IssueTracker

I implemented the ScaleGestureListener interface just as described in the docs, created an instance to it in my custom View class and called the listener's onTouchEvent() in my View's onTouchEvent() function:

class MyScaleGestureListener implements ScaleGestureDetector.OnScaleGestureListener
{
    @Override
    public boolean onScale(ScaleGestureDetector detector)
    {
        // some irrelevant code
        return false;
    }

    @Override
    public boolean onScaleBegin(ScaleGestureDetector detector)
    {
        // more irrelevant code
        return false;
    }

    @Override
    public void onScaleEnd(ScaleGestureDetector detector)
    {
    }
}

I am skipping most of the custom View class because it s basically a View with a MyScaleGestureListener member. Here is the view's onTouchEvent():

    @Override
    public boolean onTouchEvent(MotionEvent event)
    {
        boolean result = mScaleGestureDetector.onTouchEvent(event);

        // result is always true here, so I need another way to check for a detected scaling gesture
        boolean isScaling = result = mScaleGestureDetector.isInProgress();
        if (!isScaling)
        {
            // if no scaling is performed check for other gestures (fling, long tab, etc.)
            result = mCommonGestureDetector.onTouchEvent(event);
        }

        // some irrelevant checks...

        return result ? result : super.onTouchEvent(event);
    }

As I mentioned in the comments, mScaleGestureDetector.onTouchEvent(event); always returns true. Irrelevant what is returned in the listener's onScale*() functions, it even returns true for non-scale MotionEvents like single taps or move actions.

This problem occurred on my Galaxy Tab (honeycomb/3.2) and on the emulator. I check the web and found other people having the same problem. Then I finally looked into the android 4.2.1 source file for the ScaleGestureDetector (here: https://android.googlesource.com/platform/frameworks/base/+/android-4.2.1_r1/core/java/android/view/ScaleGestureDetector.java) (I used that version because I thought that issue might have been fixed already) and actually there are only 'return true' statements used in that function.

Cheers!
Anselm