Android - basic gesture detection

I've been battling to get fling gesture detection working on my Android application today. I've been looking at these sources;

• Detect Gestures - Tutorial

• SDK docs

• Calculator Code

Nothing has worked for me so far and I was hoping for some pointers.

What I have is a GridLayout that contains 9 ImageViews. The source can be found here: Romain Guys's Grid Layout.

That file is take from Romain Guy's Photostream application and has only been slightly adapted.

For the simple click situation I need only set the onClickListener for each ImageView I add to be the main activity which implements View.OnClickListener. It seems infinitely more complicated to implement something that recognizes a fling. I presume this is because it may span views?

• If my activity implements OnGestureListener I don't know how to set that as the gesture listener for the Grid or the Image views that I add.

  public class SelectFilterActivity extends Activity implements
     View.OnClickListener, OnGestureListener { ...

• If my activity implements OnTouchListener then I have no onFling method to override (it has two events as parameters allowing me to determine if the fling was noteworthy).

  public class SelectFilterActivity extends Activity implements
      View.OnClickListener, OnTouchListener { ...

• If I make a custom View, like GestureImageView that extends ImageView I don't know how to tell the activity that a fling has occurred from the view. In any case, I tried this and the methods weren't called when I touched the screen.

I really just need a concrete example of this working across views. What, when and how should I attach this listener? I need to be able to detect single clicks also.

// Gesture detection
mGestureDetector = new GestureDetector(this, new GestureDetector.SimpleOnGestureListener() {

    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
        int dx = (int) (e2.getX() - e1.getX());
        // don't accept the fling if it's too short
        // as it may conflict with a button push
        if (Math.abs(dx) > MAJOR_MOVE && Math.abs(velocityX) > Math.absvelocityY)) {
            if (velocityX > 0) {
                moveRight();
            } else {
                moveLeft();
            }
            return true;
        } else {
            return false;
        }
    }
});

Is it possible to lay a transparent view over the top of my screen to capture flings? If I choose not to inflate my child image views from XML can I pass the GestureDetector as a constructor parameter to a new subclass of ImageView that I create?

This is the very simple activity that I'm trying to get the fling detection to work for:SelectFilterActivity (Adapted from photostream).

Any advice would be greatly appreciated. Apologies if the question is disjointed, please ask for clarification and I'll happily tell you the specifics of what I've tried.

• Android

• asked 8 years ago
• B Butts