Android View事件分发机制 三 (Activity）

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/u012417380/article/details/77990362

在上面两篇的分析中，我们知道View中的事件是由ViewGroup组件分发的，但是根ViewGroup又是由Activity承载的，所以这次我们探讨Actitity与事件分发机制的关系。

一、小例子分析

首先写一个小例子进行分析，该例子源码与上节中小例子源码基本相同，只是重写了Activity中几个方法。

1 项目源码

自定义Button

public class TestButton extends Button {

    public static final String CLICK_EXAMPLE_4 = "ClickExample4";

    public TestButton(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent event) {

        Log.i(CLICK_EXAMPLE_4,"TestButton dispatchTouchEvent--action= "+event.getAction());
        return super.dispatchTouchEvent(event);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        Log.i(CLICK_EXAMPLE_4,"TestButton onTouchEvent--action= "+event.getAction());
        return super.onTouchEvent(event);
    }
}

自定义LinearLayout

public class TestLinearLayout extends LinearLayout {

    public static final String CLICK_EXAMPLE_4 = "ClickExample4";

    public TestLinearLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        Log.i(CLICK_EXAMPLE_4,"TestLinearLayout onInterceptTouchEvent--action= "+ev.getAction());
        return super.onInterceptTouchEvent(ev);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        Log.i(CLICK_EXAMPLE_4,"TestLinearLayout onTouchEvent--action= "+event.getAction());
        return super.onTouchEvent(event);
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        Log.i(CLICK_EXAMPLE_4,"TestLinearLayout dispatchTouchEvent--action= "+ev.getAction());
        return super.dispatchTouchEvent(ev);
    }
}

布局文件：

<?xml version="1.0" encoding="utf-8"?>
<com.lengyu.free.example4.TestLinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/my_linear"
android:layout_width="match_parent" 
android:layout_height="match_parent"
android:gravity="center"

>

<com.lengyu.free.example4.TestButton
    android:id="@+id/my_btn"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Click Me!"/>
</com.lengyu.free.example4.TestLinearLayout>

MainActivity文件

public class MainActivity extends Activity implements View.OnClickListener,View.OnTouchListener{

    public static final String CLICK_EXAMPLE_4 = "ClickExample4";
    private  TestLinearLayout mLayout;
    private  TestButton mButton;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mButton=(TestButton)this.findViewById(R.id.my_btn);
        mLayout=(TestLinearLayout)this.findViewById(R.id.my_linear);
        mButton.setOnClickListener(this);
        mLayout.setOnClickListener(this);

        mButton.setOnTouchListener(this);
        mLayout.setOnTouchListener(this);
    }



    @Override
    public void onClick(View v) {
        Log.i(CLICK_EXAMPLE_4,"OnClickListener--onClick--"+v);
    }

    @Override
    public boolean onTouch(View v, MotionEvent event) {
        Log.i(CLICK_EXAMPLE_4,"OnTouchListener--onTouch--action="+event.getAction()+"--"+v);
        return false;
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {

        Log.i(CLICK_EXAMPLE_4,"MainActivity--dispatchTouchEvent--action="+ev.getAction());
        return super.dispatchTouchEvent(ev);
    }

    @Override
    public void onUserInteraction() {
        Log.i(CLICK_EXAMPLE_4,"MainActivity--onUserInteraction");
        super.onUserInteraction();
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        Log.i(CLICK_EXAMPLE_4,"MainActivity onTouchEvent--action= "+event.getAction());
        return super.onTouchEvent(event);
    }
}

2.事件分析

事件1：点击Button区域

09-15 05:40:45.361 8285-8285/com.lengyu.free.example4 I/ClickExample4: MainActivity--dispatchTouchEvent--action=0
09-15 05:40:45.361 8285-8285/com.lengyu.free.example4 I/ClickExample4: MainActivity--onUserInteraction
09-15 05:40:45.361 8285-8285/com.lengyu.free.example4 I/ClickExample4: TestLinearLayout dispatchTouchEvent--action= 0
09-15 05:40:45.361 8285-8285/com.lengyu.free.example4 I/ClickExample4: TestLinearLayout onInterceptTouchEvent--action= 0
09-15 05:40:45.361 8285-8285/com.lengyu.free.example4 I/ClickExample4: TestButton dispatchTouchEvent--action= 0
09-15 05:40:45.361 8285-8285/com.lengyu.free.example4 I/ClickExample4: OnTouchListener--onTouch--action=0--com.lengyu.free.example4.TestButton{b304e150 VFED..C. ......I. 166,345-313,417 #7f0c0051 app:id/my_btn}
09-15 05:40:45.361 8285-8285/com.lengyu.free.example4 I/ClickExample4: TestButton onTouchEvent--action= 0
09-15 05:40:45.461 8285-8285/com.lengyu.free.example4 I/ClickExample4: MainActivity--dispatchTouchEvent--action=1
09-15 05:40:45.461 8285-8285/com.lengyu.free.example4 I/ClickExample4: TestLinearLayout dispatchTouchEvent--action= 1
09-15 05:40:45.461 8285-8285/com.lengyu.free.example4 I/ClickExample4: TestLinearLayout onInterceptTouchEvent--action= 1
09-15 05:40:45.461 8285-8285/com.lengyu.free.example4 I/ClickExample4: TestButton dispatchTouchEvent--action= 1
09-15 05:40:45.461 8285-8285/com.lengyu.free.example4 I/ClickExample4: OnTouchListener--onTouch--action=1--com.lengyu.free.example4.TestButton{b304e150 VFED..C. ...P..I. 166,345-313,417 #7f0c0051 app:id/my_btn}
09-15 05:40:45.461 8285-8285/com.lengyu.free.example4 I/ClickExample4: TestButton onTouchEvent--action= 1
09-15 05:40:45.461 8285-8285/com.lengyu.free.example4 I/ClickExample4: OnClickListener--onClick--com.lengyu.free.example4.TestButton{b304e150 VFED..C. ...P..I. 166,345-313,417 #7f0c0051 app:id/my_btn}

可以看到分发ACTION_DOWN事件时，触发了Activity的dispatchTouchEvent 方法，onUserInteraction方法,接着触发了ViewGroup事件，和之前的一样，而分发ACTION_UP事件只触发了Activity的dispatchTouchEvent ，接着触发了ViewGroup事件

事件二： 点击Button区域之外的区域

09-15 05:41:56.662 8285-8285/com.lengyu.free.example4 I/ClickExample4: MainActivity--dispatchTouchEvent--action=0
09-15 05:41:56.662 8285-8285/com.lengyu.free.example4 I/ClickExample4: MainActivity--onUserInteraction
09-15 05:41:56.662 8285-8285/com.lengyu.free.example4 I/ClickExample4: TestLinearLayout dispatchTouchEvent--action= 0
09-15 05:41:56.662 8285-8285/com.lengyu.free.example4 I/ClickExample4: TestLinearLayout onInterceptTouchEvent--action= 0
09-15 05:41:56.662 8285-8285/com.lengyu.free.example4 I/ClickExample4: OnTouchListener--onTouch--action=0--com.lengyu.free.example4.TestLinearLayout{b304d9d8 V.E...C. ......I. 0,0-480,762 #7f0c0050 app:id/my_linear}
09-15 05:41:56.662 8285-8285/com.lengyu.free.example4 I/ClickExample4: TestLinearLayout onTouchEvent--action= 0
09-15 05:41:56.762 8285-8285/com.lengyu.free.example4 I/ClickExample4: MainActivity--dispatchTouchEvent--action=1
09-15 05:41:56.762 8285-8285/com.lengyu.free.example4 I/ClickExample4: TestLinearLayout dispatchTouchEvent--action= 1
09-15 05:41:56.762 8285-8285/com.lengyu.free.example4 I/ClickExample4: OnTouchListener--onTouch--action=1--com.lengyu.free.example4.TestLinearLayout{b304d9d8 V.E...C. ...P..I. 0,0-480,762 #7f0c0050 app:id/my_linear}
09-15 05:41:56.762 8285-8285/com.lengyu.free.example4 I/ClickExample4: TestLinearLayout onTouchEvent--action= 1
09-15 05:41:56.762 8285-8285/com.lengyu.free.example4 I/ClickExample4: OnClickListener--onClick--com.lengyu.free.example4.TestLinearLayout{b304d9d8 V.E...C. ...P..I. 0,0-480,762 #7f0c0050 app:id/my_linear}

可以看到分发ACTION_DOWN事件时，触发了Activity的dispatchTouchEvent 方法，onUserInteraction方法,接着触发了ViewGroup事件，和之前的一样，而分发ACTION_UP事件只触发了Activity的dispatchTouchEvent ，接着触发了ViewGroup事件

二、源码分析

然后我们查看Activity的源码

1.dispatchTouchEvent

 public boolean dispatchTouchEvent(MotionEvent ev) {
        if (ev.getAction() == MotionEvent.ACTION_DOWN) {
            onUserInteraction();
        }
        if (getWindow().superDispatchTouchEvent(ev)) {
            return true;
        }
        return onTouchEvent(ev);
    }

可以看到 行到行 ，如果是ACTION_DOWN事件，则先调用onUserInteraction方法，跟进去发现该方法是空的。

接着调用getWindow方法返回Window对象，并调用其中的superDispatchTouchEvent 方法.其实Window类是一个抽象类，superDispatchTouchEvent方法是其中的一个抽象方法。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);

注释提示不需要用户实现，而Window的真正唯一实现类是PhoneWindow，下面是PhoneWindow中的superDispatchTouchEvent(MotionEvent event)

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

可以看到调用mDecor 对象superDispatchTouchEvent 方法，mDecor 是 DecorView 类的一个实例，DecorView 是PhoneWindow 类的一个内部类，它继承自FrameLayout 类，查看
DecorView类的superDispatchTouchEvent 方法。

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

可以看到DecorView 类调用根布局Framlayout 的dispatchTouchEvent 。总结起来调用流程就是Activity.superDispatchTouchEvent->PhoneWindow.superDispatchTouchEvent->DecorView.superDispatchTouchEvent->FrameLayout(ViewGroup).dispatchTouchEvent

参考文章
http://blog.csdn.net/yanbober/article/details/45932123

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