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Android的事件分发机制

Android的事件有点击事件、滑动事件等，这些都是由触摸事件组成的，如点击事件就是由触摸ACTION_DOWN(按下屏幕事件)和ACTION_UP（离开事件）组成。

以下分析一下Android事件分发机制，先post上一些代码：

父容器，继承ViewGroup，重写了dispatchTouchEvent(MotionEvent ev)，onInterceptTouchEvent(MotionEvent ev)和onTouchEvent(MotionEvent ev)函数

import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.widget.LinearLayout;

public class TouchEventFather extends LinearLayout {

    public TouchEventFather(Context context) {
        super(context);
    }

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

    public boolean dispatchTouchEvent(MotionEvent ev) {
        LogUtil.d("TouchEventFather | dispatchTouchEvent --> " + TouchEventUtil.getTouchAction(ev.getAction()));
        return super.dispatchTouchEvent(ev);
    }

    public boolean onInterceptTouchEvent(MotionEvent ev) {
        LogUtil.d("TouchEventFather | onInterceptTouchEvent --> " + TouchEventUtil.getTouchAction(ev.getAction()));
        return super.onInterceptTouchEvent(ev);
        //return false;
    }

    public boolean onTouchEvent(MotionEvent ev) {
        LogUtil.d("TouchEventFather | onTouchEvent -->" + TouchEventUtil.getTouchAction(ev.getAction()));
        return super.onTouchEvent(ev);
    }

}

子控件，继承View，重写了dispatchTouchEvent(MotionEvent ev)，onTouchEvent(MotionEvent ev)函数

import android.R.bool;
import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.widget.Button;
import android.widget.LinearLayout;

public class TouchEventChild extends Button {

    public TouchEventChild(Context context) {
        super(context);
    }

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

    public boolean dispatchTouchEvent(MotionEvent ev) {
        LogUtil.d(" TouchEventChilds | dispatchTouchEvent --> " + TouchEventUtil.getTouchAction(ev.getAction()));

        //super.dispatchTouchEvent(ev);
        return super.dispatchTouchEvent(ev);
        //return true;
    }


    public boolean onTouchEvent(MotionEvent ev) {
        boolean childEvent = super.onTouchEvent(ev);
        LogUtil.d("super.onTouchEvent(ev)返回值:" + childEvent +" TouchEventChilds | onTouchEvent --> " + TouchEventUtil.getTouchAction(ev.getAction()));
        return false;
    }

}

Activity页面，布局里有一个父容器和子控件，并且分别实现了OnClickListener和OnTouchListener接口。

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Button;

public class TouchEventActivity extends Activity {

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        TouchEventFather father = (TouchEventFather) findViewById(R.id.father);
        TouchEventChild child = (TouchEventChild) findViewById(R.id.childs);
        Button btn = (Button) findViewById(R.id.btn);

        father.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                LogUtil.d("father | onclick --> ");
            }
        });

        father.setOnTouchListener(new View.OnTouchListener() {

            @Override
            public boolean onTouch(View v, MotionEvent event) {
                LogUtil.d("father | onTouch --> "
                        + TouchEventUtil.getTouchAction(event.getAction()));
                return false;
            }
        });

        child.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                LogUtil.d("child | onclick --> ");
            }
        });

        child.setOnTouchListener(new View.OnTouchListener() {

            @Override
            public boolean onTouch(View v, MotionEvent event) {
                LogUtil.d("child | onTouch --> "
                        + TouchEventUtil.getTouchAction(event.getAction()));
                return false;
            }
        });
    }

    public boolean dispatchTouchEvent(MotionEvent ev) {
        LogUtil.d("TouchEventActivity | dispatchTouchEvent --> "
                + TouchEventUtil.getTouchAction(ev.getAction()));
        return super.dispatchTouchEvent(ev);
    }

    public boolean onTouchEvent(MotionEvent event) {
        LogUtil.d("TouchEventActivity | onTouchEvent --> "
                + TouchEventUtil.getTouchAction(event.getAction()));

        return super.onTouchEvent(event);
    }

}

运行程序，打印出来的信息为：

- ::: I/System.out(): zrp: TouchEventActivity | dispatchTouchEvent --> ACTION_DOWN
- ::: I/System.out(): zrp: TouchEventFather | dispatchTouchEvent --> ACTION_DOWN
- ::: I/System.out(): zrp: TouchEventFather | onInterceptTouchEvent --> ACTION_DOWN
- ::: I/System.out(): zrp:  TouchEventChilds | dispatchTouchEvent --> ACTION_DOWN
- ::: I/System.out(): zrp: child | onTouch --> ACTION_DOWN
- ::: I/System.out(): zrp: super.onTouchEvent(ev)返回值:true TouchEventChilds | onTouchEvent --> ACTION_DOWN
- ::: I/System.out(): zrp: TouchEventActivity | dispatchTouchEvent --> ACTION_UP
- ::: I/System.out(): zrp: TouchEventFather | dispatchTouchEvent --> ACTION_UP
- ::: I/System.out(): zrp: TouchEventFather | onInterceptTouchEvent --> ACTION_UP
- ::: I/System.out(): zrp:  TouchEventChilds | dispatchTouchEvent --> ACTION_UP
- ::: I/System.out(): zrp: child | onTouch --> ACTION_UP
- ::: I/System.out(): zrp: super.onTouchEvent(ev)返回值:true TouchEventChilds | onTouchEvent --> ACTION_UP
- ::: I/System.out(): zrp: child | onclick -->

事件分发事件：1.ACTION_DOWN的事件传递：Activity的dispatchTouchEvent–>父容器的dispatchTouchEvent–>父容器的onInterceptTouchEvent–>子控件的dispatchTouchEvent–>子控件的OnTouchListener的onTouch–>onTouchEvent(ev) ;

接下来是ACTION_UP的事件传递：dispatchTouchEvent–>父容器的dispatchTouchEvent–>父容器的onInterceptTouchEvent–>子控件的dispatchTouchEvent–>子控件的OnTouchListener的onTouch–>onTouchEvent(ev) –>onclick;

ACTION_DOWN和ACTION_UP后，会把事件传递给OnClickListener的onclick

如果子控件的onTouch返回true，打印信息为

- ::: I/System.out(): zrp: TouchEventActivity | dispatchTouchEvent --> ACTION_DOWN
- ::: I/System.out(): zrp: TouchEventFather | dispatchTouchEvent --> ACTION_DOWN
- ::: I/System.out(): zrp: TouchEventFather | onInterceptTouchEvent --> ACTION_DOWN
- ::: I/System.out(): zrp:  TouchEventChilds | dispatchTouchEvent --> ACTION_DOWN
- ::: I/System.out(): zrp: child | onTouch --> ACTION_DOWN
- ::: I/System.out(): zrp: TouchEventActivity | dispatchTouchEvent --> ACTION_UP
- ::: I/System.out(): zrp: TouchEventFather | dispatchTouchEvent --> ACTION_UP
- ::: I/System.out(): zrp: TouchEventFather | onInterceptTouchEvent --> ACTION_UP
- ::: I/System.out(): zrp:  TouchEventChilds | dispatchTouchEvent --> ACTION_UP
- ::: I/System.out(): zrp: child | onTouch --> ACTION_UP

onTouchEvent没有被调用，最终up事件没有传递到OnClickListener的onClick。

子控件onTouchEvent默认返回true，就是允许消费事件，若返回false，子控件不消费接下来的事件。打印的消息为：

- ::: I/System.out(): zrp: TouchEventActivity | dispatchTouchEvent --> ACTION_DOWN
- ::: I/System.out(): zrp: TouchEventFather | dispatchTouchEvent --> ACTION_DOWN
- ::: I/System.out(): zrp: TouchEventFather | onInterceptTouchEvent --> ACTION_DOWN
- ::: I/System.out(): zrp:  TouchEventChilds | dispatchTouchEvent --> ACTION_DOWN
- ::: I/System.out(): zrp: child | onTouch --> ACTION_DOWN
- ::: I/System.out(): zrp: super.onTouchEvent(ev)返回值:true TouchEventChilds | onTouchEvent --> ACTION_DOWN
- ::: I/System.out(): zrp: father | onTouch --> ACTION_DOWN
- ::: I/System.out(): zrp: TouchEventFather | onTouchEvent -->ACTION_DOWN
- ::: I/System.out(): zrp: TouchEventActivity | dispatchTouchEvent --> ACTION_UP
- ::: I/System.out(): zrp: TouchEventFather | dispatchTouchEvent --> ACTION_UP
- ::: I/System.out(): zrp: father | onTouch --> ACTION_UP
- ::: I/System.out(): zrp: TouchEventFather | onTouchEvent -->ACTION_UP
- ::: I/System.out(): zrp: father | onclick -->

总结：子控件不消费事件，会把事件传递给父容器，接下来的事件都会传递给父容器。若子控件消费事件，不会把事件传递给父容器，则父容器onTouchEvent、onTouch和onClick方法不会被调用。

完整demo：http://download.csdn.net/detail/chen20142015/9801799

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