[英]Programmatically adding constraints in Swift does not work
I added the following code to center a programmatically added view: 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)
It doesn't work. 没用 The view is not centered. 视图未居中。 It is on the left still. 它在左边。
EDIT: 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!)
You need to pick a side my friend, If you are using auto layout, don't initialise your objects with a frame
. 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。 Try something like this... 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)
}
If your LineChartView
object is a subclass of UIView
then this should work, and you should have a 50x50 object in the middle of your superview. 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。
If you are going to be doing constraints like this in code you should consider using Apples Visual Formatting Language . 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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