Apps launched due to Bluetooth connection render incorrectly

[ened]

Steps to Reproduce

Bluetooth Accessory Application (via EAAccessory).

0. App killed, BT accessory off, phone on home screen
1. Turn on accessory
2. App get's launched in the background due to a Bluetooth connection (EAAccessory)
3. Tap icon on home screen to launch App in FG
4. App is not rendering properly anymore, lots of images & some text is missing

Logs

iOS Console Logs are flooded with

2020-04-29 17:17:07.485743 +0100		error	Runner	Execution of the command buffer was aborted due to an error during execution. <private>
2020-04-29 17:17:07.504637 +0100		error	Runner	Execution of the command buffer was aborted due to an error during execution. <private>
2020-04-29 17:17:07.504717 +0100		error	Runner	Execution of the command buffer was aborted due to an error during execution. <private>
2020-04-29 17:17:07.504770 +0100		error	Runner	Execution of the command buffer was aborted due to an error during execution. <private>
2020-04-29 17:17:07.504822 +0100		error	Runner	Execution of the command buffer was aborted due to an error during execution. <private>
2020-04-29 17:17:07.518071 +0100		error	Runner	Execution of the command buffer was aborted due to an error during execution. <private>

❯ flutter doctor -v
[✓] Flutter (Channel beta, v1.17.0-3.3.pre, on Mac OS X 10.15.4 19E287, locale en-GB)
    • Flutter version 1.17.0-3.3.pre at /Users/sebastian/dev/flutter
    • Framework revision 0da1ab0922 (22 hours ago), 2020-04-28 11:02:34 -0700
    • Engine revision 376ad6a64b
    • Dart version 2.8.0

 
[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
    • Android SDK at /Users/sebastian/Library/Android/sdk
    • Platform android-29, build-tools 29.0.2
    • ANDROID_HOME = /Users/sebastian/Library/Android/sdk
    • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 1.8.0_212-release-1586-b4-5784211)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 11.4.1)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 11.4.1, Build version 11E503a
    • CocoaPods version 1.9.1

[✓] Android Studio (version 3.6)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin version 45.1.1
    • Dart plugin version 192.7761
    • Java version OpenJDK Runtime Environment (build 1.8.0_212-release-1586-b4-5784211)

[✓] VS Code (version 1.44.2)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.9.1

[✓] Connected device (2 available)
    • Pixel 2           • HT83G1A03545              • android-arm64 • Android 10 (API 29)
    • Nextbase’s iPhone • 00008030-001134200288802E • ios           • iOS 13.4.1

Did not appear until 1.17+ I think, which is roughly the time Metal was activated.

[cbracken]

/cc @chinmaygarde for potential Metal implications.

[chinmaygarde]

Can't say for sure without further investigation. Will let you know.

[ened]

We have a temporary workaround:

iOS Plugin to monitor the Application State:

extension SupportPlugin {
    public func applicationDidEnterBackground(_ application: UIApplication) {
        appStateChannel.update(value: UIApplication.shared.applicationState.rawValue)
    }
    
    public func applicationWillEnterForeground(_ application: UIApplication) {
        appStateChannel.update(value: UIApplication.shared.applicationState.rawValue)
    }
    
    public func applicationDidBecomeActive(_ application: UIApplication) {
        appStateChannel.update(value: UIApplication.shared.applicationState.rawValue)
    }
    
    public func applicationWillResignActive(_ application: UIApplication) {
        appStateChannel.update(value: UIApplication.shared.applicationState.rawValue)
    }
}

The appStateChannel exposes the applicationState value to the Dart side.

Conditional rendering on Dart side

  @override
  Widget build(BuildContext context) {
    if (_appState == AppState.active) {
      // Root contains everything - MaterialApp, Scaffold etc.
      return const Root();
    } else {
      return const SizedBox();
    }
  }

[gaaclarke]

@ened can you provide sample code? Setting up an app to launch in the background as a result of a hardware connection isn't the most common thing and many developers haven't needed to learn how to do it. It would be nice to have something to run so we can see the error right away.

I looked up EAAccessory and it just looks like an API for communicating with devices, I didn't see anything about launching apps.

[ened]

@gaaclarke You'd need a compatible accessory in hardware as well. The next best thing may be to use the "App was launched due to a Remote Content" event or similar. I'll try to make some sort of example work..

[ened]

More details here and example will be prepared based on that: https://www.raywenderlich.com/5817-background-modes-tutorial-getting-started

[chinmaygarde]

Update: I think I have a reproducible test case for this. Trying to figure out what is happening.

[roeierez]

@ened We have the same problem, rendering in the background due to a silent push notification.
Thanks a lot for your workaround. One question about it is did you try to use the WidgetBindingObserver for detecting background/foreground state changes? Or is it required to use the native plugin for the workaround to work?