【转载】Android的事件分发(dispatchTouchEvent),拦截(onInterceptTouchEvent)与处理(onTouchEvent)

出处:https://blog.csdn.net/caifengyao/article/details/65437695

在Android中,View的结构是树状的,所以,当触发触摸事件的时候,其事件传递也是从上之下一层层的传递。下面我们结合例子来一点点进行分析。

首先,我们需要了解事件处理中的几个方法:

1、在ViewGroup中,事件分为dispatchTouchEvent(事件的分发),onInterceptTouchEvent(事件的拦截),onTouchEvent(事件的处理)。

2、在View中,事件分为dispatchTouchEvent(事件的分发),onTouchEvent(事件的处理)。

下面是demo的界面结构,它是由两个自定义的ViewGroup和一个自定义的View组成,并分别重写了它们的以上几个方法。


其中MyViewGroupA代码如下:

 

public class MyViewGroupA extends LinearLayout {
    public MyViewGroupA(Context context) {
        super(context);
    }

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

    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        switch (ev.getAction()){
            case MotionEvent.ACTION_DOWN:
                Log.i("MyViewGroupA","dispatchTouchEvent_ACTION_DOWN");
                break;
            case MotionEvent.ACTION_MOVE:
                Log.i("MyViewGroupA","dispatchTouchEvent_ACTION_MOVE");
                break;
            case MotionEvent.ACTION_UP:
                Log.i("MyViewGroupA","dispatchTouchEvent_ACTION_UP");
                break;
        }
        return super.dispatchTouchEvent(ev);
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        switch (ev.getAction()){
            case MotionEvent.ACTION_DOWN:
                Log.i("MyViewGroupA","onInterceptTouchEvent_ACTION_DOWN");
                break;
            case MotionEvent.ACTION_MOVE:
                Log.i("MyViewGroupA","onInterceptTouchEvent_ACTION_MOVE");
                break;
            case MotionEvent.ACTION_UP:
                Log.i("MyViewGroupA","onInterceptTouchEvent_ACTION_UP");
                break;
        }
        return super.onInterceptTouchEvent(ev);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()){
            case MotionEvent.ACTION_DOWN:
                Log.i("MyViewGroupA","onTouchEvent_ACTION_DOWN");
                break;
            case MotionEvent.ACTION_MOVE:
                Log.i("MyViewGroupA","onTouchEvent_ACTION_MOVE");
                break;
            case MotionEvent.ACTION_UP:
                Log.i("MyViewGroupA","onTouchEvent_ACTION_UP");
                break;
        }
        return super.onTouchEvent(event);
    }
}
MyViewGroupB代码如下:

 

 

public class MyViewGroupB extends LinearLayout {
    public MyViewGroupB(Context context) {
        super(context);
    }

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

    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        switch (ev.getAction()){
            case MotionEvent.ACTION_DOWN:
                Log.i("MyViewGroupB","dispatchTouchEvent_ACTION_DOWN");
                break;
            case MotionEvent.ACTION_MOVE:
                Log.i("MyViewGroupB","dispatchTouchEvent_ACTION_MOVE");
                break;
            case MotionEvent.ACTION_UP:
                Log.i("MyViewGroupB","dispatchTouchEvent_ACTION_UP");
                break;
        }
        return super.dispatchTouchEvent(ev);
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        switch (ev.getAction()){
            case MotionEvent.ACTION_DOWN:
                Log.i("MyViewGroupB","onInterceptTouchEvent_ACTION_DOWN");
                break;
            case MotionEvent.ACTION_MOVE:
                Log.i("MyViewGroupB","onInterceptTouchEvent_ACTION_MOVE");
                break;
            case MotionEvent.ACTION_UP:
                Log.i("MyViewGroupB","onInterceptTouchEvent_ACTION_UP");
                break;
        }
        return super.onInterceptTouchEvent(ev);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()){
            case MotionEvent.ACTION_DOWN:
                Log.i("MyViewGroupB","onTouchEvent_ACTION_DOWN");
                break;
            case MotionEvent.ACTION_MOVE:
                Log.i("MyViewGroupB","onTouchEvent_ACTION_MOVE");
                break;
            case MotionEvent.ACTION_UP:
                Log.i("MyViewGroupB","onTouchEvent_ACTION_UP");
                break;
        }
        return super.onTouchEvent(event);
    }
}
MyView代码如下:

 

 

public class MyView extends View {
    public MyView(Context context) {
        super(context);
    }

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

    @Override
    public boolean dispatchTouchEvent(MotionEvent event) {
        switch (event.getAction()){
            case MotionEvent.ACTION_DOWN:
                Log.i("MyView","dispatchTouchEvent_ACTION_DOWN");
                break;
            case MotionEvent.ACTION_MOVE:
                Log.i("MyView","dispatchTouchEvent_ACTION_MOVE");
                break;
            case MotionEvent.ACTION_UP:
                Log.i("MyView","dispatchTouchEvent_ACTION_UP");
                break;
        }
        return super.dispatchTouchEvent(event);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()){
            case MotionEvent.ACTION_DOWN:
                Log.i("MyView","onTouchEvent_ACTION_DOWN");
                break;
            case MotionEvent.ACTION_MOVE:
                Log.i("MyView","onTouchEvent_ACTION_MOVE");
                break;
            case MotionEvent.ACTION_UP:
                Log.i("MyView","onTouchEvent_ACTION_UP");
                break;
        }
        return super.onTouchEvent(event);
    }
}

我们说过,事件传递是由上到下的,所以最外层的View首先对事件进行操作。而我们最外层是Activity,所以事件也是从这里开始。
Activity代码如下:

 

 

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
    @Override
    public boolean dispatchTouchEvent(MotionEvent event) {
        switch (event.getAction()){
            case MotionEvent.ACTION_DOWN:
                Log.i("Activity","dispatchTouchEvent_ACTION_DOWN");
                break;
            case MotionEvent.ACTION_MOVE:
                Log.i("Activity","dispatchTouchEvent_ACTION_MOVE");
                break;
            case MotionEvent.ACTION_UP:
                Log.i("Activity","dispatchTouchEvent_ACTION_UP");
                break;
        }
        return super.dispatchTouchEvent(event);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()){
            case MotionEvent.ACTION_DOWN:
                Log.i("Activity","onTouchEvent_ACTION_DOWN");
                break;
            case MotionEvent.ACTION_MOVE:
                Log.i("Activity","onTouchEvent_ACTION_MOVE");
                break;
            case MotionEvent.ACTION_UP:
                Log.i("Activity","onTouchEvent_ACTION_UP");
                break;
        }
        return super.onTouchEvent(event);
    }
}

现在我们通过触摸MyView开始进行分析。虽然dispatchTouchEvent是事件开始的第一步,但是在开发中,我们通常很少改写它,所以我们下面只讨论其他两个方法。

 

1、对以上方法均不作处理,都返回super。这意味着我们既不拦截,也不消费。

大家看输出结果:

I/Activity: dispatchTouchEvent_ACTION_DOWN


I/MyViewGroupA: dispatchTouchEvent_ACTION_DOWN
I/MyViewGroupA: onInterceptTouchEvent_ACTION_DOWN


I/MyViewGroupB: dispatchTouchEvent_ACTION_DOWN
I/MyViewGroupB: onInterceptTouchEvent_ACTION_DOWN


I/MyView: dispatchTouchEvent_ACTION_DOWN
I/MyView: onTouchEvent_ACTION_DOWN


I/MyViewGroupB: onTouchEvent_ACTION_DOWN
I/MyViewGroupA: onTouchEvent_ACTION_DOWN
I/Activity: onTouchEvent_ACTION_DOWN


I/Activity: dispatchTouchEvent_ACTION_MOVE
I/Activity: onTouchEvent_ACTION_MOVE


I/Activity: dispatchTouchEvent_ACTION_UP
I/Activity: onTouchEvent_ACTION_UP

结合输出结果,我们可以总结出以下的结论:

  
结合流程图,不难发现,如果我对事件既不拦截,也不消费,当触发ACTION_DOWN的时候,事件会经过Activity——MyViewGroupA——MyViewGroupB——MyView一层层的向下进行dispatchTouchEvent(分发)—onInterceptTouchEvent(拦截)调用。当到达最底层MyView后,开始触发消费操作,因为我均不消费,ACTION_DOWN将由底层一层层向上冒,移交上层处理。当抵达最上层Activity后,说明下层均不消费,之后触发的ACTION_MOVE和ACTION_UP将不再向下层分发传递,直接交由Activity分发给自己进行处理。

2、我们将MyVIewGroupB的onInterceptTouchEvent返回值改为true,其他均是super。这意味着仅仅MyViewGroupB进行事件拦截,但均无消费

输出结果如下:

I/Activity: dispatchTouchEvent_ACTION_DOWN


I/MyViewGroupA: dispatchTouchEvent_ACTION_DOWN
I/MyViewGroupA: onInterceptTouchEvent_ACTION_DOWN


I/MyViewGroupB: dispatchTouchEvent_ACTION_DOWN
I/MyViewGroupB: onInterceptTouchEvent_ACTION_DOWN


I/MyViewGroupB: onTouchEvent_ACTION_DOWN
I/MyViewGroupA: onTouchEvent_ACTION_DOWN
I/Activity: onTouchEvent_ACTION_DOWN


I/Activity: dispatchTouchEvent_ACTION_MOVE
I/Activity: onTouchEvent_ACTION_MOVE


I/Activity: dispatchTouchEvent_ACTION_UP
I/Activity: onTouchEvent_ACTION_UP

结合输出结果,总结如下:


当触发ACTION_DOWN的时候,事件依然是从Activity开始一层层向下传递,当传递到MyViewGroupB时,因为进行了事件拦截,所以执行完onInterceptTouchEvent后不再向下传递,而是直接交由MyViewGroupB的onTouchEvent进行消费处理。由于我们是只拦截,不消费,所以事件向上传递,交由上层处理,最终回到Activity。之后触发的ACTION_MOVE和ACTION_UP也不再向下传递,直接交由Activity分发给自己处理。

3、我们还是将MyViewGroupB的onInterceptTouchEvent返回super,但是将他的onTouchEvent返回true。这意味着我们不拦截,但是由MyViewGroupB进行事件处理。

输出结果如下:

I/Activity: dispatchTouchEvent_ACTION_DOWN


I/MyViewGroupA: dispatchTouchEvent_ACTION_DOWN
I/MyViewGroupA: onInterceptTouchEvent_ACTION_DOWN


I/MyViewGroupB: dispatchTouchEvent_ACTION_DOWN
I/MyViewGroupB: onInterceptTouchEvent_ACTION_DOWN


I/MyView: dispatchTouchEvent_ACTION_DOWN
I/MyView: onTouchEvent_ACTION_DOWN
I/MyViewGroupB: onTouchEvent_ACTION_DOWN


I/Activity: dispatchTouchEvent_ACTION_MOVE
I/MyViewGroupA: dispatchTouchEvent_ACTION_MOVE
I/MyViewGroupA: onInterceptTouchEvent_ACTION_MOVE
I/MyViewGroupB: dispatchTouchEvent_ACTION_MOVE
I/MyViewGroupB: onTouchEvent_ACTION_MOVE


I/Activity: dispatchTouchEvent_ACTION_UP
I/MyViewGroupA: dispatchTouchEvent_ACTION_UP
I/MyViewGroupA: onInterceptTouchEvent_ACTION_UP
I/MyViewGroupB: dispatchTouchEvent_ACTION_UP
I/MyViewGroupB: onTouchEvent_ACTION_UP

结合输出结果,总结如下:


可以看出,当触发ACTION_DOWN的时候,事件的分发传递过程和1的时候一样,从Activity开始一层层向下传递,最终传递到最底层MyView,触发消费操作,然后MyView将消费操作移交上层处理,然后到达MyViewGroupB的onTouchEvent,并且进行了消费处理,事件处理到此不在向上移交。当触发ACTION_MOVE和ACTION_UP操作时,事件依然需要由Activity开始向下分发传递,但是当传递到MyViewGroupB后,由于其消费了ACTION_DOWN,事件将不再继续向下分发,而是直接由MyViewGroupB分发给自己的onTouchEvent进行继续处理。事件处理也不再向上移交。

4、将MyViewGroupB的onInterceptTouchEvent和onTouchEvent的返回值均改为true。这意味着既拦截,又消费。

输出结果如下:

I/Activity: dispatchTouchEvent_ACTION_DOWN


I/MyViewGroupA: dispatchTouchEvent_ACTION_DOWN
I/MyViewGroupA: onInterceptTouchEvent_ACTION_DOWN


I/MyViewGroupB: dispatchTouchEvent_ACTION_DOWN
I/MyViewGroupB: onInterceptTouchEvent_ACTION_DOWN


I/MyViewGroupB: onTouchEvent_ACTION_DOWN


I/Activity: dispatchTouchEvent_ACTION_MOVE
I/MyViewGroupA: dispatchTouchEvent_ACTION_MOVE
I/MyViewGroupA: onInterceptTouchEvent_ACTION_MOVE
I/MyViewGroupB: dispatchTouchEvent_ACTION_MOVE
I/MyViewGroupB: onTouchEvent_ACTION_MOVE


I/Activity: dispatchTouchEvent_ACTION_UP
I/MyViewGroupA: dispatchTouchEvent_ACTION_UP
I/MyViewGroupA: onInterceptTouchEvent_ACTION_UP
I/MyViewGroupB: dispatchTouchEvent_ACTION_UP
I/MyViewGroupB: onTouchEvent_ACTION_UP

结合输出结果,总结如下:


当触发ACTION_DOWN的时候,依然从Activity开始向下传递,当到达MyViewGroupB的是,因为在onInterceptTouchEvent进行了拦截操作,因此不再继续向下分发传递,而是交由MyViewGroupB的onTouchEvent进行处理消费。MyViewGroupB的onTouchEvent返回的是true,说明它决定对ACTION_DOWN进行处理,因此事件也就不再移交上层处理。当触发ACTION_MOVE和ACTION_UP的时候,事件还是从Activity开始向下传递,当到达MyViewGroupB的时候,由于之前进行了拦截操作,因此,MyViewGroupB直接将事件分发给自己的onTouchEvent进行处理,不在向下分发传递。事件处理也不再向上层移交。

 

案例Demo下载地址:点击打开链接

阅读更多

 

posted @ 2018-05-16 01:04  Blue_Keroro  阅读(1153)  评论(0编辑  收藏  举报