java - 将 ArrayList 中的相同项目分组 - MusicPlayer

Question

我正在尝试将多个 ArrayList 组合起来作为音乐播放器。当前列表会生成每首歌曲的艺术家，而不仅仅是一位艺术家。希望这能更好地解释它:

我当前的一个 fragment 的代码是这样的:

public class ArtistsFragment extends Fragment {

private ArrayList<Artist> artistList;
View view;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

    view = inflater.inflate(R.layout.fragment_artists, container, false);

    GridView gvArtists = (GridView) view.findViewById(R.id.gvArtists);

    //instantiate list
    artistList = new ArrayList<>();

    //get artists from device
    getArtistList();

    // Group ArrayList..
    artistList = new ArrayList<>(new HashSet<>(artistList));

    //sort alphabetically by title
    Collections.sort(artistList, new Comparator<Artist>() {
                public int compare(Artist a, Artist b) {
                    return a.getArtist().compareTo(b.getArtist());
                }
            }
    );

    //create and set adapter
    ArtistAdapter artistAdt = new ArtistAdapter(getActivity(), artistList);
    gvArtists.setAdapter(artistAdt);

    return view;
}

void getArtistList() {
    //retrieve artist info
    ContentResolver musicResolver = getActivity().getContentResolver();
    Uri musicUri = android.provider.MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
    Cursor musicCursor = musicResolver.query(musicUri, null, null, null, null);

    if (musicCursor != null && musicCursor.moveToFirst()) {
        //get columns
        int idColumn = musicCursor.getColumnIndex
                (MediaStore.Audio.Media._ID);
        int artistColumn = musicCursor.getColumnIndex
                (MediaStore.Audio.Albums.ARTIST);
        int artColumn = musicCursor.getColumnIndex
                (MediaStore.Audio.Media.ARTIST_ID);

        //add artists to list
        do {
            long thisId = musicCursor.getLong(idColumn);
            String thisArtist = musicCursor.getString(artistColumn);
            String thisArt = musicCursor.getString(artColumn);

            artistList.add(new Artist(thisId, thisArtist, thisArt));
        }
        while (musicCursor.moveToNext());
        musicCursor.close();
    }
}

}

艺术家等级

class Artist {
private final long id;
private final String artist;
private final String art;

public Artist(long artistID, String theartist, String artistArt) {
    id = artistID;
    artist = theartist;
    art = artistArt;
}

public long getID() {
    return id;
}

public String getArtist() {
    return artist;
}

public String getArt() {
    return art;
}
}

我查看了Map，我查看了Set，现在我只是感到困惑......

那么，如何对 ArrayList 进行分组以删除不同艺术家的重复项，然后最终使用 OnPicked 将 ArrayList 更改为该组/类别中的那些分组歌曲？

我的思路是否正确，或者是否有完全不同的方法来对流派/艺术家/专辑等进行排序？

Answer 1

如果清除重复项是您唯一的问题，那么以下是如何清除列表中的所有重复项(将其转换为 Set 并返回):

Set<Artist> set = new HashSet<Artist>(artistList);
artistList = new ArrayList<Artist>(set);
//then sort it...

或一行

artistList = new ArrayList<Artist>(new HashSet<Artist>(artistList));

您还应该根据使列表中的条目唯一的字段重写 equals() 和 hashCode() 方法。