问BottomNavigationBarXF设计问题

EN

<?xml version="1.0" encoding="utf-8" ?>
<xf:BottomBarPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:xf="clr-namespace:BottomBar.XamarinForms;assembly=BottomBar.XamarinForms"
xmlns:example="clr-namespace:BottomBarXFExampleXaml;assembly=BottomBarXFExampleXaml"
             x:Class="BottomBarXFExampleXaml.BarPage">

<example:TabPage Title="Favorites" Icon="ic_favorites.png" />
<example:TabPage Title="Friends" Icon="ic_friends.png" />
<example:TabPage Title="Nearby" Icon="ic_nearby.png"  />
<example:TabPage Title="Recents" Icon="ic_recents.png"  />
<example:TabPage Title="Restaurants" Icon="ic_restaurants.png"/>
</xf:BottomBarPage>

public App()
    {
        InitializeComponent();

        MainPage = new BarPage();
    }