本篇博文是Android点击事件分发机制系列博文的第四篇，主要是从解读Activity类的源码入手，根据源码理清Activity点击事件分发原理，并掌握Activity点击事件分法机制。特别声明的是，本源码解读是基于最新的Android6.0版本。
各位童鞋可以参考下面链接进行系统学习
（一）Android6.0触摸事件分发机制解读
（二）Android6.0源码解读之View点击事件分发机制
（三）Android6.0源码解读之ViewGroup点击事件分发机制
（四）Android6.0源码解读之Activity点击事件分发机制
Android中通常点击事件用MotionEvent来表示，当一个点击操作发生时，事件最先传递给当前的Activity，由Activity的dispatchTouchEvent来进行事件的分发，具体工作是由Activity内部的Window来完成的。Window会将事件传递给decor view，decor view一般就是当前界面的底层容器（即setContentView所设置的View的父容器），通过Activity.getWindow.getDecorView()可以获得。关于Activity事件分发机制的源码，我们重点来看下dispatchTouchEvent方法。
（一）dispatchTouchEvent源码解析
/**
* Called to process touch screen events. You can override this to
* intercept all touch screen events before they are dispatched to the
* window. Be sure to call this implementation for touch screen events
* that should be handled normally.
*
* @param ev The touch screen event.
*
* @return boolean Return true if this event was consumed.
*/
public boolean dispatchTouchEvent(MotionEvent ev) {
if (ev.getAction() == MotionEvent.ACTION_DOWN) {
// 这是个空方法
onUserInteraction();
}
//一开始事件交给Activity所附属的Window进行派发，如果返回true，整个事件循环就结束了，返回false意味着事件没人处理，所有人的onTouchEvent都返回了false，那么Activity就要来做最后的收场。
if (getWindow().superDispatchTouchEvent(ev)) {
return true;
}
return onTouchEvent(ev);
}onUserInteraction方法
/**
* Called as part of the activity lifecycle when an activity is about to go
* into the background as the result of user choice. For example, when the
* user presses the Home key, {@link #onUserLeaveHint} will be called, but
* when an incoming phone call causes the in-call Activity to be automatically
* brought to the foreground, {@link #onUserLeaveHint} will not be called on
* the activity being interrupted. In cases when it is invoked, this method
* is called right before the activity's {@link #onPause} callback.
*
* <p>This callback and {@link #onUserInteraction} are intended to help
* activities manage status bar notifications intelligently; specifically,
* for helping activities determine the proper time to cancel a notfication.
*
* @see #onUserInteraction()
*/
protected void onUserLeaveHint() {
}（二）onTouchEvent源码解析
通常一个点击操作要是没有被Activity下的任何View处理，则Activity的onTouchEvent将会被调用。返回值为true表明你已经消费了这个事件，false则表示没有消费（默认）。
/**
* Called when a touch screen event was not handled by any of the views
* under it. This is most useful to process touch events that happen
* outside of your window bounds, where there is no view to receive it.
*
* @param event The touch screen event being processed.
*
* @return Return true if you have consumed the event, false if you haven't.
* The default implementation always returns false.
*/
public boolean onTouchEvent(MotionEvent event) {
// mWindow对象其实就是dispatchTouchEvent方法里的getWindow()对象
if (mWindow.shouldCloseOnTouch(this, event)) {
finish();
return true;
}
return false;
}事件传递给ViewGroup
接下来我们看Window是如何将事件传递给ViewGroup的。通过源代码我们知道Window是一个抽象类，而Window的superDispatchTouchEvent方法也是个抽象方法，我们来看下。
/**
* Used by custom windows, such as Dialog, to pass the touch screen event
* further down the view hierarchy. Application developers should
* not need to implement or call this.
*
*/
public abstract boolean superDispatchTouchEvent(MotionEvent event);既然superDispatchTouchEvent是个抽象方法，那么我们去看下它的实现类PhoneWindow是如何处理点击事件的。
@Override
public boolean superDispatchTouchEvent(MotionEvent event) {
return mDecor.superDispatchTouchEvent(event);
}通过以上源码不难发现，PhoneWindow将事件直接传递给了Decor View。我们来看下这里的DecorView。
private final class DecorView extends FrameLayout implements RootViewSurfaceTaker
// This is the top-level view of the window, containing the window decor.
private DecorView mDecor;
@Override
public final View getDecorView() {
if (mDecor == null) {
installDecor();
}
return mDecor;
}
通常我们通过((ViewGroup)getWindow().getDecorView().findViewById(android.R.id.content)).getChildAt(0)这种方式获取Activity所设置的View。这个mDecor显然就是getWindow().getDecorView()返回的View，而我们通过setContentView设置的View是它的一个子View。目前事件传递到了DecorView 这里，由于DecorView 继承自FrameLayout且是我们的父View，所以最终事件会传递给我们的View。从这里开始，事件已经传递到我们的顶级View了，所谓的顶级View实际上是最底层View，也叫根View。
参考：《Android开发的艺术》