Partial results using speech recognition

Question

I created a simple application inspired by this example in order to test all the available options (ie extra). I read about the EXTRA_PARTIAL_RESULTS extra and if I enable this option I should receive from the server any partial results related to a speech recognition. However, when I add this extra to the ACTION_RECOGNIZE_SPEECH intent, the voice recognition does not work anymore: the list does not display any results.

protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == VOICE_RECOGNITION_REQUEST_CODE) {
        switch(resultCode) {
        case RESULT_OK:
            Log.i(TAG, "RESULT_OK");
            processResults(data);
            break;
        case RESULT_CANCELED:
            Log.i(TAG, "RESULT_CANCELED");
            break;
        case RecognizerIntent.RESULT_AUDIO_ERROR:
            Log.i(TAG, "RESULT_AUDIO_ERROR");
            break;
        case RecognizerIntent.RESULT_CLIENT_ERROR:
            Log.i(TAG, "RESULT_CLIENT_ERROR");
            break;
        case RecognizerIntent.RESULT_NETWORK_ERROR:
            Log.i(TAG, "RESULT_NETWORK_ERROR");
            break;
        case RecognizerIntent.RESULT_NO_MATCH:
            Log.i(TAG, "RESULT_NO_MATCH");
            break;
        case RecognizerIntent.RESULT_SERVER_ERROR:
            Log.i(TAG, "RESULT_SERVER_ERROR");
            break;
        default:
            Log.i(TAG, "RESULT_UNKNOWN");
            break;
        }
    }
    Log.i(TAG, "Intent data: " + data);
    super.onActivityResult(requestCode, resultCode, data);
}

private void processResults(Intent data) {
    Log.i(TAG, "processResults()");

    ArrayList<String> matches = data.getStringArrayListExtra(RecognizerIntent.EXTRA_RESULTS);

    // list of results
    ListView listOfResults = (ListView)(findViewById(R.id.list_of_results));
    listOfResults.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, matches));

    // number of elements of above list
    TextView resultsCount = (TextView)(findViewById(R.id.results_count));
    resultsCount.setText(getString(R.string.results_count_label) + ": " + matches.size());
}

When this option is enabled, the number of elements in the list of results is equal to 1 and this one result is an empty string. What is the reason for this behavior?

ADDED DETAILS I used the following code in order to enable EXTRA_PARTIAL_RESULTS option (on Android 2.3.5).

Intent intent = new Intent(RecognizerIntent.ACTION_RECOGNIZE_SPEECH);
intent.putExtra(RecognizerIntent.EXTRA_LANGUAGE_MODEL, ...);
intent.putExtra(RecognizerIntent.EXTRA_PARTIAL_RESULTS, true);
intent.putExtra(RecognizerIntent.EXTRA_MAX_RESULTS, 3);
intent.putExtra(RecognizerIntent.EXTRA_PROMPT, ...);
startActivityForResult(intent, VOICE_RECOGNITION_REQUEST_CODE);   // where VOICE_RECOGNITION_REQUEST_CODE is a "global variable"

However, enabling this option, the ArrayList<String> matches in processResults method has only one empty element.

Solution

I suggest not relying on PARTIAL_RESULTS because the Google documentation says this: The server may ignore a request for partial results in some or all cases.

In my experience, Google almost always ignores requests for partial results.

However, I don't believe that setting EXTRA_PARTIAL_RESULTS should stop normal EXTRA_RESULTS from being returned. It should just have no effect. I have tested this in my code and adding EXTRA_PARTIAL_RESULTS doesn't change the output.

Also, unless you are using SpeechRecognizer, Android won't send you those error codes.

To see that EXTRA_PARTIAL_RESULTS does not interfere with the results. Get the code from here then add the extra within this method:

private void sendRecognizeIntent()
{
    Intent intent = new Intent(RecognizerIntent.ACTION_RECOGNIZE_SPEECH);
    intent.putExtra(RecognizerIntent.EXTRA_LANGUAGE_MODEL,
            RecognizerIntent.LANGUAGE_MODEL_FREE_FORM);
    intent.putExtra(RecognizerIntent.EXTRA_PARTIAL_RESULTS, true);
    intent.putExtra(RecognizerIntent.EXTRA_PROMPT, "Say the magic word");
    intent.putExtra(RecognizerIntent.EXTRA_MAX_RESULTS, 100);
    startActivityForResult(intent, SPEECH_REQUEST_CODE);
}