当键盘未被聚焦时，如何使iOS搜索栏上的“取消”可点击？[Xamarin表单]

using UIKit;
using Xamarin.Forms;
using Xamarin.Forms.Platform.iOS;

[assembly: ExportRenderer(typeof(SearchBar), typeof(CustomSearchBarRenderer))]
namespace YourNamespace.iOS
{
    public class CustomSearchBarRenderer : SearchBarRenderer
    {
        protected override void OnElementChanged(ElementChangedEventArgs<SearchBar> e)
        {
            base.OnElementChanged(e);

            if (Control != null)
            {
                Control.ShowsCancelButton = true;
            }
        }
    }
}

using Xamarin.Forms.PlatformConfiguration;
using Xamarin.Forms.PlatformConfiguration.iOSSpecific;

protected override void OnStart()
{
    base.OnStart();

    // 应用自定义渲染器
    var searchBar = new SearchBar();
    searchBar.On<iOS>().SetUseLegacySearchBar(true);
    MainPage = new MainPage(searchBar);
}