如何向 Xamarin Forms App Shell Tabbar 添加顶部边框

Question

使用 Xamarin Forms App Shell 模板，很明显如何更改 Tabbar 的背景颜色，但我看不到添加顶部边框甚至阴影的方法，这在许多选项卡栏样式中很常见。

Answer 1

安卓：

您可以使用CreateBottomNavViewAppearanceTracker为底部视图更改某些内容。

  [assembly: ExportRenderer(typeof(AppShell), typeof(ShellCustomRenderer))]
namespace ShellDemo.Droid
{
class ShellCustomRenderer : ShellRenderer
{

    public ShellCustomRenderer(Context context) : base(context)
    {
    }

    protected override IShellBottomNavViewAppearanceTracker CreateBottomNavViewAppearanceTracker(ShellItem shellItem)
    {
        return new CustomBottomNavAppearance();
    }
}

public class CustomBottomNavAppearance : IShellBottomNavViewAppearanceTracker
{
    public void Dispose()
    {

    }

    public void ResetAppearance(BottomNavigationView bottomView)
    {

    }

    public void SetAppearance(BottomNavigationView bottomView, IShellAppearanceElement appearance)
    {
        //put your code here
       
    }
}
}

IOS：

您可以使用CreateTabBarAppearanceTracker来更改标签栏。

  [assembly: ExportRenderer(typeof(AppShell), typeof(ShellCustomRenderer))]
namespace ShellDemo.iOS
{
public class ShellCustomRenderer : ShellRenderer
{
    protected override IShellTabBarAppearanceTracker CreateTabBarAppearanceTracker()
    {
        return new TabBarAppearance();
    }

}

public class TabBarAppearance : IShellTabBarAppearanceTracker
{
    public void Dispose()
    {

    }

    public void ResetAppearance(UITabBarController controller)
    {
        
    }

    public void SetAppearance(UITabBarController controller, ShellAppearance appearance)
    {
    }

    public void UpdateLayout(UITabBarController controller)
    {
    }
}
}