/**
* Created by gyzhong on 15/3/22.
*/
public class PullZoomListView extends ListView {
/*头部View 的容器*/
private FrameLayout mHeaderContainer;
/*头部View 的图片*/
private ImageView mHeaderImg;
/*屏幕的高度*/
private int mScreenHeight;
/*屏幕的宽度*/
private int mScreenWidth;
private int mHeaderHeight;
/*无效的点*/
private static final int INVALID_POINTER = -1;
/*滑动动画执行的时间*/
private static final int MIN_SETTLE_DURATION = 200; // ms
/*定义了一个时间插值器，根据ViewPage控件来定义的*/
private static final Interpolator sInterpolator = new Interpolator() {
public float getInterpolation(float t) {
t -= 1.0f;
return t * t * t * t * t + 1.0f;
}
};
/*记录上一次手指触摸的点*/
private float mLastMotionX;
private float mLastMotionY;
/*当前活动的点Id,有效的点的Id*/
protected int mActivePointerId = INVALID_POINTER;
/*开始滑动的标志距离*/
private int mTouchSlop;
/*放大的倍数*/
private float mScale;
/*上一次放大的倍数*/
private float mLastScale;
/*最大放大的倍数*/
private final float mMaxScale = 2.0f;
/*是否需要禁止ListView 的事件响应*/
private boolean isNeedCancelParent;
/*这个不解释*/
private OnScrollListener mScrollListener ;
/*下拉刷新的阈值*/
private final float REFRESH_SCALE = 1.20F;
/*下拉刷新监听*/
private OnRefreshListener mRefreshListener ;
public PullZoomListView(Context context) {
super(context);
init(context);
}
public PullZoomListView(Context context, AttributeSet attrs) {
super(context, attrs);
init(context);
}
public PullZoomListView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init(context);
}
private void init(Context context) {
/*这里获取的是一个无用值，可忽略*/
final ViewConfiguration configuration = ViewConfiguration.get(context);
mTouchSlop = ViewConfigurationCompat.getScaledPagingTouchSlop(configuration);
/*创建头部View 的容器*/
mHeaderContainer = new FrameLayout(context);
/*获取屏幕的像素值*/
DisplayMetrics metrics = new DisplayMetrics();
((Activity) context).getWindowManager().getDefaultDisplay().getMetrics(metrics);
mScreenHeight = metrics.heightPixels;
mScreenWidth = metrics.widthPixels;
/*设置头部View 的初始大小*/
mHeaderHeight = (int) ((9 * 1.0f / 16) * mScreenWidth);
LayoutParams absLayoutParams = new LayoutParams(mScreenWidth, mHeaderHeight);
mHeaderContainer.setLayoutParams(absLayoutParams);
/*创建图片显示的View*/
mHeaderImg = new ImageView(context);
FrameLayout.LayoutParams imgLayoutParams = new FrameLayout.LayoutParams
(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT);
mHeaderImg.setScaleType(ImageView.ScaleType.CENTER_CROP);
mHeaderImg.setLayoutParams(imgLayoutParams);
mHeaderContainer.addView(mHeaderImg);
/*增加头部View*/
addHeaderView(mHeaderContainer);
/*设置监听事件*/
super.setOnScrollListener(new InternalScrollerListener() );
}
/*处理事件用*/
@Override
public boolean onTouchEvent(MotionEvent ev) {
final int action = ev.getAction() & MotionEventCompat.ACTION_MASK;
switch (action) {
case MotionEvent.ACTION_DOWN:
/*计算 x，y 的距离*/
int index = MotionEventCompat.getActionIndex(ev);
mActivePointerId = MotionEventCompat.getPointerId(ev, index);
if (mActivePointerId == INVALID_POINTER)
break;
mLastMotionX = MotionEventCompat.getX(ev, index);
mLastMotionY = MotionEventCompat.getY(ev, index);
// 结束动画，目前没做处理，可忽略
abortAnimation();
/*计算算一次放缩的比例*/
mLastScale = (this.mHeaderContainer.getBottom() / this.mHeaderHeight);
/*当按下的时候把这个标志为设为有效*/
isNeedCancelParent = true ;
break;
case MotionEvent.ACTION_MOVE:
int indexMove = MotionEventCompat.getActionIndex(ev);
mActivePointerId = MotionEventCompat.getPointerId(ev, indexMove);
if (mActivePointerId == INVALID_POINTER) {
/*这里相当于松手*/
finishPull();
isNeedCancelParent = true ;
} else {
/*这是一个关键值，通过这个值来判断是否需要放大图片*/
if (mHeaderContainer.getBottom() >= mHeaderHeight) {
ViewGroup.LayoutParams params = this.mHeaderContainer.getLayoutParams();
final float y = MotionEventCompat.getY(ev, indexMove);
float dy = y - mLastMotionY;
float f = ((y - this.mLastMotionY + this.mHeaderContainer
.getBottom()) / this.mHeaderHeight - this.mLastScale)
/ 2.0F + this.mLastScale;
if ((this.mLastScale <= 1.0D) && (f <= this.mLastScale)) {
params.height = this.mHeaderHeight;
this.mHeaderContainer.setLayoutParams(params);
return super.onTouchEvent(ev);
}
/*这里设置紧凑度*/
dy = dy * 0.5f * (mHeaderHeight * 1.0f / params.height);
mLastScale = (dy + params.height) * 1.0f / mHeaderHeight;
mScale = clamp(mLastScale, 1.0f, mMaxScale);
// Log.v(“zgy”, “=======mScale=====” + mLastScale+”,f = “+f);
params.height = (int) (mHeaderHeight * mScale);
mHeaderContainer.setLayoutParams(params);
mLastMotionY = y;
/*这里，如果图片有放大，则屏蔽ListView 的其他事件响应*/
if(isNeedCancelParent ){
isNeedCancelParent = false;
MotionEvent motionEvent = MotionEvent.obtain(ev);
motionEvent.setAction(MotionEvent.ACTION_CANCEL);
super.onTouchEvent(motionEvent);
}
return true;
}
mLastMotionY = MotionEventCompat.getY(ev, indexMove);
}
break;
case MotionEvent.ACTION_UP:
/*结束事件响应，做相应的操作*/
finishPull();
break;
case MotionEvent.ACTION_POINTER_UP:
/*这里需要注意，多点处理，这里的处理方式是：如果有两个手指按下，抬起的是后按下的手指，则不做处理
* 如果抬起的是最先按下的手指，则复原图片效果。
* */
int pointUpIndex = MotionEventCompat.getActionIndex(ev);
int pointId = MotionEventCompat.getPointerId(ev, pointUpIndex);
if (pointId == mActivePointerId) {
/*松手执行结束拖拽操作*/
/*结束事件响应，做相应的操作*/
finishPull();
}
break;
}
return super.onTouchEvent(ev);
}
@Override
public void setOnScrollListener(OnScrollListener l) {
mScrollListener = l ;
}
private void abortAnimation() {
/*啥都没做，暂时没做而已*/
}
private void finishPull() {
mActivePointerId = INVALID_POINTER;
/*这是一个阈值，如果成立，则表示图片已经放大了，在手指抬起的时候需要复原图片*/
if (mHeaderContainer.getBottom() > mHeaderHeight){
// Log.v(“zgy”, “===super====onTouchEvent========”);
/<em>这里是下拉刷新的阈值，当达到了，则表示需要刷新，可以添加刷新动画</em>/
if (mScale > REFRESH_SCALE){
if (mRefreshListener != null){
mRefreshListener.onRefresh();
}
}
//图片复原动画
pullBackAnimation();
}
}
/**
* 这是属性动画的知识，不懂的可以去看看属性动画的知识
*/
private void pullBackAnimation(){
ValueAnimator pullBack = ValueAnimator.ofFloat(mScale , 1.0f);
pullBack.setInterpolator(sInterpolator);
pullBack.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator animation) {
float value = (float) animation.getAnimatedValue();
LayoutParams params = (LayoutParams) mHeaderContainer.getLayoutParams();
params.height = (int) (mHeaderHeight * value);
mHeaderContainer.setLayoutParams(params);
}
});
pullBack.setDuration((long) (MIN_SETTLE_DURATION*mScale));
pullBack.start();
}
/**
* 通过事件和点的 id 来获取点的索引
*
* @param ev
* @param id
* @return
*/
private int getPointerIndex(MotionEvent ev, int id) {
int activePointerIndex = MotionEventCompat.findPointerIndex(ev, id);
if (activePointerIndex == -1)
mActivePointerId = INVALID_POINTER;
return activePointerIndex;
}
public void setOnRefreshListener(OnRefreshListener l){
mRefreshListener = l ;
}
public ImageView getHeaderImageView() {
return this.mHeaderImg;
}
private float clamp(float value, float min, float max) {
return Math.min(Math.max(value, min), max);
}
private class InternalScrollerListener implements OnScrollListener{
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
if (mScrollListener != null){
mScrollListener.onScrollStateChanged(view,scrollState);
}
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
float diff = mHeaderHeight - mHeaderContainer.getBottom();
if ((diff > 0.0F) && (diff < mHeaderHeight)) {
int i = (int) (0.3D * diff);
mHeaderImg.scrollTo(0, -i);
} else if (mHeaderImg.getScrollY() != 0) {
mHeaderImg.scrollTo(0, 0);
}
Log.v("zgy","=========height==="+getScrolledY());
if (mScrollListener != null){
mScrollListener.onScroll(view, firstVisibleItem, visibleItemCount, totalItemCount);
}
}
}
public int getScrolledY() {
View c = getChildAt(0);
if (c == null) {
return 0;
}
int firstVisiblePosition = getFirstVisiblePosition();
int top = c.getTop();
int headerHeight = 0;
if (firstVisiblePosition >= 1) {
headerHeight = mHeaderHeight;
}
return -top + firstVisiblePosition * c.getHeight() + headerHeight;
}
public interface OnRefreshListener {
void onRefresh() ;
}
public void computeRefresh(){
if (mActivePointerId != INVALID_POINTER){
}
}
}
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