暂停功能无法正常工作从firebase的mp3文件

Question

play.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        MediaPlayer mediaPlayer=new MediaPlayer();
        try {
            mediaPlayer.setDataSource("https://firebasestorage.googleapis.com/v0/b/photo-on-birthday-cake-cccf5.appspot.com/o/birthday%20(1).mp3?alt=media&token=c1e988b4-f482-4020-8057-53c68195d2fc");
            mediaPlayer.setOnPreparedListener(new MediaPlayer.OnPreparedListener() {
                @Override
                public void onPrepared(MediaPlayer mediaPlayer) {
                    if(flag==0) {
                        mediaPlayer.start();
                        Toast.makeText(MusicActivity.this, "start", Toast.LENGTH_SHORT).show();
                        flag=1;
                        play.setBackgroundResource(R.drawable.ic_pause_circle_outline_black_24dp);
                    } else {
                        mediaPlayer.pause();
                        Toast.makeText(MusicActivity.this, "Stop", Toast.LENGTH_SHORT).show();
                        flag=0;
                    }
                }
            });
            mediaPlayer.prepare();
        }

        catch (IOException e){
            e.printStackTrace();
        }
    }
});

我尝试了这段代码，但是在进行播放时这在暂停功能上不起作用。