What is the role of MediaMetadata.displayTitle in media3?

[yt8492]

Before media3, Now Playing Card media title refers METADATA_KEY_DISPLAY_TITLE like this.

val mediaMetadataCompatBuilder = MediaMetadataCompat.Builder().apply {
      putString(MediaMetadataCompat.METADATA_KEY_DISPLAY_TITLE, playable.title)
      putString(MediaMetadataCompat.METADATA_KEY_DISPLAY_SUBTITLE, playable.subtitle)
      putString(MediaMetadataCompat.METADATA_KEY_ART_URI, playable.artUri)
}

But in media3, when I set displayTitle to MediaMetadata, it seems not working. here is reproducible example.
yt8492@9c959e2

Is this behavior correct? If true, what role is displayTitle in media3?

[marcbaechinger]

Thanks for your report.

Media3 is using MediaMetadata.title and converts from and to legacy keys here and here.

So as a Media3 user you can just use MediaMetadata.title. This removes ambiguity for Media3 users and you are still backwards compatible for users of the legacy or platform controller API that need to check both variants.

This behavior seems to be sensible to me. Are you using different values for displayTitle and title in your app and if you do, what is the reason to do so?

[yt8492]

@marcbaechinger
Thank you for the answer.

Are you using different values for displayTitle and title in your app and if you do, what is the reason to do so?

In my case, I only set a value for displayTitle and not for title. There is no particular reason, I simply replaced from ExoPlayer2 to Media3.

ExoPlayer2

val mediaMetadataCompatBuilder = MediaMetadataCompat.Builder().apply {
      putString(MediaMetadataCompat.METADATA_KEY_DISPLAY_TITLE, playable.title)
      putString(MediaMetadataCompat.METADATA_KEY_DISPLAY_SUBTITLE, playable.subtitle)
      putString(MediaMetadataCompat.METADATA_KEY_ART_URI, playable.artUri)
}

Media3

val metadata = MediaMetadata.Builder()
        .setDisplayTitle(playable.title)
        .setSubtitle(playable.subtitle)
        .setArtworkUri(playable.artUri)
        .build()

This worked fine most of the cases, but some devices (Xperia, OPPO, etc.) were crashing because they could not get the title from the MediaMetadata.

17:19:20.643  E  java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object android.os.Bundle.get(java.lang.String)' on a null object reference
--------- beginning of crash
17:19:24.875  E  FATAL EXCEPTION: SysUiBg
                 Process: com.android.systemui, PID: 22574
                 java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.media.MediaMetadata.getString(java.lang.String)' on a null object reference
                 	at com.android.systemui.media.MediaDataManager.loadMediaDataInBg(MediaDataManager.kt:500)
                 	at com.android.systemui.media.MediaDataManager.access$loadMediaDataInBg(MediaDataManager.kt:103)
                 	at com.android.systemui.media.MediaDataManager$loadMediaData$1.run(MediaDataManager.kt:308)
                 	at android.os.Handler.handleCallback(Handler.java:938)
                 	at android.os.Handler.dispatchMessage(Handler.java:99)
                 	at android.os.Looper.loopOnce(Looper.java:233)
                 	at android.os.Looper.loop(Looper.java:344)
                 	at android.os.HandlerThread.run(HandlerThread.java:67)

I think this is a bug on the custom os side because MediaDataManager.loadMediaDataInBg in AOSP does a null check, so the NPE should not occur.
I tried setting the value to title as well as displayTitle, and it was improved.

So as a Media3 user you can just use MediaMetadata.title. This removes ambiguity for Media3 users and you are still backwards compatible for users of the legacy or platform controller API that need to check both variants.

I understand. Maybe my fixes in #928 will help in the migration from ExoPlayer2 to Media3, but I think it's not necessary.

[yt8492]

Or, if displayTitle has no role, we can delete displayTitle property from MediaMetadata. It seems more simple.