src/com/android/settings/TextToSpeechSettings.java

/*
 * Copyright (C) 2009 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.settings;

import static android.provider.Settings.Secure.TTS_DEFAULT_COUNTRY;
import static android.provider.Settings.Secure.TTS_DEFAULT_LANG;
import static android.provider.Settings.Secure.TTS_DEFAULT_RATE;
import static android.provider.Settings.Secure.TTS_DEFAULT_SYNTH;
import static android.provider.Settings.Secure.TTS_DEFAULT_VARIANT;
import static android.provider.Settings.Secure.TTS_ENABLED_PLUGINS;
import static android.provider.Settings.Secure.TTS_USE_DEFAULTS;

import android.app.AlertDialog;
import android.content.ActivityNotFoundException;
import android.content.ContentResolver;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.preference.CheckBoxPreference;
import android.preference.ListPreference;
import android.preference.Preference;
import android.preference.Preference.OnPreferenceClickListener;
import android.preference.PreferenceGroup;
import android.provider.Settings;
import android.provider.Settings.SettingNotFoundException;
import android.speech.tts.TextToSpeech;
import android.speech.tts.TextToSpeech.EngineInfo;
import android.speech.tts.TtsEngines;
import android.text.TextUtils;
import android.util.Log;

import java.util.ArrayList;
import java.util.List;
import java.util.Locale;
import java.util.StringTokenizer;

public class TextToSpeechSettings extends SettingsPreferenceFragment implements
        Preference.OnPreferenceChangeListener, Preference.OnPreferenceClickListener,
        TextToSpeech.OnInitListener {

    private static final String TAG = "TextToSpeechSettings";

    private static final String KEY_TTS_PLAY_EXAMPLE = "tts_play_example";
    private static final String KEY_TTS_INSTALL_DATA = "tts_install_data";
    private static final String KEY_TTS_USE_DEFAULT = "toggle_use_default_tts_settings";
    private static final String KEY_TTS_DEFAULT_RATE = "tts_default_rate";
    private static final String KEY_TTS_DEFAULT_LANG = "tts_default_lang";
    private static final String KEY_TTS_DEFAULT_COUNTRY = "tts_default_country";
    private static final String KEY_TTS_DEFAULT_VARIANT = "tts_default_variant";
    private static final String KEY_TTS_DEFAULT_SYNTH = "tts_default_synth";
    private static final String KEY_TTS_ENGINES = "tts_engines_section";

    private static final String KEY_PLUGIN_ENABLED_PREFIX = "ENABLED_";
    private static final String KEY_PLUGIN_SETTINGS_PREFIX = "SETTINGS_";

    // TODO move default Locale values to TextToSpeech.Engine
    private static final String DEFAULT_LANG_VAL = "eng";
    private static final String DEFAULT_COUNTRY_VAL = "USA";
    private static final String DEFAULT_VARIANT_VAL = "";

    private static final String LOCALE_DELIMITER = "-";

    private Preference         mPlayExample = null;
    private Preference         mInstallData = null;
    private CheckBoxPreference mUseDefaultPref = null;
    private ListPreference     mDefaultRatePref = null;
    private ListPreference     mDefaultLocPref = null;
    private ListPreference     mDefaultSynthPref = null;
    private PreferenceGroup    mEnginesGroup;

    private String             mDefaultLanguage = null;
    private String             mDefaultCountry = null;
    private String             mDefaultLocVariant = null;
    private int                mDefaultRate = TextToSpeech.Engine.DEFAULT_RATE;

    // Index of the current string to use for the demo.
    private int      mDemoStringIndex = 0;

    private boolean mEnableDemo = false;
    private boolean mVoicesMissing = false;

    private TextToSpeech mTts = null;
    private TtsEngines mEnginesHelper = null;
    private boolean mTtsStarted = false;

    /**
     * Request code (arbitrary value) for voice data check through
     * startActivityForResult.
     */
    private static final int VOICE_DATA_INTEGRITY_CHECK = 1977;
    private static final int GET_SAMPLE_TEXT = 1983;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.tts_settings);

        getActivity().setVolumeControlStream(TextToSpeech.Engine.DEFAULT_STREAM);

        mEnableDemo = false;
        mTtsStarted = false;

        Locale currentLocale = Locale.getDefault();
        mDefaultLanguage = currentLocale.getISO3Language();
        mDefaultCountry = currentLocale.getISO3Country();
        mDefaultLocVariant = currentLocale.getVariant();

        mPlayExample = findPreference(KEY_TTS_PLAY_EXAMPLE);
        mPlayExample.setOnPreferenceClickListener(this);

        mInstallData = findPreference(KEY_TTS_INSTALL_DATA);
        mInstallData.setOnPreferenceClickListener(this);

        mUseDefaultPref = (CheckBoxPreference) findPreference(KEY_TTS_USE_DEFAULT);
        mDefaultSynthPref = (ListPreference) findPreference(KEY_TTS_DEFAULT_SYNTH);
        mDefaultRatePref = (ListPreference) findPreference(KEY_TTS_DEFAULT_RATE);
        mDefaultLocPref = (ListPreference) findPreference(KEY_TTS_DEFAULT_LANG);

        mEnginesGroup = (PreferenceGroup) findPreference(KEY_TTS_ENGINES);

        mTts = new TextToSpeech(getActivity().getApplicationContext(), this);
        mEnginesHelper = new TtsEngines(getActivity().getApplicationContext());

        initDefaultSettings();
        addEngineSpecificSettings();
    }

    @Override
    public void onStart() {
        super.onStart();
        if (mTtsStarted){
            // whenever we return to this screen, we don't know the state of the
            // system, so we have to recheck that we can play the demo, or it must be disabled.
            // TODO make the TTS service listen to "changes in the system", i.e. sd card un/mount
            updateWidgetState();
            checkVoiceData();
        }
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        if (mTts != null) {
            mTts.shutdown();
        }
    }

    @Override
    public void onPause() {
        super.onPause();
        if ((mDefaultRatePref != null) && (mDefaultRatePref.getDialog() != null)) {
            mDefaultRatePref.getDialog().dismiss();
        }
        if ((mDefaultLocPref != null) && (mDefaultLocPref.getDialog() != null)) {
            mDefaultLocPref.getDialog().dismiss();
        }
        if ((mDefaultSynthPref != null) && (mDefaultSynthPref.getDialog() != null)) {
            mDefaultSynthPref.getDialog().dismiss();
        }
    }

    private void addEngineSpecificSettings() {
        Context context = getActivity();
        List<EngineInfo> engines = mTts.getEngines();
        for (EngineInfo engine : engines) {
            final String engineName = engine.name;
            if (!engine.system) {
                CheckBoxPreference enablePref = new CheckBoxPreference(context);
                enablePref.setKey(KEY_PLUGIN_ENABLED_PREFIX + engineName);
                enablePref.setTitle(engine.label);
                enablePref.setOnPreferenceClickListener(this);
                mEnginesGroup.addPreference(enablePref);
            }

            if (engineHasSettings(engineName)) {
                Preference pref = new Preference(context);
                pref.setKey(KEY_PLUGIN_SETTINGS_PREFIX + engineName);
                pref.setTitle(engine.label);
                CharSequence settingsLabel = getResources().getString(
                        R.string.tts_engine_name_settings, engine.label);
                pref.setSummary(settingsLabel);
                // TODO: Add a new API for this.
                pref.setOnPreferenceClickListener(new OnPreferenceClickListener() {
                            public boolean onPreferenceClick(Preference preference) {
                                Intent i = new Intent();
                                i.setClassName(engineName,
                                        engineName + ".EngineSettings");
                                startActivity(i);
                                return true;
                            }
                        });
                mEnginesGroup.addPreference(pref);
            }
        }
    }

    private boolean engineHasSettings(String enginePackageName) {
        PackageManager pm = getPackageManager();
        Intent i = new Intent();
        i.setClassName(enginePackageName, enginePackageName + ".EngineSettings");
        if (pm.resolveActivity(i, PackageManager.MATCH_DEFAULT_ONLY) != null){
            return true;
        }
        return false;
    }

    private void initDefaultSettings() {
        ContentResolver resolver = getContentResolver();

        // Find the default TTS values in the settings, initialize and store the
        // settings if they are not found.

        // "Use Defaults"
        int useDefault = Settings.Secure.getInt(resolver, TTS_USE_DEFAULTS,
                TextToSpeech.Engine.USE_DEFAULTS);
        mUseDefaultPref.setChecked(useDefault == 1);
        mUseDefaultPref.setOnPreferenceChangeListener(this);

        // Default synthesis engine
        loadEngines();
        mDefaultSynthPref.setOnPreferenceChangeListener(this);

        // Default rate
        try {
            mDefaultRate = Settings.Secure.getInt(resolver, TTS_DEFAULT_RATE);
        } catch (SettingNotFoundException e) {
            // default rate setting not found, initialize it
            mDefaultRate = TextToSpeech.Engine.DEFAULT_RATE;
            Settings.Secure.putInt(resolver, TTS_DEFAULT_RATE, mDefaultRate);
        }
        mDefaultRatePref.setValue(String.valueOf(mDefaultRate));
        mDefaultRatePref.setOnPreferenceChangeListener(this);

        // Default language / country / variant : these three values map to a single ListPref
        // representing the matching Locale
        initDefaultLang();
        mDefaultLocPref.setOnPreferenceChangeListener(this);
    }

    /**
     * Ask the current default engine to launch the matching CHECK_TTS_DATA activity
     * to check the required TTS files are properly installed.
     */
    private void checkVoiceData() {
        String defaultEngine = mTts.getDefaultEngine();
        if (TextUtils.isEmpty(defaultEngine)) return;
        Intent intent = new Intent(TextToSpeech.Engine.ACTION_CHECK_TTS_DATA);
        intent.setPackage(defaultEngine);
        try {
            Log.v(TAG, "Checking voice data: " + intent.toUri(0));
            startActivityForResult(intent, VOICE_DATA_INTEGRITY_CHECK);
        } catch (ActivityNotFoundException ex) {
            Log.e(TAG, "Failed to check TTS data, no acitivty found for " + intent + ")");
        }
    }


    /**
     * Ask the current default engine to launch the matching INSTALL_TTS_DATA activity
     * so the required TTS files are properly installed.
     */
    private void installVoiceData() {
        String defaultEngine = mTts.getDefaultEngine();
        if (TextUtils.isEmpty(defaultEngine)) return;
        Intent intent = new Intent(TextToSpeech.Engine.ACTION_INSTALL_TTS_DATA);
        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        intent.setPackage(defaultEngine);
        try {
            Log.v(TAG, "Installing voice data: " + intent.toUri(0));
            startActivity(intent);
        } catch (ActivityNotFoundException ex) {
            Log.e(TAG, "Failed to install TTS data, no acitivty found for " + intent + ")");
        }
    }

    /**
     * Ask the current default engine to return a string of sample text to be
     * spoken to the user.
     */
    private void getSampleText() {
        String defaultEngine = mTts.getDefaultEngine();
        if (TextUtils.isEmpty(defaultEngine)) return;
        Intent intent = new Intent(TextToSpeech.Engine.ACTION_GET_SAMPLE_TEXT);
        intent.putExtra("language", mDefaultLanguage);
        intent.putExtra("country", mDefaultCountry);
        intent.putExtra("variant", mDefaultLocVariant);
        intent.setPackage(defaultEngine);
        try {
            Log.v(TAG, "Getting sample text: " + intent.toUri(0));
            startActivityForResult(intent, GET_SAMPLE_TEXT);
        } catch (ActivityNotFoundException ex) {
            Log.e(TAG, "Failed to get sample text, no acitivty found for " + intent + ")");
        }
    }

    /**
     * Called when the TTS engine is initialized.
     */
    public void onInit(int status) {
        if (status == TextToSpeech.SUCCESS) {
            mEnableDemo = true;
            if (mDefaultLanguage == null) {
                mDefaultLanguage = Locale.getDefault().getISO3Language();
            }
            if (mDefaultCountry == null) {
                mDefaultCountry = Locale.getDefault().getISO3Country();
            }
            if (mDefaultLocVariant == null) {
                mDefaultLocVariant = new String();
            }
            mTts.setLanguage(new Locale(mDefaultLanguage, mDefaultCountry, mDefaultLocVariant));
            updateWidgetState();
            checkVoiceData();
            mTtsStarted = true;
            Log.v(TAG, "TTS engine for settings screen initialized.");
        } else {
            Log.v(TAG, "TTS engine for settings screen failed to initialize successfully.");
            mEnableDemo = false;
        }
        updateWidgetState();
    }

    /**
     * Called when voice data integrity check returns
     */
    @Override
    public void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == VOICE_DATA_INTEGRITY_CHECK) {
            onVoiceDataIntegrityCheckDone(data);
        } else if (requestCode == GET_SAMPLE_TEXT) {
            onSampleTextReceived(resultCode, data);
        }
    }

    private void onVoiceDataIntegrityCheckDone(Intent data) {
        if (data == null){
            Log.e(TAG, "TTS data check failed data = null");
            // The CHECK_TTS_DATA activity for the plugin did not run properly;
            // disable the preview and install controls and return.
            mEnableDemo = false;
            mVoicesMissing = false;
            updateWidgetState();
            return;
        }
        Log.v(TAG, "TTS data check completed, data = " + data.toUri(0));
        ArrayList<String> available =
                data.getStringArrayListExtra(TextToSpeech.Engine.EXTRA_AVAILABLE_VOICES);
        ArrayList<String> unavailable =
                data.getStringArrayListExtra(TextToSpeech.Engine.EXTRA_UNAVAILABLE_VOICES);
        if (available == null || unavailable == null){
            Log.e(TAG, "TTS data check failed (available == == null)");
            // The CHECK_TTS_DATA activity for the plugin did not run properly;
            // disable the preview and install controls and return.
            mEnableDemo = false;
            mVoicesMissing = false;
            updateWidgetState();
            return;
        }
        if (available.size() > 0){
            if (mTts == null) {
                mTts = new TextToSpeech(getActivity(), this);
            }

            updateDefaultLocPref(available);

            mEnableDemo = true;
            // Make sure that the default language can be used.
            int languageResult = mTts.setLanguage(
                    new Locale(mDefaultLanguage, mDefaultCountry, mDefaultLocVariant));
            if (languageResult < TextToSpeech.LANG_AVAILABLE){
                Locale currentLocale = Locale.getDefault();
                mDefaultLanguage = currentLocale.getISO3Language();
                mDefaultCountry = currentLocale.getISO3Country();
                mDefaultLocVariant = currentLocale.getVariant();
                languageResult = mTts.setLanguage(
                        new Locale(mDefaultLanguage, mDefaultCountry, mDefaultLocVariant));
                // If the default Locale isn't supported, just choose the first available
                // language so that there is at least something.
                if (languageResult < TextToSpeech.LANG_AVAILABLE){
                    parseLocaleInfo(mDefaultLocPref.getEntryValues()[0].toString());
                    mTts.setLanguage(
                            new Locale(mDefaultLanguage, mDefaultCountry, mDefaultLocVariant));
                }
                ContentResolver resolver = getContentResolver();
                Settings.Secure.putString(resolver, TTS_DEFAULT_LANG, mDefaultLanguage);
                Settings.Secure.putString(resolver, TTS_DEFAULT_COUNTRY, mDefaultCountry);
                Settings.Secure.putString(resolver, TTS_DEFAULT_VARIANT, mDefaultLocVariant);
            }
        } else {
            mEnableDemo = false;
        }

        if (unavailable.size() > 0){
            mVoicesMissing = true;
        } else {
            mVoicesMissing = false;
        }

        updateWidgetState();
    }

    private void updateDefaultLocPref(ArrayList<String> availableLangs) {
        CharSequence[] entries = new CharSequence[availableLangs.size()];
        CharSequence[] entryValues = new CharSequence[availableLangs.size()];
        int selectedLanguageIndex = -1;
        String selectedLanguagePref = mDefaultLanguage;
        if (mDefaultCountry.length() > 0) {
            selectedLanguagePref = selectedLanguagePref + LOCALE_DELIMITER +
                    mDefaultCountry;
        }
        if (mDefaultLocVariant.length() > 0) {
            selectedLanguagePref = selectedLanguagePref + LOCALE_DELIMITER +
                    mDefaultLocVariant;
        }
        for (int i = 0; i < availableLangs.size(); i++) {
            String[] langCountryVariant = availableLangs.get(i).split("-");
            Locale loc = null;
            if (langCountryVariant.length == 1){
                loc = new Locale(langCountryVariant[0]);
            } else if (langCountryVariant.length == 2){
                loc = new Locale(langCountryVariant[0], langCountryVariant[1]);
            } else if (langCountryVariant.length == 3){
                loc = new Locale(langCountryVariant[0], langCountryVariant[1],
                                 langCountryVariant[2]);
            }
            if (loc != null){
                entries[i] = loc.getDisplayName();
                entryValues[i] = availableLangs.get(i);
                if (entryValues[i].equals(selectedLanguagePref)) {
                    selectedLanguageIndex = i;
                }
            }
        }
        mDefaultLocPref.setEntries(entries);
        mDefaultLocPref.setEntryValues(entryValues);
        if (selectedLanguageIndex > -1) {
            mDefaultLocPref.setValueIndex(selectedLanguageIndex);
        }
    }

    private void onSampleTextReceived(int resultCode, Intent data) {
        if (resultCode == TextToSpeech.LANG_AVAILABLE) {
            String sample = getActivity().getString(R.string.tts_demo);
            if (data != null && data.getStringExtra("sampleText") != null) {
                sample = data.getStringExtra("sampleText");
            }
            Log.v(TAG, "Got sample text: " + sample);
            if (mTts != null) {
                mTts.speak(sample, TextToSpeech.QUEUE_FLUSH, null);
            }
        } else {
            // TODO: Display an error here to the user.
            Log.e(TAG, "Did not have a sample string for the requested language");
        }
    }

    public boolean onPreferenceChange(Preference preference, Object objValue) {
        if (KEY_TTS_USE_DEFAULT.equals(preference.getKey())) {
            // "Use Defaults"
            int value = ((Boolean) objValue) ? 1 : 0;
            Settings.Secure.putInt(getContentResolver(), TTS_USE_DEFAULTS, value);
            Log.i(TAG, "TTS 'use default' settings changed, now " + value);
        } else if (KEY_TTS_DEFAULT_RATE.equals(preference.getKey())) {
            // Default rate
            mDefaultRate = Integer.parseInt((String) objValue);
            try {
                Settings.Secure.putInt(getContentResolver(), TTS_DEFAULT_RATE, mDefaultRate);
                if (mTts != null) {
                    mTts.setSpeechRate(mDefaultRate / 100.0f);
                }
                Log.v(TAG, "TTS default rate changed, now " + mDefaultRate);
            } catch (NumberFormatException e) {
                Log.e(TAG, "could not persist default TTS rate setting", e);
            }
        } else if (KEY_TTS_DEFAULT_LANG.equals(preference.getKey())) {
            // Default locale
            ContentResolver resolver = getContentResolver();
            parseLocaleInfo((String) objValue);
            Settings.Secure.putString(resolver, TTS_DEFAULT_LANG, mDefaultLanguage);
            Settings.Secure.putString(resolver, TTS_DEFAULT_COUNTRY, mDefaultCountry);
            Settings.Secure.putString(resolver, TTS_DEFAULT_VARIANT, mDefaultLocVariant);
            Log.v(TAG, "TTS default lang/country/variant set to "
                    + mDefaultLanguage + "/" + mDefaultCountry + "/" + mDefaultLocVariant);
            if (mTts != null) {
                mTts.setLanguage(new Locale(mDefaultLanguage, mDefaultCountry, mDefaultLocVariant));
            }
            int newIndex = mDefaultLocPref.findIndexOfValue((String)objValue);
            Log.v(TAG, " selected is " + newIndex);
            mDemoStringIndex = newIndex > -1 ? newIndex : 0;
        } else if (KEY_TTS_DEFAULT_SYNTH.equals(preference.getKey())) {
            String defaultEng = objValue.toString();
            Settings.Secure.putString(getContentResolver(), TTS_DEFAULT_SYNTH, defaultEng);
            if (mTts != null) {
                mTts.setEngineByPackageName(defaultEng);
                mEnableDemo = false;
                mVoicesMissing = false;
                updateWidgetState();
                checkVoiceData();
            }
            Log.v(TAG, "The default synth is: " + objValue.toString());
        }

        return true;
    }


    /**
     * Called when mPlayExample or mInstallData is clicked
     */
    public boolean onPreferenceClick(Preference preference) {
        if (preference == mPlayExample) {
            // Get the sample text from the TTS engine; onActivityResult will do
            // the actual speaking
            getSampleText();
            return true;
        } else if (preference == mInstallData) {
            installVoiceData();
            // quit this activity so it needs to be restarted after installation of the voice data
            finish();
            return true;
        } else if (preference.getKey().startsWith(KEY_PLUGIN_ENABLED_PREFIX)) {
            final CheckBoxPreference chkPref = (CheckBoxPreference) preference;
            if (chkPref.isChecked()) {
                chkPref.setChecked(false);
                AlertDialog d = (new AlertDialog.Builder(getActivity()))
                        .setTitle(android.R.string.dialog_alert_title)
                        .setIcon(android.R.drawable.ic_dialog_alert)
                        .setMessage(
                                getActivity().getString(R.string.tts_engine_security_warning,
                                chkPref.getTitle()))
                        .setCancelable(true)
                        .setPositiveButton(android.R.string.ok,
                                new DialogInterface.OnClickListener() {
                                    public void onClick(DialogInterface dialog, int which) {
                                        chkPref.setChecked(true);
                                        loadEngines();
                                    }
                        })
                        .setNegativeButton(android.R.string.cancel,
                                new DialogInterface.OnClickListener() {
                                    public void onClick(DialogInterface dialog, int which) {
                                    }
                        })
                        .create();
                d.show();
            } else {
                loadEngines();
            }
            return true;
        }
        return false;
    }

    private void updateWidgetState() {
        mPlayExample.setEnabled(mEnableDemo);
        mUseDefaultPref.setEnabled(mEnableDemo);
        mDefaultRatePref.setEnabled(mEnableDemo);
        mDefaultLocPref.setEnabled(mEnableDemo);

        mInstallData.setEnabled(mVoicesMissing);
    }


    private void parseLocaleInfo(String locale) {
        StringTokenizer tokenizer = new StringTokenizer(locale, LOCALE_DELIMITER);
        mDefaultLanguage = "";
        mDefaultCountry = "";
        mDefaultLocVariant = "";
        if (tokenizer.hasMoreTokens()) {
            mDefaultLanguage = tokenizer.nextToken().trim();
        }
        if (tokenizer.hasMoreTokens()) {
            mDefaultCountry = tokenizer.nextToken().trim();
        }
        if (tokenizer.hasMoreTokens()) {
            mDefaultLocVariant = tokenizer.nextToken().trim();
        }
    }


    /**
     *  Initialize the default language in the UI and in the preferences.
     *  After this method has been invoked, the default language is a supported Locale.
     */
    private void initDefaultLang() {
        // if there isn't already a default language preference
        if (!hasLangPref()) {
            // if the current Locale is supported
            if (isCurrentLocSupported()) {
                // then use the current Locale as the default language
                useCurrentLocAsDefault();
            } else {
                // otherwise use a default supported Locale as the default language
                useSupportedLocAsDefault();
            }
        }

        // Update the language preference list with the default language and the matching
        // demo string (at this stage there is a default language pref)
        ContentResolver resolver = getContentResolver();
        mDefaultLanguage = Settings.Secure.getString(resolver, TTS_DEFAULT_LANG);
        mDefaultCountry = Settings.Secure.getString(resolver, TTS_DEFAULT_COUNTRY);
        mDefaultLocVariant = Settings.Secure.getString(resolver, TTS_DEFAULT_VARIANT);

        // update the demo string
        mDemoStringIndex = mDefaultLocPref.findIndexOfValue(mDefaultLanguage + LOCALE_DELIMITER
                + mDefaultCountry);
        if (mDemoStringIndex > -1){
            mDefaultLocPref.setValueIndex(mDemoStringIndex);
        }
    }

    /**
     * (helper function for initDefaultLang() )
     * Returns whether there is a default language in the TTS settings.
     */
    private boolean hasLangPref() {
        ContentResolver resolver = getContentResolver();
        String language = Settings.Secure.getString(resolver, TTS_DEFAULT_LANG);
        if ((language == null) || (language.length() < 1)) {
            return false;
        }
        String country = Settings.Secure.getString(resolver, TTS_DEFAULT_COUNTRY);
        if (country == null) {
            return false;
        }
        String variant = Settings.Secure.getString(resolver, TTS_DEFAULT_VARIANT);
        if (variant == null) {
            return false;
        }
        return true;
    }

    /**
     * (helper function for initDefaultLang() )
     * Returns whether the current Locale is supported by this Settings screen
     */
    private boolean isCurrentLocSupported() {
        String currentLocID = Locale.getDefault().getISO3Language() + LOCALE_DELIMITER
                + Locale.getDefault().getISO3Country();
        return (mDefaultLocPref.findIndexOfValue(currentLocID) > -1);
    }

    /**
     * (helper function for initDefaultLang() )
     * Sets the default language in TTS settings to be the current Locale.
     * This should only be used after checking that the current Locale is supported.
     */
    private void useCurrentLocAsDefault() {
        Locale currentLocale = Locale.getDefault();
        ContentResolver resolver = getContentResolver();
        Settings.Secure.putString(resolver, TTS_DEFAULT_LANG, currentLocale.getISO3Language());
        Settings.Secure.putString(resolver, TTS_DEFAULT_COUNTRY, currentLocale.getISO3Country());
        Settings.Secure.putString(resolver, TTS_DEFAULT_VARIANT, currentLocale.getVariant());
    }

    /**
     * (helper function for initDefaultLang() )
     * Sets the default language in TTS settings to be one known to be supported
     */
    private void useSupportedLocAsDefault() {
        ContentResolver resolver = getContentResolver();
        Settings.Secure.putString(resolver, TTS_DEFAULT_LANG, DEFAULT_LANG_VAL);
        Settings.Secure.putString(resolver, TTS_DEFAULT_COUNTRY, DEFAULT_COUNTRY_VAL);
        Settings.Secure.putString(resolver, TTS_DEFAULT_VARIANT, DEFAULT_VARIANT_VAL);
    }

    private void loadEngines() {
        List<EngineInfo> engines = mEnginesHelper.getEngines();
        updateUserEnabledEngines(engines);

        ArrayList<CharSequence> entries = new ArrayList<CharSequence>();
        ArrayList<CharSequence> values = new ArrayList<CharSequence>();
        StringBuilder enabledEngines = new StringBuilder();

        for (EngineInfo engine : engines) {
            Log.v(TAG, "Engine: " + engine);
            if (mEnginesHelper.isEngineEnabled(engine.name)) {
                entries.add(engine.label);
                values.add(engine.name);
            }
        }


        CharSequence entriesArray[] = new CharSequence[entries.size()];
        CharSequence valuesArray[] = new CharSequence[values.size()];

        mDefaultSynthPref.setEntries(entries.toArray(entriesArray));
        mDefaultSynthPref.setEntryValues(values.toArray(valuesArray));

        // Set the selected engine based on the saved preference
        String selectedEngine = Settings.Secure.getString(getContentResolver(), TTS_DEFAULT_SYNTH);
        int selectedEngineIndex = mDefaultSynthPref.findIndexOfValue(selectedEngine);
        if (selectedEngineIndex == -1){
            selectedEngineIndex = mDefaultSynthPref.findIndexOfValue(
                    mEnginesHelper.getHighestRankedEngineName());
        }
        if (selectedEngineIndex >= 0) {
            mDefaultSynthPref.setValueIndex(selectedEngineIndex);
        }
    }

    /*
     * Write out the list of engines enabled by the user to a
     * shared preference.
     */
    private void updateUserEnabledEngines(List<EngineInfo> engines) {
        StringBuilder enginesList = new StringBuilder();
        for (EngineInfo engine : engines) {
            if (isEngineUserEnabled(engine.name)) {
                if (enginesList.length() > 0) enginesList.append(' ');
                enginesList.append(engine.name);
            }
        }

        ContentResolver resolver = getContentResolver();
        Settings.Secure.putString(resolver, TTS_ENABLED_PLUGINS, enginesList.toString());
    }

    private boolean isEngineUserEnabled(String engineName) {
        String enginePref = KEY_PLUGIN_ENABLED_PREFIX + engineName;
        return getPreferenceManager().getSharedPreferences().getBoolean(enginePref, false);
    }

}