the method tabs.setFlexGrowForEnclosedTabs(1); doesn't work!!!

Hi, I want to centrate the tabs in the navbar using this: tabs.setFlexGrowForEnclosedTabs(1);
but doesn’t work!

Here all the code:

public MainApp() {
	Tab mainTab = new Tab("Home");
	Div mainPage = new Div();
	mainPage.setText("Welcome to Fake Store!");

	Tab productsTab = new Tab("Products");
	Div productsPage = new Div();
	productsPage.setText("2222");

	Tab usersTab = new Tab("Products");
	Div usersPage = new Div();
	usersPage.setText("3333");

	Tabs tabs = new Tabs(mainTab, productsTab, usersTab);
	tabs.setFlexGrowForEnclosedTabs(1);
	appLayout.addToNavbar(tabs);
}

Why?