Handling swipes with modal pages - xamarin

Question

I have a modal page that contains an absolute layout space in which I insert my widgets, in particular a scrollable list widget, which is a custom class derived from AbsoluteLayout:
public ListWidget(List<ListItem> items)
{
list_items = items;
BackgroundColor = Color.Transparent;
tap = new TapGestureRecognizer();
tap.Tapped += Tap_Handler;
list = new ListView()
{
BackgroundColor = Color.Transparent,
HasUnevenRows = true,
VerticalOptions = LayoutOptions.Center
};
list.ItemTapped += Tap_Handler;
list.ItemTemplate = new DataTemplate(typeof(CustomCell));
list.ItemsSource = list_items;
SetLayoutBounds(list, new Rectangle(0.0, 0.0, 1.0, 1.0));
SetLayoutFlags(list, AbsoluteLayoutFlags.All);
Children.Add(list);
}
Nothing fancy, as you see. Now, the page (a ContentPage) in question is loaded by a PushModalAsync() call, but here comes the problem:
If I swipe down on the list, the modal page gets hidden and I cannot get it back, since when I try I get this warning:
Warning: Attempt to present <Xamarin_Forms_Platform_iOS_ModalWrapper: 0x7f970601c580> on <Xamarin_Forms_Platform_iOS_PageRenderer: 0x7f9703f54b50> whose view is not in the window hierarchy!
Apparently, no PopModalAsync() is called in this case.
I have tried overriding this by using a gesture recognizer:
// in the constructor...
space.GestureRecognizers.Add(swipeDown);
listwidget.GestureRecognizers.Add(swipeDown);
}
// where my hopes crushed
void Swiper_Handler(object sender, SwipedEventArgs e)
{
System.Diagnostics.Debug.Print("SWIPED sender {0} args {1}", sender, e);
if (sender == listwidget)
{
System.Diagnostics.Debug.Print("LIST WIDGET! ABORT!");
return;
}
switch (e.Direction)
{
case SwipeDirection.Left:
System.Diagnostics.Debug.Print("Swiped to LEFT");
break;
case SwipeDirection.Right:
System.Diagnostics.Debug.Print("Swiped to RIGHT");
break;
case SwipeDirection.Up:
System.Diagnostics.Debug.Print("Swiped to UP");
break;
case SwipeDirection.Down:
System.Diagnostics.Debug.Print("Swiped to DOWN");
Navigation.PopModalAsync();
break;
}
}
But it won't work:
enabling swipe down on space will pop the page, but I cannot scroll the list
enabling swipe down on listwidget will hide the page, I cannot scroll the list, and I get the above error
removing gestures will hide the page, I cannot scroll the list, and I get the above error
enabling swipe on both space and listwidget will pop the page, but I cannot scroll the list
How can I make a scrollable list with a modal page coexist?
Any hints are greatly appreciated.