save android theme using shared preferences

Hello I am trying to save a theme with shared preferences. When the user clicks a button with a certain theme I want that theme to be set as default and saved so when they reopen the app its still that new theme.

Main Activity:

/** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        Utils.onActivityCreateSetTheme(this);
        setContentView(R.layout.activity_main);

        findViewById(R.id.button1).setOnClickListener(this);
        findViewById(R.id.button2).setOnClickListener(this);
        findViewById(R.id.button3).setOnClickListener(this);


    }
    @Override
    public void onClick(View v)
    {
        switch (v.getId())
        {
            case R.id.button1:
                Utils.changeToTheme(this, Utils.THEME_DEFAULT);
                break;
            case R.id.button2:
                Utils.changeToTheme(this, Utils.THEME_WHITE);
                break;
            case R.id.button3:
                Utils.changeToTheme(this, Utils.THEME_BLUE);
                break;
        }
    }
}

Utils:

public class Utils{
private static int sTheme;
public final static int THEME_DEFAULT = 0;
public final static int THEME_WHITE = 1;
public final static int THEME_BLUE = 2;
/**
 * Set the theme of the Activity, and restart it by creating a new Activity of the same type.
 */
public static void changeToTheme(Activity activity, int theme)
{
    sTheme = theme;
    activity.finish();
    activity.startActivity(new Intent(activity, activity.getClass()));
}
/** Set the theme of the activity, according to the configuration.
 * @param activity*/
public static void onActivityCreateSetTheme(MainActivity activity)
{
    switch (sTheme)
    {
        default:
        case THEME_DEFAULT:
            activity.setTheme(R.style.AppTheme);
            break;
        case THEME_WHITE:
            activity.setTheme(R.style.MyTheme);
            break;
        case THEME_BLUE:
            activity.setTheme(R.style.My2Theme);
            break;

I also want the theme to be saved for all activities not just the one where the button is clicked. Thanks

Solution

Here you can find a tutorial about SharedPreferences , basically you should store the number of the selected theme and when the app starts, check which one is stored on SharedPreferences. After retrieving the value you could "store" it globally to check the theme number on other activities (this way, you don't have to check SharedPreferences every time, just when the app starts).

UPDATE 0

Here a class that handles SharedPreference stuff:

public class SharedPreferencesManager {
/**
 * SharedPreferences to store the settings. This way, they'll be available next time the user starts the app
 */
private SharedPreferences sPreferences;
/**
 * Editor to make changes on sharedPreferences
 */
private SharedPreferences.Editor sEditor;

/**
 * The class itself
 */
private Context context;

public SharedPreferencesManager(Context context){
    this.context = context;
    sPreferences = PreferenceManager.getDefaultSharedPreferences(context);
}

private SharedPreferences.Editor getEditor(){
    return sPreferences.edit();
}

/**
 * Store a boolean value in sharedPreferences
 * @param tag identifies the value
 * @param value the value itself
 */

public void storeBoolean(String tag, boolean value){
    sEditor = getEditor();
    sEditor.putBoolean(tag,value);
    sEditor.commit();
}
/**
 * Store a string in sharedPreferences
 * @param tag identifies the value
 * @param str the string itself
 */

public void storeString(String tag, String str){
    sEditor = getEditor();
    sEditor.putString(tag, str);
    sEditor.commit();
}

/**
 *
 * @param tag identifies the value
 * @param defValue default value
 * @return the stored or default value
 */

public boolean retrieveBoolean(String tag, boolean defValue){
    return sPreferences.getBoolean(tag,defValue);

}

/**
 *
 * @param tag identifies the string
 * @param defStr default string
 * @return the stored or default string
 */

public String retrieveString(String tag, String defStr){
    return sPreferences.getString(tag, defStr);
}

/**
 *
 * @param tag identifies the value
 * @param defValue default value
 * @return the stored or default value
 */
public int retrieveInt(String tag, int defValue){
    return sPreferences.getInt(tag, defValue);
}

/**
 *
 * @param tag identifies the value
 * @param defValue the value itself
 */
public void storeInt(String tag, int defValue){
    sEditor = getEditor();
    sEditor.putInt(tag, defValue);
    sEditor.commit();
}
//Incorrect Bracket Closing Removal.

Using this class you can store and retrieve diferent type of values on/from SharedPreferences. In your case, you'll need to store the value of a theme. You have:

public final static int THEME_DEFAULT = 0;
public final static int THEME_WHITE = 1;
public final static int THEME_BLUE = 2;

So, after the user choose a theme you should call:

new SharedPreferencesManager(getApplicationContext()).storeInt("theme", THEME_WHITE);

You could call this function on your onClick() handler, or where you think it's better :)

To retrieve which theme value is stored, call the below code on your onCreate method:

Utils.changeToTheme(this, new SharedPreferencesManager(this).retrieveInt("theme", THEME_WHITE));

Remember that when you want to retrieve a value from the SharedPreferences, will have to pass the default value, so if nothing related to the tag "theme" is stored, it will return the default value.

I didn't test this code, maybe you'll have to adpat it a little.