停止并在Mediaplayer中播放mp3

Question

I have placed two mp3 songs in raw folder. I have used two buttons to play them. I am calling it as below:

public class Songs extends Activity implements OnClickListener {

    private Button mBtn1, mBtn2, mBtn3, mBtn4, mBtn5, mBtn6, mBtn7, mBtn8, mBtn9, mBtn10;
    MediaPlayer mp;
    boolean playing = false;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.songs);

        mBtn1 = (Button) findViewById(R.id.button1);
        mBtn2 = (Button) findViewById(R.id.button2);

        mBtn1.setOnClickListener(this);
        mBtn2.setOnClickListener(this);
    }


    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub

        else if (v.getId() == mBtn1.getId()) {

            if (playing) {
                mp.stop();
                mp.pause();
                playing = false;
            } else {
                MediaPlayer mp = MediaPlayer.create(Songs.this, R.raw.chahun);
                mp.start();
                playing = true;
                //  mp.release();
            }
        } else if (v.getId() == mBtn2.getId()) {

            if (playing) {
                mp.stop();
                mp.pause();
                playing = false;
            } else {
                MediaPlayer mp = MediaPlayer.create(Songs.this, R.raw.sunn);
                mp.start();
                playing = true;
                //  mp.release();
            }

        }
    }
} 

But I think it is giving error while stopping the song. I'm getting error as following:

 05-21 11:49:23.006: E/AndroidRuntime(15436): FATAL EXCEPTION: main
    05-21 11:49:23.006: E/AndroidRuntime(15436): java.lang.NullPointerException
    05-21 11:49:23.006: E/AndroidRuntime(15436):    at com.qwinix.lucia.Songs.onClick(Songs.java:99)
    05-21 11:49:23.006: E/AndroidRuntime(15436):    at android.view.View.performClick(View.java:3517)
    05-21 11:49:23.006: E/AndroidRuntime(15436):    at android.view.View$PerformClick.run(View.java:14155)
    05-21 11:49:23.006: E/AndroidRuntime(15436):    at android.os.Handler.handleCallback(Handler.java:605)
    05-21 11:49:23.006: E/AndroidRuntime(15436):    at android.os.Handler.dispatchMessage(Handler.java:92)
    05-21 11:49:23.006: E/AndroidRuntime(15436):    at android.os.Looper.loop(Looper.java:154)
    05-21 11:49:23.006: E/AndroidRuntime(15436):    at android.app.ActivityThread.main(ActivityThread.java:4624)
    05-21 11:49:23.006: E/AndroidRuntime(15436):    at java.lang.reflect.Method.invokeNative(Native Method)
    05-21 11:49:23.006: E/AndroidRuntime(15436):    at java.lang.reflect.Method.invoke(Method.java:511)
    05-21 11:49:23.006: E/AndroidRuntime(15436):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:809)
    05-21 11:49:23.006: E/AndroidRuntime(15436):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:576)
    05-21 11:49:23.006: E/AndroidRuntime(15436):    at dalvik.system.NativeStart.main(Native Method)

Can anyone please solve this? Thanks

Answer 1

you forget to initialize mp instance of MediaPlayer . so you will need to initialize mp instead of creating new one on Button Click as:

if (v.getId() == mBtn1.getId()) {

    if (playing) {
            .....
    } else {
        mp = MediaPlayer.create(Songs.this, R.raw.chahun);
            ....
    }
} else if (v.getId() == mBtn2.getId()) {

    if (playing) {
            ......
    } else {
        mp = MediaPlayer.create(Songs.this, R.raw.sunn);
            .....
    }

}

}

Answer 2

You have'nt read the documentation properly that's why you are facing this exception

 if (playing) {

     if (mp != null) {
         mp.pause();
     }    
 }

If you media is already playing . First of all apply a check for its null condition then don't call stop() method make it pause by calling pause().

Reason of the exception

Before calling stop() method we have to pause the media first.

Refer the official docs

public void stop ()

Stops playback after playback has been stopped or paused.

It is clearly saying has been paused means either you have to pause the play back by calling Pause() or it gets stopped after completion.

http://developer.android.com/reference/android/media/MediaPlayer.html#stop%28%29

Sugesstion -- One of the goods method for debugging which I really follow is as soon as I am getting exception I started finding all the possible causes for that exception wether I have done all the things correct or not. If not getting solved then I use to read the documents of the methods from the use of which the exception is generated.