How to detect click and longClick on canvas

Question

Hi i'm working on a Battleships game in Android and currently i'm trying to implement the ship positioning activity.

I have a custum view with onDraw representing the board on which you position the ships.

I want to be able to rotate ships by singletapping them and drag a ship by longclicking it. The thing is i can't just use onClick and onLongClick because i need to know where was the click on the canvas. I tried using onTouch but that didn't work. I also tried using GestureDetector but it just meseed up everything.

Do you have any suggestions on how to approach this logic?

score 0 · Answer 1 · edited May 23 '17 at 10:28

You will need to use View.OnTouchListener.

Set the touch listener to your canvas with view.setOnTouchListener(listener).
Implement your touch listener. You will need to implement the onTouch(View v, MotionEvent event) method. In this method, you will have access to the touch event, and you will be able to decide, if it is a simple click, a long press, etc, and do the appropriate action.

You can read more about it in this answer on SO.

score 0 · Accepted Answer · answered Nov 19 '15 at 05:47

i need to know where was the click on the canvas

You have a custom view, hence you can easily use GestureDetector.SimpleOnGestureListener. Just override the onTouchEvent() of your CustomView and use the onLongPress of the GestureDetector. I would suggest you to handle this within the CustomView itself, rather than do it in Activity or Fragment. This would keep things modularized.

You can follow the code below to get this done:

CustomView.java

public class CustomView extends View {

        private GestureDetectorCompat mGestureDetector;
        private LongPressGestureListener longPressGestureListener;

        CustomView(Context context, AttributeSet attrs) {
            super(context, attrs);
            longPressGestureListener= new LongPressGestureListener(this);
            mGestureDetector = new GestureDetectorCompat(context, longPressGestureListener);
        }

        @Override
        public boolean onTouchEvent(MotionEvent event) {
            mGestureDetector.onTouchEvent(event);
            // Handle any other event here, if not long press.
            return true;
        }
}

LongPressGestureListener.java

public class LongPressGestureListener extends GestureDetector.SimpleOnGestureListener {

        @Override
        public void onLongPress(MotionEvent e) {
            super.onLongPress(e);
            // e will give you the location and everything else you want
            // This is where you will be doing whatever you want to.
            int eIndex = MotionEventCompat.getActionIndex(e);
            float eX = MotionEventCompat.getX(e, eIndex);
            float eY = MotionEventCompat.getY(e, eIndex);
            Log.d("X:Y = " + eX + " : " + eY);
        }

        @Override
        public boolean onDown(MotionEvent e) {
            return true;
        }
}

How to detect click and longClick on canvas

2 Answers2