Android 事件拦截

1、事件的三种状态

1、分发：dispatchTouchEvent;
2、拦截：onInterceptTouchEvent；
3、处理：onTouchEvent；

结论：
1、ViewGroup只有dispatchTouchEvent、onInterceptTouchEvent和onTouchEvent;
1、View只有dispatchTouchEvent和onTouchEvent;

2、公共代码

实例图.png

 btn_click.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Log.e(TAG, "onClick");
            }
        });

<?xml version="1.0" encoding="utf-8"?>
<com.leo.clickevent.MyFrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity"
    android:background="@color/teal_700"
    >


    <com.leo.clickevent.MyButton
        android:id="@+id/btn_click"
        android:layout_width="200dp"
        android:layout_height="200dp"
        android:background="@color/purple_200"
        android:text="子控件"
        />

</com.leo.clickevent.MyFrameLayout>

//自定义MyButton 
public class MyButton extends Button {
    private static final String TAG = "lyy";

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

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

    public MyButton(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    // 只要事件来到改View，这个方法肯定执行
    @Override
    public boolean dispatchTouchEvent(MotionEvent event) {
        Log.e(TAG, "dispatchTouchEvent: 子View");
        return super.dispatchTouchEvent(event);
    }

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

}

3、viewGroup拦截

//自定义MyFrameLayout 
public class MyFrameLayout extends FrameLayout {
    private static final String TAG = "lyy";

    public MyFrameLayout(@NonNull Context context) {
        super(context);
    }

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

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

    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        Log.e(TAG, "dispatchTouchEvent: 父容器");
        return super.dispatchTouchEvent(ev);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        Log.e(TAG, "onTouchEvent: 父容器");
        return super.onTouchEvent(event);
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        Log.e(TAG, "onInterceptTouchEvent: 父容器");
//        return super.onInterceptTouchEvent(ev);
        //返回为true，代表拦截
        return true;
    }
}

点击子View执行结果：

dispatchTouchEvent: 父容器
onInterceptTouchEvent: 父容器
onTouchEvent: 父容器

1、可以看到执行了ViewGroup的 dispatchTouchEvent、onInterceptTouchEvent、和onTouchEvent；

4、viewGroup不拦截

public class MyFrameLayout extends FrameLayout {
    private static final String TAG = "lyy";

    public MyFrameLayout(@NonNull Context context) {
        super(context);
    }

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

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

    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        Log.e(TAG, "dispatchTouchEvent: 父容器");
        return super.dispatchTouchEvent(ev);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        Log.e(TAG, "onTouchEvent: 父容器");
        return super.onTouchEvent(event);
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        Log.e(TAG, "onInterceptTouchEvent: 父容器");
        //不拦截
        return super.onInterceptTouchEvent(ev);
    }
}

点击子View执行结果：

dispatchTouchEvent: 父容器
onInterceptTouchEvent: 父容器
dispatchTouchEvent: 子View
onTouchEvent: MotionEvent.ACTION_DOWN = 0
dispatchTouchEvent: 父容器
onInterceptTouchEvent: 父容器
dispatchTouchEvent: 子View
onTouchEvent: MotionEvent.ACTION_UP = 1

1、可以看到先执行ViewGroup的dispatchTouchEvent、onInterceptTouchEvent然后执行子View的onTouchEvent: MotionEvent.ACTION_DOWN ；
2、接着执行ViewGroup的dispatchTouchEvent、onInterceptTouchEvent然后执行子View的onTouchEvent: MotionEvent.ACTION_UP；