Android触摸事件传递机制（一）

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在开发过程中会经常遇到View与ViewGroup嵌套的问题，如ViewPager嵌套Fragment，而Fragment中又需要实现一个广告滑动，此时广告滑动就会与ViewPager的滑动事件产生冲突，而深入理解Android触摸事件的传递机制则是解决问题的关键。

一.触摸事件的类型（主要有三种）

1.MotionEvent.ACTION_DOWN：手指按下屏幕触发。
2.MotionEvent.ACTION_MOVE：手指在屏幕上移动触发。
3.MotionEvent.ACTION_UP：手指抬起时触发。

二.事件传递的三个阶段

1.方法介绍:

1).分发（DisPatch）：对应的方法为：public boolean dispatchTouchEvent(MotionEvent ev)，该方法的返回值决定了是否将事件向子视图传递：true:不传递；false：不传递；super.dispatchTouchEvent(ev)：传递。
2).拦截（InterCept）：对应的方法为：public boolean onInterceptTouchEvent(MotionEvent ev)，该方法只有ViewGroup和其子类才有，该方法的返回值决定了是否拦截事件：true：拦截；false：不拦截；super.onInterceptTouchEvent(ev)：不拦截。
3).消费（Consume）：对应的方法为：public boolean onTouchEvent(MotionEvent event)，该方法的返回值决定了是否处理该事件：true：处理；false：不处理；super.onTouchEvent(event)：将会调用onClick()方法。

2.Activity与View事件传递演示

1）.View代码（继承TextView重写onTouchEvent和dispatchTouchEvent方法）
public class MyTextView extends TextView {
    public MyTextView(Context context) {
        super(context);
    }

    public MyTextView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
    }

    public MyTextView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()){
            case MotionEvent.ACTION_DOWN:
                Log.e("MyTextView","onTouchEvent：ACTION_DOWN");
                break;
            case MotionEvent.ACTION_MOVE:
                Log.e("MyTextView","onTouchEvent：ACTION_MOVE");
                break;
            case MotionEvent.ACTION_UP:
                Log.e("MyTextView","onTouchEvent：ACTION_UP");
                break;
        }
        return super.onTouchEvent(event);
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent event) {
        switch (event.getAction()){
            case MotionEvent.ACTION_DOWN:
                Log.e("MyTextView","dispatchTouchEvent：ACTION_DOWN");
                break;
            case MotionEvent.ACTION_MOVE:
                Log.e("MyTextView","dispatchTouchEvent：ACTION_MOVE");
                break;
            case MotionEvent.ACTION_UP:
                Log.e("MyTextView","dispatchTouchEvent：ACTION_UP");
                break;
        }
        return super.dispatchTouchEvent(event);
    }
}
2）.Activity代码（重写dispatchTouchEvent和onTouchEvent并为MyTextView设置触摸事件）
public class MainActivity extends AppCompatActivity implements View.OnClickListener,View.OnTouchListener{

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        MyTextView myTextView=findViewById(R.id.tv);
        myTextView.setOnClickListener(this);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()){
            case MotionEvent.ACTION_DOWN:
                Log.e("MainActivity","onTouchEvent：ACTION_DOWN");
                break;
            case MotionEvent.ACTION_MOVE:
                Log.e("MainActivity","onTouchEvent：ACTION_MOVE");
                break;
            case MotionEvent.ACTION_UP:
                Log.e("MainActivity","onTouchEvent：ACTION_UP");
                break;
        }
        return super.onTouchEvent(event);
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        switch (ev.getAction()){
            case MotionEvent.ACTION_DOWN:
                Log.e("MainActivity","dispatchTouchEvent：ACTION_DOWN");
                break;
            case MotionEvent.ACTION_MOVE:
                Log.e("MainActivity","dispatchTouchEvent：ACTION_MOVE");
                break;
            case MotionEvent.ACTION_UP:
                Log.e("MainActivity","dispatchTouchEvent：ACTION_UP");
                break;
        }
        return super.dispatchTouchEvent(ev);
    }

    @Override
    public void onClick(View v) {
        Log.e("MyTextView","onClick");
    }

    @Override
    public boolean onTouch(View v, MotionEvent event) {
        switch (event.getAction()){
            case MotionEvent.ACTION_DOWN:
                Log.e("MainActivity","onTouch：ACTION_DOWN");
                break;
            case MotionEvent.ACTION_MOVE:
                Log.e("MainActivity","onTouch：ACTION_MOVE");
                break;
            case MotionEvent.ACTION_UP:
                Log.e("MainActivity","onTouch：ACTION_UP");
                break;
        }
        return false;
    }
}
3）.设置不同返回值时的结果
◇保持默认值
07-23 13:55:25.707 16976-16976/com.itfitness.viewandviewgroup E/MainActivity: dispatchTouchEvent：ACTION_DOWN
07-23 13:55:25.717 16976-16976/com.itfitness.viewandviewgroup E/MyTextView: dispatchTouchEvent：ACTION_DOWN
onTouchEvent：ACTION_DOWN
07-23 13:55:25.797 16976-16976/com.itfitness.viewandviewgroup E/MainActivity: dispatchTouchEvent：ACTION_UP
07-23 13:55:25.797 16976-16976/com.itfitness.viewandviewgroup E/MyTextView: dispatchTouchEvent：ACTION_UP
onTouchEvent：ACTION_UP
07-23 13:55:25.807 16976-16976/com.itfitness.viewandviewgroup E/MyTextView: onClick
◇改变Activity的dispatchTouchEvent方法返回值
true:（事件没有分发下去）
07-23 13:56:53.557 17565-17565/com.itfitness.viewandviewgroup E/MainActivity: dispatchTouchEvent：ACTION_DOWN
07-23 13:56:53.657 17565-17565/com.itfitness.viewandviewgroup E/MainActivity: dispatchTouchEvent：ACTION_UP
false：（事件同样没有分发下去）
07-23 13:58:16.377 18010-18010/com.itfitness.viewandviewgroup E/MainActivity: dispatchTouchEvent：ACTION_DOWN
07-23 13:58:16.457 18010-18010/com.itfitness.viewandviewgroup E/MainActivity: dispatchTouchEvent：ACTION_UP
◇改变MyTextView的dispatchTouchEvent方法返回值
true:（事件在MyTextView的dispatchTouchEvent方法被阻断）
07-23 13:59:39.087 18470-18470/com.itfitness.viewandviewgroup E/MainActivity: dispatchTouchEvent：ACTION_DOWN
07-23 13:59:39.087 18470-18470/com.itfitness.viewandviewgroup E/MyTextView: dispatchTouchEvent：ACTION_DOWN
07-23 13:59:39.177 18470-18470/com.itfitness.viewandviewgroup E/MainActivity: dispatchTouchEvent：ACTION_UP
07-23 13:59:39.187 18470-18470/com.itfitness.viewandviewgroup E/MyTextView: dispatchTouchEvent：ACTION_UP
false:（ACTION_DOWN事件在MyTextView的dispatchTouchEvent方法被阻断，并且MainActivity中执行了onTouchEvent方法）
07-23 14:03:03.517 19115-19115/com.itfitness.viewandviewgroup E/MainActivity: dispatchTouchEvent：ACTION_DOWN
07-23 14:03:03.517 19115-19115/com.itfitness.viewandviewgroup E/MyTextView: dispatchTouchEvent：ACTION_DOWN
07-23 14:03:03.517 19115-19115/com.itfitness.viewandviewgroup E/MainActivity: onTouchEvent：ACTION_DOWN
07-23 14:03:03.597 19115-19115/com.itfitness.viewandviewgroup E/MainActivity: dispatchTouchEvent：ACTION_UP
onTouchEvent：ACTION_UP
◇改变MyTextView的onTouchEvent返回值
true：（ACTION_DOWN事件传递到MyTextView并没有执行onClick方法）
07-23 14:07:47.317 20046-20046/com.itfitness.viewandviewgroup E/MainActivity: dispatchTouchEvent：ACTION_DOWN
07-23 14:07:47.317 20046-20046/com.itfitness.viewandviewgroup E/MyTextView: dispatchTouchEvent：ACTION_DOWN
onTouchEvent：ACTION_DOWN
07-23 14:07:47.387 20046-20046/com.itfitness.viewandviewgroup E/MainActivity: dispatchTouchEvent：ACTION_UP
07-23 14:07:47.387 20046-20046/com.itfitness.viewandviewgroup E/MyTextView: dispatchTouchEvent：ACTION_UP
onTouchEvent：ACTION_UP
false：（MyTextView没有消费事件反给了MainActivity并且没有执行onClick方法）
07-23 14:11:44.027 20717-20717/com.itfitness.viewandviewgroup E/MainActivity: dispatchTouchEvent：ACTION_DOWN
onTouchEvent：ACTION_DOWN
07-23 14:11:44.067 20717-20717/com.itfitness.viewandviewgroup E/MainActivity: dispatchTouchEvent：ACTION_UP
onTouchEvent：ACTION_UP

三.Activity与View事件传递总结

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