How to update default error text in media browser for Android Auto?

Question

I am working on the Android auto media app and I want to set custom error text (or custom background text) when loading items has failed due to a network error etc. By default there are only two edge case scenarios:

1. "No items" text will be displayed when MediaBrowserServiceCompat's onLoadChildren() method returns an empty list.
2. Generic "Something went wrong" text with an exclamation mark icon is when an error occurred.

Is there any way I can update one or another? So far I found only one media app that displays a custom message for the second scenario in Android auto. That's Spotify with a message "Spotify is currently set to offline", though the default error icon is the same. I couldn't find any mentioning of the error messages in MediaBrowserServiceCompat documentation and will appreciate any help.

What I've tried so far setting the error state for the media session and returning a null as a result:

@Override
    public void onLoadChildren(@NonNull final String parentId, @NonNull final Result<List<MediaBrowserCompat.MediaItem>> result) {
        // some logic ...

        PlaybackStateCompat errorState = new PlaybackStateCompat.Builder()
                .setActions(PlaybackStateCompat.ACTION_STOP)
                .setErrorMessage(PlaybackStateCompat.ERROR_CODE_UNKNOWN_ERROR, "MY CUSTOM ERROR TEXT!").build();
        mediaSession.setPlaybackState(errorState);
        // result.sendError(new Bundle()); // <- does nothing
        // result.sendResult(Collections.emptyList()); // default "No items" message will be displayed
        result.sendResult(null);  // <-- this should trigger an error
}

MediaBrowserServiceCompat.Result has a method sendError but it should only be called on custom action (according to the documentation) and there are no examples of how to use it:

https://developer.android.com/reference/androidx/media/MediaBrowserServiceCompat.Result.html#sendError(android.os.Bundle)

Answer 1

我找到了答案，MediaSessionCompat的播放状态应该更新为STATE_ERROR。这是显示错误的示例代码：

void setErrorState(String errorMessage) {
        PlaybackStateCompat playbackState = new PlaybackStateCompat.Builder()
                .setState(PlaybackStateCompat.STATE_ERROR, 0, 0f)
                .setErrorMessage(
                        PlaybackStateCompat.ERROR_CODE_AUTHENTICATION_EXPIRED,
                        errorMessage
                )
                .build();
        mediaSession.setPlaybackState(playbackState);
    }