Android 空指针异常无法实现播放功能

  public void initMedia(String url) throws IOException {
        try {
            mediaPlayer = new MediaPlayer();
            mediaPlayer.setDataSource(url);
            mediaPlayer.prepare();
        } catch (Exception e){
            Toast.makeText(getApplication(),"出了点问题！",Toast.LENGTH_SHORT).show();
 private Handler handler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            SongsDetail songsdetail = (SongsDetail) msg.obj;
            try {
                Log.d(TAG, "handleMessage: 创建音乐对象");
                initMedia(songsdetail.getUrl());
                seekBar.setMax(mediaPlayer.getDuration());
                textView_total.setText(getTime(mediaPlayer.getDuration()));
                textView_songsTitle.setText(songsdetail.getSongName());
            } catch (IOException e) {
                e.printStackTrace();
错误日志是这样的
E/AndroidRuntime: FATAL EXCEPTION: main
    Process: hnkjzyxy.class3202.ending, PID: 13471
    java.lang.NullPointerException: uriString
        at android.net.Uri$StringUri.<init>(Uri.java:476)
        at android.net.Uri$StringUri.<init>(Unknown Source:0)
        at android.net.Uri.parse(Uri.java:438)
        at android.media.MediaPlayer.setDataSource(MediaPlayer.java:1147)
        at android.media.MediaPlayer.setDataSource(MediaPlayer.java:1141)
        at android.media.MediaPlayer.setDataSource(MediaPlayer.java:1108)
        at hnkjzyxy.class3202.ending.SongsDetailActivity.initMedia(SongsDetailActivity.java:152)
        at hnkjzyxy.class3202.ending.SongsDetailActivity$1.handleMessage(SongsDetailActivity.java:87)
        at android.os.Handler.dispatchMessage(Handler.java:105)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6541)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
希望有人可以给我解释一下，错误原因以及解决方案，十分感谢