c# - 如何在 MonoTouch 中为继承 View 创建 UIAppearance 代理？

Question

我创建了 UIButton 的子类，它充当 UIBarButtonItem 内的自定义后退按钮:

 - - - - - - - - - - - - - - - - - 
|         UIBarButtonItem         |

|     ------------------------    |
     /                       |
|    \ BackButton : UIButton |    |
      ------------------------
|  _  _  _  _  _  _  _  _  _  _  _|

当我将代码切换为使用 UIAppearance 时，我注意到 BackButton.Appearance 毫不奇怪地继承自 UIButton.Appearance，因此，更改它会更改整个应用程序中的所有 UIButton，而不仅仅是我的自定义按钮。

我知道我可以使用 AppearanceWhenContainedIn 但是，因为 UIBarButtonItem 不是外观容器，我必须在它们之间插入另一个 View 来识别后退按钮，我不想做。

如何为具有 UIButton.UIButtonAppearance 中所有可用方法的自定义 UIButton 子类提供 UIAppearance 代理？我注意到它的构造函数是内部的。

Answer 1

虽然可能有一个更简单的答案，但我最终直接继承了 UIAppearance 并复制粘贴了 UIButton 和 UIButton+UIButtonAppearance 的相关部分> 绑定(bind) MonoDevelop C# 反汇编器的实现并修复内部字段。

返回按钮内部:

static readonly IntPtr class_ptr = Class.GetHandle(typeof(BackButton));

public new static BackButtonAppearance Appearance
{
    get {
        return new BackButtonAppearance (Messaging.IntPtr_objc_msgSend (class_ptr, UIAppearance.SelectorAppearance));
    }
}

public new static BackButtonAppearance AppearanceWhenContainedIn (params Type[] containers)
{
    return new BackButtonAppearance (UIAppearance.GetAppearance (class_ptr, containers));
}

嵌套BackButtonAppearance:

public class BackButtonAppearance : UIAppearance {
    public BackButtonAppearance(IntPtr handle) : base(handle) { }

    // These are copied from UIButton disassembly:

    static readonly IntPtr selSetBackgroundImageForState_ = Selector.GetHandle ("setBackgroundImage:forState:");
    static readonly IntPtr selSetTitleShadowColorForState_ = Selector.GetHandle ("setTitleShadowColor:forState:");            
    static readonly IntPtr selSetTitleColorForState_ = Selector.GetHandle ("setTitleColor:forState:");

    // These are copied from UIButton+UIButtonAppearance disassembly,
    // with internal UIButton.selSet* fields replaced by fields declared above.

    [Export ("setBackgroundImage:forState:"), CompilerGenerated]
    public virtual void SetBackgroundImage (UIImage image, UIControlState forState)
    {
        UIApplication.EnsureUIThread ();
        if (this.IsDirectBinding) {
            Messaging.void_objc_msgSend_IntPtr_UInt32 (base.Handle, selSetBackgroundImageForState_, (image != null) ? image.Handle : IntPtr.Zero, (uint)forState);
        } else {
            Messaging.void_objc_msgSendSuper_IntPtr_UInt32 (base.SuperHandle, selSetBackgroundImageForState_, (image != null) ? image.Handle : IntPtr.Zero, (uint)forState);
        }
    }


    [Export ("setTitleColor:forState:"), CompilerGenerated]
    public virtual void SetTitleColor (UIColor color, UIControlState forState)
    {
        UIApplication.EnsureUIThread ();
        if (this.IsDirectBinding) {
            Messaging.void_objc_msgSend_IntPtr_UInt32 (base.Handle, selSetTitleColorForState_, (color != null) ? color.Handle : IntPtr.Zero, (uint)forState);
        } else {
            Messaging.void_objc_msgSendSuper_IntPtr_UInt32 (base.SuperHandle, selSetTitleColorForState_, (color != null) ? color.Handle : IntPtr.Zero, (uint)forState);
        }
    }

    [Export ("setTitleShadowColor:forState:"), CompilerGenerated]
    public virtual void SetTitleShadowColor (UIColor color, UIControlState forState)
    {
        UIApplication.EnsureUIThread ();
        if (this.IsDirectBinding) {
            Messaging.void_objc_msgSend_IntPtr_UInt32 (base.Handle, selSetTitleShadowColorForState_, (color != null) ? color.Handle : IntPtr.Zero, (uint)forState);
        } else {
            Messaging.void_objc_msgSendSuper_IntPtr_UInt32 (base.SuperHandle, selSetTitleShadowColorForState_, (color != null) ? color.Handle : IntPtr.Zero, (uint)forState);
        }
    }
}

这使我能够将自定义 View 支持 UIAppearance 风格的 API。