安卓实现音乐播放时报错

问题遇到的现象和发生背景

在Android Studio上写了一个音乐播放器，但是会报错。

问题相关代码，请勿粘贴截图

 private Handler handler = new Handler(){
        @Override
        public void handleMessage(Message msg) {
            SongsDetail songsdetail = (SongsDetail) msg.obj;
            //用Media加载音乐
            try {
                Log.d(TAG, "handleMessage: 创建音乐对象");
                //获取需求的数据，给MediaPlayer初始化
                initMedia(songsdetail.getUrl());
                //设置SeekBar最大值
                seekBar.setMax(mediaPlayer.getDuration());
                //显示总时长
                textView_total.setText(getTime(mediaPlayer.getDuration()));
                //显示歌名
                textView_songsTitle.setText(songsdetail.getSongName());
            } catch (IOException e) {
                Toast.makeText(getApplication(),"出了点问题！",Toast.LENGTH_SHORT).show();
            }
        }
    };

 public void initMedia(String url) throws IOException {
        try {
            mediaPlayer = new MediaPlayer();
            mediaPlayer.setDataSource(url);
        } catch (Exception e){
            Toast.makeText(getApplication(),"出了点问题！",Toast.LENGTH_SHORT).show();
        }
        mediaPlayer.prepare();
    }

运行结果及报错内容

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: hnkjzyxy.class3202.ending, PID: 10245
    java.lang.IllegalStateException
        at android.media.MediaPlayer._prepare(Native Method)
        at android.media.MediaPlayer.prepare(MediaPlayer.java:1259)
        at hnkjzyxy.class3202.ending.SongsDetailActivity.initMedia(SongsDetailActivity.java:111)
        at hnkjzyxy.class3202.ending.SongsDetailActivity$1.handleMessage(SongsDetailActivity.java:48)
        at android.os.Handler.dispatchMessage(Handler.java:105)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6541)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)

mediaPlayer.prepare(); 放在 mediaPlayer.setDataSource(url); 之前。