Question

I have this class used in the API demos:

public class TextToSpeechActivity extends Activity implements TextToSpeech.OnInitListener {

     static int currentHelloIndex = 0;
private static final String TAG = "TextToSpeechDemo";

public static TextToSpeech mTts;
private Button mAgainButton;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.text_to_speech);

    // Initialize text-to-speech. This is an asynchronous operation.
    // The OnInitListener (second argument) is called after initialization completes.
    mTts = new TextToSpeech(this,
        this  // TextToSpeech.OnInitListener
        );

    // The button is disabled in the layout.
    // It will be enabled upon initialization of the TTS engine.
    mAgainButton = (Button) findViewById(R.id.again_button);

    mAgainButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            sayHello();
        }
    });
}

@Override
public void onDestroy() {
    // Don't forget to shutdown!
    if (mTts != null) {
        mTts.stop();
        mTts.shutdown();
    }

    super.onDestroy();
}

// Implements TextToSpeech.OnInitListener.
@Override
public void onInit(int status) {
    // status can be either TextToSpeech.SUCCESS or TextToSpeech.ERROR.
    if (status == TextToSpeech.SUCCESS) {
        // Set preferred language to US english.
        // Note that a language may not be available, and the result will indicate this.
        int result = mTts.setLanguage(Locale.US);
        // Try this someday for some interesting results.
        // int result mTts.setLanguage(Locale.FRANCE);
        if (result == TextToSpeech.LANG_MISSING_DATA ||
            result == TextToSpeech.LANG_NOT_SUPPORTED) {
           // Lanuage data is missing or the language is not supported.
            Log.e(TAG, "Language is not available.");
        } else {
            // Check the documentation for other possible result codes.
            // For example, the language may be available for the locale,
            // but not for the specified country and variant.

            // The TTS engine has been successfully initialized.
            // Allow the user to press the button for the app to speak again.
            mAgainButton.setEnabled(true);
            // Greet the user.
            sayHello();
        }
    } else {
        // Initialization failed.
        Log.e(TAG, "Could not initialize TextToSpeech.");
    }
}


private static final String[] HELLOS = {
  "What is a string of words that satisfy the grammatical rules of a sentence",
  "Salutations",
  "Greetings",
  "Howdy",
  "What's crack-a-lackin?",
  "That explains the stench!"
};


public static void sayHello() {
    // Select a random hello.

    int helloLength = HELLOS.length;
    String hello = HELLOS[currentHelloIndex];
    currentHelloIndex = (currentHelloIndex + 1) % helloLength;
    mTts.speak(hello,
        TextToSpeech.QUEUE_FLUSH,  // Drop all pending entries in the playback queue.
        null);


  }

}

I then have another class with an Onclick button and call the sayHello(); method by using TextToSpeech.sayHello(); This gives me a process closed error and says null exception error in logcat source not found etc. Please can someone help me with this problem. Thanks

Answer 1

Your current design has a significant flaw. mTts is only initialised in the onCreate method of TextToSpeechActivity, but then you try and call a method on this object in a static method from another class. There is no way to be sure that mTts is not null when your other class calls sayHello(). Further, even if mTts was not null, it had this passed into the constructor, which is your instance of TextToSpeechActivity, so I have no idea if TextToSpeech would even work when created for a totally different Activity.

I think you need to rethink your class design.