!!! Android error on start: called start() while already started

[Shakle]

After some update recently - wether it was Android 13 QPR 2 (March Pixel update) or Flutter 3.7.7 on first camera initialization I get this error. In Example app it also happens. Did not check on other devices. I also guess that something related to it causes a crash from time to time when disabling/enabling camera.

ℹ️ Environment:

• Pixel 7 Pro. Android 13 march 2023

✅ Steps to reproduce:

1. Grant permissions to camera
2. Freshly open an app
3. Open camera screen

💡 Actual result:

• mobile_scanner: MobileScannerException: code genericError, message: Called start() while already started

👍 Expected result:

• no error

[tsomone]

You can do the trick by reloading camera with this code,

errorBuilder: (context, error, child) {
controller.stop();
controller.start();
return ScannerReloadingWidget(error: error);
}

its not recommended, but its working in my case

[BryceCYB]

Add controller.stop(); in initState works for me.

  void initState() {
     // To fix on start error
    controller.stop();
    super.initState();
  }

[sebatorresi]

In my case I did

void initState() { cameraController.stop(); super.initState(); }

[Ishchik]

It also reproduces when hitting Hot Restart on the screen with MobileScanner and navigating back to it

[arnabonetraker]

@juliansteenbakker MobileScannerException: code genericError, message: Called start() while already started.
mobile_scanner: ^3.2.0 on flutter: 3.7.12.

[maulikchak]

same issue

[tologonkudaiberdiuulu]

Any progress @juliansteenbakker ?

[Logaritma26]

same

[JoshPark1]

We are seeing the same issue on iOS. Adding controller.stop() to initState does not resolve the issue.

[sanriodev]

We are seeing the same issue on iOS. Adding controller.stop() to initState does not resolve the issue.

Have you tried this?

#589 (comment)

While I definitelly think instantiating a new controller everytime isn't the prettiest I ended up using the same workaround as the user who wrote the comment.

Works fine for me. Maybe this can help?

I am still hoping this is getting fixed anytime soon though.

[navaronbracke]

This should no longer occur with the new beta, version 5.0.0-beta.1 , as the lifecycle is now no longer managed by mobile_scanner itself, due to issues with widget tree reparenting.

[cbassols]

This should no longer occur with the new beta, version 5.0.0-beta.1 , as the lifecycle is now no longer managed by mobile_scanner itself, due to issues with widget tree reparenting.

I've been fighting with this issue for the last two hours in the version 5.0.0-beta.2.
If I make a hot restart, I get "MobileScannerException: code genericError, message: Called start() while already started!"
The only way I have to make it work is completely closing the App and reopening it.

[navaronbracke]

I am aware that we should handle hot reload better, we have a tracking issue for that specifically:
#773

I still need to figure out if we can intercept it internally, or provide users with guidance around the use of reassemble().

[Quelich]

In my case, users were navigated to a new page that includes the scanner but when i do this back-and-forth navigation multiple times i was getting this error in debug console:
W/WindowOnBackDispatcher(11079): OnBackInvokedCallback is not enabled for the application. W/WindowOnBackDispatcher(11079): Set 'android:enableOnBackInvokedCallback="true"' in the application manifest. with generic error called start() while already started

so i have updated AndroidManifest.xml in android/app/src/main by adding this line android:enableOnBackInvokedCallback="true" and it works.

For example:

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="your.package.name">

    <application
        android:label="Your App Name"
        android:name="${applicationName}"
        android:icon="@mipmap/ic_launcher"
        android:enableOnBackInvokedCallback="true">
        <!-- ... other application configurations ... -->
    </application>

</manifest>

However, this change only works for targeting Android 13 (API level 33) and above.