ExoPlayer: java.lang.AbstractMethodError with gradle version 3.5.3

I can reliably reproduce the problem with your setup. I think it still works as intended because you directly depend on the aar file and the problem goes away once you change the dependency to implementation project(path: ':exolibrary-debug')

The underlying issue is that the aar file doesn’t contain any dependency declaration and that’s why the dexing step can’t resolve the methods successfully. According to the post linked above, full dependency declarations are required from 3.5.3 onwards.

To tell gradle about the dependencies, you need a pom file as published by Maven for example. If you were publishing your library to Maven and then include it directly from there (i.e. using the aar + the pom file), it probably works again. You could also try to use a local Maven repository including pom files, following the instructions here. I haven’t tried it because it’s no longer ExoPlayer related and we can’t provide support for generic gradle issues. Might be worth a try though.

Based on the above, I’ll close this issue as working as intended. It only occurs if you depend on an aar directly without full dependency declaration, so anyone depending on ExoPlayer through the normal way will not see any issues.

@tonihei Actually the issue persists. I finally found the cause. It’s a bug in Gradle Plugin and it has something to do with Dexing Artifact Transformations. Steps to reproduce:

1. Create a library that is using Exo Player, e.g. init the player add EventListener and return it
2. Create App that uses the generated aar from step 1.
3. In the App call the library method that returns the player

You will see the crash:

java.lang.AbstractMethodError: abstract method "void com.google.android.exoplayer2.Player$EventListener.onTimelineChanged(com.google.android.exoplayer2.Timeline, int)"
        at com.google.android.exoplayer2.ExoPlayerImpl$PlaybackInfoUpdate.lambda$run$0$ExoPlayerImpl$PlaybackInfoUpdate(ExoPlayerImpl.java:804)
        at com.google.android.exoplayer2.-$$Lambda$ExoPlayerImpl$PlaybackInfoUpdate$N_S5kRfhaRTAkH28P5luFgKnFjQ.invokeListener(Unknown Source:2)
        at com.google.android.exoplayer2.BasePlayer$ListenerHolder.invoke(BasePlayer.java:182)
        at com.google.android.exoplayer2.ExoPlayerImpl.invokeAll(ExoPlayerImpl.java:845)
        at com.google.android.exoplayer2.ExoPlayerImpl.access$000(ExoPlayerImpl.java:43)
        at com.google.android.exoplayer2.ExoPlayerImpl$PlaybackInfoUpdate.run(ExoPlayerImpl.java:802)
        at com.google.android.exoplayer2.ExoPlayerImpl.notifyListeners(ExoPlayerImpl.java:736)
        at com.google.android.exoplayer2.ExoPlayerImpl.updatePlaybackInfo(ExoPlayerImpl.java:710)
        at com.google.android.exoplayer2.ExoPlayerImpl.handlePlaybackInfo(ExoPlayerImpl.java:652)
        at com.google.android.exoplayer2.ExoPlayerImpl.handleEvent(ExoPlayerImpl.java:595)
        at com.google.android.exoplayer2.ExoPlayerImpl$1.handleMessage(ExoPlayerImpl.java:127)
        at android.os.Handler.dispatchMessage(Handler.java:107)
        at android.os.Looper.loop(Looper.java:214)

The crash doesn’t happen if I create a maven repo that includes the Exo Player dependencies automatically by using transitive true. If not using transitive true and providing the Exo Player dependencies inside the app’s build.gradle file it crashes. There is a workaround that fixes this issue by using: android.enableDexingArtifactTransform=false This however is not a solution for me as I can’t force users to do this in their App.

Please refer to https://issuetracker.google.com/issues/139821726 and https://www.reddit.com/r/androiddev/comments/d0e1mi/gradle_plugin_350_causes_abstractmethoderror_for/

Edit: The min API level needs to be below 21.