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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(); } }
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原文地址：http://www.cnblogs.com/zhujiabin/p/4249411.html
