Xamarin 和 ios 锚点约束不起作用

Question

如果我将此代码添加到基本启动项目的 ViewDidLoad 中，则红色视图无处可见......我认为它应该显示在窗口的顶部中心...我做错了什么？

var redview = new UIView(new CGRect(0, 0, 100, 200));
redview.BackgroundColor = UIColor.Red;
redview.TranslatesAutoresizingMaskIntoConstraints = false;
View.AddSubview(redview);
redview.TopAnchor.ConstraintEqualTo(this.View.TopAnchor).Active = true;
redview.CenterXAnchor.ConstraintEqualTo(this.View.CenterXAnchor).Active = true;

Answer 1

因为您已经设置了redView的框架，这将与Constraint冲突。 参考以下代码

var redview = new UIView();
redview.BackgroundColor = UIColor.Red;
redview.TranslatesAutoresizingMaskIntoConstraints = false;
View.AddSubview(redview);
redview.TopAnchor.ConstraintEqualTo(this.View.TopAnchor).Active = true;
redview.CenterXAnchor.ConstraintEqualTo(this.View.CenterXAnchor).Active = true;
redview.WidthAnchor.ConstraintEqualTo(100).Active=true;
redview.HeightAnchor.ConstraintEqualTo(200).Active = true;