Question

i’ve got a class extended from simple on gesture and i’m working with the onfling method:

class MyGestureListener extends GestureDetector.SimpleOnGestureListener{
    @Override
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
            float velocityY) {
        // TODO Auto-generated method stub
        float e1_X = e1.getX();
        float e1_Y = e1.getY();
        float e2_X = e1.getX();
        float e2_Y = e2.getY();
        if(velocityX > 0 && velocityX > velocityY){
            text.setText("Swipe left");
        }else if(velocityX < 0 && velocityX < velocityY){
            text.setText("Swipe right");
        }else if(velocityY < 0 && velocityX > velocityY){
            text.setText("Swipe down");
        }else if(velocityY > 0 && velocityX < velocityY){
            text.setText("Swipe up");
        }
        return super.onFling(e1, e2, velocityX, velocityY);
    }
}

I know it depends on certain angles but i can’t do it, i tried with the velocityX, and velocityY, it’s working only if you do it precisely . But what i want is an angle of “mistake” : if you swipe diagonally for example up and right i need to choose which is the good way.

Answer 1

You should check speed and distance. Here is an example of horizontal swipe detector. You can add vertical detection in the same manner.

public class HSwipeDetector extends SimpleOnGestureListener {
    private static final int SWIPE_MIN_DISTANCE = 120;
    private static final int SWIPE_MAX_OFF_PATH = 250;
    private static final int SWIPE_THRESHOLD_VELOCITY = 200;

    @Override
    public boolean onFling(final MotionEvent e1, final MotionEvent e2, final float velocityX, final float velocityY) {
        if (Math.abs(e1.getY() - e2.getY()) > SWIPE_MAX_OFF_PATH) {  return false;  }

        /* positive value means right to left direction */
        final float distance = e1.getX() - e2.getX();
        final boolean enoughSpeed = Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY;
        if(distance > SWIPE_MIN_DISTANCE && enoughSpeed) {
            // right to left swipe
            onSwipeLeft();
            return true;
        }  else if (distance < -SWIPE_MIN_DISTANCE && enoughSpeed) {
            // left to right swipe
            onSwipeRight();
            return true;
        } else {
            // oooou, it didn't qualify; do nothing
            return false;
        }
    }

    protected void onSwipeLeft() { 
        // do your stuff here
    }

    protected void onSwipeRight() {   
        // do your stuff here
    }
}