How to provide multiple theme options in application?

Question

I want to give the user the option of choosing between several different colour themes in my app in the settings activity. I know how to bundle/save/load the prefs, nevertheless I'm having trouble accomplishing this.

I have defined my colors in colors.xml, defined several themes in v21styles.xml, and added the options to a listview in the SettingsActivity.java.

The only part I am having difficulty with is actually applying the new themes. I would like to set up a switch statement to apply the themes using the built in android methods, but am not exactly how to accomplish this on API 21 (lolipop).

public class SettingsActivity extends PreferenceActivity {
/**
 * Determines whether to always show the simplified settings UI, where
 * settings are presented in a single list. When false, settings are shown
 * as a master/detail two-pane view on tablets. When true, a single pane is
 * shown on tablets.
 */
private static final boolean ALWAYS_SIMPLE_PREFS = false;


@Override
protected void onPostCreate(Bundle savedInstanceState) {
    super.onPostCreate(savedInstanceState);

    setupSimplePreferencesScreen();
}

/**
 * Shows the simplified settings UI if the device configuration if the
 * device configuration dictates that a simplified, single-pane UI should be
 * shown.
 */
private void setupSimplePreferencesScreen() {
    if (!isSimplePreferences(this)) {
        return;
    }

    // In the simplified UI, fragments are not used at all and we instead
    // use the older PreferenceActivity APIs.

    // Add 'general' preferences.
    addPreferencesFromResource(R.xml.pref_general);


}

/**
 * {@inheritDoc}
 */
@Override
public boolean onIsMultiPane() {
    return isXLargeTablet(this) && !isSimplePreferences(this);
}

/**
 * Helper method to determine if the device has an extra-large screen. For
 * example, 10" tablets are extra-large.
 */
private static boolean isXLargeTablet(Context context) {
    return (context.getResources().getConfiguration().screenLayout
            & Configuration.SCREENLAYOUT_SIZE_MASK) >= Configuration.SCREENLAYOUT_SIZE_XLARGE;
}

/**
 * Determines whether the simplified settings UI should be shown. This is
 * true if this is forced via {@link #ALWAYS_SIMPLE_PREFS}, or the device
 * doesn't have newer APIs like {@link PreferenceFragment}, or the device
 * doesn't have an extra-large screen. In these cases, a single-pane
 * "simplified" settings UI should be shown.
 */
private static boolean isSimplePreferences(Context context) {
    return ALWAYS_SIMPLE_PREFS
            || Build.VERSION.SDK_INT < Build.VERSION_CODES.HONEYCOMB
            || !isXLargeTablet(context);
}

/**
 * {@inheritDoc}
 */
@Override
@TargetApi(Build.VERSION_CODES.HONEYCOMB)
public void onBuildHeaders(List target) {
    if (!isSimplePreferences(this)) {
        loadHeadersFromResource(R.xml.pref_headers, target);
    }
}

/**
 * A preference value change listener that updates the preference's summary
 * to reflect its new value.
 */
private static Preference.OnPreferenceChangeListener sBindPreferenceSummaryToValueListener = new Preference.OnPreferenceChangeListener() {
    @Override
    public boolean onPreferenceChange(Preference preference, Object value) {
        String stringValue = value.toString();

        if (preference instanceof ListPreference) {
            // For list preferences, look up the correct display value in
            // the preference's 'entries' list.
            ListPreference listPreference = (ListPreference) preference;
            int index = listPreference.findIndexOfValue(stringValue);

            // Set the summary to reflect the new value.
            preference.setSummary(
                    index >= 0
                            ? listPreference.getEntries()[index]
                            : null);

        } else if (preference instanceof RingtonePreference) {
            // For ringtone preferences, look up the correct display value
            // using RingtoneManager.
            if (TextUtils.isEmpty(stringValue)) {
                // Empty values correspond to 'silent' (no ringtone).
                preference.setSummary(R.string.pref_ringtone_silent);

            } else {
                Ringtone ringtone = RingtoneManager.getRingtone(
                        preference.getContext(), Uri.parse(stringValue));

                if (ringtone == null) {
                    // Clear the summary if there was a lookup error.
                    preference.setSummary(null);
                } else {
                    // Set the summary to reflect the new ringtone display
                    // name.
                    String name = ringtone.getTitle(preference.getContext());
                    preference.setSummary(name);
                }
            }

        } else {
            // For all other preferences, set the summary to the value's
            // simple string representation.


            preference.setSummary(stringValue);
        }
        return true;
    }
};

/**
 * Binds a preference's summary to its value. More specifically, when the
 * preference's value is changed, its summary (line of text below the
 * preference title) is updated to reflect the value. The summary is also
 * immediately updated upon calling this method. The exact display format is
 * dependent on the type of preference.
 *
 * @see #sBindPreferenceSummaryToValueListener
 */
private static void bindPreferenceSummaryToValue(Preference preference) {
    // Set the listener to watch for value changes.
    preference.setOnPreferenceChangeListener(sBindPreferenceSummaryToValueListener);

    // Trigger the listener immediately with the preference's
    // current value.
    sBindPreferenceSummaryToValueListener.onPreferenceChange(preference,
            PreferenceManager
                    .getDefaultSharedPreferences(preference.getContext())
                    .getString(preference.getKey(), ""));
}

/**
 * This fragment shows general preferences only. It is used when the
 * activity is showing a two-pane settings UI.
 */
@TargetApi(Build.VERSION_CODES.HONEYCOMB)
public static class GeneralPreferenceFragment extends PreferenceFragment {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.pref_general);

        // Bind the summaries of EditText/List/Dialog/Ringtone preferences
        // to their values. When their values change, their summaries are
        // updated to reflect the new value, per the Android Design
        // guidelines.
        bindPreferenceSummaryToValue(findPreference("example_text"));
        bindPreferenceSummaryToValue(findPreference("example_list"));
    }
}

/**
 * This fragment shows notification preferences only. It is used when the
 * activity is showing a two-pane settings UI.
 */
@TargetApi(Build.VERSION_CODES.HONEYCOMB)
public static class NotificationPreferenceFragment extends PreferenceFragment {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.pref_notification);

        // Bind the summaries of EditText/List/Dialog/Ringtone preferences
        // to their values. When their values change, their summaries are
        // updated to reflect the new value, per the Android Design
        // guidelines.
        bindPreferenceSummaryToValue(findPreference("notifications_new_message_ringtone"));
    }
}

/**
 * This fragment shows data and sync preferences only. It is used when the
 * activity is showing a two-pane settings UI.
 */
@TargetApi(Build.VERSION_CODES.HONEYCOMB)
public static class DataSyncPreferenceFragment extends PreferenceFragment {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.pref_data_sync);

        // Bind the summaries of EditText/List/Dialog/Ringtone preferences
        // to their values. When their values change, their summaries are
        // updated to reflect the new value, per the Android Design
        // guidelines.
        bindPreferenceSummaryToValue(findPreference("sync_frequency"));
    }
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.

    switch (item.getItemId()) {
        case R.string.theme:
            //apply red theme
            R.style.RedTheme;
            break;
        case R.style.IndigoTheme:
            //apply blue theme
        case R.style.AppTheme:
            //apply default theme
            return true;

    }
    return super.onOptionsItemSelected(item);
}}

The part at the bottom is where I am trying to do the actual theme swapping. Is this the correct way to handle preference options even though it's technically not a "menu item"?

I have defined the theme names in my styles.xml, and v21/styles.xml. In the manifest the theme is set to AppTheme. I just want to be able to swap themes when the user selects a new theme in the preferences activity.

How to provide multiple theme options in application?

Answers (1)

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