NullPointerException when running setMediaItem

[alexelisenko]

When the background service is running and playing an item, if I call AudioService.stop(), then play() on a new item, I call the AudioServiceBackground.setMediaItem() method and get the following error:

03:58:49.305 90 info flutter.tools E/MethodChannel#ryanheise.com/audioServiceBackground(31568): Failed to handle method call
03:58:49.305 91 info flutter.tools E/MethodChannel#ryanheise.com/audioServiceBackground(31568): java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String[] java.lang.String.split(java.lang.String)' on a null object reference
03:58:49.305 92 info flutter.tools E/MethodChannel#ryanheise.com/audioServiceBackground(31568): 	at com.ryanheise.audioservice.AudioService.getResourceId(AudioService.java:136)
03:58:49.305 93 info flutter.tools E/MethodChannel#ryanheise.com/audioServiceBackground(31568): 	at com.ryanheise.audioservice.AudioService.buildNotification(AudioService.java:188)
03:58:49.305 94 info flutter.tools E/MethodChannel#ryanheise.com/audioServiceBackground(31568): 	at com.ryanheise.audioservice.AudioService.updateNotification(AudioService.java:285)
03:58:49.305 95 info flutter.tools E/MethodChannel#ryanheise.com/audioServiceBackground(31568): 	at com.ryanheise.audioservice.AudioService.setMetadata(AudioService.java:398)
03:58:49.305 96 info flutter.tools E/MethodChannel#ryanheise.com/audioServiceBackground(31568): 	at com.ryanheise.audioservice.AudioServicePlugin$BackgroundHandler.onMethodCall(AudioServicePlugin.java:543)
03:58:49.305 97 info flutter.tools E/MethodChannel#ryanheise.com/audioServiceBackground(31568): 	at io.flutter.plugin.common.MethodChannel$IncomingMethodCallHandler.onMessage(MethodChannel.java:201)
03:58:49.305 98 info flutter.tools E/MethodChannel#ryanheise.com/audioServiceBackground(31568): 	at io.flutter.view.FlutterNativeView$PlatformMessageHandlerImpl.handleMessageFromDart(FlutterNativeView.java:188)
03:58:49.305 99 info flutter.tools E/MethodChannel#ryanheise.com/audioServiceBackground(31568): 	at io.flutter.embedding.engine.FlutterJNI.handlePlatformMessage(FlutterJNI.java:202)
03:58:49.305 100 info flutter.tools E/MethodChannel#ryanheise.com/audioServiceBackground(31568): 	at android.os.MessageQueue.nativePollOnce(Native Method)
03:58:49.305 101 info flutter.tools E/MethodChannel#ryanheise.com/audioServiceBackground(31568): 	at android.os.MessageQueue.next(MessageQueue.java:326)
03:58:49.305 102 info flutter.tools E/MethodChannel#ryanheise.com/audioServiceBackground(31568): 	at android.os.Looper.loop(Looper.java:160)
03:58:49.305 103 info flutter.tools E/MethodChannel#ryanheise.com/audioServiceBackground(31568): 	at android.app.ActivityThread.main(ActivityThread.java:6680)
03:58:49.305 104 info flutter.tools E/MethodChannel#ryanheise.com/audioServiceBackground(31568): 	at java.lang.reflect.Method.invoke(Native Method)
03:58:49.305 105 info flutter.tools E/MethodChannel#ryanheise.com/audioServiceBackground(31568): 	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
03:58:49.305 106 info flutter.tools E/MethodChannel#ryanheise.com/audioServiceBackground(31568): 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)

Any help or ideas on what could be wrong would be greatly appreciated.

[ryanheise]

Hi @alexelisenko , essentially start and stop are counterparts which start up and shut down the background isolate, and it is only between the time that the background isolate is started and stopped that you may send messages to it. For example, play and pause (and pretty much all the other methods) can only communicate with the background isolate once it is started.

So two solutions to your general problem are:

1. If you expect to continue playing audio soon after stopping, consider calling pause instead of stop so that the background isolate stays alive awaiting further commands.
2. Otherwise if stop makes more sense for your application, just remember that you need to call start to start the background isolate up again if you need to bring the background isolate back.

Regarding your error message, it's interesting that it's coming from the background isolate which actually should no longer be alive since it was stopped. This suggests to me that your call to AudioService.stop has not been correctly handled by your background isolate. In your onStop callback, you need to make sure that you actually do let the background isolate shut down (i.e. the Future returned by your onStart method needs to complete).

[alexelisenko]

Once again, thank you for the insight/wisdom :). I refactored to pause audio when switching audio files, then called stop() on the AudioPlayer, while keeping the service running, then playing again once the new file has been sent via customAction and loaded into notification.

[github-actions]

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