Controller ignoring trigger when immediately fired onInit

[alestiago]

Description

Firing an input trigger when the controller is added has no effect (the trigger get's fully ignored).

  void _onRiveInit(Artboard artboard) {
    final controller = StateMachineController.fromArtboard(
      artboard,
      'State Machine 1',
    )!;
    artboard.addController(controller);
    controller.getTriggerInput('fail')!.fire(); // Gets dropped, doesn't have any effect.
  }

Keep reading for further context.

Steps To Reproduce

1. Create a Flutter project:

flutter create rive_issue --platforms web

2. Add rive dependency (from rive_issue):

dart pub add rive

3. Download the .riv from JC Toon's Login Screen Character from the Rive Marketplace.

4. Save the login_screen_character.riv within rive_issue/assets.

5. Declare the login_screen_character.riv in the pubspec.yaml:

# rive_flutter/pubspec.yaml

# ...

flutter:
  uses-material-design: true
  assets:
    - assets/login_screen_character.riv

6. Replace the entire main.dart with the folling example:

import 'package:flutter/material.dart';
import 'package:rive/rive.dart';

void main() {
  runApp(const _Example());
}

class _Example extends StatelessWidget {
  const _Example();

  void _onRiveInit(Artboard artboard) {
    final controller = StateMachineController.fromArtboard(
      artboard,
      'State Machine 1',
    )!;
    artboard.addController(controller);
    controller.getTriggerInput('fail')!.fire(); // Gets dropped, doesn't have any effect.
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: const Text('Rive Example')),
        body: Center(
          child: RiveAnimation.asset(
            'assets/login_screen_character.riv',
            fit: BoxFit.cover,
            animations: const ['idle'],
            onInit: _onRiveInit,
          ),
        ),
      ),
    );
  }
}

7. Run the application and observe how the Rive character doesn't react to the fail trigger.

8. Replace the main.dart file with the following example:

import 'package:flutter/material.dart';
import 'package:rive/rive.dart';

void main() {
  runApp(const _Example());
}

class _Example extends StatelessWidget {
  const _Example();

  void _onRiveInit(Artboard artboard) {
    final controller = StateMachineController.fromArtboard(
      artboard,
      'State Machine 1',
    )!;
    artboard.addController(controller);
    WidgetsBinding.instance.addPostFrameCallback((_) {
      controller.getTriggerInput('fail')!.fire(); // Now, the fail trigger has effect.
    });
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: const Text('Rive Example')),
        body: Center(
          child: RiveAnimation.asset(
            'assets/login_screen_character.riv',
            fit: BoxFit.cover,
            animations: const ['idle'],
            onInit: _onRiveInit,
          ),
        ),
      ),
    );
  }
}

9. Notice how the fail trigger now has effect.

Source .riv/.rev file

• Download from JCToon's https://rive.app/marketplace/3469-7899-login-screen-character/

Note: I couldn't attach it to the issue since I got the error "GitHub file type not allowed .riv"

Expected behavior

Either:
(A) The trigger event should have some effect (as with postFrameCallback)
(B) Include Dart documentation on when the controller is ready to accept inputs, currently artboard.addController documentation is quite limited:

  /// Add an animation controller to this artboard. Playing will be scheduled if
  /// it's already playing.
  bool addController(RiveAnimationController controller) {

Screenshots

Without postFrameCallback (no effect):

Screen.Recording.2025-07-14.at.10.40.31.mov

With postFrameCallback (does trigger):

Screen.Recording.2025-07-14.at.10.38.05.mov

Device & Versions

• rive 0.13.20

# pubspec.lock
  rive:
    dependency: "direct main"
    description:
      name: rive
      sha256: "2551a44fa766a7ed3f52aa2b94feda6d18d00edc25dee5f66e72e9b365bb6d6c"
      url: "https://pub.dev"
    source: hosted
    version: "0.13.20"
  rive_common:
    dependency: transitive
    description:
      name: rive_common
      sha256: "2ba42f80d37a4efd0696fb715787c4785f8a13361e8aea9227c50f1e78cf763a"
      url: "https://pub.dev"
    source: hosted
    version: "0.4.15"

• flutter doctor summary:

Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 3.32.0, on macOS 15.5 24F74 darwin-arm64, locale en-ES)
[✓] Android toolchain - develop for Android devices (Android SDK version 36.0.0)
[✓] Xcode - develop for iOS and macOS (Xcode 16.4)
[✓] Chrome - develop for the web
[✓] Android Studio (version 2025.1)
[✓] VS Code (version 1.101.2)
[✓] Connected device (2 available)
[✓] Network resources

• No issues found!

Additional context

• N/A

[HayesGordon]

@alestiago, the Rive runtime has been updated to support an entirely new API which was part of a much larger effort to get Rive Flutter updated with the native Rive C++ runtime. More information can be found here:

• Migration Guide
• Rive Native for Flutter
• Rive Flutter Docs

There is no path for us to update this old package code (what you're using above). If you can replicate the same logic with the new package, version 0.14.0-dev1, we can take a look. Closing this for now but please reopen if you have the same or similar issues with the new package.