Button btn1 = new Button("Sign Up");
btn1.setBackForeColors(Colors.P_500, Colors.ON_P_500);
btn1.addPressListener((e) -> {
MaterialWindow mw = new MaterialWindow("Sign Up",new Presenter() {
public Container getView() {
//put all the window content here
Button btn2 = new Button("Sign in");
btn2.setBackForeColors(Colors.P_500, Colors.ON_P_500);
btn2.addPressListener((e) -> {
MaterialWindow mw = new MaterialWindow("Sign in",new Presenter() {
public Container getView() {
//put all the window content here