ScrollView inside GestureDetector: Dispatch Touch Events - dart

Question

I have a GestureDetector that´s responsible for dragging a container up and down, to change the height. The contents of the container may be too long, so the content must be scrolled.
I can´t figure out how to dispatch the touch event to the correct component, I tried it with a IgnorePointer and change the ignoring property.
class _SlideSheetState extends State<SlideSheet>
bool _ignoreScrolling = true;
GestureDetector(
onVerticalDragUpdate: (DragUpdateDetails details) {
if(isDraggedUp) {
setState(() {
_ignoreScrolling = false
});
}
// update height of container, omitted for simplicity
},
child: NotificationListener(
onNotification: (ScrollNotification notification) {
if(notification is OverscrollNotification) {
if(notification.overscroll < 0) {
// the scrollview is scrolled to top
setState(() {
_ignoreScrolling = true;
});
}
}
},
child: IgnorePointer(
ignoring: _ignoreScrolling,
child: SingleChildScrollView(
physics: ClampingScrollPhysics(),
child: Container(
// ...
)
)
)
)
Does anybody know a good way to dispatch touch events up or down the Widget tree? Because in my solution, obviously, you always have to make one touch event just to change the "listener" from GestureDetector to SingleChildScrollView, which is annoying for the user, to say the least.

Answer 1

I was working on the same kind of widget today. You don't need the GestureDetector containing the NotificationListener. It's redundant and from my experience overrides the scrollListener within it or under it (depending on if you place it in a parent/child scenario or a stack scenario). Handle everything within the NotificationListener itself. Including updating your container's height. If you need the scrollable container to grow before you can scroll then I put mine in a stack with an "expanded" bool which then reactively built a gesture detector on top of the scroll container. Then when it was expanded I used the NotificationListener to handle it's drag displacement.
Stack(children:[
NotificationListener(/* scroll view stuff */),
expanded ? GestureDetector() : Container()
]);