[Android] Cancel detector gestures when a native view above them takes over the touch

packages/react-native-gesture-handler/android/src/main/java/com/swmansion/gesturehandler/core/GestureHandlerOrchestrator.kt

@@ -390,10 +390,17 @@ class GestureHandlerOrchestrator(
   }
 
   /**
-   * Cancels handlers whose view opted out of surviving a native view taking over the touch stream.
+   * Cancels handlers that shouldn't survive a native view taking over the touch stream: handlers
+   * whose view opted out through its hook (buttons), and handlers attached through a detector that
+   * haven't activated, native gestures included.
    */
-  fun cancelHandlersOnNativeTouchGrab(grabbedMidGesture: Boolean) = cancelHandlersMatching {
-    it is NativeViewGestureHandler && it.shouldCancelOnNativeTouchGrab(grabbedMidGesture)
+  fun cancelHandlersOnNativeTouchGrab(grabbedMidGesture: Boolean, downTime: Long) = cancelHandlersMatching {
+    val cancelledByHook = it is NativeViewGestureHandler && it.shouldCancelOnNativeTouchGrab(grabbedMidGesture)
+    val cancelledByDetector = !it.isActive &&
+      GestureHandler.usesNativeOrVirtualDetector(it.actionType) &&
+      it.hostDetectorView?.shouldCancelOnNativeTouchGrab(grabbedMidGesture, downTime) == true
+
+    cancelledByHook || cancelledByDetector
   }
 
   /**

packages/react-native-gesture-handler/android/src/main/java/com/swmansion/gesturehandler/react/RNGestureHandlerDetectorView.kt

@@ -1,6 +1,7 @@
 package com.swmansion.gesturehandler.react
 
 import android.content.Context
+import android.view.MotionEvent
 import android.view.View
 import com.facebook.react.bridge.ReadableArray
 import com.facebook.react.uimanager.ThemedReactContext
@@ -22,6 +23,10 @@ class RNGestureHandlerDetectorView(context: Context) : ReactViewGroup(context) {
   private var subscribedVirtualHandlers: MutableMap<Int, MutableSet<Int>> = mutableMapOf()
   private var moduleId: Int = -1
 
+  // Down time of the last DOWN that native dispatch delivered to this view. Handler delivery
+  // bypasses `dispatchTouchEvent`, so a DOWN intercepted by an ancestor never updates it.
+  private var lastNativeDownTime = -1L
+
   data class VirtualChildren(val handlerTags: List<Int>, val viewTag: Int)
 
   fun setHandlerTags(handlerTags: ReadableArray?) {
@@ -44,6 +49,22 @@ class RNGestureHandlerDetectorView(context: Context) : ReactViewGroup(context) {
     super.onDetachedFromWindow()
   }
 
+  override fun dispatchTouchEvent(event: MotionEvent): Boolean {
+    if (event.actionMasked == MotionEvent.ACTION_DOWN) {
+      lastNativeDownTime = event.downTime
+    }
+    return super.dispatchTouchEvent(event)
+  }
+
+  /**
+   * A native view takes over the touch stream with `requestDisallowInterceptTouchEvent`, which only
+   * bubbles up, so handlers of detectors below it are never notified. Mirror the rule buttons use:
+   * cancel when the grab happens after DOWN, or when it happens on DOWN and kept the event from
+   * reaching this detector (e.g. a scroll view catching a fling).
+   */
+  fun shouldCancelOnNativeTouchGrab(grabbedMidGesture: Boolean, downTime: Long) =
+    grabbedMidGesture || lastNativeDownTime != downTime
+
   override fun requestDisallowInterceptTouchEvent(disallowIntercept: Boolean) {
     super.requestDisallowInterceptTouchEvent(disallowIntercept)
     if (!disallowIntercept) {

packages/react-native-gesture-handler/android/src/main/java/com/swmansion/gesturehandler/react/RNGestureHandlerRootHelper.kt

@@ -143,9 +143,9 @@ class RNGestureHandlerRootHelper(private val context: ReactContext, wrappedView:
    * request alone doesn't say what the caller did with the event: a scrollable calls it when it
    * takes over the touch, but e.g. a nested pager calls it already on DOWN, just to keep its
    * ancestors from stealing a swipe it may recognize later, and the event still reaches the
-   * button - at request time both calls look identical. They only become
-   * distinguishable once the native dispatch completes (did the button receive the DOWN?), which
-   * is why cancellation runs here instead of in `requestDisallowInterceptTouchEvent`.
+   * button or detector - at request time both calls look identical. They only become
+   * distinguishable once the native dispatch completes (did the button or detector receive the
+   * DOWN?), which is why cancellation runs here instead of in `requestDisallowInterceptTouchEvent`.
    */
   fun onNativeDispatchEnd(event: MotionEvent) {
     passingNativeTouch = false
@@ -156,7 +156,7 @@ class RNGestureHandlerRootHelper(private val context: ReactContext, wrappedView:
       val grabbedMidGesture = event.actionMasked != MotionEvent.ACTION_DOWN &&
         event.actionMasked != MotionEvent.ACTION_POINTER_DOWN
 
-      orchestrator?.cancelHandlersOnNativeTouchGrab(grabbedMidGesture)
+      orchestrator?.cancelHandlersOnNativeTouchGrab(grabbedMidGesture, event.downTime)
     }
   }