如何在Xamarin.Forms中不经意地更改TabbedPage的背景？

Question

我尝试更改BarBackgroundColor属性，但只有第一种情况是开关工作并设置紫色。 CurrentPageChanged事件正在触发但不更改背景颜色。另外如何改变单个标签背景的背景。

在我的public partial class Tabbed : TabbedPage

中

    public void changeColorOfTabBar(int index)
    {      
        switch (index)
        {
            case 0:
                BarBackgroundColor = Color.FromHex(Constants.evrensel_purple);
                break;
            case 1:
                BarBackgroundColor = Color.FromHex(Constants.evrensel_green);
                break;
            case 2:
                BarBackgroundColor = Color.FromHex(Constants.evrensel_blue);
                break;
            default:
                BarBackgroundColor = Color.FromHex(Constants.color_blue);
                break;
        }
    }
    public void createTabs(LoginResponse response)
    {

        Children.Add(new HomeTab(response) { Title = "Home", Icon = "home.png" });
        Children.Add(new TimesheetTab(response) { Title = "Timesheet", Icon = "timesheet.png" });
        Children.Add(new MyLeavesTab(response) { Title = "My Leaves", Icon = "leave.png", });
    }
    public Tabbed (LoginResponse response,LoggedInfo info)
    {
        InitializeComponent();
        Title = "Welcome, " + _serviceEmployee.getEmployeeByUserId(response.userid).fullnameReplaced;
        CurrentPageChanged += (sender, args) =>
        {
            var index = Children.IndexOf(CurrentPage);
            changeColorOfTabBar(index);
        };
        createTabs(response);

        res = response;           
    }