Use the following functions to add shared preferences and to fetch the saved values from all activities.

public static void setDefaults(String key, String value, Context context) {
    SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(context);
    SharedPreferences.Editor editor = preferences.edit();
    editor.putString(key, value);
    editor.apply(); // or editor.commit() in case you want to write data instantly
}

public static String getDefaults(String key, Context context) {
    SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(context);
    return preferences.getString(key, null);
}