Android在途中停止文字转语音

Question

我有一个片段，可以播放文件中的文本到语音。在播放时，我想通过按设备上的“后退”按钮来停止TTS。目前，只有在TTS完成后，它才会响应后退键。我已经尝试了很多事情，但是找不到解决方案。简而言之，我的代码是：

mTts=new TextToSpeech(getApplicationContext(), new TextToSpeech.OnInitListener() {

@Override
public void onInit(int status) {
    // TODO Auto-generated method stub
    if(status == TextToSpeech.SUCCESS){
    int result=mTts.setLanguage(Locale.UK);
    if(result==TextToSpeech.LANG_MISSING_DATA ||
        result==TextToSpeech.LANG_NOT_SUPPORTED){
        showLog("This Language is not supported");
    }
    else{
        String filePath="In the beginning God created the heavens and the earth. Now the earth proved to be formless and waste. ";

        ttsTextbox.setText(filePath);

        mTts.setPitch(ttsPitch);
        mTts.setSpeechRate(ttsRate);


        //adjust sound level
        AudioManager am = (AudioManager) getSystemService(Context.AUDIO_SERVICE);
        //store curr volume
        int amCurrVol = am.getStreamVolume(am.STREAM_MUSIC);
        int amStreamMusicMaxVol = am.getStreamMaxVolume(am.STREAM_MUSIC);
        am.setStreamVolume(am.STREAM_MUSIC, (ttsVolume*amStreamMusicMaxVol)/100, (ttsVolume*amStreamMusicMaxVol)/100);


        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
        mTts.speak(filePath, TextToSpeech.QUEUE_FLUSH, null, "99");
        } else {
        HashMap<String, String> params = new HashMap<String, String>();
        params.put(TextToSpeech.Engine.KEY_PARAM_UTTERANCE_ID,"99");
        mTts.speak(filePath, TextToSpeech.QUEUE_FLUSH, params);
        }
    }
    }
    else
    showLog("Initilization Failed!");
}
});

，后退按钮侦听器是：

    @Override
public void onBackPressed() {
    showLog("----back key pressed");
    super.onBackPressed();
    if(mTts.isSpeaking()){
        showLog("----stopping tts because back key pressed");
        stopTTS();
    }
    return;
}