Android: How do I get string from resources using its name?

The link you are referring to seems to work with strings generated at runtime. The strings from strings.xml are not created at runtime. You can get them via

String mystring = getResources().getString(R.string.mystring);

getResources() is a method of the Context class. If you are inside a Activity or a Service (which extend Context) you can use it like in this snippet.

Also note that the whole language dependency can be taken care of by the android framework. Simply create different folders for each language. If english is your default language, just put the english strings into res/values/strings.xml. Then create a new folder values-ru and put the russian strings with identical names into res/values-ru/strings.xml. From this point on android selects the correct one depending on the device locale for you, either when you call getString() or when referencing strings in XML via @string/mystring. The ones from res/values/strings.xml are the fallback ones, if you don't have a folder covering the users locale, this one will be used as default values.

See Localization and Providing Resources for more information.

Not from activities only:

public static String getStringByIdName(Context context, String idName) {
    Resources res = context.getResources();
    return res.getString(res.getIdentifier(idName, "string", context.getPackageName()));
}

Verify if your packageName is correct. You have to refer for the root package of your Android application.

private String getStringResourceByName(String aString) {
      String packageName = getPackageName();
      int resId = getResources().getIdentifier(aString, "string", packageName);
      return getString(resId);
    }

getResources().getString(getResources().getIdentifier("propertyName", "string", getPackageName()))