android - 我想将一些数据从一个活动路径到另一个活动，但 onActivityResult 方法不起作用

Question

首先，我创建了一个名为的类，GetMusics.java因此我想将音乐名称传递给MusicPlater.java类，但onActivityResult方法不起作用。我不知道我在哪里犯了错误。

这是GetMusic.java课

public class GetMusics extends ListActivity{

private final String SD_PATH = Environment.getExternalStorageDirectory().getPath();
List<String> songs = new ArrayList<String>();
MediaPlayer mp = new MediaPlayer();

class Mp3Filter implements FilenameFilter{

    @Override
    public boolean accept(File dir, String filename) {
        // TODO Auto-generated method stub
        return filename.endsWith(".mp3");
    }

}
@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.music_layout);
    updateMusicList();
}

private void updateMusicList(){
    File file = new File(SD_PATH);
    if(file.listFiles(new Mp3Filter()).length>0){
        for(File f : file.listFiles(new Mp3Filter()) ){
            songs.add(f.getName());
        }
    }
    ArrayAdapter<String> adapter = new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_dropdown_item_1line,
            songs);
    setListAdapter(adapter);
}

@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
    // TODO Auto-generated method stub
    super.onListItemClick(l, v, position, id);
    Intent i = new Intent(GetMusics.this,MusicPlayer.class);
    i.putExtra("song_name", songs.get(position));
    setResult(100,i);
    finish();

}

}

这是 MusicPlayer.java 类

public class MusicPlayer extends Activity {

MediaPlayer mp = new MediaPlayer();

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.music_player);
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    // TODO Auto-generated method stub
    super.onActivityResult(requestCode, resultCode, data);
    if(resultCode==100){
        String song_name = data.getStringExtra("song_name");
        mp.reset();
        try {
            mp.setDataSource(Environment.getExternalStorageDirectory()
                    .getPath() + "/" + song_name);
            mp.prepare();
            mp.start();
        } catch (IllegalArgumentException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IllegalStateException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}
}