Java Can'；看不到mediacontroller按钮

我已经实现了

mediaplayer

和

mediacontroller

，但看不到控制器按钮，如播放/暂停或音频的

positionbar

。音乐开始播放，但GUI没有出现。 代码：

---

我是一个初学者，所以这可能是一个实现错误，所以请给出修改后的代码

我还没有真正正确地实现MediaController（它仍然没有出现）。因此，作为权宜之计，我使用播放/暂停、前进/后退按钮代替MediaController，而progressSlider可以使用SeekBar

package mybitchinapp.cortana.com.musica;

import android.media.AudioManager;
import android.media.MediaPlayer;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
import android.widget.MediaController;
import android.widget.MediaController.MediaPlayerControl;

public class MainActivity extends AppCompatActivity implements MediaPlayerControl {

    private MediaPlayer player;
    private MediaController controller;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        player = MediaPlayer.create(this, R.raw.music);
        player.setAudioStreamType(AudioManager.STREAM_MUSIC);
//        controller = new MediaController(MainActivity.this);
        setController();
        player.start();

    }

    private void setController () {
        controller = new MediaController(this);
        controller.setPrevNextListeners(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                playNext();
            }
        }, new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                playPrev();
            }
        });

        controller.setMediaPlayer(this);
        controller.setAnchorView(findViewById (R.id.main)); // This is the main activity
        controller.setEnabled(true);
        controller.show (10000);
    }

    public void playPrev () {

    }

    public void playNext () {

    }

    @Override
    protected void onPause() {
        super.onPause();
        player.pause();
    }



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

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

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

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

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

    @Override
    public void seekTo(int pos) {

    }

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

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

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

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

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

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