我已经阅读了官方文档,但我不明白这种方法的作用:

@Override
public void onLoadChildren(final String parentMediaId,
final Result<List<MediaItem>> result) {

...
// Assume for example that the music catalog is already loaded/cached.

List<MediaItem> mediaItems = new ArrayList<>();

// Check if this is the root menu:
if (MY_MEDIA_ROOT_ID.equals(parentMediaId)) {

  // build the MediaItem objects for the top level,
  // and put them in the mediaItems list

  where is documented this part? how to build the media item?

} else {

  // examine the passed parentMediaId to see which submenu we're at,
  // and put the children of that menu in the mediaItems list
}
...
}

如果我想在电话里播放音乐,
如何根据手机的音乐“构建媒体项”?

最佳答案

我的答复有点晚了,但我希望这会有助于今后的怀疑。
在您的service.java中

case MEDIA_ID_ROOT:
    for (MediaMetadataCompat track : mMusicProvider.getAllMusics()) {

        String mediaId = track.getDescription().getMediaId();
        //Artist song
        String title = String.valueOf(track.getDescription().getTitle());
        //Artist name
        String subTitle = String.valueOf(track.getDescription().getSubtitle());
        //Artist album
        String descriptin = String.valueOf(track.getDescription().getDescription());
        //Song duration
        Long duration = track.getLong(MediaMetadataCompat.METADATA_KEY_DURATION);

        Bundle songDuration = new Bundle();
        songDuration.putLong(MediaMetadataCompat.METADATA_KEY_DURATION, duration);

        MediaDescriptionCompat desc =
                new MediaDescriptionCompat.Builder()
                        .setMediaId(mediaId)
                        .setTitle(title)
                        .setSubtitle(subTitle)
                        .setDescription(descriptin)
                        .setExtras(songDuration)
                        .build();

        MediaBrowserCompat.MediaItem songList =
                new MediaBrowserCompat.MediaItem(desc,
                        MediaBrowserCompat.MediaItem.FLAG_PLAYABLE);
        mediaItems.add(songList);
    }
    break;

mmusicprovider是我模型的对象
在provider.java中
// Categorized caches for music track data:
   private final LinkedHashMap<String, MediaMetadataCompat> mMusicListById;

public Iterable<MediaMetadataCompat> getAllMusics() {

    if (mCurrentState != State.INITIALIZED || mMusicListById.isEmpty()) {
        return Collections.emptyList();
    }
    return mMusicListById.values();
}

mediabrowsercompat.mediaitem基本上可以有mediaid、title、subtitle、description、iconbitmap、iconuri、bundle。在我的情况下,我需要这首歌的持续时间,所以我添加了一个额外的包。您可以添加更多的附加功能,如作曲家、年份、曲目编号等。
如果不需要任何额外信息,可以调用getDescription()。
for (MediaMetadataCompat track : mMusicProvider.getAllMusics()) {
    MediaBrowserCompat.MediaItem bItem =
            new MediaBrowserCompat.MediaItem(track.getDescription(),
                    MediaBrowserCompat.MediaItem.FLAG_PLAYABLE);

    mediaItems.add(bItem);

07-28 04:24