Allow GestureHandlerRootView to be manually made active

Author: j-piasecki

android/src/main/java/com/swmansion/gesturehandler/core/GestureHandlerOrchestrator.kt

@@ -6,6 +6,7 @@ import android.view.MotionEvent
 import android.view.View
 import android.view.ViewGroup
 import android.widget.EditText
+import com.swmansion.gesturehandler.react.RNGestureHandlerRootView
 import java.util.*
 
 class GestureHandlerOrchestrator(
@@ -497,6 +498,17 @@ class GestureHandlerOrchestrator(
   }
 
   private fun extractGestureHandlers(viewGroup: ViewGroup, coords: FloatArray, pointerId: Int): Boolean {
+    if (viewGroup is RNGestureHandlerRootView && viewGroup != wrapperView && viewGroup.isActive()) {
+      // When we encounter another active root view while traversing the view hierarchy, we want
+      // to stop there so that it can handle the gesture attached under it itself.
+      // This helps in cases where a view may call `requestDisallowInterceptTouchEvent` (which would
+      // cancel all gestures handled by its parent root view) but there may be some gestures attached
+      // to views under it which should work. Adding another root view under that particular view
+      // would allow the gesture to be recognized even though the parent root view cancelled its gestures.
+      // We want to stop here so the gesture receives event only once.
+      return false
+    }
+
     val childrenCount = viewGroup.childCount
     for (i in childrenCount - 1 downTo 0) {
       val child = viewConfigHelper.getChildInDrawingOrderAtIndex(viewGroup, i)
@@ -523,8 +535,19 @@ class GestureHandlerOrchestrator(
     return false
   }
 
-  private fun traverseWithPointerEvents(view: View, coords: FloatArray, pointerId: Int): Boolean =
-    when (viewConfigHelper.getPointerEventsConfigForView(view)) {
+  private fun traverseWithPointerEvents(view: View, coords: FloatArray, pointerId: Int): Boolean {
+    if (view is RNGestureHandlerRootView && view != wrapperView && view.isActive()) {
+      // When we encounter another active root view while traversing the view hierarchy, we want
+      // to stop there so that it can handle the gesture attached under it itself.
+      // This helps in cases where a view may call `requestDisallowInterceptTouchEvent` (which would
+      // cancel all gestures handled by its parent root view) but there may be some gestures attached
+      // to views under it which should work. Adding another root view under that particular view
+      // would allow the gesture to be recognized even though the parent root view cancelled its gestures.
+      // We want to stop here so the gesture receives event only once.
+      return false
+    }
+
+    return when (viewConfigHelper.getPointerEventsConfigForView(view)) {
       PointerEventsConfig.NONE -> {
         // This view and its children can't be the target
         false
@@ -569,6 +592,7 @@ class GestureHandlerOrchestrator(
           )
       }
     }
+  }
 
   private fun canReceiveEvents(view: View) =
     view.visibility == View.VISIBLE && view.alpha >= minimumAlphaForTraversal

android/src/main/java/com/swmansion/gesturehandler/react/RNGestureHandlerRootView.kt

@@ -12,10 +12,12 @@ import com.facebook.react.views.view.ReactViewGroup
 
 class RNGestureHandlerRootView(context: Context?) : ReactViewGroup(context) {
   private var _enabled = false
+  private var active = false
   private var rootHelper: RNGestureHandlerRootHelper? = null // TODO: resettable lateinit
+
   override fun onAttachedToWindow() {
     super.onAttachedToWindow()
-    _enabled = !hasGestureHandlerEnabledRootView(this)
+    _enabled = active || !hasGestureHandlerEnabledRootView(this)
     if (!_enabled) {
       Log.i(
         ReactConstants.TAG,
@@ -43,6 +45,17 @@ class RNGestureHandlerRootView(context: Context?) : ReactViewGroup(context) {
     super.requestDisallowInterceptTouchEvent(disallowIntercept)
   }
 
+  // Those methods refer to different variables because we need to enforce at least
+  // one of the Root Views to be enabled to intecept events. By default only the
+  // top-most view is enabled, but users may want to enable more views to be able
+  // to work around some native views calling `requestDisallowInterceptTouchEvent`,
+  // which prevents gestures from working.
+  fun isActive() = _enabled
+
+  fun setActive(active: Boolean) {
+    this.active = active
+  }
+
   companion object {
     private fun hasGestureHandlerEnabledRootView(viewGroup: ViewGroup): Boolean {
       UiThreadUtil.assertOnUiThread()

android/src/main/java/com/swmansion/gesturehandler/react/RNGestureHandlerRootViewManager.kt

@@ -4,6 +4,7 @@ import com.facebook.react.module.annotations.ReactModule
 import com.facebook.react.uimanager.ThemedReactContext
 import com.facebook.react.uimanager.ViewGroupManager
 import com.facebook.react.uimanager.ViewManagerDelegate
+import com.facebook.react.uimanager.annotations.ReactProp
 import com.facebook.react.viewmanagers.RNGestureHandlerRootViewManagerDelegate
 import com.facebook.react.viewmanagers.RNGestureHandlerRootViewManagerInterface
 
@@ -34,6 +35,11 @@ class RNGestureHandlerRootViewManager :
     view.tearDown()
   }
 
+  @ReactProp(name = "active")
+  override fun setActive(view: RNGestureHandlerRootView, active: Boolean) {
+    view.setActive(active)
+  }
+
   /**
    * The following event configuration is necessary even if you are not using
    * GestureHandlerRootView component directly.

android/src/paper/java/com/facebook/react/viewmanagers/RNGestureHandlerRootViewManagerDelegate.java

@@ -20,6 +20,12 @@ public RNGestureHandlerRootViewManagerDelegate(U viewManager) {
   }
   @Override
   public void setProperty(T view, String propName, @Nullable Object value) {
-    super.setProperty(view, propName, value);
+    switch (propName) {
+      case "active":
+        mViewManager.setActive(view, value == null ? false : (boolean) value);
+        break;
+      default:
+        super.setProperty(view, propName, value);
+    }
   }
 }

android/src/paper/java/com/facebook/react/viewmanagers/RNGestureHandlerRootViewManagerInterface.java

@@ -12,5 +12,5 @@
 import android.view.View;
 
 public interface RNGestureHandlerRootViewManagerInterface<T extends View> {
-  // No props
+  void setActive(T view, boolean value);
 }

docs/docs/installation.md

@@ -66,6 +66,10 @@ Note that `GestureHandlerRootView` acts like a normal `View`. So if you want it
 If you're using gesture handler in your component library, you may want to wrap your library's code in the GestureHandlerRootView component. This will avoid extra configuration for the user.
 :::
 
+:::tip
+If you're having trouble with gestures not working when inside a component provided by a third-party library, even though you've wrapped the entry point with `<GestureHandlerRootView>`, you can try adding another `<GestureHandlerRootView active>` closer to the place the gestures are defined. This way, you can prevent Android from canceling relevant gestures when one of the native views tries to grab lock for delivering touch events.
+:::
+
 ### Linking
 
 > **Important**: You only need to do this step if you're using React Native 0.59 or lower. Since v0.60, linking happens automatically.

src/fabric/RNGestureHandlerRootViewNativeComponent.ts

@@ -1,6 +1,8 @@
 import codegenNativeComponent from 'react-native/Libraries/Utilities/codegenNativeComponent';
 import type { ViewProps } from 'react-native';
 
-interface NativeProps extends ViewProps {}
+interface NativeProps extends ViewProps {
+  active?: boolean;
+}
 
 export default codegenNativeComponent<NativeProps>('RNGestureHandlerRootView');