Blank screen on initializing UnityWidget, iOS

[jafitz26]

On first running the UnityWidget, the Unity Game's sound plays, but a blank screen is pulled up, on iOS only. This screen is the same color as my main app's loading screen.

If I hot restart the app from this screen, the Unity game's sound continues playing behind the main app, and after navigating back to the UnityWidget, the Unity game runs as intended.

The only work around I've found is automating a pop back to the main app, then rerunning the UnityWidget, which is not a good user experience.

--
Error output:

CrashReporter: initialized
Built from '2021.2/staging' branch, Version '2021.2.11f1 (e50cafbb4399)', Build type 'Release', Scripting Backend 'il2cpp'
MemoryManager: Using 'Default' Allocator.
[UnityMemory] Configuration Parameters - Can be set up in boot.config
"memorysetup-bucket-allocator-granularity=16"
"memorysetup-bucket-allocator-bucket-count=8"
"memorysetup-bucket-allocator-block-size=4194304"
"memorysetup-bucket-allocator-block-count=1"
"memorysetup-main-allocator-block-size=16777216"
"memorysetup-thread-allocator-block-size=16777216"
"memorysetup-gfx-main-allocator-block-size=16777216"
"memorysetup-gfx-thread-allocator-block-size=16777216"
"memorysetup-cache-allocator-block-size=4194304"
"memorysetup-typetree-allocator-block-size=2097152"
"memorysetup-profiler-bucket-allocator-granularity=16"
"memorysetup-profiler-bucket-allocator-bucket-count=8"
"memorysetup-profiler-bucket-allocator-block-size=4194304"
"memorysetup-profiler-bucket-allocator-block-count=1"
"memorysetup-profiler-allocator-block-size=16777216"
"memorysetup-profiler-editor-allocator-block-size=1048576"
"memorysetup-temp-allocator-size-main=4194304"
"memorysetup-job-temp-allocator-block-size=2097152"
"memorysetup-job-temp-allocator-block-size-background=1048576"
"memorysetup-job-temp-allocator-reduction-small-platforms=262144"
"memorysetup-temp-allocator-size-background-worker=32768"
"memorysetup-temp-allocator-size-job-worker=262144"
"memorysetup-temp-allocator-size-preload-manager=262144"
"memorysetup-temp-allocator-size-nav-mesh-worker=65536"
"memorysetup-temp-allocator-size-audio-worker=65536"
"memorysetup-temp-allocator-size-cloud-worker=32768"
"memorysetup-temp-allocator-size-gfx=262144"
-> applicationDidFinishLaunching()
-> applicationWillEnterForeground()
-> applicationDidBecomeActive()
Unexpected node type.
Unexpected node type.
GfxDevice: creating device client; threaded=1; jobified=0
Initializing Metal device caps: Apple A9 GPU
Initialize engine version: 2021.2.11f1 (e50cafbb4399)
flutter: in onUnityCreated
CrashReporter: No pending report exists at /var/mobile/Containers/Data/Application/D17E09AB-1621-4810-8A8E-EDBB1BE93C4C/Library/Caches/CrashReports/crash-pending.plcrash

[Drarox]

Exact same issue here, on iOS only, the UnityWidget is blank but the sound of the Unity game is playing.

I tried to pop back the screen after x seconds and then rerunning the UnityWidget and it's working then like you said, but it's not user friendly.

It was perfectly working a few weeks ago, I'm trying to figure out since when it's not working anymore because I did many upgrades.

What I have tried so far without any results :

• Updating flutter_unity_widget from 4.2.4 to 2020.3.25
• Using an older version of Unity (2020.3.20 which was working fine in the past) to be sure it's not related, I'm currently with the latest 2020.3.28

I have also recently updated Flutter from 2.8.1 to 2.10.1, I have not tried yet if this could be related to the issue.

[Drarox]

As a workaround for the moment for iOS, I pop the UnityWidget on the first opening in the onUnityCreated and then relaunch it 1 second after it's closed (don't relaunch it immediately or the same issue will still be there). This causes for the user only a blinking the first time opening, but it's working then.

[steven-voon]

@Drarox i ran into the same problem, would you mind to share with me your solution on “pop the widget and relaunch it after 1 sec” part ?
I’m from Unity and still new to flutter, I will be very appreciate if you are willing to share with me.

[jafitz26]

There may be a better way to do this, but my solution to popping the widget and relaunching it was to use two Future.delayed() in onUnityCreated. So something like:

widget.isInit ? Future.delayed(
Duration(milliseconds: 300),
() async {
Navigator.of(context).pop();
Future.delayed(
Duration(milliseconds: 500),
() async {
widget.initCallback();
},
);
},
) : null;

The initCallback() in the enclosing Class pushes the Class with the UnityWidget in it again:

Navigator.push(
context,
PageRouteBuilder(
pageBuilder: (context, animation1, animation2) => UnityClass(isInit: false, initCallback: initCallback,),
transitionDuration: Duration.zero,
reverseTransitionDuration: Duration.zero,
));

I also added a loading screen at the top of a Stack that pops after another Future.delayed duration.

[steven-voon]

@jafitz26 thanks for the sharing, I don’t quite understand the part on widget.isinit and widget.initCallback is it possible for you to share the whole code for me to learn about it?

[jafitz26]

Sure, here is the code within the context of the two classes I'm using:

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

  @override
  _FlutterPageState createState() => _FlutterPageState();
}

class _FlutterPageState extends State<FlutterPage> {

  void initCallback(){
    Navigator.push(
        context,
        PageRouteBuilder(
          pageBuilder: (context, animation1, animation2) => UnityPage(isInit: false, initCallback: (){},),
          transitionDuration: Duration.zero,
          reverseTransitionDuration: Duration.zero,
        ));
  }


  @override
  Widget build(BuildContext context) {
    return TextButton(
      onPressed: (){
        Navigator.push(
            context,
            PageRouteBuilder(
              pageBuilder: (context, animation1, animation2) => UnityPage(isInit: true, initCallback: initCallback,),
              transitionDuration: Duration.zero,
              reverseTransitionDuration: Duration.zero,
            ));

      },
      child: Text('Launch'),
    );
  }
}

class UnityPage extends StatefulWidget {
  UnityPage({required this.initCallback, required this.isInit,});

  VoidCallback initCallback;
  bool isInit;

  @override
  _UnityPageState createState() => _UnityPageState();
}

class _UnityPageState extends State<UnityPage> {

  late UnityWidgetController unityWidgetController;

  void _onUnityCreated(controller) async {

    this.unityWidgetController = await controller;

    widget.isInit ? Future.delayed(
      Duration(milliseconds: 300),
          () async {
            await unityWidgetController.pause();
            Navigator.of(context).pop();
        Future.delayed(
          Duration(milliseconds: 500),
              () async {
            widget.initCallback();
          },
        );
      },
    ) : null;
  }

  @override
  Widget build(BuildContext context) {
    return   UnityWidget(
      onUnityCreated: _onUnityCreated,
    );
  }
}

[WellingtonBipo]

@jafitz26 thanks for the sharing, I don’t quite understand the part on widget.isinit and widget.initCallback is it possible for you to share the whole code for me to learn about it?

Other approach that works for me is remove the UnityWidget for the widget tree.

You can use the same time intervals and instead of navigate between pages you can call setState and with a conditional, remove from the widget tree.

Like this:

bool _maintainUnity = false;

@override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Stack(
        children: [
          if (_maintainUnity) _unityWidget,
        ],
      ),
    );
  }

[steven-voon]

@jafitz26 thanks for the sharing your code, I had a quick implementation just now and it does work on iPad but something went wrong when it comes to iPhone, i will check on it myself and share it here if I managed to found the cause of it.

@WellingtonBipo thanks for the generous sharing ! Will try your suggestion today,

[Holosynthetic]

This is an issue related to the flutter_unity_widget iOS framework. If you take a look at the UnityPlayerUtils.swift file, you'll notice the createPlayer method never invokes the callback with the UnityFramework's rootView on first load. It's expecting the UnityReady notification to perform the callback, but it's never posted.

For now, I've changed the method body to the following and it works:

if unityIsInitiallized() && _isUnityReady {
    completed(controller?.rootView)
    return
}

DispatchQueue.main.async {
    // Always keep Flutter window on top
    let flutterLevel = UIWindow.Level.normal.rawValue + 1.0
    UIApplication.shared.keyWindow?.windowLevel = UIWindow.Level(flutterLevel)

    self.initUnity()
    self._isUnityReady = true
    completed(controller?.rootView)
    self.listenAppState()
}

[WellingtonBipo]

@Holosynthetic thanks very much. It's works fine. The only problem is that this file is inside flutter_unity_widget and if you delete the package and run flutter pub get you have to change the code again.

And to make easy to find the file, follow the path ios/.symlinks/plugins/flutter_unity_widget/ios/Classes/UnityPlayerUtils.swift (flutter_unity_widget folder is a link)
or
.pub-cach/host/pub.dartlang.org/flutter_unity_widget/ios/Classes/UnityPlayerUtils.swift

[bonfry]

Hi, I've a similar problem but with Android. I would like understand if solutions writed in this issue work also on Android. Thanks and sorry for my english