public static final String PREFS_NAME = "MyPrefsFile";
private static final String PREF_USERNAME = "username";
private static final String PREF_PASSWORD = "password";

getSharedPreferences(PREFS_NAME,MODE_PRIVATE)
    .edit()
    .putString(PREF_USERNAME, username)
    .putString(PREF_PASSWORD, password)
    .commit();

SharedPreferences pref = getSharedPreferences(PREFS_NAME,MODE_PRIVATE);
String username = pref.getString(PREF_USERNAME, null);
String password = pref.getString(PREF_PASSWORD, null);

if (username == null || password == null) {
//Prompt for username and password
}


Alternatively, if you don't want to name a preferences file you can just use the default:


SharedPreferences pref = PreferenceManager.getDefaultSharedPreferences(this);