s を 音量 volume で発話する
private void speak(String s,float volume){
if (Build.VERSION.SDK_INT >= 21) {
Bundle params = new Bundle();
params.putFloat(TextToSpeech.Engine.KEY_PARAM_VOLUME, volume);
textToSpeech.speak(s, TextToSpeech.QUEUE_FLUSH,params,null);
} else {
HashMap<String, String> params = new HashMap<>();
params.put(TextToSpeech.Engine.KEY_PARAM_VOLUME, String.valueOf(volume));
textToSpeech.speak(s, TextToSpeech.QUEUE_FLUSH, params);
}
}