Vertical and Horizontal gestures in Android

Question

I would like my GestureOverlayView to detect both purely horizontal as well as vertical gestures.

From http://android-developers.blogspot.com/2009/10/gestures-on-android-16.html

"orientation: indicates the scroll orientation of the views underneath. In this case the list scrolls vertically, which means that any horizontal gestures (like action_delete) can immediately be recognized as a gesture. Gestures that start with a vertical stroke must contain at least one horizontal component to be recognized. In other words, a simple vertical line cannot be recognized as a gesture since it would conflict with the list's scrolling."

Seems like a catch-22, if the android:orientation is set to vertical, I can only have horizontal swipes, and if the android:orientation is set to horizontal, I can only have vertical swipes. How can I get around this requirement?

Answer 1

I had run into this problem at a hackathon. There's no way you can solve it with GestureOverlayView, so you have to use motion events. GestureOverlayView however works with slightly more "detailed" gestures, like a circle. What I've noticed is that GestureOverlayView best works for closed figures. So, motionEvent sensor it is. I found the code here. I modified Gav's answer for vertical swipes too. Haven't tested it though, but positive that it should work.

Here's an example:

public class SelectFilterActivity extends Activity implements OnClickListener
{

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;
private GestureDetector gestureDetector;
View.OnTouchListener gestureListener;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    /* ... */

    // Gesture detection
    gestureDetector = new GestureDetector(new MyGestureDetector());
    gestureListener = new View.OnTouchListener() {
        public boolean onTouch(View v, MotionEvent event) {
            return gestureDetector.onTouchEvent(event);
        }
    };

}

class MyGestureDetector extends SimpleOnGestureListener {
    @Override
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
        try {
            // downward swipe
            if (Math.abs(e1.getY() - e2.getY()) > SWIPE_MAX_OFF_PATH && Math.abs(velocityY) > SWIPE_THRESHOLD_VELOCITY)
                Toast.makeText(SelectFilterActivity.this, "Downward Swipe", Toast.LENGTH_SHORT).show();
 else if (Math.abs(e2.getY() - e1.getY()) > SWIPE_MAX_OFF_PATH && Math.abs(velocityY) > SWIPE_THRESHOLD_VELOCITY)
                Toast.makeText(SelectFilterActivity.this, "Upward Swipe", Toast.LENGTH_SHORT).show();
            // right to left swipe
            else if(e1.getX() - e2.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {
                Toast.makeText(SelectFilterActivity.this, "Left Swipe", Toast.LENGTH_SHORT).show();
            }  else if (e2.getX() - e1.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {
                Toast.makeText(SelectFilterActivity.this, "Right Swipe", Toast.LENGTH_SHORT).show();
            }
        } catch (Exception e) {
            // nothing
        }
        return false;
    }

}

Now add it to the views where you'd like gesture detection,

// Do this for each view added to the grid
    imageView.setOnClickListener(SelectFilterActivity.this); 
    imageView.setOnTouchListener(gestureListener);

Cheers to Gav for the code!

Answer 2

All you have to do, is set the GestureStrokeAngleThreshold to a value closer to 90 (I used 90f)

The default value of the angle threashold is 40.0f because of which your simple vertical gestures would be skipped