如何在CodenameOne中使用Android TextToSpeech？

Question

I'd like to include text-to-speech functionality in my Codename One android app, but I can't seem to get it to work. As Codename One does not provide this capability in its API, I'm trying to create a Native interface to handle it using the google maps cn1lib as an example.

Here's what I've got so far:

NativeTTS.java

public class NativeTTS extends NativeInterface {
    public int speakString (String hello);
}

NativeTTSImpl.java

public class NativeTTSImpl implements OnInitListener, LifecycleListener,
                                      IntentResultListener {

    private TextToSpeech tts;

    public void initialize () {
        AndroidNativeUtil.addLifecycleListener (this);
    }

    public void deinitialize () {
        AndroidNativeUtil.removeLifecycleListener (this);
    }

    public int speakString(String text) {
        return tts.speak (text, TextToSpeech.QUEUE_FLUSH, null);
    }


    public void onInit (int status) {
        if ( status == TextToSpeech.SUCCESS ) {
            tts.setLanguage (Locale.US);
        }
    }


    public boolean isSupported() {
        return true;
    }

    public void onActivityResult (int requestCode, int resultCode, Intent data) {
        if ( resultCode == TextToSpeech.Engine.CHECK_VOICE_DATA_PASS )
            tts = new TextToSpeech (AndroidNativeUtil.getActivity (), this);
        else {
            Intent installIntent = new Intent ();
            installIntent.setAction (TextToSpeech.Engine.ACTION_CHECK_TTS_DATA);
            AndroidNativeUtil.getActivity ().startActivity (installIntent);
        }
    }

    public void onCreate (Bundle savedInstanceState) {
        Intent intent = new Intent ();
        intent.setAction (TextToSpeech.Engine.ACTION_CHECK_TTS_DATA);
        AndroidNativeUtil.startActivityForResult (intent, this);
    }


    public void onDestroy () {
        if ( tts != null ) {
            tts.stop ();
            tts.shutdown ();
        }
    }


    public void onResume () {}
    public void onPause  () {}
    public void onLowMemory () {}
    public void onSaveInstanceState (Bundle b) {}

}

I'm attempting to use it back in my app like so:

NativeTTS tts = (NativeTTS) NativeLookup.create (NativeTTS.class);
if ( tts != null && tts.isSupported () ) {
    int success = tts.speakString ("Hello World");
}

However, I'm getting a NullPointerException when I call tts.speakString (...) . I think the problem is that NativeTTSImpl.initialize() never gets called, and I'm clueless as to how/when I should call it.

Answer 1

You need to actually invoke initialize.

The lifecycle listener will only work for lifecycle events that occur after you register it not before, if you want more lifecycle events you can register an activity via the manifest but I'm not sure you need all of that complexity.

I don't see why speak doesn't do something like:

if(tts == null) {
    tts = new TextToSpeech (AndroidNativeUtil.getActivity (), this);
}

Answer 2

The real problem was waiting for the TextToSpeech engine to initialize before calling tts.speak(..) . I solved this by adding a boolean to indicate when TTS initialization has finished and to submit String s to a queue before initialization is complete. Here's the new native implementation code:

public class NativeTTSImpl implements OnInitListener {

    private static TextToSpeech tts;
    private static boolean ttsInitialized = false;
    private static final ConcurrentLinkedQueue<String> queue = 
        new ConcurrentLinkedQueue<String>();

    public void speakString (String text) {
        if ( tts == null ) {
            tts = new TextToSpeech (AndroidNativeUtil.getActivity (), this);
        }

        if ( ttsInitialized ) {
            tts.speak (text, TextToSpeech.QUEUE_FLUSH, null);
        } else {
            queue.add (text);
        }
    }


    public void onInit (int status) {
        if ( status == TextToSpeech.SUCCESS ) {
            tts.setLanguage (Locale.US);
            ttsInitialized = true;
            while ( !queue.isEmpty () ) {
                tts.speak (queue.poll (), TextToSpeech.QUEUE_FLUSH, null);
            }
        }
    }


    public boolean isSupported () {
        return true;
    }
}