0

所以我正在使用这段代码来访问我想要播放的歌曲的数据，但是每当我使用媒体播放器时我都会收到空指针异常。我用 toast 来检查文件名，即文件的路径是否正确，但它即将到来出来就好了。

protected void onListItemClick(ListView l, View v, int position, long id) {
        // TODO Auto-generated method stub
    //  super.onListItemClick(l, v, position, id);
    //  l.setClickable(false);
         music_column_index = musiccursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DATA);
                            musiccursor.moveToPosition(position);
                            String filename = musiccursor.getString(music_column_index);

                      try {
                        mMediaPlayer.setDataSource(filename);
                        mMediaPlayer.prepare();
                        mMediaPlayer.start();
                    } catch (IllegalArgumentException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    } catch (SecurityException 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();
                    }

        Toast.makeText(getApplicationContext(),filename, Toast.LENGTH_LONG).show();

    }

我在这条线上遇到错误

mMediaPlayer.setDataSource(filename);

日志猫：-

06-17 17:31:36.716: E/AndroidRuntime(5059): FATAL EXCEPTION: main
06-17 17:31:36.716: E/AndroidRuntime(5059): java.lang.NullPointerException
06-17 17:31:36.716: E/AndroidRuntime(5059):     at prac.tise_music.MainActivity.onListItemClick(MainActivity.java:136)
06-17 17:31:36.716: E/AndroidRuntime(5059):     at android.app.ListActivity$2.onItemClick(ListActivity.java:342)
06-17 17:31:36.716: E/AndroidRuntime(5059):     at android.widget.AdapterView.performItemClick(AdapterView.java:284)
06-17 17:31:36.716: E/AndroidRuntime(5059):     at android.widget.ListView.performItemClick(ListView.java:3569)
06-17 17:31:36.716: E/AndroidRuntime(5059):     at android.widget.AbsListView$PerformClick.run(AbsListView.java:1831)
06-17 17:31:36.716: E/AndroidRuntime(5059):     at android.os.Handler.handleCallback(Handler.java:587)
06-17 17:31:36.716: E/AndroidRuntime(5059):     at android.os.Handler.dispatchMessage(Handler.java:92)
06-17 17:31:36.716: E/AndroidRuntime(5059):     at android.os.Looper.loop(Looper.java:150)
06-17 17:31:36.716: E/AndroidRuntime(5059):     at android.app.ActivityThread.main(ActivityThread.java:4389)
06-17 17:31:36.716: E/AndroidRuntime(5059):     at java.lang.reflect.Method.invokeNative(Native Method)
06-17 17:31:36.716: E/AndroidRuntime(5059):     at java.lang.reflect.Method.invoke(Method.java:507)
06-17 17:31:36.716: E/AndroidRuntime(5059):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:849)
06-17 17:31:36.716: E/AndroidRuntime(5059):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:607)
06-17 17:31:36.716: E/AndroidRuntime(5059):     at dalvik.system.NativeStart.main(Native Method)
4

2 回答 2

0

如果您正在从外部存储读取文件，那么首先在您的清单中给出“读取外部存储权限”。因为您无法读取文件。

于 2013-06-17T12:11:50.263 回答
0

这里讨论了一个类似的问题。

可能它符合您的目的。

还有一个建议，试试MediaPlayer.create()，你也可能想在播放器实际准备好之后才开始，像这样：

于 2013-06-17T12:21:47.997 回答