扩展方法在调用中不可用 class

Question

我正在尝试引用一个 class 的扩展方法，但出现以下错误："Error: UIColor does not contain a definition for 'FromHex'"。我的设置如下。我在我的错误来源行的开头添加了一个箭头（箭头不是我的代码的一部分）。

我有一个警报 class:

using System;
using UIKit;
using System.Linq;
using MyApp.iOS;

[assembly: Xamarin.Forms.Dependency(typeof(MyApp.iOS.Alert))]
namespace MyApp.iOS {

    public class Alert : IAlert {
        public void ShowAlert(string title, string message, string button) {
            ShowAlert(title, message, button, null);
        }

        public void ShowAlert(string title, string message, string button, string hexColor) {
            var okAlertController = UIAlertController.Create(title, message, UIAlertControllerStyle.Alert);
            okAlertController.AddAction(UIAlertAction.Create(button, UIAlertActionStyle.Default, null));

            if (hexColor != null) {
                UIView firstSubView = okAlertController.View.Subviews.First();
                UIView alertContentView = firstSubView.Subviews.First();
                foreach (UIView subSubView in alertContentView.Subviews) {
                    --> subSubView.BackgroundColor = UIColor.FromHex(hexColor); // This line is where I'm getting the error
                }

                okAlertController.View.TintColor = UIColor.Black;
            }

            var window = UIApplication.SharedApplication.KeyWindow;
            var viewController = window.RootViewController;
            while (viewController.PresentedViewController != null) viewController = viewController.PresentedViewController;

            var navigationController = viewController as UINavigationController;
            if (navigationController != null) viewController = navigationController.ViewControllers.Last();

            viewController.PresentViewController(okAlertController, true, null);
        }
    }

}

我有一个 UIColorExtensions class:

using System;
using System.Globalization;
using UIKit;

namespace MyApp.iOS {

    public static class UIColorExtensions {
        public static UIColor FromHex(this UIColor color, string hex) {
            float a = 255, r = 0, g = 0, b = 0;

            if (hex.StartsWith("#")) {
                string hexColor = hex.Substring(1);

                if (hexColor.Length == 8) {
                    float.TryParse(hexColor.Substring(0, 2), NumberStyles.HexNumber, CultureInfo.CurrentCulture, out a);
                    hexColor = hexColor.Substring(2, 6);
                }

                if (hexColor.Length == 6) {
                    float.TryParse(hexColor.Substring(2, 2), NumberStyles.HexNumber, CultureInfo.CurrentCulture, out r);
                    float.TryParse(hexColor.Substring(4, 2), NumberStyles.HexNumber, CultureInfo.CurrentCulture, out g);
                    float.TryParse(hexColor.Substring(6, 2), NumberStyles.HexNumber, CultureInfo.CurrentCulture, out b);
                }

                return UIColor.FromRGBA(r, g, b, a);
            }

            return null;
        }
    }

}

我不知道我做错了什么。

这是我目前尝试过的方法：

正在重新启动 IDE
清理、重建
删除我的警报中命名空间行上方的装配线 class

Answer 1

问题是 UIColor 不是 class 的实例，因此必须执行类似 UIColor.Red.FromHex(hex) 的操作或修改您的扩展方法以另一种方式处理它。

扩展方法在调用中不可用 class

Extension method not available in calling class

c#

extension-methods

xamarin.ios

xamarin

xamarin.forms