如何在Android中使用音频恢复活动？

Question

我已经实现了媒体播放器。 我只有一个活动。 当我开始活动时，我的音乐开始播放，当我按下“后退”按钮时，音乐剪辑处于暂停状态，而当我再次开始活动时，音乐又恢复了正常。 但是在歌曲结束后我尝试恢复我的应用程序后出现错误。 应用程序崩溃了，我在后按方法（ mp.pause(); ）中收到了IllegalStateException异常。

请查看下面的代码，并建议我是否做错了什么。

public class Audio_Activity extends Activity 
{
    private  MediaPlayer mp;
    Button btnStartStop ;

    int length;
    SharedPreferences prefs;
    ImageView imgVw;

    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.audio);
        init();
        imgVw.setImageResource(R.raw.teddy_two);

        prefs = PreferenceManager.getDefaultSharedPreferences(this);

        mp=MediaPlayer.create(Audio_Activity.this,R.raw.ennamo_yadho);
        Log.e("Song is playing","in  Mediya Player ");
        Log.e("Current ","Position -> " + length);
        mp.setLooping(false);
        mp.start();
        btnChapter.setEnabled(false);

        mp.setOnCompletionListener(new MediaPlayer.OnCompletionListener() 
        {
            @Override
            public void onCompletion(MediaPlayer mp) 
            {
                // TODO Auto-generated method stub
                mp.stop();
                mp.release();
                btnChapter.setEnabled(true);
                System.out.println("Music is over and Button is enable !!!!!!");
            }
        });
    }

     @Override
        public void onConfigurationChanged(Configuration newConfig) {
            super.onConfigurationChanged(newConfig);

            // Checks the orientation of the screen
            if (newConfig.orientation == Configuration.ORIENTATION_LANDSCAPE) {
                Toast.makeText(this, "landscape", Toast.LENGTH_SHORT).show();
            } else if (newConfig.orientation == Configuration.ORIENTATION_PORTRAIT){
                Toast.makeText(this, "portrait", Toast.LENGTH_SHORT).show();
            }
        }

     @Override
     public void onPause()
     {
          super.onStop();

          SharedPreferences. Editor prefsEdit = prefs.edit();

          int position = mp.getCurrentPosition();
          prefsEdit.putInt("mediaPosition", position);
          prefsEdit.commit();
        }

     @Override
        protected void onResume() 
        {
            super.onResume();
            System.out.println("Activity is Resume !!!");

                  int position = prefs.getInt("mediaPosition", 0);
                  mp.seekTo(position);
        }

    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) 
    {
        if ((keyCode == KeyEvent.KEYCODE_BACK)) 
        { 
            if(mp!= null)
            {
                f(mp.isPlaying())
                {
                    mp.pause();
                }
            }
            finish();
            return true;
        }
        return super.onKeyDown(keyCode, event);
    }
}

这是我的原木猫

07-09 11:52:01.057: I/System.out(6854): Music is over and Button is enable !!!!!!
07-09 11:52:03.297: D/AndroidRuntime(6854): Shutting down VM
07-09 11:52:03.297: W/dalvikvm(6854): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
07-09 11:52:03.339: E/AndroidRuntime(6854): FATAL EXCEPTION: main
07-09 11:52:03.339: E/AndroidRuntime(6854): java.lang.IllegalStateException
07-09 11:52:03.339: E/AndroidRuntime(6854):     at android.media.MediaPlayer.isPlaying(Native Method)
07-09 11:52:03.339: E/AndroidRuntime(6854):     at com.audio_demo.Audio_Activity.onKeyDown(Audio_Activity.java:203)
07-09 11:52:03.339: E/AndroidRuntime(6854):     at android.view.KeyEvent.dispatch(KeyEvent.java:2609)
07-09 11:52:03.339: E/AndroidRuntime(6854):     at android.app.Activity.dispatchKeyEvent(Activity.java:2375)
07-09 11:52:03.339: E/AndroidRuntime(6854):     at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchKeyEvent(PhoneWindow.java:1847)
07-09 11:52:03.339: E/AndroidRuntime(6854):     at android.view.ViewRootImpl.deliverKeyEventPostIme(ViewRootImpl.java:3701)
07-09 11:52:03.339: E/AndroidRuntime(6854):     at android.view.ViewRootImpl.handleImeFinishedEvent(ViewRootImpl.java:3651)
07-09 11:52:03.339: E/AndroidRuntime(6854):     at android.view.ViewRootImpl$ViewRootHandler.handleMessage(ViewRootImpl.java:2818)
07-09 11:52:03.339: E/AndroidRuntime(6854):     at android.os.Handler.dispatchMessage(Handler.java:99)
07-09 11:52:03.339: E/AndroidRuntime(6854):     at android.os.Looper.loop(Looper.java:137)
07-09 11:52:03.339: E/AndroidRuntime(6854):     at android.app.ActivityThread.main(ActivityThread.java:5041)
07-09 11:52:03.339: E/AndroidRuntime(6854):     at java.lang.reflect.Method.invokeNative(Native Method)
07-09 11:52:03.339: E/AndroidRuntime(6854):     at java.lang.reflect.Method.invoke(Method.java:511)
07-09 11:52:03.339: E/AndroidRuntime(6854):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
07-09 11:52:03.339: E/AndroidRuntime(6854):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
07-09 11:52:03.339: E/AndroidRuntime(6854):     at dalvik.system.NativeStart.main(Native Method)
07-09 11:52:28.787: I/Process(6854): Sending signal. PID: 6854 SIG: 9

Answer 1

据我了解，问题在于onResume（）中的mp.seekTo（posiotion）或onPause（）方法中的mp.getCurrentPosition。 该异常可能是因为未初始化媒体播放器。 根据收听者的意见，当歌曲结束时，您使播放器停止并释放，并且在mp.seekTo（position）行的onResume中导致该异常。 在OnCompletion（）方法以及onResume和onpPause方法中删除mp.release（）行。 您还需要做另一件事。 在代码中使用布尔值可以了解Mediaplayer是否已播放完毕。 如下更改您的onCreat：

public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.audio);
        init();
        imgVw.setImageResource(R.raw.teddy_two);

        prefs = PreferenceManager.getDefaultSharedPreferences(this);

        mp=MediaPlayer.create(Audio_Activity.this,R.raw.ennamo_yadho);
        Log.e("Song is playing","in  Mediya Player ");
        Log.e("Current ","Position -> " + length);
        mp.setLooping(false);
        mp.start();
        prefsEdit.putInt("mediaplaying", true);
        prefsEdit.commit();
        btnChapter.setEnabled(false);

    mp.setOnCompletionListener(new MediaPlayer.OnCompletionListener() 
    {
        @Override
        public void onCompletion(MediaPlayer mp) 
        {
            // TODO Auto-generated method stub
            mp.stop();
            prefsEdit.putInt("mediaplaying", false);
            prefsEdit.commit();
            btnChapter.setEnabled(true);
            System.out.println("Music is over and Button is enable !!!!!!");
        }
    });

     @Override
     public void onPause()
     {
          super.onStop();

          SharedPreferences. Editor prefsEdit = prefs.edit();
          boolean isPlaying=prefs.getBoolean("mediaplaying",false);
          if(isPlaying){
              int position = mp.getCurrentPosition();
              prefsEdit.putInt("mediaPosition", position);
              prefsEdit.commit();
          }
        }

     @Override
        protected void onResume() 
        {
            super.onResume();
            System.out.println("Activity is Resume !!!");
            boolean isPlaying=prefs.getBoolean("mediaplaying",false);
            if(isPlaying){
                int position = prefs.getInt("mediaPosition", 0);
                mp.seekTo(position);
            }
        }