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a simplified code example of how Discord's Android app selectively allows child views of OverlappingPanelsLayout to handle their own horizontal scrolls
class PanelsChildGestureRegionObserver : View.OnLayoutChangeListener {
...
override fun onLayoutChange(
view: View?,
left: Int,
top: Int,
right: Int,
bottom: Int,
oldLeft: Int,
oldTop: Int,
oldRight: Int,
oldBottom: Int
) {
if (view != null) {
val coordinates = intArrayOf(0, 0)
view.getLocationOnScreen(coordinates)
val x = coordinates[0]
val y = coordinates[1]
val absoluteLeft = x + left
val absoluteTop = y + top
val absoluteRight = x + right
val absoluteBottom = y + bottom
viewIdToGestureRegionMap[view.id] = Rect(
absoluteLeft,
absoluteTop,
absoluteRight,
absoluteBottom
)
publishGestureRegionsUpdate()
}
}
private fun publishGestureRegionsUpdate() {
val gestureRegions = viewIdToGestureRegionMap.values.toList()
gestureRegionsListeners.forEach { gestureRegionsListener ->
gestureRegionsListener.onGestureRegionsUpdate(gestureRegions)
}
}
}
class ChatInputFragment: Fragment() {
private val container: View by bindView(R.id.chat_input_container)
override fun onViewCreated(
view: View,
savedInstanceState: Bundle?
) {
super.onViewCreated(view, savedInstanceState)
// Provider.get() returns a lazily instantiated
// activity-scoped singleton.
container.addOnLayoutChangeListener(
PanelsChildGestureRegionObserver.Provider.get()
)
}
}
class PanelsFragment: Fragment(),
PanelsChildGestureRegionObserver.GestureRegionsListener {
private val panels: OverlappingPanelsLayout by bindView(R.id.overlapping_panels)
...
override fun onGestureRegionsUpdate(gestureRegions: List<Rect>) {
panels.setChildGestureRegions(gestureRegions)
}
}
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