[英]Programmatically adding constraints in Swift does not work
我添加了以下代码以使以编程方式添加的视图居中:
let horizontalConstraint = NSLayoutConstraint(item: newView!, attribute: NSLayoutAttribute.CenterX, relatedBy: NSLayoutRelation.Equal, toItem: view, attribute: NSLayoutAttribute.CenterX, multiplier: 1, constant: 0)
view.addConstraint(horizontalConstraint)
没用 视图未居中。 它在左边。
编辑:
override func viewDidLoad() {
super.viewDidLoad()
newView = LineChartView(frame: CGRectMake(0, 0, 50, 50))
newView?.delegate = self
newView?.drawBordersEnabled = true
newView?.noDataText = "No Data"
newView?.noDataTextDescription = "No Data"
newView?.borderColor = UIColor.blackColor()
self.view.addSubview(newView!)
我的朋友需要挑一面,如果您使用的是自动布局,请不要使用frame
初始化对象。 试试这样的东西...
var newView:LineChartView!
override func viewDidLoad() {
super.viewDidLoad()
newView = LineChartView()
newView.translatesAutoresizingMaskIntoConstraints = false
newView.delegate = self
newView.drawBordersEnabled = true
newView.noDataText = "No Data"
newView.noDataTextDescription = "No Data"
newView.borderColor = UIColor.blackColor()
self.view.addSubview(newView)
let width = NSLayoutConstraint(item: newView, attribute: .Width, relatedBy: .Equal, toItem: nil, attribute: .NotAnAttribute, multiplier: 1, constant: 50)
let height = NSLayoutConstraint(item: newView, attribute: .Height, relatedBy: .Equal, toItem: nil, attribute: .NotAnAttribute, multiplier: 1, constant: 50)
newView.addConstraint(width)
newView.addConstraint(height)
let x = NSLayoutConstraint(item: newView, attribute: .CenterX, relatedBy: .Equal, toItem: self.view, attribute: .CenterX, multiplier: 1, constant: 0)
let y = NSLayoutConstraint(item: newView, attribute: .CenterY, relatedBy: .Equal, toItem: self.view, attribute: .CenterY, multiplier: 1, constant: 0)
self.view.addConstraint(x)
self.view.addConstraint(y)
}
如果LineChartView
对象是UIView
的子类,则这应该可以工作,并且您的超级视图中间应该有50x50的对象。
如果要在代码中进行此类约束,则应考虑使用Apples Visual Formatting Language 。
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