Recognizing multiple keywords using PocketSphinx

you can use addKeywordSearch which uses to file with keyphrases. One phrase per line with threshold for each phrase in //, for example

up /1.0/
down /1.0/
left /1.0/
right /1.0/
forwards /1e-1/

Threshold must be selected to avoid false alarms.

Thanks to Nikolay's tip (see his answer above), I have developed the following code which works fine, and does not recognize words unless they're on the list. You can copy and paste this directly over the main class in the PocketSphinxDemo code:

public class PocketSphinxActivity extends Activity implements RecognitionListener
{
private static final String DIGITS_SEARCH = "digits";
private SpeechRecognizer recognizer;

@Override
public void onCreate(Bundle state)
{
    super.onCreate(state);

    setContentView(R.layout.main);

    ((TextView) findViewById(R.id.caption_text)).setText("Preparing the recognizer");

    try
    {
        Assets assets = new Assets(PocketSphinxActivity.this);
        File assetDir = assets.syncAssets();
        setupRecognizer(assetDir);
    }
    catch (IOException e)
    {
        // oops
    }

    ((TextView) findViewById(R.id.caption_text)).setText("Say up, down, left, right, forwards, backwards");

    reset();
}

@Override
public void onPartialResult(Hypothesis hypothesis)
{
}

@Override
public void onResult(Hypothesis hypothesis)
{
    ((TextView) findViewById(R.id.result_text)).setText("");

    if (hypothesis != null)
    {
        String text = hypothesis.getHypstr();
        makeText(getApplicationContext(), text, Toast.LENGTH_SHORT).show();
    }
}

@Override
public void onBeginningOfSpeech()
{
}

@Override
public void onEndOfSpeech()
{
    reset();
}

private void setupRecognizer(File assetsDir)
{
    File modelsDir = new File(assetsDir, "models");

    recognizer = defaultSetup().setAcousticModel(new File(modelsDir, "hmm/en-us-semi"))
                               .setDictionary(new File(modelsDir, "dict/cmu07a.dic"))
                               .setRawLogDir(assetsDir).setKeywordThreshold(1e-20f)
                               .getRecognizer();

    recognizer.addListener(this);

    File digitsGrammar = new File(modelsDir, "grammar/digits.gram");
    recognizer.addKeywordSearch(DIGITS_SEARCH, digitsGrammar);
}

private void reset()
{
    recognizer.stop();
    recognizer.startListening(DIGITS_SEARCH);
}
}

Your digits.gram file should be something like:

up /1e-1/
down /1e-1/
left /1e-1/
right /1e-1/
forwards /1e-1/
backwards /1e-1/

You should experiment with the thresholds within the double slashes // for performance, where 1e-1 represents 0.1 (I think). I think the maximum is 1.0.

And it's 5.30pm so I can stop working now. Result.