how to implemenent android video player in full screen

i have implemented android video player , but i don't need like this how i need mean when opening activity i need to pay video half screen in center when i click button full screen button then i need t pay in full screen , how to implement it help me....

VideoPlayerActivity

public class VideoPlayerActivity extends Activity implements SurfaceHolder.Callback, MediaPlayer.OnPreparedListener, VideoControllerView.MediaPlayerControl {

    SurfaceView videoSurface;
    MediaPlayer player;
    VideoControllerView controller;

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

        videoSurface = (SurfaceView) findViewById(R.id.videoSurface);
        SurfaceHolder videoHolder = videoSurface.getHolder();
        videoHolder.addCallback(this);

        player = new MediaPlayer();
        controller = new VideoControllerView(this);

        try {
            player.setAudioStreamType(AudioManager.STREAM_MUSIC);
            player.setDataSource(this, Uri.parse("http:/myipadree/sites/default/files/759226_639541239394676_1125470178_n.mp4"));
            player.setOnPreparedListener(this);
        } catch (IllegalArgumentException e) {
            e.printStackTrace();
        } catch (SecurityException e) {
            e.printStackTrace();
        } catch (IllegalStateException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        controller.show();
        return false;
    }

    // Implement SurfaceHolder.Callback
    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {

    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        player.setDisplay(holder);
        player.prepareAsync();
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {

    }
    // End SurfaceHolder.Callback

    // Implement MediaPlayer.OnPreparedListener
    @Override
    public void onPrepared(MediaPlayer mp) {
        controller.setMediaPlayer(this);
        controller.setAnchorView((FrameLayout) findViewById(R.id.videoSurfaceContainer));
        player.start();
    }
    // End MediaPlayer.OnPreparedListener

    // Implement VideoMediaController.MediaPlayerControl
    @Override
    public boolean canPause() {
        return true;
    }

    @Override
    public boolean canSeekBackward() {
        return true;
    }

    @Override
    public boolean canSeekForward() {
        return true;
    }

    @Override
    public int getBufferPercentage() {
        return 0;
    }

    @Override
    public int getCurrentPosition() {
        return player.getCurrentPosition();
    }

    @Override
    public int getDuration() {
        return player.getDuration();
    }

    @Override
    public boolean isPlaying() {
        return player.isPlaying();
    }

    @Override
    public void pause() {
        player.pause();
    }

    @Override
    public void seekTo(int i) {
        player.seekTo(i);
    }

    @Override
    public void start() {
        player.start();
    }

    @Override
    public boolean isFullScreen() {
        return false;
    }

    @Override
    public void toggleFullScreen() {

    }
    // End VideoMediaController.MediaPlayer

it is working perfect but it opening full screen if i modify layout file width and height then how to implement full screen and button full screen button