【Android 事件分发】事件分发源码分析 ( Activity 中各层级的事件传递 | Activity -＞ PhoneWindow -＞ DecorView -＞ ViewGroup )

public class Activity extends ContextThemeWrapper
        implements LayoutInflater.Factory2,
        Window.Callback, KeyEvent.Callback,
        OnCreateContextMenuListener, ComponentCallbacks2,
        Window.OnWindowDismissedCallback, WindowControllerCallback,
        AutofillManager.AutofillClient {
    /**
     * 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) {
          // 判定是否是第一次按下 
          // 该方法与事件传递机制流程无关 
          // 提供给用户按下时可以执行的业务逻辑 
            onUserInteraction();
        }
  // getWindow() 获取的是 PhoneWindow 窗口 
  // 调用 PhoneWindow 的 superDispatchTouchEvent ; 
        if (getWindow().superDispatchTouchEvent(ev)) {
            return true;
        }
        return onTouchEvent(ev);
    }
    public void onUserInteraction() {
    }
}

public class PhoneWindow extends Window implements MenuBuilder.Callback {
    // This is the top-level view of the window, containing the window decor.
    private DecorView mDecor;
    @Override
    public boolean superDispatchTouchEvent(MotionEvent event) {
        return mDecor.superDispatchTouchEvent(event);
    }
}

public class DecorView extends FrameLayout implements RootViewSurfaceTaker, WindowCallbacks {
    public boolean superDispatchTouchEvent(MotionEvent event) {
        return super.dispatchTouchEvent(event);
    }
}

@UiThread
public abstract class ViewGroup extends View implements ViewParent, ViewManager {
    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
    }
}