更改呈现的视图控制器约束

Question

我试了一段时间寻找答案。 我想要做的是更改与他的“父亲”有关的ViewController的约束。 这是我尝试执行的操作，但出现错误：

 partial void BackAction(Foundation.NSObject sender)
 {
   /// My "parent" view controller - the one that presented this view
   UIViewController ApplicationViewController = Application.GetPresentedViewController("ApplicationViewController");
   /// Here I am trying to update the constrains in relation with his father  
   View.AddConstraint(NSLayoutConstraint.Create(ApplicationViewController.View, NSLayoutAttribute.LeftMargin, NSLayoutRelation.Equal, 1, 30));
   /// and also let the view digest the constrains
   View.UpdateConstraints();
 }

添加约束时，出现以下错误：

Objective-C exception thrown.  
Name: NSInvalidArgumentException 
Reason: NSLayoutConstraint for <UILayoutContainerView: 0x104903e70; frame = (0 0; 375 812); autoresize = W+H; layer = <CALayer: 0x1c802ff20>>: 
A multiplier of 0 or a nil second item together with a location for the first attribute creates an illegal constraint of a location equal to a constant. 
Location attributes must be specified in pairs.

请帮我找出来，谢谢

Answer 1

您需要添加缺少的view参数。

创建（NSObject，NSLayoutAttribute，NSLayoutRelation，NSObject，NSLayoutAttribute，nfloat，nfloat）

View.AddConstraint(NSLayoutConstraint.Create(ApplicationViewController.View, NSLayoutAttribute.LeftMargin, NSLayoutRelation.Equal,View,NSLayoutAttribute.LeftMargin,1, 30));