[camera] Improving handling when camera permissions are not granted.

[panmari]

Description

If camera permissions are not granted, the plugin currently throws an exception in Java:

E/MethodChannel#plugins.flutter.io/camera(22476): Failed to handle method call
E/MethodChannel#plugins.flutter.io/camera(22476): java.lang.ClassCastException: android.hardware.camera2.CameraAccessException cannot be cast to java.lang.RuntimeException
E/MethodChannel#plugins.flutter.io/camera(22476): 	at io.flutter.plugins.camera.MethodCallHandlerImpl.handleException(MethodCallHandlerImpl.java:172)
E/MethodChannel#plugins.flutter.io/camera(22476): 	at io.flutter.plugins.camera.MethodCallHandlerImpl.lambda$onMethodCall$0$MethodCallHandlerImpl(MethodCallHandlerImpl.java:66)
E/MethodChannel#plugins.flutter.io/camera(22476): 	at io.flutter.plugins.camera.-$$Lambda$MethodCallHandlerImpl$OMU5dV7VCKXKBT37_ThIybqlHuo.onResult(Unknown Source:6)
E/MethodChannel#plugins.flutter.io/camera(22476): 	at io.flutter.plugins.camera.CameraPermissions.requestPermissions(CameraPermissions.java:49)
E/MethodChannel#plugins.flutter.io/camera(22476): 	at io.flutter.plugins.camera.MethodCallHandlerImpl.onMethodCall(MethodCallHandlerImpl.java:57)
E/MethodChannel#plugins.flutter.io/camera(22476): 	at io.flutter.plugin.common.MethodChannel$IncomingMethodCallHandler.onMessage(MethodChannel.java:226)
E/MethodChannel#plugins.flutter.io/camera(22476): 	at io.flutter.embedding.engine.dart.DartMessenger.handleMessageFromDart(DartMessenger.java:85)
E/MethodChannel#plugins.flutter.io/camera(22476): 	at io.flutter.embedding.engine.FlutterJNI.handlePlatformMessage(FlutterJNI.java:631)
E/MethodChannel#plugins.flutter.io/camera(22476): 	at android.os.MessageQueue.nativePollOnce(Native Method)
E/MethodChannel#plugins.flutter.io/camera(22476): 	at android.os.MessageQueue.next(MessageQueue.java:336)
E/MethodChannel#plugins.flutter.io/camera(22476): 	at android.os.Looper.loop(Looper.java:174)
E/MethodChannel#plugins.flutter.io/camera(22476): 	at android.app.ActivityThread.main(ActivityThread.java:7356)
E/MethodChannel#plugins.flutter.io/camera(22476): 	at java.lang.reflect.Method.invoke(Native Method)
E/MethodChannel#plugins.flutter.io/camera(22476): 	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
E/MethodChannel#plugins.flutter.io/camera(22476): 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)

That's because the code attempts to cast a CameraAccessException to a RuntimeException. I think that part of the code is executed unintentionally: what's desired at this point is to fully handle the exception in Java and pass it to dart, i.e. don't throw it again.

Related Issues

Checklist

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• I read the [Contributor Guide] and followed the process outlined there for submitting PRs.
• My PR includes unit or integration tests for all changed/updated/fixed behaviors (See [Contributor Guide]).
• All existing and new tests are passing.
• I updated/added relevant documentation (doc comments with ///).
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• I read and followed the [Flutter Style Guide].
• The title of the PR starts with the name of the plugin surrounded by square brackets, e.g. [shared_preferences]
• I updated pubspec.yaml with an appropriate new version according to the [pub versioning philosophy].
• I updated CHANGELOG.md to add a description of the change.
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Breaking Change

Does your PR require plugin users to manually update their apps to accommodate your change?

• Yes, this is a breaking change (please indicate a breaking change in CHANGELOG.md and increment major revision).
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[panmari]

@bparrishMines any concerns?

[bparrishMines]

LGTM

Thanks for the contribution! I changed the CHANGELOG exception to be more specific.

[bparrishMines]

This change does still need a test. It should be possible to revoke camera permissions for a test and then verify you don't see the cast exception when opening the camera. Some code we already have for controlling camera permissions on Android: https://github.com/flutter/plugins/blob/master/packages/camera/example/test_driver/camera_e2e_test.dart

[panmari]

Thanks for taking a look! I'm not quite sure how to create a test here, can you help me with these two things?

1. Would the test live in the package or in the example, like the e2e test you linked?
2. How would I formulate the expectation of this test? The error currently doesn't crash the app, it only prints the failure I quote in my initial comment above. Would I need to run the test with some flag to make these type of errors fatal?

[panmari]

@bparrishMines do you have any advice?

[bparrishMines]

@cyanglaz Do you know of a way to properly test this? It looks like we grant permissions before running the test and revoke permissions at the end. I don't think the e2e provides a way to revoke permission in the middle of the test. I'm considering merging this without tests.

[cyanglaz]

@bparrishMines I'm not sure either. Maybe we can use a flutter driver test instead of e2e to test this?
@dnfield might know how to test this with e2e.

[panmari]

@dnfield Dan, do you have an idea how to create a test?

[panmari]

@bparrishMines any guidance on how to progress here?

[panmari]

@bparrishMines any suggestion on how to resolve the situation? I still would love to add a test, I'm just not sure how to write it.

[bparrishMines]

I don't believe we currently have a good way to test this, but the code looks good and this needs to be fixed. Merging