javascript - Google's Text-To-Speech API from Android app

Question

I want to use Google's Text-To-Speech API in an Android app but I only could find the way to do it from web (Chrome). This is my first attempt to play "Hello world" from the app.

playTTS is the onClick and it is been executed, but no sound is played. Is there any JS/Java library I need to import? Is it possible to generate an audio file from it?

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    myBrowser = new WebView(this);
    if (savedInstanceState == null) {
        getSupportFragmentManager().beginTransaction()
                .add(R.id.container, new PlaceholderFragment()).commit();
    }
}

public void playTTS(View view) {
    myBrowser.loadUrl("javascript:speechSynthesis.speak(
         SpeechSynthesisUtterance('Hello World'))");
}

Answer 1

In Android java code your Activity/other Class should implement TextToSpeech.OnInitListener. You will get a TextToSpeech instance by calling TextToSpeech(context, this). (Where context refers to your application's Context -- can be this in an Activity.) You will then receive a onInit() callback with status which tells whether the TTS engine is available or not.

You can talk by calling tts.speak(textToBeSpoken, TextToSpeech.QUEUE_FLUSH, null) or tts.speak(textToBeSpoken, TextToSpeech.QUEUE_ADD, null). The first one will interrupt any "utterance" that is still being spoken and the latter one will add the new "utterance" to a queue. The last parameter is not mandatory. It could be an "utterance id" defined by you in case you want to monitor the TTS status by setting an UtteranceProgressListener. (Not necessary)

In Java code a simple "TTS talker" class could be something like:

public class MyTtsTalker implements TextToSpeech.OnInitListener {

  private TextToSpeech tts;
  private boolean ttsOk;

  // The constructor will create a TextToSpeech instance.
  MyTtsTalker(Context context) {
    tts = new TextToSpeech(context, this);
  }

  @Override
  // OnInitListener method to receive the TTS engine status
  public void onInit(int status) {
    if (status == TextToSpeech.SUCCESS) {
      ttsOk = true;
    }
    else {
      ttsOk = false;
    }
  }

  // A method to speak something
  @SuppressWarnings("deprecation") // Support older API levels too.
  public void speak(String text, Boolean override) {
    if (ttsOk) {
      if (override) {
        tts.speak(text, TextToSpeech.QUEUE_FLUSH, null);    
      }    
      else {
        tts.speak(text, TextToSpeech.QUEUE_ADD, null);    
      }
    }
  }
}