvent.ACTION_CANCEL || action == MotionEvent.ACTION_UP) {
// Release the drag.
if (DEBUG)
Log.v(TAG, "Intercept done!");
mIsBeingDragged = false;
mIsUnableToDrag = false;
mActivePointerId = INVALID_POINTER;
if (mVelocityTracker != null) {
mVelocityTracker.recycle();
mVelocityTracker = null;
}
return false;
}
// Nothing more to do here if we have decided whether or not we
// are dragging.
if (action != MotionEvent.ACTION_DOWN) {
if (mIsBeingDragged) {
if (DEBUG)
Log.v(TAG, "Intercept returning true!");
return true;
}
if (mIsUnableToDrag) {
if (DEBUG)
Log.v(TAG, "Intercept returning false!");
return false;
}
}
switch (action) {
case MotionEvent.ACTION_MOVE: {
/*
* mIsBeingDragged == false, otherwise the shortcut would have
* caught it. Check whether the user has moved far enough from his
* original down touch.
*/
/*
* Locally do absolute value. mLastMotionY is set to the y value of
* the down event.
*/
final int activePointerId = mActivePointerId;
if (activePointerId == INVALID_POINTER) {
// If we don‘t have a valid id, the touch down wasn‘t on
// content.
break;
}
final int pointerIndex = MotionEventCompat.findPointerIndex(ev, activePointerId);
final float y = MotionEventCompat.getY(ev, pointerIndex);
final float dy = y - mLastMotionY;
final float yDiff = Math.abs(dy);
final float x = MotionEventCompat.getX(ev, pointerIndex);
final float xDiff = Math.abs(x - mInitialMotionX);
if (DEBUG)
Log.v(TAG, "Moved x to " + x + "," + y + " diff=" + xDiff + "," + yDiff);
if (dy != 0 && !isGutterDrag(mLastMotionY, dy) && canScroll(this, false, (int) dy, (int) x, (int) y)) {
// Nested view has scrollable area under this point. Let it be
// handled there.
mLastMotionX = x;
mLastMotionY = y;
mIsUnableToDrag = true;
return false;
}
if (yDiff > mTouchSlop && yDiff * 0.5f > xDiff) {
if (DEBUG)
Log.v(TAG, "Starting drag!");
mIsBeingDragged = true;
requestParentDisallowInterceptTouchEvent(true);
setScrollState(SCROLL_STATE_DRAGGING);
mLastMotionY = dy > 0 ? mInitialMotionY + mTouchSlop : mInitialMotionY - mTouchSlop;
mLastMotionX = x;
setScrollingCacheEnabled(true);
} else if (xDiff > mTouchSlop) {
// The finger has moved enough in the vertical
// direction to be counted as a drag... abort
// any attempt to drag horizontally, to work correctly
// with children that have scrolling containers.
if (DEBUG)
Log.v(TAG, "Starting unable to drag!");
mIsUnableToDrag = true;
}
if (mIsBeingDragged) {
// Scroll to follow the motion event
if (performDrag(y)) {
ViewCompat.postInvalidateOnAnimation(this);
}
}
break;
}
case MotionEvent.ACTION_DOWN: {
/*
* Remember location of down touch. ACTION_DOWN always refers to
* pointer index 0.
*/
mLastMotionX = mInitialMotionX = ev.getX();
mLastMotionY = mInitialMotionY = ev.getY();
mActivePointerId = MotionEventCompat.getPointerId(ev, 0);
mIsUnableToDrag = false;
mScroller.computeScrollOffset();
if (mScrollState == SCROLL_STATE_SETTLING && Math.abs(mScroller.getFinalY() - mScroller.getCurrY()) > mCloseEnough) {
// Let the user ‘catch‘ the pager as it animates.
mScroller.abortAnimation();
mPopulatePending = false;
populate();
mIsBeingDragged = true;
requestParentDisallowInterceptTouchEvent(true);
setScrollState(SCROLL_STATE_DRAGGING);
} else {
completeScroll(false);
mIsBeingDragged = false;
}
if (DEBUG)
Log.v(TAG, "Down at " + mLastMotionX + "," + mLastMotionY + " mIsBeingDragged=" + mIsBeingDragged + "mIsUnableToDrag=" + mIsUnableToDrag);
break;
}
case MotionEventCompat.ACTION_POINTER_UP:
onSecondaryPointerUp(ev);
break;
}
if (mVelocityTracker == null) {
mVelocityTracker = VelocityTracker.obtain();
}
mVelocityTracker.addMovement(ev);
/*
* The only time we want to intercept motion events is if we are in the
* drag mode.
*/
return mIsBeingDragged;
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
if (mFakeDragging) {
// A fake drag is in progress already, ignore this real one
// but still eat the touch events.
// (It is likely that the user is multi-touching the screen.)
return true;
}
if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) {
// Don‘t handle edge touches immediately -- they may actually belong
// to one of our
// descendants.
return false;
}
if (mAdapter == null || mAdapter.getCount() == 0) {
// Nothing to present or scroll; nothing to touch.
return false;
}
if (mVelocityTracker == null) {
mVelocityTracker = VelocityTracker.obtain();
}
mVelocityTracker.addMovement(ev);
final int action = ev.getAction();
boolean needsInvalidate = false;
switch (action & MotionEventCompat.ACTION_MASK) {
case MotionEvent.ACTION_DOWN: {
mScroller.abortAnimation();
mPopulatePending = false;
populate();
// Remember where the motion event started
mLastMotionX = mInitialMotionX = ev.getX();
mLastMotionY = mInitialMotionY = ev.getY();
mActivePointerId = MotionEventCompat.getPointerId(ev, 0);
break;
}
case MotionEvent.ACTION_MOVE:
if (!mIsBeingDragged) {
final int pointerIndex = MotionEventCompat.findPointerIndex(ev, mActivePointerId);
final float y = MotionEventCompat.getY(ev, pointerIndex);
final float yDiff = Math.abs(y - mLastMotionY);
final float x = MotionEventCompat.getX(ev, pointerIndex);
final float xDiff = Math.abs(x - mLastMotionX);
if (DEBUG)
Log.v(TAG, "Moved x to " + x + "," + y + " diff=" + xDiff + "," + yDiff);
if (yDiff > mTouchSlop && yDiff > xDiff) {
if (DEBUG)
Log.v(TAG, "Starting drag!");
mIsBeingDragged = true;
requestParentDisallowInterceptTouchEvent(true);
mLastMotionY = y - mInitialMotionY > 0 ? mInitialMotionY + mTouchSlop : mInitialMotionY - mTouchSlop;
mLastMotionX = x;
setScrollState(SCROLL_STATE_DRAGGING);
setScrollingCacheEnabled(true);
// Disallow Parent Intercept, just in case
ViewParent parent = getParent();
if (parent != null) {
parent.requestDisallowInterceptTouchEvent(true);
}
}
}
// Not else! Note that mIsBeingDragged can be set above.
if (mIsBeingDragged) {
// Scroll to follow the motion event
final int activePointerIndex = MotionEventCompat.findPointerIndex(ev, mActivePointerId);
final float y = MotionEventCompat.getY(ev, activePointerIndex);
needsInvalidate |= performDrag(y);
}
break;
case MotionEvent.ACTION_UP:
if (mIsBeingDragged) {
final VelocityTracker velocityTracker = mVelocityTracker;
velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
int initialVelocity = (int) VelocityTrackerCompat.getYVelocity(velocityTracker, mActivePointerId);
mPopulatePending = true;
final int height = getClientHeight();
final int scrollY = getScrollY();
final ItemInfo ii = infoForCurrentScrollPosition();
final int currentPage = ii.position;
final float pageOffset = (((float) scrollY / height) - ii.offset) / ii.heightFactor;
final int activePointerIndex = MotionEventCompat.findPointerIndex(ev, mActivePointerId);
final float y = MotionEventCompat.getY(ev, activePointerIndex);
final int totalDelta = (int) (y - mInitialMotionY);
int nextPage = determineTargetPage(currentPage, pageOffset, initialVelocity, totalDelta);
setCurrentItemInternal(nextPage, true, true, initialVelocity);
mActivePointerId = INVALID_POINTER;
endDrag();
needsInvalidate = mTopEdge.onRelease() | mBottomEdge.onRelease();
}
break;
case MotionEvent.ACTION_CANCEL:
if (mIsBeingDragged) {
scrollToItem(mCurItem, true, 0, false);
mActivePointerId = INVALID_POINTER;
endDrag();
needsInvalidate = mTopEdge.onRelease() | mBottomEdge.onRelease();
}
break;
case MotionEventCompat.ACTION_POINTER_DOWN: {
final int index = MotionEventCompat.getActionIndex(ev);
final float y = MotionEventCompat.getY(ev, index);
mLastMotionY = y;
mActivePointerId = MotionEventCompat.getPointerId(ev, index);
break;
}
case MotionEventCompat.ACTION_POINTER_UP:
onSecondaryPointerUp(ev);
mLastMotionY = MotionEventCompat.getY(ev, MotionEventCompat.findPointerIndex(ev, mActivePointerId));
break;
}
if (needsInvalidate) {
ViewCompat.postInvalidateOnAnimation(this);
}
return true;
}
private void requestParentDisallowInterceptTouchEvent(boolean disallowIntercept) {
final ViewParent parent = getParent();
if (parent != null) {
parent.requestDisallowInterceptTouchEvent(disallowIntercept);
}
}
private boolean performDrag(float y) {
boolean needsInvalidate = false;
final float deltaY = mLastMotionY - y;
mLastMotionY = y;
float oldScrollY = getScrollY();
float scrollY = oldScrollY + deltaY;
final int height = getClientHeight();
float topBound = height * mFirstOffset;
float bottomBound = height * mLastOffset;
boolean topAbsolute = true;
boolean bottomAbsolute = true;
final ItemInfo firstItem = mItems.get(0);
final ItemInfo lastItem = mItems.get(mItems.size() - 1);
if (firstItem.position != 0) {
topAbsolute = false;
topBound = firstItem.offset * height;
}
if (lastItem.position != mAdapter.getCount() - 1) {
bottomAbsolute = false;
bottomBound = lastItem.offset * height;
}
if (scrollY < topBound) {
if (topAbsolute) {
float over = topBound - scrollY;
needsInvalidate = mTopEdge.onPull(Math.abs(over) / height);
}
scrollY = topBound;
} else if (scrollY > bottomBound) {
if (bottomAbsolute) {
float over = scrollY - bottomBound;
needsInvalidate = mBottomEdge.onPull(Math.abs(over) / height);
}
scrollY = bottomBound;
}
// Don‘t lose the rounded component
mLastMotionX += scrollY - (int) scrollY;
scrollTo(getScrollX(), (int) scrollY);
pageScrolled((int) scrollY);
return needsInvalidate;
}
/**
* @return Info about the page at the current scroll position. This can be
* synthetic for a missing middle page; the ‘object‘ field can be
* null.
*/
private ItemInfo infoForCurrentScrollPosition() {
final int height = getClientHeight();
final float scrollOffset = height > 0 ? (float) getScrollY() / height : 0;
final float marginOffset = height > 0 ? (float) mPageMargin / height : 0;
int lastPos = -1;
float lastOffset = 0.f;
float lastHeight = 0.f;
boolean first = true;
ItemInfo lastItem = null;
for (int i = 0; i < mItems.size(); i++) {
ItemInfo ii = mItems.get(i);
float offset;
if (!first && ii.position != lastPos + 1) {
// Create a synthetic item for a missing page.
ii = mTempItem;
ii.offset = lastOffset + lastHeight + marginOffset;
ii.position = lastPos + 1;
ii.heightFactor = mAdapter.getPageWidth(ii.position);
i--;
}
offset = ii.offset;
final float topBound = offset;
final float bottomBound = offset + ii.heightFactor + marginOffset;
if (first || scrollOffset >= topBound) {
if (scrollOffset < bottomBound || i == mItems.size() - 1) {
return ii;
}
} else {
return lastItem;
}
first = false;
lastPos = ii.position;
lastOffset = offset;
lastHeight = ii.heightFactor;
lastItem = ii;
}
return lastItem;
}
private int determineTargetPage(int currentPage, float pageOffset, int velocity, int deltaY) {
int targetPage;
if (Math.abs(deltaY) > mFlingDistance && Math.abs(velocity) > mMinimumVelocity) {
targetPage = velocity > 0 ? currentPage : currentPage + 1;
} else {
final float truncator = currentPage >= mCurItem ? 0.4f : 0.6f;
targetPage = (int) (currentPage + pageOffset + truncator);
}
if (mItems.size() > 0) {
final ItemInfo firstItem = mItems.get(0);
final ItemInfo lastItem = mItems.get(mItems.size() - 1);
// Only let the user target pages we have items for
targetPage = Math.max(firstItem.position, Math.min(targetPage, lastItem.position));
}
return targetPage;
}
@Override
public void draw(Canvas canvas) {
super.draw(canvas);
boolean needsInvalidate = false;
final int overScrollMode = ViewCompat.getOverScrollMode(this);
if (overScrollMode == ViewCompat.OVER_SCROLL_ALWAYS || (overScrollMode == ViewCompat.OVER_SCROLL_IF_CONTENT_SCROLLS && mAdapter != null && mAdapter.getCount() > 1)) {
if (!mTopEdge.isFinished()) {
final int restoreCount = canvas.save();
final int height = getHeight();
final int width = getWidth() - getPaddingLeft() - getPaddingRight();
canvas.translate(getPaddingLeft(), mFirstOffset * height);
mTopEdge.setSize(width, height);
needsInvalidate |= mTopEdge.draw(canvas);
canvas.restoreToCount(restoreCount);
}
if (!mBottomEdge.isFinished()) {
final int restoreCount = canvas.save();
final int height = getHeight();
final int width = getWidth() - getPaddingLeft() - getPaddingRight();
canvas.rotate(180);
canvas.translate(-width - getPaddingLeft(), -(mLastOffset + 1) * height);
mBottomEdge.setSize(width, height);
needsInvalidate |= mBottomEdge.draw(canvas);
canvas.restoreToCount(restoreCount);
}
} else {
mTopEdge.finish();
mBottomEdge.finish();
}
if (needsInvalidate) {
// Keep animating
ViewCompat.postInvalidateOnAnimation(this);
}
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
// Draw the margin drawable between pages if needed.
if (mPageMargin > 0 && mMarginDrawable != null && mItems.size() > 0 && mAdapter != null) {
final int scrollY = getScrollY();
final int height = getHeight();
final float marginOffset = (float) mPageMargin / height;
int itemIndex = 0;
ItemInfo ii = mItems.get(0);
float offset = ii.offset;
final int itemCount = mItems.size();
final int firstPos = ii.position;
final int lastPos = mItems.get(itemCount - 1).position;
for (int pos = firstPos; pos < lastPos; pos++) {
while (pos > ii.position && itemIndex < itemCount) {
ii = mItems.get(++itemIndex);
}
float drawAt;
if (pos == ii.position) {
drawAt = (ii.offset + ii.heightFactor) * height;
offset = ii.offset + ii.heightFactor + marginOffset;
} else {
float heightFactor = mAdapter.getPageWidth(pos);
drawAt = (offset + heightFactor) * height;
offset += heightFactor + marginOffset;
}
if (drawAt + mPageMargin > scrollY) {
mMarginDrawable.setBounds(mLeftPageBounds, (int) drawAt, mRightPageBounds, (int) (drawAt + mPageMargin + 0.5f));
mMarginDrawable.draw(canvas);
}
if (drawAt > scrollY + height) {
break; // No more visible, no sense in continuing
}
}
}
}
/**
* Start a fake drag of the pager.
* <p/>
* <p>
* A fake drag can be useful if you want to synchronize the motion of the
* ViewPager with the touch scrolling of another view, while still letting
* the ViewPager control the snapping motion and fling behavior. (e.g.
* parallax-scrolling tabs.) Call {@link #fakeDragBy(float)} to simulate the
* actual drag motion. Call {@link #endFakeDrag()} to complete the fake drag
* and fling as necessary.
* <p/>
* <p>
* During a fake drag the ViewPager will ignore all touch events. If a real
* drag is already in progress, this method will return false.
*
* @return true if the fake drag began successfully, false if it could not
* be started.
* @see #fakeDragBy(float)
* @see #endFakeDrag()
*/
public boolean beginFakeDrag() {
if (mIsBeingDragged) {
return false;
}
mFakeDragging = true;
setScrollState(SCROLL_STATE_DRAGGING);
mInitialMotionY = mLastMotionY = 0;
if (mVelocityTracker == null) {
mVelocityTracker = VelocityTracker.obtain();
} else {
mVelocityTracker.clear();
}
final long time = SystemClock.uptimeMillis();
final MotionEvent ev = MotionEvent.obtain(time, time, MotionEvent.ACTION_DOWN, 0, 0, 0);
mVelocityTracker.addMovement(ev);
ev.recycle();
mFakeDragBeginTime = time;
return true;
}
/**
* End a fake drag of the pager.
*
* @see #beginFakeDrag()
* @see #fakeDragBy(float)
*/
public void endFakeDrag() {
if (!mFakeDragging) {
throw new IllegalStateException("No fake drag in progress. Call beginFakeDrag first.");
}
final VelocityTracker velocityTracker = mVelocityTracker;
velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
int initialVelocity = (int) VelocityTrackerCompat.getYVelocity(velocityTracker, mActivePointerId);
mPopulatePending = true;
final int height = getClientHeight();
final int scrollY = getScrollY();
final ItemInfo ii = infoForCurrentScrollPosition();
final int currentPage = ii.position;
final float pageOffset = (((float) scrollY / height) - ii.offset) / ii.heightFactor;
final int totalDelta = (int) (mLastMotionY - mInitialMotionY);
int nextPage = determineTargetPage(currentPage, pageOffset, initialVelocity, totalDelta);
setCurrentItemInternal(nextPage, true, true, initialVelocity);
endDrag();
mFakeDragging = false;
}
/**
* Fake drag by an offset in pixels. You must have called
* {@link #beginFakeDrag()} first.
*
* @param yOffset
* Offset in pixels to drag by.
* @see #beginFakeDrag()
* @see #endFakeDrag()
*/
public void fakeDragBy(float yOffset) {
if (!mFakeDragging) {
throw new IllegalStateException("No fake drag in progress. Call beginFakeDrag first.");
}
mLastMotionY += yOffset;
float oldScrollY = getScrollY();
float scrollY = oldScrollY - yOffset;
final int height = getClientHeight();
float topBound = height * mFirstOffset;
float bottomBound = height * mLastOffset;
final ItemInfo firstItem = mItems.get(0);
final ItemInfo lastItem = mItems.get(mItems.size() - 1);
if (firstItem.position != 0) {
topBound = firstItem.offset * height;
}
if (lastItem.position != mAdapter.getCount() - 1) {
bottomBound = lastItem.offset * height;
}
if (scrollY < topBound) {
scrollY = topBound;
} else if (scrollY > bottomBound) {
scrollY = bottomBound;
}
// Don‘t lose the rounded component
mLastMotionY += scrollY - (int) scrollY;
scrollTo(getScrollX(), (int) scrollY);
pageScrolled((int) scrollY);
// Synthesize an event for the VelocityTracker.
final long time = SystemClock.uptimeMillis();
final MotionEvent ev = MotionEvent.obtain(mFakeDragBeginTime, time, MotionEvent.ACTION_MOVE, 0, mLastMotionY, 0);
mVelocityTracker.addMovement(ev);
ev.recycle();
}
/**
* Returns true if a fake drag is in progress.
*
* @return true if currently in a fake drag, false otherwise.
* @see #beginFakeDrag()
* @see #fakeDragBy(float)
* @see #endFakeDrag()
*/
public boolean isFakeDragging() {
return mFakeDragging;
}
private void onSecondaryPointerUp(MotionEvent ev) {
final int pointerIndex = MotionEventCompat.getActionIndex(ev);
final int pointerId = MotionEventCompat.getPointerId(ev, pointerIndex);
if (pointerId == mActivePointerId) {
// This was our active pointer going up. Choose a new
// active pointer and adjust accordingly.
final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
mLastMotionY = MotionEventCompat.getY(ev, newPointerIndex);
mActivePointerId = MotionEventCompat.getPointerId(ev, newPointerIndex);
if (mVelocityTracker != null) {
mVelocityTracker.clear();
}
}
}
private void endDrag() {
mIsBeingDragged = false;
mIsUnableToDrag = false;
if (mVelocityTracker != null) {
mVelocityTracker.recycle();
mVelocityTracker = null;
}
}
private void setScrollingCacheEnabled(boolean enabled) {
if (mScrollingCacheEnabled != enabled) {
mScrollingCacheEnabled = enabled;
if (USE_CACHE) {
final int size = getChildCount();
for (int i = 0; i < size; ++i) {
final View child = getChildAt(i);
if (child.getVisibility() != GONE) {
child.setDrawingCacheEnabled(enabled);
}
}
}
}
}
public boolean internalCanScrollVertically(int direction) {
if (mAdapter == null) {
return false;
}
final int height = getClientHeight();
final int scrollY = getScrollY();
if (direction < 0) {
return (scrollY > (int) (height * mFirstOffset));
} else if (direction > 0) {
return (scrollY < (int) (height * mLastOffset));
} else {
return false;
}
}
/**
* Tests scrollability within child views of v given a delta of dx.
*
* @param v
* View to test for horizontal scrollability
* @param checkV
* Whether the view v passed should itself be checked for
* scrollability (true), or just its children (false).
* @param dy
* Delta scrolled in pixels
* @param x
* X coordinate of the active touch point
* @param y
* Y coordinate of the active touch point
* @return true if child views of v can be scrolled by delta of dx.
*/
protected boolean canScroll(View v, boolean checkV, int dy, int x, int y) {
if (v instanceof ViewGroup) {
final ViewGroup group = (ViewGroup) v;
final int scrollX = v.getScrollX();
final int scrollY = v.getScrollY();
final int count = group.getChildCount();
// Count backwards - let topmost views consume scroll distance
// first.
for (int i = count - 1; i >= 0; i--) {
// TODO: Add versioned support here for transformed views.
// This will not work for transformed views in Honeycomb+
final View child = group.getChildAt(i);
if (y + scrollY >= child.getTop() && y + scrollY < child.getBottom() && x + scrollX >= child.getLeft() && x + scrollX < child.getRight() && canScroll(child, true, dy, x + scrollX - child.getLeft(), y + scrollY - child.getTop())) {
return true;
}
}
}
return checkV && ViewCompat.canScrollVertically(v, -dy);
}
@Override
public boolean dispatchKeyEvent(KeyEvent event) {
// Let the focused view and/or our descendants get the key first
return super.dispatchKeyEvent(event) || executeKeyEvent(event);
}
/**
* You can call this function yourself to have the scroll view perform
* scrolling from a key event, just as if the event had been dispatched to
* it by the view hierarchy.
*
* @param event
* The key event to execute.
* @return Return true if the event was handled, else false.
*/
public boolean executeKeyEvent(KeyEvent event) {
boolean handled = false;
if (event.getAction() == KeyEvent.ACTION_DOWN) {
switch (event.getKeyCode()) {
case KeyEvent.KEYCODE_DPAD_LEFT:
handled = arrowScroll(FOCUS_LEFT);
break;
case KeyEvent.KEYCODE_DPAD_RIGHT:
handled = arrowScroll(FOCUS_RIGHT);
break;
case KeyEvent.KEYCODE_TAB:
if (Build.VERSION.SDK_INT >= 11) {
// The focus finder had a bug handling FOCUS_FORWARD and
// FOCUS_BACKWARD
// before Android 3.0. Ignore the tab key on those devices.
if (KeyEventCompat.hasNoModifiers(event)) {
handled = arrowScroll(FOCUS_FORWARD);
} else if (KeyEventCompat.hasModifiers(event, KeyEvent.META_SHIFT_ON)) {
handled = arrowScroll(FOCUS_BACKWARD);
}
}
break;
}
}
return handled;
}
public boolean arrowScroll(int direction) {
View currentFocused = findFocus();
if (currentFocused == this) {
currentFocused = null;
} else if (currentFocused != null) {
boolean isChild = false;
for (ViewParent parent = currentFocused.getParent(); parent instanceof ViewGroup; parent = parent.getParent()) {
if (parent == this) {
isChild = true;
break;
}
}
if (!isChild) {
// This would cause the focus search down below to fail in fun
// ways.
final StringBuilder sb = new StringBuilder();
sb.append(currentFocused.getClass().getSimpleName());
for (ViewParent parent = currentFocused.getParent(); parent instanceof ViewGroup; parent = parent.getParent()) {
sb.append(" => ").append(parent.getClass().getSimpleName());
}
Log.e(TAG, "arrowScroll tried to find focus based on non-child " + "current focused view " + sb.toString());
currentFocused = null;
}
}
boolean handled = false;
View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction);
if (nextFocused != null && nextFocused != currentFocused) {
if (direction == View.FOCUS_UP) {
// If there is nothing to the left, or this is causing us to
// jump to the right, then what we really want to do is page
// left.
final int nextTop = getChildRectInPagerCoordinates(mTempRect, nextFocused).top;
final int currTop = getChildRectInPagerCoordinates(mTempRect, currentFocused).top;
if (currentFocused != null && nextTop >= currTop) {
handled = pageUp();
} else {
handled = nextFocused.requestFocus();
}
} else if (direction == View.FOCUS_DOWN) {
// If there is nothing to the right, or this is causing us to
// jump to the left, then what we really want to do is page
// right.
final int nextDown = getChildRectInPagerCoordinates(mTempRect, nextFocused).bottom;
final int currDown = getChildRectInPagerCoordinates(mTempRect, currentFocused).bottom;
if (currentFocused != null && nextDown <= currDown) {
handled = pageDown();
} else {
handled = nextFocused.requestFocus();
}
}
} else if (direction == FOCUS_UP || direction == FOCUS_BACKWARD) {
// Trying to move left and nothing there; try to page.
handled = pageUp();
} else if (direction == FOCUS_DOWN || direction == FOCUS_FORWARD) {
// Trying to move right and nothing there; try to page.
handled = pageDown();
}
if (handled) {
playSoundEffect(SoundEffectConstants.getContantForFocusDirection(direction));
}
return handled;
}
private Rect getChildRectInPagerCoordinates(Rect outRect, View child) {
if (outRect == null) {
outRect = new Rect();
}
if (child == null) {
outRect.set(0, 0, 0, 0);
return outRect;
}
outRect.left = child.getLeft();
outRect.right = child.getRight();
outRect.top = child.getTop();
outRect.bottom = child.getBottom();
ViewParent parent = child.getParent();
while (parent instanceof ViewGroup && parent != this) {
final ViewGroup group = (ViewGroup) parent;
outRect.left += group.getLeft();
outRect.right += group.getRight();
outRect.top += group.getTop();
outRect.bottom += group.getBottom();
parent = group.getParent();
}
return outRect;
}
boolean pageUp() {
if (mCurItem > 0) {
setCurrentItem(mCurItem - 1, true);
return true;
}
return false;
}
boolean pageDown() {
if (mAdapter != null && mCurItem < (mAdapter.getCount() - 1)) {
setCurrentItem(mCurItem + 1, true);
return true;
}
return false;
}
/**
* We only want the current page that is being shown to be focusable.
*/
@Override
public void addFocusables(ArrayList<View> views, int direction, int focusableMode) {
final int focusableCount = views.size();
final int descendantFocusability = getDescendantFocusability();
if (descendantFocusability != FOCUS_BLOCK_DESCENDANTS) {
for (int i = 0; i < getChildCount(); i++) {
final View child = getChildAt(i);
if (child.getVisibility() == VISIBLE) {
ItemInfo ii = infoForChild(child);
if (ii != null && ii.position == mCurItem) {
child.addFocusables(views, direction, focusableMode);
}
}
}
}
// we add ourselves (if focusable) in all cases except for when we are
// FOCUS_AFTER_DESCENDANTS and there are some descendants focusable.
// this is
// to avoid the focus search finding layouts when a more precise search
// among the focusable children would be more interesting.
if (descendantFocusability != FOCUS_AFTER_DESCENDANTS ||
// No focusable descendants
(focusableCount == views.size())) {
// Note that we can‘t call the superclass here, because it will
// add all views in. So we need to do the same thing View does.
if (!isFocusable()) {
return;
}
if ((focusableMode & FOCUSABLES_TOUCH_MODE) == FOCUSABLES_TOUCH_MODE && isInTouchMode() && !isFocusableInTouchMode()) {
return;
}
if (views != null) {
views.add(this);
}
}
}
/**
* We only want the current page that is being shown to be touchable.
*/
@Override
public void addTouchables(ArrayList<View> views) {
// Note that we don‘t call super.addTouchables(), which means that
// we don‘t call View.addTouchables(). This is okay because a ViewPager
// is itself not touchable.
for (int i = 0; i < getChildCount(); i++) {
final View child = getChildAt(i);
if (child.getVisibility() == VISIBLE) {
ItemInfo ii = infoForChild(child);
if (ii != null && ii.position == mCurItem) {
child.addTouchables(views);
}
}
}
}
/**
* We only want the current page that is being shown to be focusable.
*/
@Override
protected boolean onRequestFocusInDescendants(int direction, Rect previouslyFocusedRect) {
int index;
int increment;
int end;
int count = getChildCount();
if ((direction & FOCUS_FORWARD) != 0) {
index = 0;
increment = 1;
end = count;
} else {
index = count - 1;
increment = -1;
end = -1;
}
for (int i = index; i != end; i += increment) {
View child = getChildAt(i);
if (child.getVisibility() == VISIBLE) {
ItemInfo ii = infoForChild(child);
if (ii != null && ii.position == mCurItem) {
if (child.requestFocus(direction, previouslyFocusedRect)) {
return true;
}
}
}
}
return false;
}
@Override
public boolean dispatchPopulateAccessibilityEvent(AccessibilityEvent event) {
// Dispatch scroll events from this ViewPager.
if (event.getEventType() == AccessibilityEventCompat.TYPE_VIEW_SCROLLED) {
return super.dispatchPopulateAccessibilityEvent(event);
}
// Dispatch all other accessibility events from the current page.
final int childCount = getChildCount();
for (int i = 0; i < childCount; i++) {
final View child = getChildAt(i);
if (child.getVisibility() == VISIBLE) {
final ItemInfo ii = infoForChild(child);
if (ii != null && ii.position == mCurItem && child.dispatchPopulateAccessibilityEvent(event)) {
return true;
}
}
}
return false;
}
@Override
protected ViewGroup.LayoutParams generateDefaultLayoutParams() {
return new LayoutParams();
}
@Override
protected ViewGroup.LayoutParams generateLayoutParams(ViewGroup.LayoutParams p) {
return generateDefaultLayoutParams();
}
@Override
protected boolean checkLayoutParams(ViewGroup.LayoutParams p) {
return p instanceof LayoutParams && super.checkLayoutParams(p);
}
@Override
public ViewGroup.LayoutParams generateLayoutParams(AttributeSet attrs) {
return new LayoutParams(getContext(), attrs);
}
class MyAccessibilityDelegate extends AccessibilityDelegateCompat {
@Override
public void onInitializeAccessibilityEvent(View host, AccessibilityEvent event) {
super.onInitializeAccessibilityEvent(host, event);
event.setClassName(ViewPager.class.getName());
final AccessibilityRecordCompat recordCompat = AccessibilityRecordCompat.obtain();
recordCompat.setScrollable(canScroll());
if (event.getEventType() == AccessibilityEventCompat.TYPE_VIEW_SCROLLED && mAdapter != null) {
recordCompat.setItemCount(mAdapter.getCount());
recordCompat.setFromIndex(mCurItem);
recordCompat.setToIndex(mCurItem);
}
}
@Override
public void onInitializeAccessibilityNodeInfo(View host, AccessibilityNodeInfoCompat info) {
super.onInitializeAccessibilityNodeInfo(host, info);
info.setClassName(ViewPager.class.getName());
info.setScrollable(canScroll());
if (internalCanScrollVertically(1)) {
info.addAction(AccessibilityNodeInfoCompat.ACTION_SCROLL_FORWARD);
}
if (internalCanScrollVertically(-1)) {
info.addAction(AccessibilityNodeInfoCompat.ACTION_SCROLL_BACKWARD);
}
}
@Override
public boolean performAccessibilityAction(View host, int action, Bundle args) {
if (super.performAccessibilityAction(host, action, args)) {
return true;
}
switch (action) {
case AccessibilityNodeInfoCompat.ACTION_SCROLL_FORWARD: {
if (internalCanScrollVertically(1)) {
setCurrentItem(mCurItem + 1);
return true;
}
}
return false;
case AccessibilityNodeInfoCompat.ACTION_SCROLL_BACKWARD: {
if (internalCanScrollVertically(-1)) {
setCurrentItem(mCurItem - 1);
return true;
}
}
return false;
}
return false;
}
private boolean canScroll() {
return (mAdapter != null) && (mAdapter.getCount() > 1);
}
}
private class PagerObserver extends DataSetObserver {
@Override
public void onChanged() {
dataSetChanged();
}
@Override
public void onInvalidated() {
dataSetChanged();
}
}
/**
* Layout parameters that should be supplied for views added to a ViewPager.
*/
public static class LayoutParams extends ViewGroup.LayoutParams {
/**
* true if this view is a decoration on the pager itself and not a view
* supplied by the adapter.
*/
public boolean isDecor;
/**
* Gravity setting for use on decor views only: Where to position the
* view page within the overall ViewPager container; constants are
* defined in {@link android.view.Gravity}.
*/
public int gravity;
/**
* Width as a 0-1 multiplier of the measured pager width
*/
float heightFactor = 0.f;
/**
* true if this view was added during layout and needs to be measured
* before being positioned.
*/
boolean needsMeasure;
/**
* Adapter position this view is for if !isDecor
*/
int position;
/**
* Current child index within the ViewPager that this view occupies
*/
int childIndex;
public LayoutParams() {
super(FILL_PARENT, FILL_PARENT);
}
public LayoutParams(Context context, AttributeSet attrs) {
super(context, attrs);
final TypedArray a = context.obtainStyledAttributes(attrs, LAYOUT_ATTRS);
gravity = a.getInteger(0, Gravity.TOP);
a.recycle();
}
}
static class ViewPositionComparator implements Comparator<View> {
@Override
public int compare(View lhs, View rhs) {
final LayoutParams llp = (LayoutParams) lhs.getLayoutParams();
final LayoutParams rlp = (LayoutParams) rhs.getLayoutParams();
if (llp.isDecor != rlp.isDecor) {
return llp.isDecor ? 1 : -1;
}
return llp.position - rlp.position;
}
}
}
然后在自己的Activity中的处理
package com.example.test;
import java.util.Locale;
import android.app.Activity;
import android.app.FragmentManager;
import android.graphics.drawable.ColorDrawable;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
public class MainActivity extends FragmentActivity {
private static final float MIN_SCALE = 0.75f;
private static final float MIN_ALPHA = 0.75f;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
VerticalViewPager verticalViewPager = (VerticalViewPager) findViewById(R.id.verticalviewpager);
verticalViewPager.setAdapter(new DummyAdapter(getSupportFragmentManager()));
verticalViewPager.setPageMargin(getResources().getDimensionPixelSize(R.dimen.pagemargin));
verticalViewPager.setPageMarginDrawable(new ColorDrawable(getResources().getColor(android.R.color.holo_green_dark)));
verticalViewPager.setPageTransformer(true, new ViewPager.PageTransformer() {
@Override
public void transformPage(View view, float position) {
int pageWidth = view.getWidth();
int pageHeight = view.getHeight();
if (position < -1) { // [-Infinity,-1)
// This page is way off-screen to the left.
view.setAlpha(0);
} else if (position <= 1) { // [-1,1]
// Modify the default slide transition to shrink the page as
// well
float scaleFactor = Math.max(MIN_SCALE, 1 - Math.abs(position));
float vertMargin = pageHeight * (1 - scaleFactor) / 2;
float horzMargin = pageWidth * (1 - scaleFactor) / 2;
if (position < 0) {
view.setTranslationY(vertMargin - horzMargin / 2);
} else {
view.setTranslationY(-vertMargin + horzMargin / 2);
}
// Scale the page down (between MIN_SCALE and 1)
view.setScaleX(scaleFactor);
view.setScaleY(scaleFactor);
// Fade the page relative to its size.
view.setAlpha(MIN_ALPHA + (scaleFactor - MIN_SCALE) / (1 - MIN_SCALE) * (1 - MIN_ALPHA));
} else { // (1,+Infinity]
// This page is way off-screen to the right.
view.setAlpha(0);
}
}
});
}
public class DummyAdapter extends FragmentPagerAdapter {
public DummyAdapter(android.support.v4.app.FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
// getItem is called to instantiate the fragment for the given page.
// Return a PlaceholderFragment (defined as a static inner class
// below).
return PlaceholderFragment.newInstance(position + 1);
}
@Override
public int getCount() {
// Show 3 total pages.
return 3;
}
@Override
public CharSequence getPageTitle(int position) {
// Locale l = Locale.getDefault();
switch (position) {
case 0:
return "PAGE 1";
case 1:
return "PAGE 2";
case 2:
return "PAGE 3";
}
return null;
}
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
/**
* The fragment argument representing the section number for this
* fragment.
*/
private static final String ARG_SECTION_NUMBER = "section_number";
/**
* Returns a new instance of this fragment for the given section number.
*/
public static PlaceholderFragment newInstance(int sectionNumber) {
PlaceholderFragment fragment = new PlaceholderFragment();
Bundle args = new Bundle();
args.putInt(ARG_SECTION_NUMBER, sectionNumber);
fragment.setArguments(args);
return fragment;
}
public PlaceholderFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_layout, container, false);
TextView textView = (TextView) rootView.findViewById(R.id.textview);
textView.setText(Integer.toString(getArguments().getInt(ARG_SECTION_NUMBER)));
return rootView;
}
}
}
其中有些动画的效果 ，github上也有人实现这样的效果，但是对v4包的依赖，不适用于在一些新的V4包；但是上面的方式经测试完美兼容；
相关的Demo如下：
http://files.cnblogs.com/kingfly13/Test.zip
时间： 2024-10-15 04:27:41