Question

我试图创建一个找到所有mp3歌曲的应用程序，这个代码就是我得到的，但是我无法测试这段代码，因为它崩溃了，没有任何错误，我是什么＆＃39我做错了吗？

我的班级找到歌曲：

   public class SongsManager {
    private ArrayList<Song> songsList;

    public ArrayList<Song> getMp3Songs(Context ctx) {
        Uri allSongsUri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
        String selection = MediaStore.Audio.Media.IS_MUSIC + " != 0";
        Cursor cursor =  ctx.getContentResolver().query(allSongsUri, null, null, null, selection);
        if (cursor != null) {
            if (cursor.moveToFirst()) {
                do {
                    Song song = new Song(cursor.getInt(cursor.getColumnIndex(MediaStore.Audio.Media._ID)),
                            cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.DISPLAY_NAME)),
                            cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.ARTIST)),
                            cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.DATA)));
                    songsList.add(song);
                } while (cursor.moveToNext());
            }
            cursor.close();
        }
        return songsList;
    }
}

我的活动：

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        SongsManager songsManager = new SongsManager();
        ArrayList<Song> songList = songsManager.getMp3Songs(this);
        ArrayAdapter<Song> adapterSongList = new ArrayAdapter<Song>(this, android.R.layout.simple_list_item_1, songList);
        ListView listView = (ListView) findViewById(R.id.musicList);
        listView.setAdapter(adapterSongList);
    }
}

我的歌曲课程：

public class Song {
    private long id;
    private String title;
    private String artist;
    private String path;
        public Song(long songID, String songTitle, String songArtist, String songPath) {
        id = songID;
        title = songTitle;
        artist = songArtist;
        path = songPath;
    }
    public long getID(){
        return id;
    }
    public String getTitle(){
        return title;
    }
    public String getArtist(){
        return artist;
    }
    public String getPath(){
        return path;
    }
    public void setTitle(String title_param){
        title = title_param;
    }
    public void setArtist(String artist_param){
        title = artist_param;
    }
    public void setPath(String path_param){
        path = path_param;
    }
    public String toString(){
        return getTitle();
    }
}

Answer 1

您使用了错误的语法。 “选择”不正确，因为这是排序顺序。

例如：

         private final Uri uri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
         public Cursor getAllTracks(Context context) {
    // gets all tracks

    ContentResolver cr = context.getContentResolver();
    final String[] columns = {track_id, track_no, artist, track_name,
            album, duration, path, year, composer};
    return cr.query(uri, columns, null, null, null);
}

来自文档：

    query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder)

查询给定的URI，在结果集上返回一个Cursor。

在android

1 个答案: