Android-关于Cursor空指针的有关问题

最近几天无聊自己动手写个音乐播放器，用到Cursor来取得数据库中音乐文件的

信息，但是当用到Cursor的时候总是报空指针错误，后来发现是模拟器上没有

音乐文件，使用Cursor的时候 ，若Cursor中没有结果，则Cursor的对象则为空

，所以在使用Cursor的时候最好先判断Cursor对象是否为空且其结果是否大于等于1，

以下是最开始的代码：

private void getSongMessage(){		String TITLE = MediaStore.Audio.Media.TITLE;		String DATA = MediaStore.Audio.Media.DATA;		String ALBUM = MediaStore.Audio.Media.ALBUM;		String ARTIST = MediaStore.Audio.Media.ARTIST;		Uri uri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;		ContentResolver cr = getContentResolver(); 		Cursor cs = cr.query(uri, null, null, null, null);  		while (cs.moveToNext()) {			String title = cs.getString(cs.getColumnIndex(TITLE));			String data = cs.getString(cs.getColumnIndex(DATA));			String album = cs.getString(cs.getColumnIndex(ALBUM));			String artist = cs.getString(cs.getColumnIndex(ARTIST));			MusicData.title.add(title);			MusicData.data.add(data);			MusicData.album.add(album);			MusicData.artist.add(artist);		}	}

以下 是修改后的代码：

 private void getSongMessage(){		String TITLE = MediaStore.Audio.Media.TITLE;		String DATA = MediaStore.Audio.Media.DATA;		String ALBUM = MediaStore.Audio.Media.ALBUM;		String ARTIST = MediaStore.Audio.Media.ARTIST;		Uri uri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;		ContentResolver cr = getContentResolver(); 		Cursor cs = cr.query(uri, null, null, null, null);  		if(cs != null && cs.getCount() >= 1){			while (cs.moveToNext()) {				String title = cs.getString(cs.getColumnIndex(TITLE));				String data = cs.getString(cs.getColumnIndex(DATA));				String album = cs.getString(cs.getColumnIndex(ALBUM));				String artist = cs.getString(cs.getColumnIndex(ARTIST));				MusicData.title.add(title);				MusicData.data.add(data);				MusicData.album.add(album);				MusicData.artist.add(artist);			}		}else{			Toast.makeText(this, "No Data", Toast.LENGTH_LONG).show();		}	}