onPostExecute（）在doInBackground（）在API 23中完成之前执行

Question

我想创建一个包含toggleButton的无线电应用程序，因为在收音机执行之前应始终显示progressBar。

我正在尝试显示一个ProgressBar，直到doInBackground（）完成。我的代码适用于所有android版本execpt android api 23（android marshmallow 6.0），其中onPostExecute（）在doInBackground（）之前执行。这是我的代码：

主要内容：

    ToggleButton MusicButton;
    MediaPlayer mediaPlayer;
    String stream = "RADIO_URL";
    boolean prepared = false;
    boolean started = false ;
    public static final String PREFS_NAME = "MyPrefsFile1";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
          mediaPlayer = new MediaPlayer();
        if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.LOLLIPOP) {
            AudioAttributes attribs = new AudioAttributes.Builder().setUsage(AudioAttributes.USAGE_MEDIA).setContentType(AudioAttributes.CONTENT_TYPE_MUSIC).build();
            mediaPlayer.setAudioAttributes(attribs);

        }else {
            mediaPlayer.setAudiostreamType(AudioManager.STREAM_MUSIC);
        }
        new PlayerTask().execute(stream);

        /****/
        MusicButton = (ToggleButton) findViewById(R.id.toggleButton);
        MusicButton.setVisibility(View.INVISIBLE);
        MusicButton.setOnCheckedChangeListener(new OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                if ( started && MusicButton.isChecked()) {
                    started=false;
                    mediaPlayer.pause();
                    MusicButton.setChecked(true);
                } else {
                    started=true;
                    mediaPlayer.start();
                    MusicButton.setChecked(false);
                }
            }
        });

 class PlayerTask extends AsyncTask<String,Void,Boolean> {
        ProgressBar radio = (ProgressBar)findViewById(R.id.radioloading);
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            radio.setVisibility(View.VISIBLE);
        }
        @Override
        protected Boolean doInBackground(String... strings) {
            try {
                mediaPlayer.setDataSource(strings[0]);
                mediaPlayer.prepare();
                prepared=true;
            } catch (IOException e) {
                e.printStackTrace();
            }
            return prepared;
        }
        @Override
        protected void onPostExecute(Boolean aBoolean) {
            super.onPostExecute(aBoolean);
            MusicButton.setVisibility(View.VISIBLE);
            MusicButton.setChecked(true);
            radio.setVisibility(View.GONE);
        }
    }