无法可靠地调用UtteranceProgressListener

Question

I am writing an Android app to fetch the latest email from a folder and play it using TTS. I want to be able to use it whilst driving so it has to be mostly automatic. Everything so far is working fine until I attempt to capture when the TextToSpeech has finished speaking so we can move on to the next email.

Here is the complete MainActivity.java file:

package uk.co.letsdelight.emailreader;

import android.os.AsyncTask;
import android.os.Bundle;
import android.speech.tts.TextToSpeech;
import android.speech.tts.UtteranceProgressListener;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ImageButton;
import android.widget.TextView;
import android.widget.Toast;

import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;

import java.util.Properties;

import javax.mail.Folder;
import javax.mail.Message;
import javax.mail.Multipart;
import javax.mail.Session;
import javax.mail.Store;
import javax.mail.internet.MimeBodyPart;

public class MainActivity extends AppCompatActivity implements TextToSpeech.OnInitListener {

public TextToSpeech tts;
private Bundle ttsParam = new Bundle();
public UtteranceProgressListener utListener;
private boolean isPlaying = false;
private Properties imap = new Properties();
private String textToSpeak = "";

@Override
public void onInit(int ttsStatus) {
    if (ttsStatus == TextToSpeech.SUCCESS) {
        utListener = new UtteranceProgressListener() {
            @Override
            public void onStart(String s) {
                TextView status = findViewById(R.id.status);
                status.setText("started reading (Listener)");
            }

            @Override
            public void onDone(String s) {
                Toast.makeText(getApplicationContext(), "Done Event Listener", Toast.LENGTH_LONG).show();
                TextView status = findViewById(R.id.status);
                status.setText("finished reading (Listener)");
                /*ImageButton i = findViewById(R.id.playButton);
                i.setImageResource(R.drawable.button_play);*/
                isPlaying = false;
            }

            @Override
            public void onStop(String s, boolean b) {
                Toast.makeText(getApplicationContext(), "Stop Event Listener", Toast.LENGTH_LONG).show();
                TextView status = findViewById(R.id.status);
                status.setText("stopped reading (Listener)");
                /*ImageButton i = findViewById(R.id.playButton);
                i.setImageResource(R.drawable.button_play);*/
                isPlaying = false;
            }

            @Override
            public void onError(String s) {
                Toast.makeText(getApplicationContext(), "Error Event Listener", Toast.LENGTH_LONG).show();
                TextView status = findViewById(R.id.status);
                status.setText("Error reading email");
                ImageButton i = findViewById(R.id.playButton);
                i.setImageResource(R.drawable.button_play);
                isPlaying = false;
            }
        };
        tts.setOnUtteranceProgressListener(utListener);
        TextView status = findViewById(R.id.status);
        status.setText("initialised");
    } else {
        TextView status = findViewById(R.id.status);
        status.setText("failed to initialise");
    }
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    imap.setProperty("mail.store.protocol", "imap");
    imap.setProperty("mail.imaps.port", "143");
    tts = new TextToSpeech(this,this);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}

public void restartPressed(View v) {
    if (isPlaying) {
        tts.stop();
        speak();
    }
}

public void playPressed(View v) {
    ImageButton i = (ImageButton) v;
    if (isPlaying) {
        isPlaying = false;
        i.setImageResource(R.drawable.button_play);
        TextView status = findViewById(R.id.status);
        status.setText("");
        if (tts != null) {
            tts.stop();
        }
    } else {
        isPlaying = true;
        i.setImageResource(R.drawable.button_stop);
        new Reader().execute();
    }
}

class Reader extends AsyncTask<String, Void, String> {
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        TextView status = findViewById(R.id.status);
        status.setText("fetching email");
    }

    @Override
    protected String doInBackground(String... params) {
        String toRead = "nothing to fetch";
        try {
            Session session = Session.getDefaultInstance(imap, null);
            Store store = session.getStore();
            store.connect(getText(R.string.hostname).toString(), getText(R.string.username).toString(), getText(R.string.password).toString());
            Folder inbox = store.getFolder("INBOX.Articles.listen");
            if (inbox.exists() && inbox.getMessageCount() > 0) {
                inbox.open(Folder.READ_ONLY);
                Message msg = inbox.getMessage(inbox.getMessageCount() - 6);
                if (msg.getContentType().contains("multipart")) {
                    Multipart multiPart = (Multipart) msg.getContent();
                    MimeBodyPart part = (MimeBodyPart) multiPart.getBodyPart(multiPart.getCount() - 1);
                    toRead = part.getContent().toString();
                } else {
                    toRead = msg.getContent().toString();
                }
            } else {
                toRead = "The folder is empty or doesn't exist";
            }
        } catch (Throwable ex) {
            toRead = "Error fetching email - " + ex.toString();
        }
        return toRead;
    }

    @Override
    protected void onPostExecute(String s) {
        super.onPostExecute(s);
        String body;
        TextView status = findViewById(R.id.status);
        status.setText("");
        try {
            Document doc = Jsoup.parse(s);
            body = doc.body().text();
        } catch (Throwable ex) {
            body = "Error parsing email - " + ex.toString();
        }
        status.setText("email successfully fetched");
        textToSpeak = body;
        if (isPlaying) {
            speak();
        }
    }
}

private void speak() {
    int maxLength = TextToSpeech.getMaxSpeechInputLength();
    if (textToSpeak.length() > maxLength) {
        textToSpeak = "The email text is too long! The maximum length is " + maxLength + " characters";
    }
    ttsParam.putString(TextToSpeech.Engine.KEY_PARAM_UTTERANCE_ID, "EmailReader");
    tts.speak(textToSpeak, TextToSpeech.QUEUE_FLUSH, ttsParam, "EmailReader");
}

@Override
protected void onDestroy() {
    if (tts != null) {
        tts.stop();
        tts.shutdown();
    }
    super.onDestroy();
}
}

The inner class Reader works fine. doInBackground fetches the email and onPostExec strips out any HTML to leave the actual text content of the email. This is passed to the speak() method which does the actual speaking and works.

The issue is with the onUtteranceProgressListener .

Sometimes the onStart(String s) method is called, sometimes it isn't! It seems to never be called the first time the email read out. Mostly it is called for subsequent calls to speak() but not always. About 1 in 5 times it fails to get called. If the listener is called the status displays 'started reading (Listener)' otherwise it shows 'email successfully fetched'.

onDone , onError and onStop are never called.

I have tried using different utteranceID and Bundle values in the tts.speak() call but this makes to difference.

When the app is started, the first status display is 'initialised' which means that the onUtteranceListener must have been set within the onInit method. The TextToSpeech object is instantiated within the activity's onCreate method.

I have looked through all the information I can find which has mostly suggested getting the utteranceID correct. What else can I try in order to get a better understanding of this problem please?

Answer 1

The problem is that the onDone() method (and in fact any of the progress callbacks) is run on a background thread, and therefore the Toast is not going to work, and any code that accesses your UI such as setText(...) may or may not work.

So... the methods probably are being called, but you just can't see that.

The solution to this would be to surround the code in your callbacks with runOnUiThread() like this:

@Override
public void onDone(String s) {

    runOnUiThread(new Runnable() {
        @Override
        public void run() {
            Toast.makeText(getApplicationContext(), "Done Event Listener", Toast.LENGTH_LONG).show();
            TextView status = findViewById(R.id.status);
            status.setText("finished reading (Listener)");
            /*ImageButton i = findViewById(R.id.playButton);
            i.setImageResource(R.drawable.button_play);*/
            isPlaying = false;
        }
    });

}

Note: It's probably best to initialize your TextView in onCreate() along with everything else instead of in the progress callbacks.

Also, the purpose of the utteranceID is to give each call to speak() a unique identifier that is then passed back to you as the "String s" argument in the progress callbacks.

It's a good idea to give each call to speak a new ("most recent") ID using some kind of random number generator, and then checking it in the progress callbacks.

You can see a similar question and answer regarding this here .

Side note:

Since you have a "restart" button, you should know that on APIs <23, calls to TextToSpeech.stop() will cause the onDone() in your progress listener to be called. On APIs 23+, it calls onStop() instead.

Answer 2

First, make sure you actually have a problem and not a race between who sets the text in what order. Use log statements to make sure it is not actually called.

Try setting queueMode to QUEUE_ADD like:

tts.speak(textToSpeak, TextToSpeech.QUEUE_ADD, ttsParam, "EmailReader");

maybe subsequent calls are cancelling the listener's events from previous texts inputs, as QUEUE_FLUSH suggests.

Also the bundle isn't really needed there, you can set it to null.

Hope any of these helps.