ios - 以编程方式自动布局

Question

我创建了一个名为“holderView”的 UIView，对我来说问题是它只出现在我希望 iPhone 6 上出现的位置，因为这是我创建和测试它的地方。我在其他设备上测试了它，“holderView”位于不同的位置。这是代码:

var holderView = UIView()
let holderWidth = defaultTimeCapImage?.size.width
let holderHeight = (defaultTimeCapImage?.size.height)! + (vineTimeCapImage?.size.height)! + (instagramTimeCapImage?.size.height)! + 40

    self.holderView.hidden = false
    self.holderView.translatesAutoresizingMaskIntoConstraints = false
    self.addSubview(self.holderView)



    let holderViewCenterXConstraint = NSLayoutConstraint(item: self.holderView, attribute: NSLayoutAttribute.CenterX, relatedBy: NSLayoutRelation.Equal, toItem: self, attribute: NSLayoutAttribute.CenterX, multiplier: 1.0, constant: 155)

    let holderViewCenterYConstraint = NSLayoutConstraint(item: self.holderView, attribute: NSLayoutAttribute.CenterY, relatedBy: NSLayoutRelation.Equal, toItem: self, attribute: NSLayoutAttribute.CenterY, multiplier: 1.0, constant: -205)

    let holderViewWidthConstraint = NSLayoutConstraint(item: self.holderView, attribute: NSLayoutAttribute.Width, relatedBy: NSLayoutRelation.Equal, toItem: nil, attribute: NSLayoutAttribute.NotAnAttribute, multiplier: 1.0, constant:holderWidth!)

     let holderViewHeightConstraint = NSLayoutConstraint(item: self.holderView, attribute: NSLayoutAttribute.Height, relatedBy: NSLayoutRelation.Equal, toItem: nil, attribute: NSLayoutAttribute.NotAnAttribute, multiplier: 1.0, constant:holderHeight)

    self.addConstraints([holderViewCenterXConstraint,holderViewCenterYConstraint, holderViewWidthConstraint,holderViewHeightConstraint])

我相信问题出在holderViewCenterXConstraint和holderViewCenterYConstraint上，我将常量更改为值，以将“holderView”放在我想要在iPhone 6上的位置。

我怎样才能让这个holderView在所有屏幕尺寸上都处于正确的位置？如果问题是常量，我应该如何更改它？

Answer 1

虽然宽度和高度相同，但将常数设置为 zero

let holderViewCenterXConstraint = NSLayoutConstraint(item:
    self.holderView, attribute: NSLayoutAttribute.CenterX, relatedBy: NSLayoutRelation.Equal, toItem: self, attribute: NSLayoutAttribute.CenterX, multiplier: 1.0, constant: 0)

        let holderViewCenterYConstraint = NSLayoutConstraint(item: self.holderView, attribute: NSLayoutAttribute.CenterY, relatedBy: NSLayoutRelation.Equal, toItem: self, attribute: NSLayoutAttribute.CenterY, multiplier: 1.0, constant: 0)