如何在Xamarin.Forms ios中更改工具栏图标的颜色

using Xamarin.Forms.Platform.iOS;

[assembly: ExportRenderer(typeof(Xamarin.Forms.NavigationPage), typeof(CustomNavigationRenderer))]
namespace YourNamespace.iOS
{
    public class CustomNavigationRenderer : NavigationRenderer
    {
        protected override void OnElementChanged(VisualElementChangedEventArgs e)
        {
            base.OnElementChanged(e);

            if (e?.NewElement != null)
            {
                // 设置工具栏背景颜色
                NavigationBar.BarTintColor = UIColor.FromRGB(255, 0, 0);

                // 设置工具栏图标颜色
                NavigationBar.TintColor = UIColor.White;
            }
        }
    }
}

using YourNamespace.iOS;
using Xamarin.Forms;

namespace YourNamespace.iOS
{
    [Register("AppDelegate")]
    public partial class AppDelegate : global::Xamarin.Forms.Platform.iOS.FormsApplicationDelegate
    {
        public override bool FinishedLaunching(UIApplication app, NSDictionary options)
        {
            global::Xamarin.Forms.Forms.Init();
            LoadApplication(new App());

            // 注册自定义渲染器
            Xamarin.Forms.Platform.iOS.Forms.SetTitleViewAppearance(UINavigationBar.Appearance);

            return base.FinishedLaunching(app, options);
        }
    }
}