The problem comes from the VelocityTracker used by the
GestureDetector. The tracker has a pool of 1 instance but there's a
bug in the pool management which causes both your GestureDetector and
ListView to use the *same* VelocityTracker. This means the tracker
receives most events twice.
I just fixed this issue in Cupcake.
On Tue, Mar 31, 2009 at 4:01 PM, focuser <linto...@gmail.com> wrote:
>
> OK, but could you explain briefly why the GestureDetector would have
> such side effect? In the code above I don't see any events being
> stolen nor any new events being created. Original events are just
> passed to FrameLayout.dispatchTouchEvent as if there's no
> GestureDetector used.
>
> I even tried the following but it makes no difference.
> public boolean dispatchTouchEvent(MotionEvent ev) {
> MotionEvent oldEv = ev.obtain();
> boolean handled = mGestureDetector.onTouchEvent(ev);
> return super.dispatchTouchEvent(oldEv);
> }
>
> On Mar 31, 12:07 pm, Romain Guy <romain...@google.com> wrote:
>> Unfortunately I don't see any possible workaround :(
>>
>>
>>
>> On Tue, Mar 31, 2009 at 11:40 AM, focuser <linto...@gmail.com> wrote:
>>
>> > Thanks Romain,
>>
>> > I have just filed ithttp://code.google.com/p/android/issues/detail?id=2337.
>>
>> > But before it's fixed in a new release, is there any workaround or I
>> > will have to play with the VelocityTracker myself?
>>
>> > On Mar 31, 10:39 am, Romain Guy <romain...@google.com> wrote:
>> >> Hi,
>>
>> >> It looks like a bug in the VelocityTracker. Can you please file it at
>> >> b.android.com? Thanks
>>
>> >> On Tue, Mar 31, 2009 at 10:28 AM, focuser <linto...@gmail.com> wrote:
>>
>> >> > Hi,
>>
>> >> > I'm trying to use a GestureDetector in a subclass of FrameLayout,
>> >> > which has a child ListView.
>> >> > But it seems the GestureDetector has some side effect which causes
>> >> > abnormal scrolling behaviors for the child ListView, e.g. sometime
>> >> > when flinging down, the list actually scrolls upwards; when the list
>> >> > is being flung (i.e. the scrolling animation is still playing) and you
>> >> > press and hold on the list, the scroling stops (which is normal), but
>> >> > as soon as you release, the list scrolls.
>>
>> >> > The code for the layout is shown below. Apparently it actually does
>> >> > nothing extra but calling GestureDetector.onTouchEvent(). If the line
>> >> > "boolean handled = mGestureDetector.onTouchEvent(ev);" is commented
>> >> > out, the child ListView will scroll as normal. Is it because the call
>> >> > to onTouchEvent() takes some time that confuses the child ListView?
>>
>> >> > Also, it seems this problem only occurs when the list item is complex,
>> >> > e.g. consisting of multiple ImageViews, TextView etc. Everything
>> >> > works fine if it's just a list of TextView's.
>>
>> >> > public class MyLayout extends FrameLayout implements OnGestureListener
>> >> > {
>> >> > ...
>> >> > �...@override
>> >> > public boolean dispatchTouchEvent(MotionEvent ev) {
>> >> > boolean handled = mGestureDetector.onTouchEvent(ev);
>> >> > return super.dispatchTouchEvent(ev);
>> >> > }
>>
>> >> > public void onShowPress(MotionEvent e) {
>> >> > }
>>
>> >> > public boolean onSingleTapUp(MotionEvent e) {
>> >> > return false;
>> >> > }
>>
>> >> > public void onLongPress(MotionEvent e) {
>> >> > }
>>
>> >> > public boolean onDown(MotionEvent e) {
>> >> > return false;
>> >> > }
>>
>> >> > public boolean onFling(MotionEvent e1, MotionEvent e2, float
>> >> > velocityX,
>> >> > float velocityY) {
>> >> > return false;
>> >> > }
>>
>> >> > public boolean onScroll(MotionEvent e1, MotionEvent e2, float
>> >> > distanceX,
>> >> > float distanceY) {
>> >> > return false;
>> >> > }
>> >> > }
>>
>> >> --
>> >> Romain Guy
>> >> Android framework engineer
>> >> romain...@android.com
>>
>> >> Note: please don't send private questions to me, as I don't have time
>> >> to provide private support. All such questions should be posted on
>> >> public forums, where I and others can see and answer them
>>
>> --
>> Romain Guy
>> Android framework engineer
>> romain...@android.com
>>
>> Note: please don't send private questions to me, as I don't have time
>> to provide private support. All such questions should be posted on
>> public forums, where I and others can see and answer them
> >
>
--
Romain Guy
Android framework engineer
romain...@android.com
Note: please don't send private questions to me, as I don't have time
to provide private support. All such questions should be posted on
public forums, where I and others can see and answer them
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