a simplified code example of how Discord's Android app selectively allows child views of OverlappingPanelsLayout to handle their own horizontal scrolls
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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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