MediaPlayer onStop（）NullPointerException

Question

SharedProperties.java

public void initPlayMusic(Context context, int count) {
    playMusic = MediaPlayer.create(context, count);
    playMusic.setVolume(100, 100);
    playMusic.setLooping(false);
}

public void playMusic() {
    playMusic.start();
}

public void stopMusic() {
    if(playMusic!=null) {
        playMusic.stop();
        playMusic.release();
        playMusic=null;
    }
}

public void initPlayMusic1(Context context, int count) {
    playMusic1 = MediaPlayer.create(context, count);
    playMusic1.setVolume(100, 100);
    playMusic1.setLooping(false);
}

public void playMusic1() {
    playMusic1.start();
}

public void stopMusic1() {
    if(playMusic1!=null) {
        playMusic1.stop();
        playMusic1.release();
        playMusic1=null;
    }
}

我的观点类

在此处将SharedProperties.java称为sp

 @Override
public void onClick(View v) {
    switch(v.getId()) {
        case R.id.backButton:
            Intent videoIntent = new Intent(PlayPage1.this,MainActivity.class);
            startActivity(videoIntent);
            finish();
            break;
        case R.id.imageView2:   
            sp.stopMusic();
            if(!test){
                test = true;
                sp.playMusic(); Toast.makeText(getApplicationContext(),"play Music ",Toast.LENGTH_SHORT).show();

            } else {
                Toast.makeText(getApplicationContext(),"play       Music1 ",Toast.LENGTH_SHORT).show();
                sp.playMusic1();
                test = false;
            }
            sp.playSFXWrong();
            sp.getSFXWrong().setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
                @Override
                public void onCompletion(MediaPlayer mp) {
                    txtone.setEnabled(true);
                    txtthree.setEnabled(true);
                }
            });
            answer=false;
            break;

        case R.id.imageView3:
            t
            sp.stopMusicx();
            if(!test){
               // Toast.makeText(getApplicationContext(),"play Music1 ",Toast.LENGTH_SHORT).show();
                test = true;
                sp.playMusic(); Toast.makeText(getApplicationContext(),"play Music ",Toast.LENGTH_SHORT).show();

            }else{
                Toast.makeText(getApplicationContext(),"play Music1 ",Toast.LENGTH_SHORT).show();
                test = false;
                sp.playMusic1();

            }
            sp.playSFXWrong();
            sp.getSFXWrong().setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
                @Override
                public void onCompletion(MediaPlayer mp) {
                    txtone.setEnabled(true);
                    txttwo.setEnabled(true);
                }
            });
            answer=false;
            break;
    }
}

如果调用stopMusic()，我可以进行此音频重叠预防;它提供NullPointerException所以请找我的错误 否则pauseMusic()也无法在这里工作。