MotionEvents not firing

Question

Im trying to draw a square on a canvas but only the MotionEvent.ACTION_DOWN is run, and then the listener stops.

The idea is when the user touches the screen it get the x1 and y1 locations and every time the onTouch is fired it must draw the rect frim x1 y1 to the current location, and lastly save the last location in x2 y2 once the user lets go of the screen.

My code looks like this:

surfaceView.setOnTouchListener(new View.OnTouchListener()
{
    @Override
    public boolean onTouch(View v, MotionEvent event)
    {
        holder = surfaceView.getHolder();
        canvas = holder.lockCanvas();
        if(event.getAction() == MotionEvent.ACTION_DOWN)
        {
            x1=event.getX();
            y1=event.getY();
        }
        else if(event.getAction() == MotionEvent.ACTION_UP)
        {
            x2=event.getX();
            y2=event.getY();
        }
        canvas.drawRect(x1, y1, event.getX(), event.getY(), paint);
        holder.unlockCanvasAndPost(canvas);
        return true;
    }
});

Can anyone give me an example.

Yes only the MotionEvent.ACTION_DOWN is fired and then it stops. — string.Empty, Feb 27 '13 at 06:14
add implements Callback to your class like this final class Surface extends SurfaceView implements Callback — ShreeshaDas, Feb 27 '13 at 06:20
Need to check all code related to this listener, because part that you provided works fine in generic case. — SSemashko, Feb 27 '13 at 06:20
What is `surfaceView` ? Is it the instance of `SurfaceView` ? — GrIsHu, Feb 27 '13 at 06:52
Put this line inside your if condition as : `if(event.getAction() == MotionEvent.ACTION_DOWN) { x1=event.getX(); y1=event.getY(); canvas.drawRect(x1, y1, event.getX(), event.getY(), paint); }` — GrIsHu, Feb 27 '13 at 07:43
i solved my issue a different way, i used 2 pointers to draw the square. `public boolean onTouch(View v, MotionEvent event) { if(event.getPointerCount()==2) { holder = surfaceView.getHolder(); canvas = holder.lockCanvas(); canvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR); x1=event.getX(0); y1=event.getY(0); x2=event.getX(1); y2=event.getY(1); canvas.drawRect(x1, y1, x2, y2, paint); holder.unlockCanvasAndPost(canvas); } return true; }` — string.Empty, Feb 27 '13 at 08:14

score 1 · Accepted Answer · answered Feb 27 '13 at 08:26

ACTION_UP triggers from above code. Try the code below and you will see the log.

I think your problem may be related with the points you get. I don't know how you defined x1, y1, x2, y2 but when declared out of scope they must be final. Try this instead.

final SurfaceView s = (SurfaceView) findViewById(R.id.surface);

final RectF rect = new RectF();

s.setOnTouchListener(new OnTouchListener() {

    @Override
    public boolean onTouch(View v, MotionEvent event) {
        SurfaceHolder holder = s.getHolder();
        Canvas canvas = holder.lockCanvas();

        if(event.getAction() == MotionEvent.ACTION_DOWN) {
            Log.d("action", "down");
            rect.left = event.getX();
            rect.top = event.getY();
        }
        if(event.getAction() == MotionEvent.ACTION_UP){
            Log.d("action", "up");
            rect.right = event.getX();
            rect.bottom = event.getY();

            Paint paint = new Paint();
            paint.setColor(Color.RED);
            canvas.drawRect(rect, paint);
        }

        holder.unlockCanvasAndPost(canvas);
        return true;
    }
});

The x1, y1, x2, y2 are not final but i got it to work without them being final. but good answer. — string.Empty, Feb 27 '13 at 09:27
I have another problem now, even when i don't lift up it still sends a ACTION_CANCEL event. Do you know why this would happen? The log says: ACTION_DOWN ACTION_MOVE ACTION_MOVE ACTION_MOVE ACTION_CANCEL — string.Empty, Feb 27 '13 at 11:33
You just need to google it. It is explained here. http://stackoverflow.com/questions/6018309/action-cancel-while-touching — akaya, Feb 27 '13 at 11:38

score 0 · Answer 2 · answered Feb 27 '13 at 06:18

Try using this.

surfaceView.setOnTouchListener(new View.OnTouchListener()
{
    @Override
    public boolean onTouch(View v, MotionEvent event)
    {

        if(event.getAction() == MotionEvent.ACTION_DOWN)
        {
            x1=event.getX();
            y1=event.getY();
        }
        else if(event.getAction() == MotionEvent.ACTION_UP)
        {
            x2=event.getX();
            y2=event.getY();

            holder = surfaceView.getHolder();
            canvas = holder.lockCanvas();
            canvas.drawRect(x1, y1, x2, y2, paint);
            holder.unlockCanvasAndPost(canvas);
        }

        return true;
    }
});

If you move your finger it calls the listener every move you do. So this code

holder = surfaceView.getHolder();
canvas = holder.lockCanvas();

and this code

canvas.drawRect(x1, y1, event.getX(), event.getY(), paint);
holder.unlockCanvasAndPost(canvas);

Will be executed, maybe that's why it's stopping.

So I put the drawRect inside the MotionEvent.ACTION_UP condition, so the drawRect will be executed once.

MotionEvents not firing

2 Answers2