fix: NPE in MediaManager.scrobble()

[tinsukE]

I was watching #16 because I'm a heavy Chromecast Audio user and tried out the latest release. While that fix made the Chromecast experience better, I was still experiencing somewhat constant crashes.

I couldn't get an exact list of steps to reproduce it, sometimes doing the same thing worked, other times it crashed. But my testing routine constantly managed to reproduce a crash by randomly trying things like:

• Start Chromecast
• Play an album
• Jump to track X
• Jump to track Y (Y < X)
• Shuffle an album

The crash was almost always a NPE on MediaManager.scrobble():

    public static void scrobble(MediaItem mediaItem, boolean submission) {
        if (mediaItem != null && Preferences.isScrobblingEnabled()) {
            getSongRepository().scrobble(mediaItem.mediaMetadata.extras.getString("id"), submission);
        }
    }

MediaMetadata.extras is nullable, but isn't being handled properly: https://developer.android.com/reference/androidx/media3/common/MediaMetadata#extras()

Instead of making a huge "check if null" chain, I bit the bullet and converted the class to Kotlin.

Besides idiomatic Kotlin changes, the only 2 logical changes were the bugfix:

    fun scrobble(mediaItem: MediaItem?, submission: Boolean) {
        val mediaItemId = mediaItem?.mediaMetadata?.extras?.getString("id") ?: return
        if (isScrobblingEnabled()) {
            songRepository.scrobble(mediaItemId, submission)
        }
    }

And a pair of extension functions ListenableFuture<MediaBrowser>?.onComplete() to remove duplicated code/logic.

Stack trace of the NPE:

19:32:31.156  E  FATAL EXCEPTION: main
    Process: com.eddyizm.tempus.debug, PID: 8386
    java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.os.Bundle.getString(java.lang.String)' on a null object reference
    at com.cappielloantonio.tempo.service.MediaManager.scrobble(MediaManager.java:442)
    at com.cappielloantonio.tempo.service.BaseMediaService$initializePlayerListener$1.onIsPlayingChanged(BaseMediaService.kt:300)
    at androidx.media3.cast.CastPlayer.lambda$setPlayerStateAndNotifyIfChanged$20(CastPlayer.java:1450)
    at androidx.media3.cast.CastPlayer$$ExternalSyntheticLambda12.invoke(D8$$SyntheticClass:0)
    at androidx.media3.common.util.ListenerSet$ListenerHolder.invoke(ListenerSet.java:342)
    at androidx.media3.common.util.ListenerSet.lambda$queueEvent$0(ListenerSet.java:226)
    at androidx.media3.common.util.ListenerSet$$ExternalSyntheticLambda1.run(D8$$SyntheticClass:0)
    at androidx.media3.common.util.ListenerSet.flushEvents(ListenerSet.java:248)
    at androidx.media3.cast.CastPlayer.updateInternalStateAndNotifyIfChanged(CastPlayer.java:1066)
    at androidx.media3.cast.CastPlayer.access$1000(CastPlayer.java:98)
    at androidx.media3.cast.CastPlayer$StatusListener.onStatusUpdated(CastPlayer.java:1608)
    at com.google.android.gms.cast.framework.media.zzbn.zzm(com.google.android.gms:play-services-cast-framework@@21.4.0:6)
    at com.google.android.gms.cast.internal.zzaq.zzY(com.google.android.gms:play-services-cast@@21.4.0:1)
    at com.google.android.gms.cast.internal.zzaq.zzO(com.google.android.gms:play-services-cast@@21.4.0:61)
    at com.google.android.gms.cast.framework.media.RemoteMediaClient.onMessageReceived(com.google.android.gms:play-services-cast-framework@@21.4.0:1)
    at com.google.android.gms.cast.zzbp.run(com.google.android.gms:play-services-cast@@21.4.0:4)
    at android.os.Handler.handleCallback(Handler.java:1070)
    at android.os.Handler.dispatchMessage(Handler.java:125)
    at android.os.Looper.dispatchMessage(Looper.java:333)
    at android.os.Looper.loopOnce(Looper.java:263)
    at android.os.Looper.loop(Looper.java:367)
    at android.app.ActivityThread.main(ActivityThread.java:9287)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:566)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:929)

And a yet more elusive Chromecast crash that I'll try to track down (not fixed here), which I think is related to shuffled playlists:

19:26:57.699  E  FATAL EXCEPTION: main
    Process: com.eddyizm.tempus.debug, PID: 5025
    java.lang.ArrayIndexOutOfBoundsException: length=0; index=8
    at androidx.media3.cast.CastTimeline.getPeriod(CastTimeline.java:181)
    at androidx.media3.common.Timeline.getPeriod(Timeline.java:1275)
    at androidx.media3.cast.CastPlayer.seekTo(CastPlayer.java:526)
    at androidx.media3.common.BasePlayer.seekTo(BasePlayer.java:213)
    at androidx.media3.common.ForwardingPlayer.seekTo(ForwardingPlayer.java:322)
    at androidx.media3.session.PlayerWrapper.seekTo(PlayerWrapper.java:144)
    at androidx.media3.session.MediaSessionStub.lambda$seekToWithMediaItemIndex$23$androidx-media3-session-MediaSessionStub(MediaSessionStub.java:841)
    at androidx.media3.session.MediaSessionStub$$ExternalSyntheticLambda14.run(D8$$SyntheticClass:0)
    at androidx.media3.session.MediaSessionStub.lambda$sendSessionResultSuccess$1(MediaSessionStub.java:182)
    at androidx.media3.session.MediaSessionStub$$ExternalSyntheticLambda84.run(D8$$SyntheticClass:0)
    at androidx.media3.session.MediaSessionStub.lambda$queueSessionTaskWithPlayerCommandForControllerInfo$13(MediaSessionStub.java:353)
    at androidx.media3.session.MediaSessionStub$$ExternalSyntheticLambda19.run(D8$$SyntheticClass:0)
    at androidx.media3.session.ConnectedControllersManager.lambda$flushCommandQueue$3$androidx-media3-session-ConnectedControllersManager(ConnectedControllersManager.java:390)
    at androidx.media3.session.ConnectedControllersManager$$ExternalSyntheticLambda0.run(D8$$SyntheticClass:0)
    at androidx.media3.session.MediaSessionImpl.lambda$callWithControllerForCurrentRequestSet$3$androidx-media3-session-MediaSessionImpl(MediaSessionImpl.java:347)
    at androidx.media3.session.MediaSessionImpl$$ExternalSyntheticLambda21.run(D8$$SyntheticClass:0)
    at androidx.media3.common.util.Util.postOrRun(Util.java:802)
    at androidx.media3.session.ConnectedControllersManager.flushCommandQueue(ConnectedControllersManager.java:384)
    at androidx.media3.session.ConnectedControllersManager.flushCommandQueue(ConnectedControllersManager.java:365)
    at androidx.media3.session.MediaSessionStub.lambda$flushCommandQueue$64$androidx-media3-session-MediaSessionStub(MediaSessionStub.java:1709)
    at androidx.media3.session.MediaSessionStub$$ExternalSyntheticLambda40.run(D8$$SyntheticClass:0)
    at androidx.media3.common.util.Util.postOrRun(Util.java:802)
    at androidx.media3.session.MediaSessionStub.flushCommandQueue(MediaSessionStub.java:1707)
    at androidx.media3.session.MediaControllerImplBase$FlushCommandQueueHandler.flushCommandQueue(MediaControllerImplBase.java:3664)
    at androidx.media3.session.MediaControllerImplBase$FlushCommandQueueHandler.handleMessage(MediaControllerImplBase.java:3657)
    at androidx.media3.session.MediaControllerImplBase$FlushCommandQueueHandler.$r8$lambda$TVKiXTCmsW2hn-6HNXqbaigkfJc(Unknown Source:0)
    at androidx.media3.session.MediaControllerImplBase$FlushCommandQueueHandler$$ExternalSyntheticLambda0.handleMessage(D8$$SyntheticClass:0)
    at android.os.Handler.dispatchMessage(Handler.java:128)
    at android.os.Looper.dispatchMessage(Looper.java:333)
    at android.os.Looper.loopOnce(Looper.java:263)
    at android.os.Looper.loop(Looper.java:367)
    at android.app.ActivityThread.main(ActivityThread.java:9287)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:566)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:929)

[tinsukE]

This is unused. Any clue of where should it be called from?

[eddyizm]

Off the top of my head I am not sure. But we can get rid of it if is not used.

How much testing have you done with this build, outside of the Chromecast?

[tinsukE]

Not much, to be honest. Although I tried to keep the conversion as 1:1 as possible.

Is there anything you think worth it manually testing?

Or I could revert the changes and just fix the NPE on Java.

[eddyizm]

No, no, I like the conversion to kotlin, just need to make sure there are no weird side effects.
I am going to figure out how to create a debug prerelease.