TextToSpeech在服务类中无法正常工作

大家好，我在我的项目中使用texttospeech，我在活动类中尝试了此代码，它工作正常，但在服务类中，它工作不正常，我在项目中使用文本进行语音转换，但抛出此错误。谁能告诉我我必须做些什么才能使其正常工作...

代码....

public class CallerService extends Service implements
    TextToSpeech.OnInitListener {

String number;

private TextToSpeech tts;

@Override
public IBinder onBind(Intent arg0) {
    // TODO Auto-generated method stub
    return null;
}

@Override
public void onCreate() {
    // TODO Auto-generated method stub
    super.onCreate();

    tts = new TextToSpeech(this, this);

}

@Override
@Deprecated
public void onStart(Intent intent, int startId) {
    // TODO Auto-generated method stub
    super.onStart(intent, startId);

    number = intent.getStringExtra("phnumber");

    fetchContacts();
}

@Override
public void onInit(int status) {
    // TODO Auto-generated method stub
     if (status != TextToSpeech.ERROR) 
     {
             tts.setLanguage(Locale.UK);
     } 
}

@Override
public void onDestroy() {
    // TODO Auto-generated method stub

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

}

public void fetchContacts() {
tts.speak("kd arjit", TextToSpeech.QUEUE_FLUSH,
                                    null);}
}
}

Logcat是...

04-07 12:27:00.028: I/TextToSpeech.java(5948): initTts() successfully bound to service
04-07 12:27:01.038: D/dalvikvm(5948): GC_EXPLICIT freed 83K, 45% free 3123K/5639K, `external 743K/1036K, paused 54ms
04-07 12:27:02.158: I/Contact Name:(5948): kd arjit
04-07 12:27:02.168: I/TextToSpeech.java - speak(5948): speak text of length 8
04-07 12:27:02.168: E/TextToSpeech.java - speak(5948): service isn't started
04-07 12:27:02.298: D/dalvikvm(5948): GC_CONCURRENT freed 375K, 48% free 3142K/5959K, external 758K/1036K, paused 2ms+4ms
04-07 12:27:02.308: W/CursorWrapperInner(5948): Cursor finalized without prior close()