Android GestureDetector with SimpleOnGestureListener within SurfaceView

问题

public class GameActivity extends Activity {
    private static final String TAG = "GameActivity";

   . . .

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

    . . .
}


public class GameView extends SurfaceView implements SurfaceHolder.Callback {
    private static final String TAG = "GameView";

    . . .

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

    private SimpleOnGestureListener gestureListener = new SimpleOnGestureListener() {
        private static final String TAG = "GestureListener";

        @Override
        public boolean onSingleTapConfirmed(MotionEvent event) {
            Log.d(TAG, "+ onSingleTapConfirmed(event:" + event + ")");
            singleTapDetected = true;
            Log.d(TAG, "- onSingleTapConfirmed()");
            return true;
        }

        @Override
        public boolean onDoubleTap(MotionEvent event) {
            Log.d(TAG, "+ onDoubleTap(event:" + event + ")");
            doubleTapDetected = true;
            Log.d(TAG, "- onDoubleTap()");
            return true;
        }
    };

    private GestureDetector gestureDetector = new GestureDetector(getContext(), gestureListener);

    . . .
}

I ran it on AVD an made a single click on the SurfaceView (GameView).
According to LogCat logs:

03-11 14:19:51.171: D/GameView(4839): + onTouchEvent(event:MotionEvent { action=ACTION_DOWN, id[0]=0, x[0]=1071.0, y[0]=437.0, toolType[0]=TOOL_TYPE_FINGER, buttonState=0, metaState=0, flags=0x0, edgeFlags=0x0, pointerCount=1, historySize=0, eventTime=27223172, downTime=27223172, deviceId=0, source=0x1002 })
03-11 14:19:51.171: D/GameView(4839): - onTouchEvent()
03-11 14:19:51.171: D/GameActivity(4839): + onTouchEvent(event:MotionEvent { action=ACTION_DOWN, id[0]=0, x[0]=1071.0, y[0]=437.0, toolType[0]=TOOL_TYPE_FINGER, buttonState=0, metaState=0, flags=0x0, edgeFlags=0x0, pointerCount=1, historySize=0, eventTime=27223172, downTime=27223172, deviceId=0, source=0x1002 })
03-11 14:19:51.171: D/GameActivity(4839): - onTouchEvent()
03-11 14:19:51.299: D/GameActivity(4839): + onTouchEvent(event:MotionEvent { action=ACTION_UP, id[0]=0, x[0]=1071.0, y[0]=437.0, toolType[0]=TOOL_TYPE_FINGER, buttonState=0, metaState=0, flags=0x0, edgeFlags=0x0, pointerCount=1, historySize=0, eventTime=27223303, downTime=27223172, deviceId=0, source=0x1002 })
03-11 14:19:51.299: D/GameActivity(4839): - onTouchEvent()

There are several questions:

Why the SimpleOnGestureListener was not called? (Even though onTouchEvent() was called and presummably the line gestureDetector.onTouchEvent(event); was executed)
Why the GameActivity's onTouchEvent() gets ACTION_DOWN and ACTION_UP, but the GameView's onTouchEvent() only gets ACTION_DOWN?

Some things I have tried

I implemented the GestureDetector on the GameActivity class with the same code as shown above and it worked as expected, calling onSingleTapConfirmed()
In GameView, instead of a private member SimpleOnGestureListener, created a private class GestureListener extends SimpleOnGestureListener and used it to construct the GestureDetector. I see the same behavior as described, no call to the listener.

回答1:

I debugged the code into the android source code, GestureDetector class. And this explains why SimpleOnGestureListener was not called:

The ACTION_DOWN is received and generates an internal TAP message to the GestureDetector message Handler.
The Handler calls the listener onSingleTapConfirmed() only if the event is not still down (!mStillDown)
The event is still down, because the ACTION_UP event was never received.

So you see, the two questions are related, when I find out why ACTION_UP is not issued I will solve the problem!

Edit

This completes the answer, now it is working.

The call to super.onTouchEvent() in GameView returns false, because the super class of SurfaceView is View, and it returns false. That's why ACTION_UP is never called
The call to super.onTouchEvent() in GameActivity returns true, that's why ACTION_UP is issued on GameActivity.

Note: If I set GameView.setclickable(true) then super.onTouchEvent() returns true. It is also an acceptable solution

Now my GameView code is:

@Override
public boolean onTouchEvent(MotionEvent event) {
    Log.d(TAG, "+ onTouchEvent(event:" + event + ")");
    gestureDetector.onTouchEvent(event);
    Log.d(TAG, "- onTouchEvent()");
    return true;
}

The current LogCat logs are:

03-11 16:32:06.629: D/GameView(5316): + onTouchEvent(event:MotionEvent { action=ACTION_DOWN, id[0]=0, x[0]=977.0, y[0]=414.0, toolType[0]=TOOL_TYPE_FINGER, buttonState=0, metaState=0, flags=0x0, edgeFlags=0x0, pointerCount=1, historySize=0, eventTime=35158623, downTime=35158623, deviceId=0, source=0x1002 })
03-11 16:32:06.629: D/GameView(5316): - onTouchEvent()
03-11 16:32:06.641: D/GameView(5316): + onTouchEvent(event:MotionEvent { action=ACTION_MOVE, id[0]=0, x[0]=978.0, y[0]=414.0, toolType[0]=TOOL_TYPE_FINGER, buttonState=0, metaState=0, flags=0x0, edgeFlags=0x0, pointerCount=1, historySize=0, eventTime=35158623, downTime=35158623, deviceId=0, source=0x1002 })
03-11 16:32:06.641: D/GameView(5316): - onTouchEvent()
03-11 16:32:06.772: D/GameView(5316): + onTouchEvent(event:MotionEvent { action=ACTION_UP, id[0]=0, x[0]=978.0, y[0]=414.0, toolType[0]=TOOL_TYPE_FINGER, buttonState=0, metaState=0, flags=0x0, edgeFlags=0x0, pointerCount=1, historySize=0, eventTime=35158772, downTime=35158623, deviceId=0, source=0x1002 })
03-11 16:32:06.772: D/GameView(5316): - onTouchEvent()
03-11 16:32:06.931: D/GestureListener(5316): + onSingleTapConfirmed(event:MotionEvent { action=ACTION_DOWN, id[0]=0, x[0]=977.0, y[0]=414.0, toolType[0]=TOOL_TYPE_FINGER, buttonState=0, metaState=0, flags=0x0, edgeFlags=0x0, pointerCount=1, historySize=0, eventTime=35158623, downTime=35158623, deviceId=0, source=0x1002 })
03-11 16:32:06.931: D/GestureListener(5316): - onSingleTapConfirmed()

来源：https://stackoverflow.com/questions/15341736/android-gesturedetector-with-simpleongesturelistener-within-surfaceview

标签

android

touch-event

gesturedetector