VerticalLayout layout = new VerticalLayout();

        usernameField = new TextField("Username:");
        layout.addComponent(usernameField);
        passwordField = new PasswordField("Password:");
        layout.addComponent(passwordField);

        Button login = new Button("Login");
        login.setClickShortcut(KeyCode.ENTER, null);
        login.addClickListener(e -> Notification.show(
                usernameField.getValue() + ":" + passwordField.getValue()));
        layout.addComponent(login);

        Window window = new Window();
        window.setContent(layout);
        addWindow(window);