I have an application which uses GestureDetector and I am replacing some images onDown and onFling (aka onUp). However in some cases onFling is not called and the outcome is not pretty :)
Have you faced such issue and have you found a fix/workaround(besides using a timeout)?
Here is a little code:
final GestureDetector gdt1 = new GestureDetector(getApplicationContext(), new MyGestureDetector(mGestDetector, R.id.weatherFrame1));
FrameLayout weatherFrame1 = (FrameLayout)findViewById(R.id.weatherFrame1);
if (weatherFrame1 != null)
{
weatherFrame1.setOnTouchListener(new View.OnTouchListener()
{
@Override
public boolean onTouch(final View view, final MotionEvent event)
{
gdt1.onTouchEvent(event);
return true;
}
});
}
And here is part of MyGestureDetector.java
public class MyGestureDetector implements GestureDetector.OnGestureListener{
{
...
@Override
public boolean onDown(MotionEvent e)
{
int index = e.getActionIndex();
int pointerId = e.getPointerId(index);
if (startingPointerId == -1)
{
Log.i("MyGestureDetector", "Pointer is " + pointerId);
if (pointerId == 0)
{
startingPosX = e.getX(pointerId);
startingPosY = e.getY(pointerId);
startingPointerId = pointerId;
if (null != mGestureListener)
{
mGestureListener.onDown(mGestureOrigin);
}
}
}
return true;
}
@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY)
{
startingPointerId = -1;
if (null != mGestureListener)
{
mGestureListener.onUp(mGestureOrigin);
}
return true;
}
}
For detecting "up" and "down" events, I would recommend something simple like this:
@Override
public boolean onTouch(final View view, final MotionEvent event) {
if (event.getAction() == MotionEvent.ACTION_UP) {
// handle up event
} else if (event.getAction() == MotionEvent.ACTION_DOWN) {
// handle down event
}
}
Edit: The most likely reason onFling isn't being called every time is because it isn't simply a way to handle UP events. Looking at the Android source code, onFling is only called when the velocity reaches the minimum velocity required to be considered a "fling." Check it out:
case MotionEvent.ACTION_UP:
mStillDown = false;
MotionEvent currentUpEvent = MotionEvent.obtain(ev);
if (mIsDoubleTapping) {
// Finally, give the up event of the double-tap
handled |= mDoubleTapListener.onDoubleTapEvent(ev);
} else if (mInLongPress) {
mHandler.removeMessages(TAP);
mInLongPress = false;
} else if (mAlwaysInTapRegion) {
handled = mListener.onSingleTapUp(ev);
} else {
// A fling must travel the minimum tap distance
final VelocityTracker velocityTracker = mVelocityTracker;
velocityTracker.computeCurrentVelocity(1000, mMaximumFlingVelocity);
final float velocityY = velocityTracker.getYVelocity();
final float velocityX = velocityTracker.getXVelocity();
if ((Math.abs(velocityY) > mMinimumFlingVelocity)
|| (Math.abs(velocityX) > mMinimumFlingVelocity)){
handled = mListener.onFling(mCurrentDownEvent, ev, velocityX, velocityY);
}
}
Most notably:
if ((Math.abs(velocityY) > mMinimumFlingVelocity)
|| (Math.abs(velocityX) > mMinimumFlingVelocity)){
handled = mListener.onFling(mCurrentDownEvent, ev, velocityX, velocityY);
}