Android events don't get fired using mEventDispatcher.dispatchEvent with the New Architecture and bridgeless off

[gabrieldonadel]

Description

While migrating some libraries to be compatible with the new architecture I notice this problem where on Android, events don't get fired when using mEventDispatcher.dispatchEvent with the New Architecture and bridgeless off, but these same events work fine when running using the old arch or with bridgeless on.

It seems that for some reason this.mFabricEventEmitter from ReactEventEmitter is null when an event is fired

Steps to reproduce

1. Using a non migrated custom view module, fire an event from the native side using mEventDispatcher.dispatchEvent()
2. Observe that the event is not received on the JS side

React Native Version

0.74.0-rc.4

Affected Platforms

Runtime - Android

Areas

Fabric - The New Renderer, Bridgeless - The New Initialization Flow

Output of npx react-native info

System:
  OS: macOS 14.0
  CPU: (12) arm64 Apple M2 Max
  Memory: 114.81 MB / 32.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 20.11.1
    path: ~/.volta/tools/image/node/20.11.1/bin/node
  Yarn:
    version: 3.6.4
    path: ~/.volta/tools/image/yarn/1.22.22/bin/yarn
  npm:
    version: 10.2.4
    path: ~/.volta/tools/image/node/20.11.1/bin/npm
  Watchman: Not Found
Managers:
  CocoaPods:
    version: 1.14.3
    path: /Users/gabriel/.rbenv/shims/pod
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 23.2
      - iOS 17.2
      - macOS 14.2
      - tvOS 17.2
      - visionOS 1.0
      - watchOS 10.2
  Android SDK:
    API Levels:
      - "22"
      - "26"
      - "30"
      - "31"
      - "33"
      - "34"
    Build Tools:
      - 26.0.3
      - 30.0.3
      - 31.0.0
      - 33.0.0
      - 33.0.1
      - 33.0.2
      - 34.0.0
    System Images:
      - android-22 | ARM 64 v8a
      - android-26 | Google APIs Intel x86_64 Atom
      - android-30 | ARM 64 v8a
      - android-33 | Google APIs ARM 64 v8a
      - android-33 | Google Play ARM 64 v8a
      - android-34 | Google Play ARM 64 v8a
    Android NDK: Not Found
IDEs:
  Android Studio: 2023.2 AI-232.10300.40.2321.11567975
  Xcode:
    version: 15.2/15C500b
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 17.0.8
    path: /usr/bin/javac
  Ruby:
    version: 2.7.8
    path: /Users/gabriel/.rbenv/shims/ruby
npmPackages:
  "@react-native-community/cli": Not Found
  react:
    installed: 18.2.0
    wanted: 18.2.0
  react-native:
    installed: 0.74.0-rc.4
    wanted: 0.74.0-rc.4
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: true
  newArchEnabled: true
iOS:
  hermesEnabled: Not found
  newArchEnabled: true

Stacktrace or Logs

Unhandled SoftException
                                                                                                    com.facebook.react.bridge.ReactNoCrashSoftException: Cannot find EventEmitter for receiveEvent: SurfaceId[1] ReactTag[16] UIManagerType[2] EventName[topChange]
                                                                                                    	at com.facebook.react.uimanager.events.ReactEventEmitter.receiveEvent(ReactEventEmitter.java:148)
                                                                                                    	at com.facebook.react.uimanager.events.Event.dispatchModern(Event.java:189)
                                                                                                    	at com.facebook.react.uimanager.events.EventDispatcherImpl$DispatchEventsRunnable.run(EventDispatcherImpl.java:376)
                                                                                                    	at android.os.Handler.handleCallback(Handler.java:942)
                                                                                                    	at android.os.Handler.dispatchMessage(Handler.java:99)
                                                                                                    	at com.facebook.react.bridge.queue.MessageQueueThreadHandler.dispatchMessage(MessageQueueThreadHandler.java:27)
                                                                                                    	at android.os.Looper.loopOnce(Looper.java:201)
                                                                                                    	at android.os.Looper.loop(Looper.java:288)
                                                                                                    	at com.facebook.react.bridge.queue.MessageQueueThreadImpl$4.run(MessageQueueThreadImpl.java:233)
                                                                                                    	at java.lang.Thread.run(Thread.java:1012)

Reproducer

https://github.com/gabrieldonadel/react-native-android-event-dispatcher-bug

Screenshots and Videos

old arch	new arch
	with bridge	bridgeless
Screen.Recording.2024-03-23.at.15.18.39.mov	Screen.Recording.2024-03-23.at.15.12.34.mov	Screen.Recording.2024-03-23.at.15.17.26.mov

[cortinico]

@gabrieldonadel Thanks for the reproducer it was extremely valuable for me to isolate the issue. A fix is forthcoming

[javache]

Noticed that in your sample, your accessing the event emitter here.

mEventDispatcher = UIManagerHelper.getEventDispatcherForReactTag((ReactContext) getContext(), getId());

I don't believe this is safe, as at this point RN will not have initialized the Id field yet, and we'll fall back to the paper event dispatcher even if this is a Fabric view.

[gabrieldonadel]

Noticed that in your sample, your accessing the event emitter here.

mEventDispatcher = UIManagerHelper.getEventDispatcherForReactTag((ReactContext) getContext(), getId());

I don't believe this is safe, as at this point RN will not have initialized the Id field yet, and we'll fall back to the paper event dispatcher even if this is a Fabric view.

I see, thanks for the explanation. If the UIManagerHelper.getEventDispatcherForReactTag call were to only occur inside the action event (e.g. onClick) this would be fine, right?

[cortinico]

I see, thanks for the explanation. If the UIManagerHelper.getEventDispatcherForReactTag call were to only occur inside the action event (e.g. onClick) this would be fine, right?

Yup I've tested this in your repro and it effectively fixes the issue 👍