3. Activity的事件分发

案例

Activity代码：

public class Main2Activity extends AppCompatActivity {
    private static final String TAG = "-EVENT";

    private RelativeLayout ll_parent;
    private Button btn_test;

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

        ll_parent = findViewById(R.id.ll_parent);
        btn_test = (Button) findViewById(R.id.btn_test);

        btn_test.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                return false;
            }
        });

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

        btn_test.setOnLongClickListener(new View.OnLongClickListener() {
            @Override
            public boolean onLongClick(View v) {
                Log.d(TAG, "onLongClick: View");
                return false;
            }
        });

        ll_parent.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                Log.d(TAG, "onTouch: viewGroup  " + event.getAction());
                return false;
            }
        });

        ll_parent.setOnLongClickListener(new View.OnLongClickListener() {
            @Override
            public boolean onLongClick(View v) {
                Log.d(TAG, "onLongClick: viewGroup  ");
                return false;
            }
        });

        ll_parent.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Log.d(TAG, "onClick: viewGroup  ");
            }
        });

    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        Log.d(TAG, "onTouchEvent: Main2Activity" + event.getAction());
        return super.onTouchEvent(event);
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        Log.d(TAG, "dispatchTouchEvent: Main2Activity " + ev.getAction());
        return super.dispatchTouchEvent(ev);
    }
}

布局文件：

<com.jiang.eventtest.TestRelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/ll_parent"
    android:layout_width="150dp"
    android:layout_height="150dp"
    android:background="#7e8"
    tools:context="com.jiang.eventtest.MainActivity">

    <com.jiang.eventtest.TestButton
        android:id="@+id/btn_test"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_centerInParent="true"
        android:text="button" />
</com.jiang.eventtest.TestRelativeLayout>

然后页面是这样的

<meta charset="utf-8">

[图片上传失败...(image-ed5e48-1523543808448)] A843C7D122C.jpeg

点击按键：

03-23 14:34:35.174 9163-9163/com.jiang.eventtest D/-EVENT: dispatchTouchEvent: Main2Activity 0
03-23 14:34:35.174 9163-9163/com.jiang.eventtest D/-EVENT: dispatchTouchEvent: viewGroup 0
03-23 14:34:35.174 9163-9163/com.jiang.eventtest D/-EVENT: onInterceptTouchEvent: viewGroup 0
03-23 14:34:35.174 9163-9163/com.jiang.eventtest D/-EVENT: dispatchTouchEvent: View 0
03-23 14:34:35.174 9163-9163/com.jiang.eventtest D/-EVENT: onTouchEvent: View 0
03-23 14:34:35.204 9163-9163/com.jiang.eventtest D/-EVENT: dispatchTouchEvent: Main2Activity 1
03-23 14:34:35.204 9163-9163/com.jiang.eventtest D/-EVENT: dispatchTouchEvent: viewGroup 1
03-23 14:34:35.204 9163-9163/com.jiang.eventtest D/-EVENT: onInterceptTouchEvent: viewGroup 1
03-23 14:34:35.204 9163-9163/com.jiang.eventtest D/-EVENT: dispatchTouchEvent: View 1
03-23 14:34:35.204 9163-9163/com.jiang.eventtest D/-EVENT: onTouchEvent: View 1
03-23 14:34:35.204 9163-9163/com.jiang.eventtest D/-EVENT: onClick: View

点击空白区域：

03-23 14:34:47.874 9163-9163/com.jiang.eventtest D/-EVENT: dispatchTouchEvent: Main2Activity 0
03-23 14:34:47.874 9163-9163/com.jiang.eventtest D/-EVENT: onTouchEvent: Main2Activity0
03-23 14:34:47.934 9163-9163/com.jiang.eventtest D/-EVENT: dispatchTouchEvent: Main2Activity 1
03-23 14:34:47.934 9163-9163/com.jiang.eventtest D/-EVENT: onTouchEvent: Main2Activity1

从上面可以看到，事件的传递顺序：

Activity:dipatchTouchEvent-->

---------------ViewGroup:onInterceptTouchEvent-->dipatchTouchEvent-->

---------------------------------------------------------------------View:dispatchTouchEvent-->onTouchEvent

---

源码

PART 1

public boolean dispatchTouchEvent(MotionEvent ev) {
        if (ev.getAction() == MotionEvent.ACTION_DOWN) {
            //空方法，当屏幕上按键（返回，home）按下，接触当前Activity时都会调用，可以根据需求重写
            onUserInteraction();
        }
        if (getWindow().superDispatchTouchEvent(ev)) {
            return true;
        }
        return onTouchEvent(ev);
    }

然后这里有一个getWindow().superDispatchTouchEvent(ev)的调用。首先Window为抽象类，superDispatchTouchEvent为抽象方法，

这里的Window对象是根据Activity attch方法中

mWindow = new PhoneWindow(this, window, activityConfigCallback) 

PhoneWindow继承了Window并重写了superDispatchTouchEvent方法

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

而DecorView继承了FrameLayout也就是一个ViewGroup。所以getWindow().superDispatchTouchEvent(ev)就是把当前的事件分发出去，如果事件被消费则返回true

如果分发出去的事件未被消费则会调用onTouchEvent

    public boolean onTouchEvent(MotionEvent event) {
        if (mWindow.shouldCloseOnTouch(this, event)) {
            finish();
            return true;
        }

        return false;
    }

Window的shouldCloseOnTouch：

    public boolean shouldCloseOnTouch(Context context, MotionEvent event) {
        if (mCloseOnTouchOutside && event.getAction() == MotionEvent.ACTION_DOWN
                && isOutOfBounds(context, event) && peekDecorView() != null) {
            return true;
        }
        return false;
    }

1. mCloseOnTouchOutside是一个boolean变量，它是由Window的android:windowCloseOnTouchOutside属性值决定；
2. isOutOfBounds(context, event)判断当前事件是否是在Activiy之外，是返回true；
3. peekDecorView返回当前Acticvty对应的mDecor。