flutter_unity_widget

Flutter unity 3D widget for embedding unity in flutter. Now you can make awesome gamified features of your app in Unity and get it rendered in a Flutter app both in fullscreen and embeddable mode. Works great on Android, iPad OS, iOS, Web.

Windows support is a work in progress.

Notes

• Use Windows or Mac to export and build your project.
  Users on Ubuntu have reported a lot of errors in the Unity export.
• Emulator support is limited and requires special setup. Please use a physical device for Android and iOS.
• Supports Unity 2019.4.3 or later, we recommend the latest LTS.
• Use only OpenGLES3 as Graphics API on Android for AR compatibility.

Notice

Need me to respond, tag me Rex Isaac Raphael.

This plugin expects you to atleast know how to use Unity Engine. If you have issues with how unity widget is presented, you can please modify your unity project build settings as you seem fit.

Moving forward, versioning of the package will change to match unity releases after proper test. Mind you this does not mean the package is not compatible with other versions, it just mean it's been tested to work with a unity version.

Windows coming soon.

Installation

First depend on the library by adding this to your packages pubspec.yaml:

• Flutter 3.0.0

  dependencies:
  flutter_unity_widget: ^2022.2.0

• Pre Flutter 3.0.0 (This version will gradually be deprecated)

  dependencies:
  flutter_unity_widget: ^2022.1.0+7

Now inside your Dart code you can import it.

import 'package:flutter_unity_widget/flutter_unity_widget.dart';

You will need to open and export a Unity project, even for running the example. Your build will fail if you only include the widget in Flutter!

Preview

30 fps gifs, showcasing communication between Flutter and Unity:

Setup

In the tutorial below, there are steps specific to each platform, denoted by a :information_source: icon followed by the platform name (Android or iOS). You can click on its icon to expand it.

Prerequisites

• An existing Flutter project (if there is none, you can create a new one)

• An existing Unity project (if there is none, you can create a new one).

• A fuw-XXXX.unitypackage file, found in the unitypackages folder. Try to use the most recent unitypackage available.

Unity project setup

These instructions assume you are using a new Unity project. If you open the example project from this repository, you can move on to the next section Unity Exporting.

1. Create a folder named unity in your Flutter project folder and move the Unity project into there.
   The Unity export will modify some files in the /android and /ios folders of your flutter project. If your Unity project is in a different location the export might (partially) fail.

   The expected path is /unity/project-name/...

2. Make sure you have downloaded a fuw-XXXX.unitypackage file mentioned in prerequisites.

3. Using Unity (hub), open the Unity project. Go to Assets > Import Package > Custom Package and select the downloaded fuw-XXXX.unitypackage file. Click on Import.

4. Go to File > Build Settings > Player Settings and change the following under the Other settings > Configuration section:

   • In Scripting Backend, change to IL2CPP

   • (Android) Target Architectures, select ARMv7 and ARM64

   • (Android) For the best compatibility set Active Input Handling to Input Manager (Old) or Both.
     (The new input system has some issues with touch input on Android)

   • (iOS) Select Target SDK depending on where you will run your app (simulator or physical device).
     We recommend starting with a physical device and the Device SDK setting, due to limited simulator support.

   • (Web) Set Publishing settings > Compression format to Brotli or Disabled.
     Some users report that Unity gets stuck on the loading screen with the Gzip setting, due to MIME type errors.

   

5. In File > Build Settings, make sure to have at least 1 scene added to your build.

Some options in the Build settings window get overridden by the plugin's export script. Attempting to change settings like Development Build, Script Debugging and Export project in this window will not make a difference. If you end up having to change a build setting that doesn't seem to respond, take a lookat the export script FlutterUnityIntegration\Editor\Build.cs.

Unity exporting

1. After importing the unitypackage, you should now see a Flutter option at the top of the Unity editor.

2. Click on Flutter and select the appropriate export option:

   • For android use Export Android Debug or Export Android Release.
     This will export to android/unityLibrary.
   • For iOS use Export iOS Debug or Export iOS Release.
     This will export to ios/UnityLibrary.
   • Do not use Flutter > Export Platform plugin as it was specially added to work with flutter_unity_cli for larger projects.
   

   If you use git, you will probably want to add these unityLibrary folders to your gitignore file. These folders can get huge and are not guaranteed to work on another computer.

   Proceed to the next section to handle iOS and Android specific setup after the export.

Platform specific setup (after Unity export)

After exporting Unity, you will need to make some small changes in your iOS or Android project.
You will likely need to do this only once. These changes remain on future Unity exports.

:information_source: iOS

1. Open the *ios/Runner.xcworkspace* (workspace, not the project) file in Xcode, right-click on the Navigator (not on an item), go to **Add Files to "Runner"** and add the *ios/UnityLibrary/Unity-Iphone.xcodeproj* file. 2. (Optional) Select the *Unity-iPhone/Data* folder and change the Target Membership for Data folder to UnityFramework. 3.1. If you're using Swift, open the *ios/Runner/AppDelegate.swift* file and change the following: ```diff import UIKit import Flutter + import flutter_unity_widget @UIApplicationMain @objc class AppDelegate: FlutterAppDelegate { override func application( _ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]? ) -> Bool { + InitUnityIntegrationWithOptions(argc: CommandLine.argc, argv: CommandLine.unsafeArgv, launchOptions) GeneratedPluginRegistrant.register(with: self) return super.application(application, didFinishLaunchingWithOptions: launchOptions) } } ``` 3.2. If you're using Objective-C, open the *ios/Runner/main.m* file and change the following: ```diff + #import "flutter_unity_widget.swift.h" int main(int argc, char * argv[]) { @autoreleasepool { + InitUnityIntegration(argc, argv); return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class])); } } ``` 4. Add the *UnityFramework.framework* file as a library to the Runner project. 5. If you use Xcode 14 or newer, and Unity older than 2021.3.17f1 or 2022.2.2f1, your app might crash when running from Xcode. Disable the `Thread Performance Checker` feature in Xcode to fix this. - In Xcode go to `Product > Scheme > Edit Scheme...` - Now With `Run` selected on the left, got to the `Diagnostics` tab and uncheck the checkbox for `Thread Performance Checker`. -----

Setup AR

The following setup for AR is done after making an export from Unity.

Warning: The XR Plugin Management package version 4.3.1 - 4.3.3 has bug that breaks Android exports.

• The bug accidentally deletes your AndroidManifest.xml file after each build, resulting in a broken export.
  Switch to version 4.2.2 or 4.4 to avoid this.

Emulators

We recommend using a physical iOS or Android device, as emulator support is limited.
Below are the limited options to use an emulator.

Communicating

Flutter-Unity

1. On a UnityWidget widget, get the UnityWidgetController received by the onUnityCreated callback.

2. Use the method postMessage to send a string, using the GameObject name and the name of a behaviour method that should be called.

Unity-Flutter

1. Select the GameObject that should execute the communication and go to Inspector > Add Component > Unity Message Manager.

2. Create a new MonoBehaviour subclass and add to the same GameObject as a script.

3. On this new behaviour, call GetComponent<UnityMessageManager>() to get a UnityMessageManager.

4. Use the method SendMessageToFlutter to send a string. Receive this message using the onUnityMessage callback of a UnityWidget.

Examples

Simple Example

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

void main() {
  runApp(
    const MaterialApp(
      home: UnityDemoScreen(),
    ),
  );
}

class UnityDemoScreen extends StatefulWidget {
  const UnityDemoScreen({Key? key}) : super(key: key);

  @override
  State<UnityDemoScreen> createState() => _UnityDemoScreenState();
}

class _UnityDemoScreenState extends State<UnityDemoScreen> {
  static final GlobalKey<ScaffoldState> _scaffoldKey =
      GlobalKey<ScaffoldState>();
  UnityWidgetController? _unityWidgetController;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      key: _scaffoldKey,
      body: SafeArea(
        bottom: false,
        child: WillPopScope(
          onWillPop: () async {
            // Pop the category page if Android back button is pressed.
            return true;
          },
          child: Container(
            color: Colors.yellow,
            child: UnityWidget(
              onUnityCreated: onUnityCreated,
            ),
          ),
        ),
      ),
    );
  }

  // Callback that connects the created controller to the unity controller
  void onUnityCreated(controller) {
    _unityWidgetController = controller;
  }
}

Communicating with and from Unity

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

void main() => runApp(const MyApp());

class MyApp extends StatefulWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  static final GlobalKey<ScaffoldState> _scaffoldKey =
      GlobalKey<ScaffoldState>();
  UnityWidgetController? _unityWidgetController;
  double _sliderValue = 0.0;

  @override
  void initState() {
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        key: _scaffoldKey,
        appBar: AppBar(
          title: const Text('Unity Flutter Demo'),
        ),
        body: Card(
          margin: const EdgeInsets.all(8),
          clipBehavior: Clip.antiAlias,
          shape: RoundedRectangleBorder(
            borderRadius: BorderRadius.circular(20.0),
          ),
          child: Stack(
            children: <Widget>[
              UnityWidget(
                onUnityCreated: onUnityCreated,
                onUnityMessage: onUnityMessage,
                onUnitySceneLoaded: onUnitySceneLoaded,
                fullscreen: false,
              ),
              Positioned(
                bottom: 20,
                left: 20,
                right: 20,
                // <You need a PointerInterceptor here on web>
                child: Card(
                  elevation: 10,
                  child: Column(
                    children: <Widget>[
                      const Padding(
                        padding: EdgeInsets.only(top: 20),
                        child: Text("Rotation speed:"),
                      ),
                      Slider(
                        onChanged: (value) {
                          setState(() {
                            _sliderValue = value;
                          });
                          setRotationSpeed(value.toString());
                        },
                        value: _sliderValue,
                        min: 0,
                        max: 20,
                      ),
                    ],
                  ),
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }

  // Communcation from Flutter to Unity
  void setRotationSpeed(String speed) {
    _unityWidgetController?.postMessage(
      'Cube',
      'SetRotationSpeed',
      speed,
    );
  }

  // Communication from Unity to Flutter
  void onUnityMessage(message) {
    print('Received message from unity: ${message.toString()}');
  }

  // Callback that connects the created controller to the unity controller
  void onUnityCreated(controller) {
    _unityWidgetController = controller;
  }

  // Communication from Unity when new scene is loaded to Flutter
  void onUnitySceneLoaded(SceneLoaded? sceneInfo) {
    if (sceneInfo != null) {
      print('Received scene loaded from unity: ${sceneInfo.name}');
      print(
          'Received scene loaded from unity buildIndex: ${sceneInfo.buildIndex}');
    }
  }
}

Props

• fullscreen (Enable or disable fullscreen mode on Android)

API

• pause() (Use this to pause unity player)
• resume() (Use this to resume unity player)
• unload() (Use this to unload unity player) *Requires Unity 2019.4.3 or later
• quit() (Use this to quit unity player)
• postMessage(String gameObject, methodName, message) (Allows you invoke commands in Unity from flutter)
• onUnityMessage(data) (Unity to flutter binding and listener)
• onUnityUnloaded() (Unity to flutter listener when unity is unloaded)

• onUnitySceneLoaded(String name, int buildIndex, bool isLoaded, bool isValid,) (Unity to flutter binding and listener when new scene is loaded)

  Troubleshooting

Location: Unity

Error:

Multiple precompiled assemblies with the same name Newtonsoft.Json.dll included on the current platform. Only one assembly with the same name is allowed per platform. (Assets/FlutterUnityIntegration/JsonDotNet/Assemblies/AOT/Newtonsoft.Json.dll)

PrecompiledAssemblyException: Multiple precompiled assemblies with the same name Newtonsoft.Json.dll included on the current platform. Only one assembly with the same name is allowed per platform.

Solution: Locate the listed dll file, in this case: Assets/FlutterUnityIntegration/JsonDotNet/Assemblies/AOT/Newtonsoft.Json.dll

• Option 1: Delete the dll file or rename the file extension (e.g. .dll.txt) to stop it from being imported.
• Option 2: Uninstall the package that conflicts in the Unity package manager (usually Version control, or Collab). The exact package can be found by looking for newtonsoft in package-lock.json

Location: Unity

Error:

The type or namespace name 'Newtonsoft' could not be found (are you missing a using directive or an assembly reference?)
The type or namespace name 'JObject' could not be found (are you missing a using directive or an assembly reference?)
The type or namespace name 'JToken' could not be found (are you missing a using directive or an assembly reference?)
The type or namespace name 'JToken' could not be found (are you missing a using directive or an assembly reference?)

Solution:

Include the Newtonsoft JsonDotNet library. It is likely already included in your project with a wrong file extension: Assets/FlutterUnityIntegration/JsonDotNet/Assemblies/AOT/Newtonsoft.Json.dll.txt Rename the .dll.txt extension to .dll in your file explorer and open Unity again.

Alternatively you can manually add the library from the Unity package manager.

Location: Unity

Error:

InvalidOperationException: The build target does not support build appending.

Solution:

1. Open the unity/project-name/Assets/FlutterUnityIntegration/Editor/Build.cs file.

1.1. On line 48, change the following:

-    var options = BuildOptions.AcceptExternalModificationsToPlayer;
+    var options = BuildOptions.AllowDebugging;
+    EditorUserBuildSettings.exportAsGoogleAndroidProject = true;

1.2. On line 115, change the following:

-    var options = BuildOptions.AcceptExternalModificationsToPlayer;
+    var options = BuildOptions.AllowDebugging;

Location: Android Studio

Error:

minSdkVersion XX cannot be smaller than version 19 declared in library 
    \ [:flutter_unity_widget] .../AndroidManifest.xml as the library might be using 
    \ APIs not available in XX

Solution:

1. Open the android/app/build.gradle file and change the following:

-    minSdkVersion XX
+    minSdkVersion 19

Location: Android Studio

Error:

e: .../FlutterUnityWidgetBuilder.kt: (15, 42): Expecting a parameter declaration
e: .../FlutterUnityWidgetBuilder.kt: (23, 25): Expecting an argument
e: .../FlutterUnityWidgetController.kt: (22, 44): Expecting a parameter declaration
e: .../FlutterUnityWidgetFactory.kt: (13, 58): Expecting a parameter declaration

Solution:

1. Open the android/build.gradle file and change the following:

-    ext.kotlin_version = '1.3.50'
+    ext.kotlin_version = '1.4.31'

Location: Android Studio

Error:

Unable to find a matching variant of project :unityLibrary:

Solution:

1. Open the android/app/build.gradle file and change the following:

     lintOptions {
         disable 'InvalidPackage'
+        checkReleaseBuilds false
     }

Flavors

Recommendation

The easiest way to apply flavors for your app would be: flutter_flavorizr.

If you use flavors in your app you will notice that especially iOS crashes while running or building your app! Here are the necessary steps for flavored apps:

Android

No changes needed. Flavors are applied without any additional setups.

iOS

For your Unity iOS-Build you have to add your flavors to your Unity iOS Configuration.

1. Check your actual Runner (your app) configurations. If you have for example the flavors:

• dev
• prod

Your Runner configurations are looking like this:

So you have the flavors:

• Debug-dev
• Profile-dev
• Release-dev
• Debug-prod
• Profile-prod
• Release-prod

These flavors needs to be added to your Unity-IPhone project.

2. Go into your Unity-IPhone project -> PROJECT Unity-IPhone -> Info:

Here you can see in the Configurations section only:

• Release
• ReleaseForProfiling
• ReleaseForRunning
• Debug

3. Copy Debug configuration twice and rename them to Debug-dev and the second to Debug-prod.

You can do that by selecting + and duplicate the configuration like this:

4. Repeat this with Release to Release-dev and Release-prod.

5. Repeat this with Release to Profile-dev and Profile-prod.

6. Your Unity-IPhone configurations should now look like this:

Web

Flutter on default doesn't support --flavor for building web. But you can set your target main.dart entrypoint (with -t main.dart) while running and building. So if you setup your flavors properly there're also no changes needed for web to apply changes for your Flutter-Unity web App.

Known issues

• Remember to disabled fullscreen in unity player settings to disable unity fullscreen.
• Unity freezes and crashes on Android, please use OpenGL3 as Graphics API.
• Project fails to build due to some native dependencies in your unity project, please integrate the native libraries for those dependencies on Android or iOS
• App crashes on screen exit and re-entry do this

  Build Setting - iOS - Other Settings - Configuration - Enable Custom Background Behaviors or iOS

• Android builds takes forever to complete Unity 2022.1.*, remove these lines from unityLibrary/build.gradle file

  commandLineArgs.add("--enable-debugger") commandLineArgs.add("--profiler-report") commandLineArgs.add("--profiler-output-file=" + workingDir + "/build/il2cpp"+ abi + "" + configuration + "/il2cpp_conv.traceevents")

Web GL

Flutter widgets stacked on top of the UnityWidget will not register clicks or taps. This is a Flutter issue and can be solved by using the PointerInterceptor package.

Example usage:

Stack(
  children: [
    UnityWidget(
      onUnityCreated: onUnityCreated,
      onUnityMessage: onUnityMessage,
      onUnitySceneLoaded: onUnitySceneLoaded,
    ),
    Positioned(
      bottom: 20,
      left: 20,
      right: 20,
      child: PointerInterceptor(
        child: ElevatedButton(
          onPressed: () {
            // do something
          },
          child: const Text('Example button'),
        ),
      ),
    ),

We already integrated this into our Examples in the /example folder.

Sponsors

Support this project with your organization. Your donations will be used to help children first and then those in need. Your logo will show up here with a link to your website. [Contribute]

Contributors ✨

Thanks goes to these wonderful people (emoji key):

Rex Raphael 💻 📖 💬 🐛 👀 ✅

Thomas Stockx 💻 📖 💬 ✅

Kris Pypen 💻 📖 💬 ✅

Lorant Csonka 📖 📹

This project follows the all-contributors specification. Contributions of any kind welcome!