处理程序不更新ActionBar标题

Question

我正在为音乐播放器编写代码，除了ActionBar之外，一切似乎都运行正常。当一首歌正在播放时，一个线程每秒都会探测该服务以改变歌曲，如果歌曲发生变化，则处理程序对象会更改UI元素。

final Handler uiHandler = new Handler() {
    @Override
    public void handleMessage(Message msg) {
        Bundle data = msg.getData();
        song = data.getParcelable("song_info");
        songText.setText(song.getSongTitle());
        artistText.setText(song.getSongArtist());
        seekBar.setMax(mService.getDuration()/1000); //All these work
        assert getSupportActionBar() != null;
        getSupportActionBar().setTitle(mService.getSongName()); //Not updating
        super.handleMessage(msg);
    }
};

这样做的是当来自线程的消息时，它会更新UI。我可以确认这是有效的，并在我需要时调用。所有文本视图和搜索栏都会根据需要进行更新。但是，getSupportActionBar（）。setTitle（...）不会更新标题栏。
如果我在同一个类的其他方法中执行此操作，则设置操作栏标题的方法相同。我在这里遗漏了什么吗？ 提前谢谢！

的更新
这里有一些活动所拥有的代码，以防它有助于攻击。

 private ServiceConnection mConnection = new ServiceConnection() {
            @Override
            public void onServiceConnected(ComponentName componentName, IBinder iBinder) {
                MusicService.MusicBinder mBinder = (MusicService.MusicBinder)iBinder;
                mService = mBinder.getService();
                pauseBtn = (ImageButton)findViewById(R.id.pause);
                seekBar.setMax(mService.getDuration()/1000);
                CounterThread cThread = new CounterThread();
                Thread counter = new Thread(cThread);
                counter.start();
                if(mService.isPaused()) {
                    pauseBtn.setImageResource(R.drawable.ic_play_arrow_white_36dp);
                }
                else {
                    pauseBtn.setImageResource(R.drawable.ic_pause_white_36dp);
                }
            }

            @Override
            public void onServiceDisconnected(ComponentName componentName) {
            }
        };

        private class CounterThread implements Runnable {
            @Override
            public void run() {
                while(true) {
                    try {
                        if(!mService.getSongName().equals(song.getSongTitle())) //This is invoked when there is a change in the song.{
                            Message msg = uiHandler.obtainMessage();
                            Bundle b = new Bundle();
                            b.putParcelable("song_info", mService.getSong());
                            msg.setData(b); //I receive this message in the handler
                            uiHandler.sendMessage(msg);
                        }
                        seekBar.setProgress(mService.getCurrPosn()/1000);
                        Thread.sleep(1000);
                    } catch (Exception e){
                        e.printStackTrace();
                    }
                }
            }
        }
@Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.song_playing);
        song = getIntent().getParcelableExtra("song_info");
        songText = (TextView) findViewById(R.id.songname);
        artistText = (TextView) findViewById(R.id.artistname);
        songText.setText(song.getSongTitle());
        artistText.setText(song.getSongArtist());
        header = getSupportActionBar();
        seekBar = (SeekBar)findViewById(R.id.seekBar);

        seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            @Override
            public void onProgressChanged(SeekBar seekBar, int i, boolean b) {
                // Do nothing
            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {
                // Do nothing
            }

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {
                int progress = seekBar.getProgress();
                mService.seek(progress*1000);
            }
        });

        assert header != null;
        header.setDisplayOptions(ActionBar.DISPLAY_SHOW_CUSTOM);
        header.setCustomView(R.layout.head_layout);
        titleText = (TextView) findViewById(R.id.titleText);
        titleText.setText(song.getSongTitle());

    }
/* 
More operations
*/
public void next(View v) {
        mService.nextSong();
        pauseBtn.setImageResource(R.drawable.ic_pause_white_36dp);

        assert header != null;
        header.setTitle(mService.getSongName());  // This works fine

        songText.setText(mService.getSongName());
        artistText.setText(mService.getArtistName());
        titleText.setText(mService.getSongName());
        seekBar.setMax(mService.getDuration()/1000);
    }

不要介意轻微的缩进偏移。