Media notification stuck when app is killed

[snaeji]

Describe the bug
If the app is killed by the device or if something crashes the media notification displays empty and cannot be swiped away. The only way to remove the notification is to open the app again and start playing audio.

Screenshots

Error messages
No error message

Minimal reproduction project
Can be reproduced with the example project

To Reproduce
Steps to reproduce the behavior:

1. Run the example project in Android Studio.
2. Press AudioPlayer.
3. Minimise the app by pressing the Home button.
4. While playing press "Stop" in Android Studio.
5. The Notification disappears for 1 second.
6. The empty notification appears again and cannot be removed.

Expected behavior
The notification should not appear again or the user should be able to swipe it away

Runtime Environment (please complete the following information if relevant):

• Device: Samsung Galaxy S8
• Android version: 9.0

Flutter 1.12.13+hotfix.8

[✓] Flutter (Channel stable, v1.12.13+hotfix.8, on Mac OS X 10.15.3 19D76, locale en-GB)
 
[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
[✓] Xcode - develop for iOS and macOS (Xcode 11.3.1)
[✓] Android Studio (version 3.5)
[✓] IntelliJ IDEA Community Edition (version 2018.2.4)
[✓] VS Code (version 1.42.1)
[✓] Connected device (1 available)

• No issues found!

Additional context
I know this sounds like a complete edge case but with all the vendor specific battery saving app killers out there this is causing a lot of complaints from our users.

And thank you for this great plugin! We are moving over to just_audio for our audioplayer to be able to allow a seeking window in HLS streams and it works like a charm.

[snaeji]

It may also be completely irrelevant but if it's to any help these are the crash logs that i have from Crashlytics.

Fatal Exception: java.lang.RuntimeException: Unable to start service com.ryanheise.audioservice.AudioService@56e2a8f with Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10200000 cmp=is.ruv.flutterspilari/.MainActivity }: java.lang.NullPointerException: Attempt to invoke interface method 'void com.ryanheise.audioservice.AudioService$ServiceListener.onStop()' on a null object reference at android.app.ActivityThread.handleServiceArgs(ActivityThread.java:4179) at android.app.ActivityThread.-wrap21() at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2119) at android.os.Handler.dispatchMessage(Handler.java:108) at android.os.Looper.loop(Looper.java:166) at android.app.ActivityThread.main(ActivityThread.java:7529) at java.lang.reflect.Method.invoke(Method.java) at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:245) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:921)

Fatal Exception: java.lang.NullPointerException: Attempt to invoke virtual method 'void io.flutter.plugin.common.MethodChannel.invokeMethod(java.lang.String, java.lang.Object)' on a null object reference at com.ryanheise.audioservice.AudioServicePlugin$BackgroundHandler.invokeMethod(AudioServicePlugin.java:712) at com.ryanheise.audioservice.AudioServicePlugin$BackgroundHandler.onAddQueueItem(AudioServicePlugin.java:567) at com.ryanheise.audioservice.AudioService$MediaSessionCallback.onAddQueueItem(AudioService.java:526) at android.support.v4.media.session.MediaSessionCompat$Callback$MediaSessionCallbackApi21.onCommand(MediaSessionCompat.java:1477) at android.media.session.MediaSession$CallbackMessageHandler.handleMessage(MediaSession.java:1575) at android.os.Handler.dispatchMessage(Handler.java:107) at android.os.Looper.loop(Looper.java:237) at android.app.ActivityThread.main(ActivityThread.java:7770) at java.lang.reflect.Method.invoke(Method.java) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1047)

[snaeji]

I also forgot one important step in the reproducing steps, sorry! The app has to be minimised for the notification to appear again.

[snaeji]

After a little reading i think i may have found a solution to this. Since the service is sticky the activity manager restarts the service if it is killed. When ActivityManager starts the service again the intent == null. We can then just call stopSelf(). I have tested it and it seems to work fine. What do you think about adding this to the onStartCommand? Would you like me to submit a PR?

if (intent == null) { stopSelf(); }

[ryanheise]

That sounds promising.

Note: My Flutter environment is broken for the time being due to a critical Dart bug. Waiting for this fix to land, hopefully soon.

[snaeji]

Damn thats too bad, good luck with that!

I created a PR for this one-liner:
#195

Tested and no issues that i'm aware of.

[ryanheise]

Hi @snaeji

I'm just wondering if making onStartCommand return Service.START_NOT_STICKY might be a better solution?

I haven't been able to reproduce this so I don't know whether or not it might solve your issue.

[snaeji]

Hi @ryanheise

I tested the following code and it works great. Better than my solution since it isn't started and killed again.

@Override
public int onStartCommand(final Intent intent, int flags, int startId) {
	//if (intent == null) { stopSelf(); }
	MediaButtonReceiver.handleIntent(mediaSession, intent);
	return START_NOT_STICKY;
}

The Android docs recommend using START_STICKY for background audio but i can't seem to find any difference between START_STICKY and START_NOT_STICKY other than the START_STICKY is restarted.

https://developer.android.com/reference/android/app/Service#START_STICKY

So i agree that this is a better solution no doubt.

[ryanheise]

Great! I'd be happy to accept the PR if you make the change.

I think START_STICKY could be useful under normal circumstances, but in a Flutter app, restarting the service does not restart the background isolate that's intended to go along with it. But it is something I'd like to make work some day.

[snaeji]

Great thank you! I opened up a new PR so it doesn't show up as two commits. I know you can squash them into one commit, but remembered that just a little to late :)

[ryanheise]

Merged, thanks again!