There's no way to release Unity resources

[Zazo032]

Describe the bug
There's no way to release resources used by UnityWidget. We are using Unity for an AR feature, and the second time you open the screen with a UnityWidget, camera lags a lot and there's no loading screen, meaning previous Unity resources were not released. Moreover, doing it 2/3 times fast enough crashes the app because it runs out of memory.

To Reproduce
In the example app, you can see a similar behavior:

1. Open rotation sample
2. "Made with Unity" loading screen is shown
3. Go back
4. Open rotation sample again
5. No "Made with Unity" screen is shown, the controller was not released/disposed properly

Expected behavior
After disposing the controller, it should stop all Unity resources

Actual behavior
Disposing/unloading the controller doesn't help with resources, and calling quit closes the app.

Smartphone (please complete the following information):

• Device: OnePlus 5
• OS: Android
• Version: 10

Additional context
Also tried using openInNativeProcess and adding the extended activity in manifest, but that way we can't communicate with messages to the Unity process.

[aaubets]

Same here. Every time I use UnityWidget a new instance was created and if I change scene in one of it onUnitySceneLoaded is called as many times it was loaded in each one of them.

[jaboyc]

I believe I am experiencing the same issue on iOS. For me, whenever another instance is created, Flutter stops receiving messages from Unity, whereas messages are being sent correctly to Unity. And, when enough instances are opened, Unity freezes.

[khal-it]

any solutions. Facing the same issue

[OGmetamonkey]

I believe I am experiencing the same issue on iOS. For me, whenever another instance is created, Flutter stops receiving messages from Unity, whereas messages are being sent correctly to Unity. And, when enough instances are opened, Unity freezes.

This is exactly what I am experiencing in iOS. Is there any explanation for this that could lead to a potential solution? @juicycleff @thomas-stockx @jaboyc

[juicycleff]

@OGmetamonkey please use v4 branch, mind you it's still in alpha. Will make an alpha release officially this week

[OGmetamonkey]

@OGmetamonkey please use v4 branch, mind you it's still in alpha. Will make an alpha release officially this week

Tried it out. I keep getting project/ios/Runner/Runner-Bridging-Header.h:2:9: 'UnityUtils.h' file not foundwhen using xcode to build the project. Any idea what's going on? @juicycleff

Rebuilt it three times while implementing every step to try and find the problem. No dice.

[OGmetamonkey]

Output:

Xcode's output:
↳
Development/project/flutter-unity-view-widget-4/ios/
Classes/FLTUnityView.swift:10:8: error: no such module 'UnityFramework'
import UnityFramework
^
Command CompileSwift failed with a nonzero exit code
Command CompileSwift failed with a nonzero exit code
Command CompileSwift failed with a nonzero exit code
note: Using new build system
note: Building targets in parallel
note: Planning build
note: Constructing build description

Encountered error while building for device.

[OGmetamonkey]

Hi @juicycleff , I just tried the latest commit of V4. I still get these errors when trying to compile for iPhone:

Development/project/ios/Runner/Runner-Bridging-Header.h:2:9: error: 'UnityUtils.h' file not found
#import "UnityUtils.h"
^
1 error generated.
:0: error: failed to emit precompiled header '/Users/metamonkey/Library/Developer/Xcode/DerivedData/Runner-dgqsyzbbuoeoncgvconxvpyumojg/Build/Intermediates.noindex/PrecompiledHeaders/Runner-Bridging-Header-swift_2GZ4YKJM5Z610-clang_D1FYERE3G02L.pch' for bridging header 'Development/project/ios/Runner/Runner-Bridging-Header.h'
2 errors generated.

I noticed there is a typo in step 3 and 4 of the iOS setup (shown below). Did you intend to remove step 3?

3. Add this to your Runner/Runner/Runner-Bridging-Header.h 4. Add to Runner/Runner/AppDelegate.swift before the GeneratedPluginRegistrant call:

[juicycleff]

@OGmetamonkey Please look at the readme in v4 branch. You need to remove unityutils.h

[OGmetamonkey]

@juicycleff I'm having trouble understanding that. Am I looking at the right thing?

[juicycleff]

@OGmetamonkey I just updated the readme

[OGmetamonkey]

@juicycleff So that actually allowed the app to build on VS Code, but still not on XCode, and when running in VSCode it's crashing when Unity is launched. 'exited sigterm'

So I tried to run 'flutter build ios' and I get the following errors:

Error output from Xcode build:
↳
** BUILD FAILED **

Xcode's output:
↳
Command CompileSwift failed with a nonzero exit code
Development/project/flutter-unity-view-widget-4/ios/Classes/FLTUnityView.swift:10:8: error:
no such module 'UnityFramework'
import UnityFramework
^
Command CompileSwift failed with a nonzero exit code
Command CompileSwift failed with a nonzero exit code
note: Using new build system
note: Building targets in parallel
note: Planning build
note: Constructing build description

Encountered error while building for device.

[juicycleff]

@Zazo032 sorry for the late reply, but you navigating away from unity widget screen does not remove unity resources, you should read up the unity as a library documentation. This has nothing to do with the flutter package. However, you can improve this by navigating to an empty unity scene, before leaving your current unity widget

[Zazo032]

@Zazo032 sorry for the late reply, but you navigating away from unity widget screen does not remove unity resources, you should read up the unity as a library documentation. This has nothing to do with the flutter package. However, you can improve this by navigating to an empty unity scene, before leaving your current unity widget

But there's no native way to "dispose" the Unity controller that is being used to be able to free resources?