如何调整视图中子视图的大小，该视图已从Xamarin.forms.View转换为UIView

// 创建父视图
UIView parentView = new UIView();
parentView.TranslatesAutoresizingMaskIntoConstraints = false;

// 创建子视图
UIView childView = new UIView();
childView.TranslatesAutoresizingMaskIntoConstraints = false;
childView.BackgroundColor = UIColor.Red;

// 将子视图添加到父视图
parentView.AddSubview(childView);

// 创建约束条件
NSLayoutConstraint widthConstraint = NSLayoutConstraint.Create(childView, NSLayoutAttribute.Width, NSLayoutRelation.Equal, null, NSLayoutAttribute.NoAttribute, 1, 200);
NSLayoutConstraint heightConstraint = NSLayoutConstraint.Create(childView, NSLayoutAttribute.Height, NSLayoutRelation.Equal, null, NSLayoutAttribute.NoAttribute, 1, 100);

// 添加约束条件到父视图
parentView.AddConstraint(widthConstraint);
parentView.AddConstraint(heightConstraint);

// 激活约束条件
parentView.TranslatesAutoresizingMaskIntoConstraints = false;

// 更新布局
widthConstraint.Constant = 300;
heightConstraint.Constant = 150;