[android-developers] Text To Speech Android 1.6 with minsdk 3

[Eric Carman]

Hello,

I was playing with adding Text to Speech to one of my applications and
have been working with it using the Android 1.6 SDK. I was hoping to
release the code such that it could be used on the earlier 1.5 OS
since there are still quite a few of these around - and this is an
upgrade. I realize that the TTS won't work on the 1.5 (at least not as
I have it here), but I didn't want the app disappearing from the
market for those devices.

At any rate, after struggling for a while with this - a lot of trial
and error - I came up with what now seems like a simple wrapper to
allow for the backward compatibility. This was mostly taken from the
Android blog entry

http://android-developers.blogspot.com/2009/04/backward-compatibility-for-android.html

so I'm not exactly breaking new ground. Also, I'm not using all of the
TTS features, hence the short list of "wrapped" methods, expand at
your leisure. I'm attaching it here for anyone to use and anyone to
comment on if I have done something really stupid. I'll comment back
if my testing uncovers anything untoward.

Wrapper Class:

package com.mydomain.myapp;

import java.util.HashMap;
import java.util.Locale;

import android.content.Context;
import android.speech.tts.TextToSpeech;

public class WrapTTS {

        private TextToSpeech mTTS;

        /* class initialization fails when this throws an exception */
        static {
                try {
                        Class.forName("android.speech.tts.TextToSpeech");
                } catch (Exception ex) {
                        throw new RuntimeException(ex);
                }
        }

        /* calling here forces class initialization */
        public static void checkAvailable() {}

        private OnInitListener onInitListener = null;
        public interface OnInitListener {
                public abstract void onInit(int status);
        }

        public WrapTTS(Context context, WrapTTS.OnInitListener listener) {
                onInitListener = listener;
                mTTS = new TextToSpeech(context,
                                new TextToSpeech.OnInitListener() {

                                        @Override
                                        public void onInit(int status) {
                                                onInitListener.onInit(status);
                                        }

                                });

        }

        public int setSpeechRate(float speechRate) {
                return mTTS.setSpeechRate(speechRate);
        }

        public void shutdown() {
                mTTS.shutdown();
        }

        public int speak(String text, int queueMode, HashMap<String, String>
params) {
                return mTTS.speak(text, queueMode, params);
        }

        public int setLanguage(Locale loc) {
                return mTTS.setLanguage(loc);
        }

        public int isLanguageAvailable(Locale loc) {
                return mTTS.isLanguageAvailable(loc);
        }
}

The following is used at the top of my main application.

        private WrapTTS mTts = null;
        private static boolean mTTSClassAvailable = false;

        /* establish whether the "TextToSpeech" class is available to us */

        static {
                try {
                        WrapTTS.checkAvailable();
                        mTTSClassAvailable = true;
                } catch (Throwable t) {
                        mTTSClassAvailable = false;
                }
        }

Use the mTTSClassAvailable to know whether to bother to even try to
set up the engine.

Hopefully it helps someone.

Best Regards,
Eric

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