深入理解深入理解 Android事件分发机制源码（基于事件分发机制源码（基于9.0））
touch事件最开始从Activity 的 dispatchTouchEvent() 方法开始的
/frameworks/base/core/java/android/app/Activity.java
/**
* 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) {
onUserInteraction();
}
//这一段逻辑很重要，我们大部分界面的touch事件，都是从这里开始传的
if (getWindow().superDispatchTouchEvent(ev)) {
return true;
}
//调用Activity自身的onTouchEvent()方法
return onTouchEvent(ev);
}
getWindow() 相信很多人都知道，我们在需要 Acitivity 全屏或者开发一些主题效果时经常用到，它是返回的 Window 对象。
/frameworks/base/core/java/android/app/Activity.java
/**
* Retrieve the current {@link android.view.Window} for the activity.
* This can be used to directly access parts of the Window API that
* are not available through Activity/Screen.
*
* @return Window The current window, or null if the activity is not
* visual.
*/
public Window getWindow() {
return mWindow;
}
在Android系统中，Window 类是一个抽象类，目前唯一的实现类是 PhoneWindow.java，我们从官方给 Window 类的注释中
就可以看出来。
/framworks/base/core/java/android/view/Window.java
/**
* Abstract base class for a top-level window look and behavior policy. An
* instance of this class should be used as the top-level view added to the
* window manager. It provides standard UI policies such as a background, title
* area, default key processing, etc.
*
* The only existing implementation of this abstract class is
* android.view.PhoneWindow, which you should instantiate when needing a
* Window.译:这个抽象类的唯一实现类是PhoneWindow，当你需要一个Window时应对首先其进行实例化
*/
public abstract class Window {
...
}
我们紧接着看 PhoneWindow 的 superDispatchTouchEvent 方法，逻辑也很简单。
/framworks/base/core/java/com/android/internal/policy/PhoneWindow.java
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