关于V4 V7 V13
1, Android Support V4, V7, V13是什么？
本质上就是三个java library。
2, 为什么要有support库？
如果在低版本Android平台上开发一个应用程序，而应用程序又想使用高版本才拥有的功能，就需要使用Support库。
3, 三个Support 库的区别和作用是什么？
Android Support v4 是最早（2011年4月份）实现的库。用在Android1.6 (API lever 4)或者更高版本之上。它包含了相对V4, V13大的多的功能。
例如：Fragment，NotificationCompat，LoadBroadcastManager，ViewPager，PageTabAtrip，Loader，FileProvider 等。
详细API 参考 http://developer.android.com/reference/android/support/v4/app/package-summary.html
Android Support v7: 这个包是为了考虑Android2.1(API level 7) 及以上版本而设计的，但是v7是要依赖v4这个包的，也就是如果要使用，两个包得同时 被引用。
v7支持了Action Bar。
Android Support v13:这个包的设计是为了android 3.2及更高版本的，一般我们都不常用，平板开发中能用到。
sdk\extras\android\support\samples\Support7Demos笔记
FloatingActionButton
代码分析：
Logger包
关于log：需要使用Log输出一些信息。那么我们就需要使用到Log FrameWork。使用及注释如下
public void initializeLogging() {
//封装android底层log框架
LogWrapper logWrapper = new LogWrapper();
// Using Log, front-end to the logging chain, emulates android.util.log method signatures.
/**
* Log的消息传递是依据一个链路依次传递的，Log传递到LogWrapper，LogWrapper传递到MessageOnlyLogFilter，MessageOnlyLogFilter传递到LogFragment
*/
Log.setLogNode(logWrapper);
// 过滤器
MessageOnlyLogFilter msgFilter = new MessageOnlyLogFilter();
logWrapper.setNext(msgFilter);
// On screen logging via a fragment with a TextView.
LogFragment logFragment = (LogFragment) getSupportFragmentManager()
.findFragmentById(R.id.log_fragment);
msgFilter.setNext(logFragment.getLogView());
Log.i(TAG, "Ready");
}涉及到的主要的类：
package com.example.android.common.logger;
/**
* Helper class for a list (or tree) of LoggerNodes.
*
* <p>When this is set as the head of the list,
* an instance of it can function as a drop-in replacement for {@link android.util.Log}.
* Most of the methods in this class server only to map a method call in Log to its equivalent
* in LogNode.</p>
*/
public class Log {
// Grabbing the native values from Android‘s native logging facilities,
// to make for easy migration and interop.
public static final int NONE = -1;
public static final int VERBOSE = android.util.Log.VERBOSE;
public static final int DEBUG = android.util.Log.DEBUG;
public static final int INFO = android.util.Log.INFO;
public static final int WARN = android.util.Log.WARN;
public static final int ERROR = android.util.Log.ERROR;
public static final int ASSERT = android.util.Log.ASSERT;
// Stores the beginning of the LogNode topology.
private static LogNode mLogNode;
/**
* Returns the next LogNode in the linked list.
*/
public static LogNode getLogNode() {
return mLogNode;
}
/**
* Sets the LogNode data will be sent to.
*/
public static void setLogNode(LogNode node) {
mLogNode = node;
}
/**
* Instructs the LogNode to print the log data provided. Other LogNodes can
* be chained to the end of the LogNode as desired.
*
* @param priority Log level of the data being logged. Verbose, Error, etc.
* @param tag Tag for for the log data. Can be used to organize log statements.
* @param msg The actual message to be logged.
* @param tr If an exception was thrown, this can be sent along for the logging facilities
* to extract and print useful information.
*/
public static void println(int priority, String tag, String msg, Throwable tr) {
if (mLogNode != null) {
mLogNode.println(priority, tag, msg, tr);
}
}
/**
* Instructs the LogNode to print the log data provided. Other LogNodes can
* be chained to the end of the LogNode as desired.
*
* @param priority Log level of the data being logged. Verbose, Error, etc.
* @param tag Tag for for the log data. Can be used to organize log statements.
* @param msg The actual message to be logged. The actual message to be logged.
*/
public static void println(int priority, String tag, String msg) {
println(priority, tag, msg, null);
}
/**
* Prints a message at VERBOSE priority.
*
* @param tag Tag for for the log data. Can be used to organize log statements.
* @param msg The actual message to be logged.
* @param tr If an exception was thrown, this can be sent along for the logging facilities
* to extract and print useful information.
*/
public static void v(String tag, String msg, Throwable tr) {
println(VERBOSE, tag, msg, tr);
}
/**
* Prints a message at VERBOSE priority.
*
* @param tag Tag for for the log data. Can be used to organize log statements.
* @param msg The actual message to be logged.
*/
public static void v(String tag, String msg) {
v(tag, msg, null);
}
/**
* Prints a message at DEBUG priority.
*
* @param tag Tag for for the log data. Can be used to organize log statements.
* @param msg The actual message to be logged.
* @param tr If an exception was thrown, this can be sent along for the logging facilities
* to extract and print useful information.
*/
public static void d(String tag, String msg, Throwable tr) {
println(DEBUG, tag, msg, tr);
}
/**
* Prints a message at DEBUG priority.
*
* @param tag Tag for for the log data. Can be used to organize log statements.
* @param msg The actual message to be logged.
*/
public static void d(String tag, String msg) {
d(tag, msg, null);
}
/**
* Prints a message at INFO priority.
*
* @param tag Tag for for the log data. Can be used to organize log statements.
* @param msg The actual message to be logged.
* @param tr If an exception was thrown, this can be sent along for the logging facilities
* to extract and print useful information.
*/
public static void i(String tag, String msg, Throwable tr) {
println(INFO, tag, msg, tr);
}
/**
* Prints a message at INFO priority.
*
* @param tag Tag for for the log data. Can be used to organize log statements.
* @param msg The actual message to be logged.
*/
public static void i(String tag, String msg) {
i(tag, msg, null);
}
/**
* Prints a message at WARN priority.
*
* @param tag Tag for for the log data. Can be used to organize log statements.
* @param msg The actual message to be logged.
* @param tr If an exception was thrown, this can be sent along for the logging facilities
* to extract and print useful information.
*/
public static void w(String tag, String msg, Throwable tr) {
println(WARN, tag, msg, tr);
}
/**
* Prints a message at WARN priority.
*
* @param tag Tag for for the log data. Can be used to organize log statements.
* @param msg The actual message to be logged.
*/
public static void w(String tag, String msg) {
w(tag, msg, null);
}
/**
* Prints a message at WARN priority.
*
* @param tag Tag for for the log data. Can be used to organize log statements.
* @param tr If an exception was thrown, this can be sent along for the logging facilities
* to extract and print useful information.
*/
public static void w(String tag, Throwable tr) {
w(tag, null, tr);
}
/**
* Prints a message at ERROR priority.
*
* @param tag Tag for for the log data. Can be used to organize log statements.
* @param msg The actual message to be logged.
* @param tr If an exception was thrown, this can be sent along for the logging facilities
* to extract and print useful information.
*/
public static void e(String tag, String msg, Throwable tr) {
println(ERROR, tag, msg, tr);
}
/**
* Prints a message at ERROR priority.
*
* @param tag Tag for for the log data. Can be used to organize log statements.
* @param msg The actual message to be logged.
*/
public static void e(String tag, String msg) {
e(tag, msg, null);
}
/**
* Prints a message at ASSERT priority.
*
* @param tag Tag for for the log data. Can be used to organize log statements.
* @param msg The actual message to be logged.
* @param tr If an exception was thrown, this can be sent along for the logging facilities
* to extract and print useful information.
*/
public static void wtf(String tag, String msg, Throwable tr) {
println(ASSERT, tag, msg, tr);
}
/**
* Prints a message at ASSERT priority.
*
* @param tag Tag for for the log data. Can be used to organize log statements.
* @param msg The actual message to be logged.
*/
public static void wtf(String tag, String msg) {
wtf(tag, msg, null);
}
/**
* Prints a message at ASSERT priority.
*
* @param tag Tag for for the log data. Can be used to organize log statements.
* @param tr If an exception was thrown, this can be sent along for the logging facilities
* to extract and print useful information.
*/
public static void wtf(String tag, Throwable tr) {
wtf(tag, null, tr);
}
}
/**
内部包装了android的Log FrameWork
Helper class which wraps Android‘s native Log utility in the Logger interface. This way
* normal DDMS output can be one of the many targets receiving and outputting logs simultaneously.
*/
public class LogWrapper implements LogNode {
// For piping: The next node to receive Log data after this one has done its work.
private LogNode mNext;
/**
* Returns the next LogNode in the linked list.
*/
public LogNode getNext() {
return mNext;
}
/**
* Sets the LogNode data will be sent to..
*/
public void setNext(LogNode node) {
mNext = node;
}
/**
* Prints data out to the console using Android‘s native log mechanism.
* @param priority Log level of the data being logged. Verbose, Error, etc.
* @param tag Tag for for the log data. Can be used to organize log statements.
* @param msg The actual message to be logged. The actual message to be logged.
* @param tr If an exception was thrown, this can be sent along for the logging facilities
* to extract and print useful information.
*/
@Override
public void println(int priority, String tag, String msg, Throwable tr) {
// There actually are log methods that don‘t take a msg parameter. For now,
// if that‘s the case, just convert null to the empty string and move on.
String useMsg = msg;
if (useMsg == null) {
useMsg = "";
}
// If an exeption was provided, convert that exception to a usable string and attach
// it to the end of the msg method.
if (tr != null) {
msg += "\n" + Log.getStackTraceString(tr);
}
// This is functionally identical to Log.x(tag, useMsg);
// For instance, if priority were Log.VERBOSE, this would be the same as Log.v(tag, useMsg)
/**
* 注意这里的Log是这个包下的package android.util
*/
Log.println(priority, tag, useMsg);
// If this isn‘t the last node in the chain, move things along.
if (mNext != null) {
mNext.println(priority, tag, msg, tr);
}
}
}
package com.example.android.common.logger;
/**
* Basic interface for a logging system that can output to one or more targets.
* Note that in addition to classes that will output these logs in some format,
* one can also implement this interface over a filter and insert that in the chain,
* such that no targets further down see certain data, or see manipulated forms of the data.
* You could, for instance, write a "ToHtmlLoggerNode" that just converted all the log data
* it received to HTML and sent it along to the next node in the chain, without printing it
* anywhere.
*/
public interface LogNode {
/**
* Instructs first LogNode in the list to print the log data provided.
* @param priority Log level of the data being logged. Verbose, Error, etc.
* @param tag Tag for for the log data. Can be used to organize log statements.
* @param msg The actual message to be logged. The actual message to be logged.
* @param tr If an exception was thrown, this can be sent along for the logging facilities
* to extract and print useful information.
*/
public void println(int priority, String tag, String msg, Throwable tr);
}
package com.example.android.common.logger;
/**
除去一些用户并不关心的的数据
* Simple {@link LogNode} filter, removes everything except the message.
* Useful for situations like on-screen log output where you don‘t want a lot of metadata displayed,
* just easy-to-read message updates as they‘re happening.
*/
public class MessageOnlyLogFilter implements LogNode {
LogNode mNext;
/**
* Takes the "next" LogNode as a parameter, to simplify chaining.
*
* @param next The next LogNode in the pipeline.
*/
public MessageOnlyLogFilter(LogNode next) {
mNext = next;
}
public MessageOnlyLogFilter() {
}
@Override
public void println(int priority, String tag, String msg, Throwable tr) {
if (mNext != null) {
getNext().println(Log.NONE, null, msg, null);
}
}
/**
* Returns the next LogNode in the chain.
*/
public LogNode getNext() {
return mNext;
}
/**
* Sets the LogNode data will be sent to..
*/
public void setNext(LogNode node) {
mNext = node;
}
}
最终执行输出Log代码，上边各种封装类都是作为消息传递chain：
/**
展示Log的View
Simple TextView which is used to output log data received through the LogNode interface.
*/
public class LogView extends TextView implements LogNode {
public LogView(Context context) {
super(context);
}
public LogView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public LogView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
/**
* Formats the log data and prints it out to the LogView.
* @param priority Log level of the data being logged. Verbose, Error, etc.
* @param tag Tag for for the log data. Can be used to organize log statements.
* @param msg The actual message to be logged. The actual message to be logged.
* @param tr If an exception was thrown, this can be sent along for the logging facilities
* to extract and print useful information.
*/
@Override
public void println(int priority, String tag, String msg, Throwable tr) {
String priorityStr = null;
// For the purposes of this View, we want to print the priority as readable text.
switch(priority) {
case android.util.Log.VERBOSE:
priorityStr = "VERBOSE";
break;
case android.util.Log.DEBUG:
priorityStr = "DEBUG";
break;
case android.util.Log.INFO:
priorityStr = "INFO";
break;
case android.util.Log.WARN:
priorityStr = "WARN";
break;
case android.util.Log.ERROR:
priorityStr = "ERROR";
break;
case android.util.Log.ASSERT:
priorityStr = "ASSERT";
break;
default:
break;
}
// Handily, the Log class has a facility for converting a stack trace into a usable string.
String exceptionStr = null;
if (tr != null) {
exceptionStr = android.util.Log.getStackTraceString(tr);
}
// Take the priority, tag, message, and exception, and concatenate as necessary
// into one usable line of text.
final StringBuilder outputBuilder = new StringBuilder();
String delimiter = "\t";
appendIfNotNull(outputBuilder, priorityStr, delimiter);
appendIfNotNull(outputBuilder, tag, delimiter);
appendIfNotNull(outputBuilder, msg, delimiter);
appendIfNotNull(outputBuilder, exceptionStr, delimiter);
// In case this was originally called from an AsyncTask or some other off-UI thread,
// make sure the update occurs within the UI thread.
((Activity) getContext()).runOnUiThread( (new Thread(new Runnable() {
@Override
public void run() {
// Display the text we just generated within the LogView.
appendToLog(outputBuilder.toString());
}
})));
if (mNext != null) {
mNext.println(priority, tag, msg, tr);
}
}
public LogNode getNext() {
return mNext;
}
public void setNext(LogNode node) {
mNext = node;
}
/** Takes a string and adds to it, with a separator, if the bit to be added isn‘t null. Since
* the logger takes so many arguments that might be null, this method helps cut out some of the
* agonizing tedium of writing the same 3 lines over and over.
* @param source StringBuilder containing the text to append to.
* @param addStr The String to append
* @param delimiter The String to separate the source and appended strings. A tab or comma,
* for instance.
* @return The fully concatenated String as a StringBuilder
*/
private StringBuilder appendIfNotNull(StringBuilder source, String addStr, String delimiter) {
if (addStr != null) {
if (addStr.length() == 0) {
delimiter = "";
}
return source.append(addStr).append(delimiter);
}
return source;
}
// The next LogNode in the chain.
LogNode mNext;
/** Outputs the string as a new line of log data in the LogView. */
public void appendToLog(String s) {
append("\n" + s);
}
}floatingactionbuttonbasic包代码分析：
说明：FloatingActionButton 这个View其实类似于一个CheckBox，当点击的时候记录当前的状态（选中或没选中），根据当期的状态来改变背景图片。背景图片是一个Selecter,状态改变自己会切换图片。这样就基本实现了FloatingActionButton 。但是，还没有让View悬浮起来。这个是5.0的一个新特性。及支持设置View在Z轴的位置。android:elevation这个属性就是设置Z轴位置的。当Z轴位置大于0时那么这个View就悬浮在其他View的上边了。
/**
* A Floating Action Button is a {@link android.widget.Checkable} view distinguished by a circled
* icon floating above the UI, with special motion behaviors.
* 继承自FrameLayout，实现了Checkable接口
*/
public class FloatingActionButton extends FrameLayout implements Checkable {
/**
* Interface definition for a callback to be invoked when the checked state
* of a compound button changes.
*/
public static interface OnCheckedChangeListener {
/**
* Called when the checked state of a FAB has changed.
*
* @param fabView The FAB view whose state has changed.
* @param isChecked The new checked state of buttonView.
*/
void onCheckedChanged(FloatingActionButton fabView, boolean isChecked);
}
/**
* An array of states.
*/
private static final int[] CHECKED_STATE_SET = {
android.R.attr.state_checked
};
private static final String TAG = "FloatingActionButton";
// A boolean that tells if the FAB is checked or not.
private boolean mChecked;
// A listener to communicate that the FAB has changed it‘s state
private OnCheckedChangeListener mOnCheckedChangeListener;
public FloatingActionButton(Context context) {
this(context, null, 0, 0);
}
public FloatingActionButton(Context context, AttributeSet attrs) {
this(context, attrs, 0, 0);
}
public FloatingActionButton(Context context, AttributeSet attrs, int defStyleAttr) {
this(context, attrs, defStyleAttr, 0);
}
public FloatingActionButton(Context context, AttributeSet attrs, int defStyleAttr,
int defStyleRes) {
super(context, attrs, defStyleAttr);
setClickable(true);
// Set the outline provider for this view. The provider is given the outline which it can
// then modify as needed. In this case we set the outline to be an oval fitting the height
// and width.
//给这个View设置outline provider。这个provider提供的outline是可以改变的。在这种情况下我们这支这个边框为填充高度和宽度
setOutlineProvider(new ViewOutlineProvider() {
@Override
public void getOutline(View view, Outline outline) {
outline.setOval(0, 0, getWidth(), getHeight());
}
});
// Finally, enable clipping to the outline, using the provider we set above
//最后，设置一下使得outline可以点击
setClipToOutline(true);
}
/**
* Sets the checked/unchecked state of the FAB.
* @param checked
*/
public void setChecked(boolean checked) {
// If trying to set the current state, ignore.
if (checked == mChecked) {
return;
}
mChecked = checked;
// Now refresh the drawable state (so the icon changes)
refreshDrawableState();
if (mOnCheckedChangeListener != null) {
mOnCheckedChangeListener.onCheckedChanged(this, checked);
}
}
/**
* Register a callback to be invoked when the checked state of this button
* changes.
*
* @param listener the callback to call on checked state change
*/
public void setOnCheckedChangeListener(OnCheckedChangeListener listener) {
mOnCheckedChangeListener = listener;
}
@Override
public boolean isChecked() {
return mChecked;
}
@Override
public void toggle() {
setChecked(!mChecked);
}
/**
* Override performClick() so that we can toggle the checked state when the view is clicked
* 当点击的时候会出发这个方法，super.performClick() 会抛出这个异常throw new RuntimeException("Stub!");打印Log
*/
@Override
public boolean performClick() {
toggle();
return super.performClick();
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
// As we have changed size, we should invalidate the outline so that is the the
// correct size
invalidateOutline();
}
/**
*
* @param extraSpace 如果不为extraSpace不为0，表示返回的int[]数组会在原始数组基础上添加额外的extraSpace个位置，在这些位置上你可以添加自己的一些额外信息
* @return
*/
@Override
protected int[] onCreateDrawableState(int extraSpace) {
final int[] drawableState = super.onCreateDrawableState(extraSpace + 1);
if (isChecked()) {
/**
* mergeDrawableStates专门用来在onCreateDrawableState返回的数组上添加一个额外的属性
*/
mergeDrawableStates(drawableState, CHECKED_STATE_SET);
}
return drawableState;
}
}
package com.example.android.floatingactionbuttonbasic;
import com.example.android.common.logger.Log;
import android.app.Activity;
import android.net.Uri;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
/**
这个Fragment将包含俩个FloatingActionButton，并监听点击事件。使用上边的Log包下的工具输出Log信息。
* This fragment inflates a layout with two Floating Action Buttons and acts as a listener to
* changes on them.
*/
public class FloatingActionButtonBasicFragment extends Fragment implements FloatingActionButton.OnCheckedChangeListener{
private final static String TAG = "FloatingActionButtonBasicFragment";
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View rootView = inflater.inflate(R.layout.fab_layout, container, false);
// Make this {@link Fragment} listen for changes in both FABs.
FloatingActionButton fab1 = (FloatingActionButton) rootView.findViewById(R.id.fab_1);
fab1.setOnCheckedChangeListener(this);
FloatingActionButton fab2 = (FloatingActionButton) rootView.findViewById(R.id.fab_2);
fab2.setOnCheckedChangeListener(this);
return rootView;
}
@Override
public void onCheckedChanged(FloatingActionButton fabView, boolean isChecked) {
// When a FAB is toggled, log the action.
switch (fabView.getId()){
case R.id.fab_1:
Log.d(TAG, String.format("FAB 1 was %s.", isChecked ? "checked" : "unchecked"));
break;
case R.id.fab_2:
Log.d(TAG, String.format("FAB 2 was %s.", isChecked ? "checked" : "unchecked"));
break;
default:
break;
}
}
}
使用：
package com.example.android.floatingactionbuttonbasic;
import android.os.Bundle;
import android.support.v4.app.FragmentTransaction;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ViewAnimator;
import com.example.android.common.activities.SampleActivityBase;
import com.example.android.common.logger.Log;
import com.example.android.common.logger.LogFragment;
import com.example.android.common.logger.LogWrapper;
import com.example.android.common.logger.MessageOnlyLogFilter;
/**
* A simple launcher activity containing a summary sample description, sample log and a custom
* {@link android.support.v4.app.Fragment} which can display a view.
* <p/>
* For devices with displays with a width of 720dp or greater, the sample log is always visible,
* on other devices it‘s visibility is controlled by an item on the Action Bar.
*/
public class MainActivity extends SampleActivityBase {
public static final String TAG = "MainActivity";
// Whether the Log Fragment is currently shown
private boolean mLogShown;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
FloatingActionButtonBasicFragment fragment = new FloatingActionButtonBasicFragment();
transaction.replace(R.id.sample_content_fragment, fragment);
transaction.commit();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onPrepareOptionsMenu(Menu menu) {
MenuItem logToggle = menu.findItem(R.id.menu_toggle_log);
logToggle.setVisible(findViewById(R.id.sample_output) instanceof ViewAnimator);
logToggle.setTitle(mLogShown ? R.string.sample_hide_log : R.string.sample_show_log);
return super.onPrepareOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.menu_toggle_log:
mLogShown = !mLogShown;
ViewAnimator output = (ViewAnimator) findViewById(R.id.sample_output);
if (mLogShown) {
output.setDisplayedChild(1);
} else {
output.setDisplayedChild(0);
}
supportInvalidateOptionsMenu();
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* Create a chain of targets that will receive log data
* 初始化Log工具
*/
@Override
public void initializeLogging() {
//封装android底层log框架
LogWrapper logWrapper = new LogWrapper();
// Using Log, front-end to the logging chain, emulates android.util.log method signatures.
/**
* Log的消息传递是依据一个链路依次传递的，Log传递到LogWrapper，LogWrapper传递到MessageOnlyLogFilter，MessageOnlyLogFilter传递到LogFragment
*/
Log.setLogNode(logWrapper);
// Filter strips out everything except the message text.
MessageOnlyLogFilter msgFilter = new MessageOnlyLogFilter();
logWrapper.setNext(msgFilter);
// On screen logging via a fragment with a TextView.
LogFragment logFragment = (LogFragment) getSupportFragmentManager()
.findFragmentById(R.id.log_fragment);
msgFilter.setNext(logFragment.getLogView());
Log.i(TAG, "Ready");
}
}
布局文件
<?xml version="1.0" encoding="UTF-8"?>
<!--
Copyright 2014, The Android Open Source Project
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License
这里还涉及到一些动画，这里不再说明。
-->
<FrameLayout android:orientation="vertical" xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<!--elevation Z轴方向的距离 这个属性是android5.0系统支持的-->
<com.example.android.floatingactionbuttonbasic.FloatingActionButton
android:id="@+id/fab_1"
android:layout_width="@dimen/fab_size"
android:layout_height="@dimen/fab_size"
android:layout_marginTop="16dp"
android:elevation="@dimen/fab_elevation"
android:background="@drawable/fab_background"
android:stateListAnimator="@animator/fab_anim"
android:layout_gravity="center_horizontal">
<!--duplicateParentState表示当前View的DrawableState直接从其父View获取，而不是从他自己获取-->
<ImageView
android:layout_width="@dimen/fab_icon_size"
android:layout_height="@dimen/fab_icon_size"
android:src="@drawable/fab_icons"
android:layout_gravity="center"
android:duplicateParentState="true"/>
</com.example.android.floatingactionbuttonbasic.FloatingActionButton>
<com.example.android.floatingactionbuttonbasic.FloatingActionButton
android:id="@+id/fab_2"
android:layout_width="@dimen/fab_size_small"
android:layout_height="@dimen/fab_size_small"
android:layout_marginTop="128dp"
android:elevation="@dimen/fab_elevation"
android:background="@drawable/fab_background"
android:stateListAnimator="@animator/fab_anim"
android:layout_gravity="center_horizontal">
<ImageView
android:layout_width="@dimen/fab_icon_size"
android:layout_height="@dimen/fab_icon_size"
android:src="@drawable/fab_icons"
android:layout_gravity="center"
android:duplicateParentState="true"/>
</com.example.android.floatingactionbuttonbasic.FloatingActionButton>
</FrameLayout>
XML文件的预览效果：
代码下载需要5.0系统
RecyclerView
效果图
代码分析：
Log输出同FloatingActionButton完全相同。这里不再分析。
View的创建过程分析：
package com.example.android.recyclerview;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.RadioButton;
/**
* 使用Fragment加载一个RecyclerView
* Demonstrates the use of {@link RecyclerView} with a {@link LinearLayoutManager} and a
* {@link GridLayoutManager}.
*/
public class RecyclerViewFragment extends Fragment {
private static final String TAG = "RecyclerViewFragment";
private static final String KEY_LAYOUT_MANAGER = "layoutManager";
private static final int SPAN_COUNT = 2;
private static final int DATASET_COUNT = 60;
private enum LayoutManagerType {
GRID_LAYOUT_MANAGER,
LINEAR_LAYOUT_MANAGER
}
protected LayoutManagerType mCurrentLayoutManagerType;
protected RadioButton mLinearLayoutRadioButton;
protected RadioButton mGridLayoutRadioButton;
protected RecyclerView mRecyclerView;
protected CustomAdapter mAdapter;
protected RecyclerView.LayoutManager mLayoutManager;
protected String[] mDataset;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Initialize dataset, this data would usually come from a local content provider or
// remote server.
//初始化数据
initDataset();
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.recycler_view_frag, container, false);
rootView.setTag(TAG);
// BEGIN_INCLUDE(initializeRecyclerView)
mRecyclerView = (RecyclerView) rootView.findViewById(R.id.recyclerView);
// LinearLayoutManager is used here, this will layout the elements in a similar fashion
// to the way ListView would layout elements. The RecyclerView.LayoutManager defines how
// elements are laid out.
//使用LinearLayoutManager来初始化RecyclerView.LayoutManager，RecyclerView.LayoutManager决定recyclerView如何布局
mLayoutManager = new LinearLayoutManager(getActivity());
mCurrentLayoutManagerType = LayoutManagerType.LINEAR_LAYOUT_MANAGER;
if (savedInstanceState != null) {
// Restore saved layout manager type.
mCurrentLayoutManagerType = (LayoutManagerType) savedInstanceState
.getSerializable(KEY_LAYOUT_MANAGER);
}
setRecyclerViewLayoutManager(mCurrentLayoutManagerType);
mAdapter = new CustomAdapter(mDataset);
// .RecyclerView设置适配器
mRecyclerView.setAdapter(mAdapter);
// END_INCLUDE(initializeRecyclerView)
//改变布局方式
mLinearLayoutRadioButton = (RadioButton) rootView.findViewById(R.id.linear_layout_rb);
mLinearLayoutRadioButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
setRecyclerViewLayoutManager(LayoutManagerType.LINEAR_LAYOUT_MANAGER);
}
});
mGridLayoutRadioButton = (RadioButton) rootView.findViewById(R.id.grid_layout_rb);
mGridLayoutRadioButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
setRecyclerViewLayoutManager(LayoutManagerType.GRID_LAYOUT_MANAGER);
}
});
return rootView;
}
/**
* Set RecyclerView‘s LayoutManager to the one given.
* 设置recyclerView的布局管理
*
* @param layoutManagerType Type of layout manager to switch to.
*/
public void setRecyclerViewLayoutManager(LayoutManagerType layoutManagerType) {
int scrollPosition = 0;
// If a layout manager has already been set, get current scroll position.
//如果当前的布局管理已近设置了，那么获得当前滑动的位置
if (mRecyclerView.getLayoutManager() != null) {
scrollPosition = ((LinearLayoutManager) mRecyclerView.getLayoutManager())
.findFirstCompletelyVisibleItemPosition();
}
//设置布局管理
switch (layoutManagerType) {
case GRID_LAYOUT_MANAGER:
mLayoutManager = new GridLayoutManager(getActivity(), SPAN_COUNT);
mCurrentLayoutManagerType = LayoutManagerType.GRID_LAYOUT_MANAGER;
break;
case LINEAR_LAYOUT_MANAGER:
mLayoutManager = new LinearLayoutManager(getActivity());
mCurrentLayoutManagerType = LayoutManagerType.LINEAR_LAYOUT_MANAGER;
break;
default:
mLayoutManager = new LinearLayoutManager(getActivity());
mCurrentLayoutManagerType = LayoutManagerType.LINEAR_LAYOUT_MANAGER;
}
//滑动到上次的位置
mRecyclerView.setLayoutManager(mLayoutManager);
mRecyclerView.scrollToPosition(scrollPosition);
}
@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
// Save currently selected layout manager.
//保存当前的布局管理对象
savedInstanceState.putSerializable(KEY_LAYOUT_MANAGER, mCurrentLayoutManagerType);
super.onSaveInstanceState(savedInstanceState);
}
/**
* Generates Strings for RecyclerView‘s adapter. This data would usually come
* from a local content provider or remote server.
* 生成数据
*/
private void initDataset() {
mDataset = new String[DATASET_COUNT];
for (int i = 0; i < DATASET_COUNT; i++) {
mDataset[i] = "This is element #" + i;
}
}
}
布局文件
<?xml version="1.0" encoding="UTF-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<RadioGroup
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center_horizontal"
android:orientation="horizontal"
android:checkedButton="@+id/linear_layout_rb">
<RadioButton android:id="@+id/linear_layout_rb"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/linear_layout_manager"/>
<RadioButton android:id="@+id/grid_layout_rb"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/grid_layout_manager"/>
</RadioGroup>
<android.support.v7.widget.RecyclerView
android:id="@+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</LinearLayout>
适配器：
package com.example.android.recyclerview;
import com.example.android.common.logger.Log;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
/**
* Provide views to RecyclerView with data from mDataSet.
* 自定义的RecyclerView数据适配器
*/
public class CustomAdapter extends RecyclerView.Adapter<CustomAdapter.ViewHolder> {
private static final String TAG = "CustomAdapter";
private String[] mDataSet;
// BEGIN_INCLUDE(recyclerViewSampleViewHolder)
/**
* Provide a reference to the type of views that you are using (custom ViewHolder)
* 提供一个指向自定义View的应用
*/
public static class ViewHolder extends RecyclerView.ViewHolder {
/**
* 这里不只可以是textView还可以是其他的View
*/
private final TextView textView;
public ViewHolder(View v) {
super(v);
// Define click listener for the ViewHolder‘s View.
//定义每一个View的点击事件
v.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Log.d(TAG, "Element " + getPosition() + " clicked.");
}
});
textView = (TextView) v.findViewById(R.id.textView);
}
public TextView getTextView() {
return textView;
}
}
// END_INCLUDE(recyclerViewSampleViewHolder)
/**
* Initialize the dataset of the Adapter.
*
* @param dataSet String[] containing the data to populate views to be used by RecyclerView.
*/
public CustomAdapter(String[] dataSet) {
mDataSet = dataSet;
}
// BEGIN_INCLUDE(recyclerViewOnCreateViewHolder)
// Create new views (invoked by the layout manager)
@Override
public ViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) {
// Create a new view.创建一个View
View v = LayoutInflater.from(viewGroup.getContext())
.inflate(R.layout.text_row_item, viewGroup, false);
return new ViewHolder(v);
}
// END_INCLUDE(recyclerViewOnCreateViewHolder)
// BEGIN_INCLUDE(recyclerViewOnBindViewHolder)
// Replace the contents of a view (invoked by the layout manager)
//由layout manager调用，替换ViewHolder的内容.在滑动的时候会不断调用这个方法来跟新视图
@Override
public void onBindViewHolder(ViewHolder viewHolder, final int position) {
Log.d(TAG, "Element " + position + " set.");
// Get element from your dataset at this position and replace the contents of the view
// with that element
//这里得到的是ViewHolder创建时传递进去的可以自定义的View
viewHolder.getTextView().setText(mDataSet[position]);
}
// END_INCLUDE(recyclerViewOnBindViewHolder)
// Return the size of your dataset (invoked by the layout manager)
@Override
public int getItemCount() {
return mDataSet.length;
}
}
说明：为什么要使用RecyclerView
从效果上说，RecyclerView和ListView是差不多的，都是列表。
①但是RecyclerViwe支持多种布局方式，可以通过设置不同的布局方式实现不同效果，这一点比较灵活。
②直接省去了当初的convertView.setTag(holder)和convertView.getTag()这些繁琐的步骤。
因为RecyclerView帮我们封装了Holder，所以我们自己写的ViewHolder就需要继承RecyclerView.ViewHolder，只有这样，RecyclerView才能帮你去管理这个ViewHolder类。
③以前的getView方法的渲染数据部分的代码相当于onBindViewHolder()，所以如果调用adapter.notifyDataSetChanged()方法，应该也会重新调用onBindViewHolder()方法才对吧？实验后，果然如此！
除了adapter.notifyDataSetChanged()这个方法之外，新的Adapter还提供了其他的方法，如下：
public final void notifyDataSetChanged()
public final void notifyItemChanged(int position)
public final void notifyItemRangeChanged(int positionStart, int itemCount)
public final void notifyItemInserted(int position)
public final void notifyItemMoved(int fromPosition, int toPosition)
public final void notifyItemRangeInserted(int positionStart, int itemCount)
public final void notifyItemRemoved(int position)
public final void notifyItemRangeRemoved(int positionStart, int itemCount)第一个方法没什么好讲的，跟以前一样。
notifyItemChanged(int position)，position数据发生了改变，那调用这个方法，就会回调对应position的onBindViewHolder()方法了，当然，因为ViewHolder是复用的，所以如果position在当前屏幕以外，也就不会回调了，因为没有意义，下次position滚动会当前屏幕以内的时候同样会调用onBindViewHolder()方法刷新数据了。其他的方法也是同样的道理。
public final void notifyItemRangeChanged(int positionStart, int itemCount)，顾名思义，可以刷新从positionStart开始itemCount数量的item了（这里的刷新指回调onBindViewHolder()方法）。
public final void notifyItemInserted(int position)，这个方法是在第position位置被插入了一条数据的时候可以使用这个方法刷新，注意这个方法调用后会有插入的动画，这个动画可以使用默认的，也可以自己定义。
public final void notifyItemMoved(int fromPosition, int toPosition)，这个方法是从fromPosition移动到toPosition为止的时候可以使用这个方法刷新
public final void notifyItemRangeInserted(int positionStart, int itemCount)，显然是批量添加。
public final void notifyItemRemoved(int position)，第position个被删除的时候刷新，同样会有动画。
public final void notifyItemRangeRemoved(int positionStart, int itemCount)，批量删除。
源码下载地址
ActivitySceneTransitionBasic(Activity场景切换)
时间： 2024-10-18 06:52:23