Android触摸事件派发机制源码分析之Activity

上篇分析

ViewGroup分析

贴上代码 MainActivity中的代码如下

package com.sparkhuu.testevent; import android.nfc.Tag; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.util.Log; import android.view.MotionEvent; import android.view.View; import android.widget.Button; import android.widget.RelativeLayout; import junit.framework.Test; import java.io.Serializable; public class MainActivity extends AppCompatActivity implements View.OnTouchListener, View.OnClickListener { public static final String TAG = "test"; RelativeLayout rl_layout; TestButton btn_view; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); rl_layout = (RelativeLayout) this.findViewById(R.id.rl_layout); btn_view = (TestButton) this.findViewById(R.id.btn_view); btn_view.setOnTouchListener(this); rl_layout.setOnTouchListener(this); btn_view.setOnClickListener(this); rl_layout.setOnClickListener(this); } @Override public boolean onTouch(View view, MotionEvent motionEvent) { Log.i(TAG, "OnTouchListener----onTouch----action" + motionEvent.getAction() + "-----" + view); return false; } @Override public void onClick(View view) { Log.i(TAG, "OnClickListener---onClick---" + view); } @Override public boolean dispatchTouchEvent(MotionEvent ev) { Log.i(TAG, "MainActivity ----- dispatchTouchEvent --- action" + ev.getAction()); return super.dispatchTouchEvent(ev); } @Override public void onUserInteraction() { Log.i(TAG, "MainActivity --- onUserInteraction "); super.onUserInteraction(); } @Override public boolean onTouchEvent(MotionEvent event) { Log.i(TAG, "MainActivity --- onTouchEvent --- action" + event.getAction()); return super.onTouchEvent(event); } }

自定义Button和Relativelayout的代码如下

package com.sparkhuu.testevent; import android.content.Context; import android.util.AttributeSet; import android.util.Log; import android.view.MotionEvent; import android.widget.Button; /** * author：sparkhuu * email:sparkhuu@gmail.com */ public class TestButton extends Button { public TestButton(Context context, AttributeSet attrs) { super(context, attrs); } @Override public boolean dispatchTouchEvent(MotionEvent event) { Log.i(MainActivity.TAG, "TestButton ----dispatchTouchEvent -- action" + event.getAction()); return super.dispatchTouchEvent(event); } @Override public boolean onTouchEvent(MotionEvent event) { Log.i(MainActivity.TAG, "TestButton ----onTouchEvent -- action" + event.getAction()); return super.onTouchEvent(event); } } package com.sparkhuu.testevent; import android.content.Context; import android.util.AttributeSet; import android.util.Log; import android.view.MotionEvent; import android.widget.RelativeLayout; /** * author：sparkhuu * email:sparkhuu@gmail.com */ public class TestRelatvieLayout extends RelativeLayout { public TestRelatvieLayout(Context context, AttributeSet attrs) { super(context, attrs); } @Override public boolean onInterceptTouchEvent(MotionEvent ev) { Log.i(MainActivity.TAG, "TestRelatvieLayout -- onInterceptTouchEvent----action" + ev.getAction()); return super.onInterceptTouchEvent(ev); } @Override public boolean dispatchTouchEvent(MotionEvent ev) { Log.i(MainActivity.TAG, "TestRelatvieLayout -- dispatchTouchEvent----action" + ev.getAction()); return super.dispatchTouchEvent(ev); } @Override public boolean onTouchEvent(MotionEvent event) { Log.i(MainActivity.TAG, "TestRelatvieLayout -- onTouchEvent----action" + event.getAction()); return super.onTouchEvent(event); } }

运行截图如下 可以发现，除了Activity中新添加的几个方法以外，其他的方法和之前分析的View和ViewGroup完全一致，对于Activity来说，Action_Down首先会触发dispatchTouchEvent，然后出发onUserInteraction,再次onTouchEvent,接着Action_Up事件触发dispatchTouchEvent后直接触发onTouchEvent也就说比down事件少触发了onInterceptaction事件。 点击Button外其他区域，日志如下 显而易见，和上面Button的结果类似 照样，我们从Activity的dispatchTouchEvent分析,源码走起

/** * 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(); } if (getWindow().superDispatchTouchEvent(ev)) { return true; } return onTouchEvent(ev); }

源码虽少，五脏俱全啊，显而易见，当触发事件是Action_down时，会调用onUserInteraction这就很好的解释了上面的困惑。下面分析下if (getWindow().superDispatchTouchEvent(ev)) { return true; }这个if判断，通过activity的attach方法可以发现这里的getWindow返回的就是PhoneWindow对象（PhoneWindow是Window的实现类），也就相当于调用PhoneWindow的superDispatchTouchEvent方法，我们先看下他的抽象类Window中的抽象方法如下

/** * 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);

从注释可以看出，用户不需要实现的方法，实际上也不行，在Activity中没有提供重写的机会，因为Window是以组合模式和Activity建立关系的，我们在看下PhoneWindow中的实现

public boolean superDispatchTouchEvent(MotionEvent event){ return mDecor.superDispatchTouchEvent(event); };

我们可以发现PhoneWindow的superDispatchTouchEvent方法内又调用了 mDecor.superDispatchTouchEvent，那么mDecor是什么呢？我们在PhoneWindow中可以发现mDecor是DecorView，DecorView本身是一个PhoneWindow的内部类，同时继承了FrameLayout实现了RootViewSurfaceTaker，他是一个真正的Activity的rootview，怎么验证它是不是rootview呢？我们可以通过Hierarchy Viewer来查看如下 可以看出，我们上面例子中setContentView，在xml中放入一个Relativelayout，这个Relativelayout中包含一个Button，上面显示这个RelatviLayout放在一个id为content的Framelayout中，我们还记得上面PhoneWindow的superDispatchTouchEvent返回了DecorView的superDispatchTouchEvent，而DecorView又是Framelayout的子类，Framelayout又是ViewGroup的子类，我们接下来看下DecorView的superDispatchTouchEvent方法

public boolean superDispatchTouchEvent(MotionEvent event){ return super.dispatchTouchEvent(event); };

搞了半天Activity中的dispatchTouchEvent的 if (getWindow().superDispatchTouchEvent(ev)) 本质上是ViewGroup的dispatchTouchEvent方法(这个ViewGroup是activity持有的root view 也就是id为content的FrameLayout) 总结： 1，首先会触发Activity的dispatchTouchEvent 2，dispatchTouchEvent如果是action_down会调用onUserInteraction 3，接着dispatchTouchEvent方法会通过Activity的root view（ID为content的framelayout）实质上是viewgroup，通过 super.dispatchTouchEvent(event)把touchevent派发给我们通过setcontentview设置的view 4，若activity下面的view拦截了touchevent（返回true），则Activity.onTouchEvent 不会执行 下面我们来看下onUserInteraction，代码如下

/** * Called whenever a key, touch, or trackball event is dispatched to the * activity. Implement this method if you wish to know that the user has * interacted with the device in some way while your activity is running. * This callback and {@link #onUserLeaveHint} are intended to help * activities manage status bar notifications intelligently; specifically, * for helping activities determine the proper time to cancel a notfication. * * <p>All calls to your activity's {@link #onUserLeaveHint} callback will * be accompanied by calls to {@link #onUserInteraction}. This * ensures that your activity will be told of relevant user activity such * as pulling down the notification pane and touching an item there. * * <p>Note that this callback will be invoked for the touch down action * that begins a touch gesture, but may not be invoked for the touch-moved * and touch-up actions that follow. * * @see #onUserLeaveHint() */ public void onUserInteraction() { }

这个方法是activity的一个方法，这个方法是空方法，那么在什么时候会调用呢？触屏点击home，menu，back键都会触发此方法，下拉statubar，旋转屏幕，锁屏不会触发，所以他会用在屏保应用上，因为当你触摸机器，马上就会触发一个事件，而这个事件又不确定是什么，正好屏保可以满足此需求，或者对于一个activity，控制多长时间没有用户相应的时候，自己消失 下面再来看下onTouchEvent

/** * 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) { if (mWindow.shouldCloseOnTouch(this, event)) { finish(); return true; } return false; }

如果一个锁屏事件没有被这个activity下任何view处理，activity的ontouchevent将会调用，这对于处理window边界之外的touch事件非常有用，因为通常是因为没有view会接受到他们，返回true表示已经消费事件，反之，则没有消费。从中看出重点就这句代码 if (mWindow.shouldCloseOnTouch(this, event))整理的mwindow就是上面的dispatchtouchevent中的getwindow对象，所以直接到window抽象类和phonewindow子类查看，发现PhoneWindow没有重写Window的shouldCloseOnTouch方法，看下Window中的shouldCloseOnTouch方法代码如下

/** @hide */ public boolean shouldCloseOnTouch(Context context, MotionEvent event) { if (mCloseOnTouchOutside && event.getAction() == MotionEvent.ACTION_DOWN && isOutOfBounds(context, event) && peekDecorView() != null) { return true; } return false; }

其实就是一个判断，判断mCloseOnTouchOutside标记是否为action_down事件，同时判断x，y坐标是不是超过Bounds，然后检查framelayout的id为content的DecorView是否为空

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