Ios Swift:Can'；在具有NSLayoutConstraint的Superview中t居中UIView

我正在尝试在父视图中居中视图，但它没有按预期居中。这是我的代码和结果的屏幕截图

emptyView.translatesAutoresizingMaskIntoConstraints = false
self.view.addSubview(emptyView)
let centerXConstraint = NSLayoutConstraint(item: emptyView, attribute: .centerX, relatedBy: .equal, toItem: self.view, attribute: .centerX, multiplier: 1, constant: 0)
let centerYConstraint = NSLayoutConstraint(item: emptyView, attribute: .centerY, relatedBy: .equal, toItem: self.view, attribute: .centerY, multiplier: 1, constant: 0)
self.view.addConstraints([centerXConstraint])
self.view.addConstraints([centerYConstraint])

试试这段代码

emptyView.translatesAutoresizingMaskIntoConstraints = false
let widthConstraint = NSLayoutConstraint(item: emptyView, attribute: NSLayoutAttribute.width, relatedBy: NSLayoutRelation.equal, toItem: nil, attribute: NSLayoutAttribute.notAnAttribute, multiplier: 1, constant: emptyView.frame.size.width)
let heightConstraint = NSLayoutConstraint(item: emptyView, attribute: NSLayoutAttribute.height, relatedBy: NSLayoutRelation.equal, toItem: nil, attribute: NSLayoutAttribute.notAnAttribute, multiplier: 1, constant: emptyView.frame.size.height)
var constraints = NSLayoutConstraint.constraints(
        withVisualFormat: "V:[superview]-(<=1)-[label]",
        options: NSLayoutFormatOptions.alignAllCenterX,
        metrics: nil,
        views: ["superview":view, "label": emptyView])

view.addConstraints(constraints)

// Center vertically
constraints = NSLayoutConstraint.constraints(
        withVisualFormat: "H:[superview]-(<=1)-[label]",
        options: NSLayoutFormatOptions.alignAllCenterY,
        metrics: nil,
        views: ["superview":view, "label": emptyView])

view.addConstraints(constraints)
view.addConstraints([ widthConstraint, heightConstraint])

emptyView.translatesAutoresizingMaskIntoConstraints=false
let widthConstraint=NSLayoutConstraint（项：emptyView，属性：NSLayoutAttribute.width，关联方式：NSLayoutRelation.equal，到项：nil，属性：NSLayoutAttribute.NotAttribute，乘数：1，常数：emptyView.frame.size.width）
let heightConstraint=NSLayoutConstraint（项目：emptyView，属性：NSLayoutAttribute.height，关联方式：NSLayoutRelation.equal，toItem:nil，属性：NSLayoutAttribute.NotAttribute，乘数：1，常数：emptyView.frame.size.height）
var constraints=NSLayoutConstraint.constraints(
使用VisualFormat：“V:[superview]-（尝试以下代码

emptyView.translatesAutoresizingMaskIntoConstraints = false
let widthConstraint = NSLayoutConstraint(item: emptyView, attribute: NSLayoutAttribute.width, relatedBy: NSLayoutRelation.equal, toItem: nil, attribute: NSLayoutAttribute.notAnAttribute, multiplier: 1, constant: emptyView.frame.size.width)
let heightConstraint = NSLayoutConstraint(item: emptyView, attribute: NSLayoutAttribute.height, relatedBy: NSLayoutRelation.equal, toItem: nil, attribute: NSLayoutAttribute.notAnAttribute, multiplier: 1, constant: emptyView.frame.size.height)
var constraints = NSLayoutConstraint.constraints(
        withVisualFormat: "V:[superview]-(<=1)-[label]",
        options: NSLayoutFormatOptions.alignAllCenterX,
        metrics: nil,
        views: ["superview":view, "label": emptyView])

view.addConstraints(constraints)

// Center vertically
constraints = NSLayoutConstraint.constraints(
        withVisualFormat: "H:[superview]-(<=1)-[label]",
        options: NSLayoutFormatOptions.alignAllCenterY,
        metrics: nil,
        views: ["superview":view, "label": emptyView])

view.addConstraints(constraints)
view.addConstraints([ widthConstraint, heightConstraint])

emptyView.translatesAutoresizingMaskIntoConstraints=false
let widthConstraint=NSLayoutConstraint（项：emptyView，属性：NSLayoutAttribute.width，关联方式：NSLayoutRelation.equal，到项：nil，属性：NSLayoutAttribute.NotAttribute，乘数：1，常数：emptyView.frame.size.width）
let heightConstraint=NSLayoutConstraint（项目：emptyView，属性：NSLayoutAttribute.height，关联方式：NSLayoutRelation.equal，toItem:nil，属性：NSLayoutAttribute.NotAttribute，乘数：1，常数：emptyView.frame.size.height）
var constraints=NSLayoutConstraint.constraints(
VisualFormat：“V:[超级视图]（这是代码

import UIKit

class ViewController: UIViewController
{
    @IBOutlet weak var emptyView: UIView!

    override func viewDidLoad()
    {
        super.viewDidLoad()
        self.emptyView.translatesAutoresizingMaskIntoConstraints = false
        let centerXConstraint = NSLayoutConstraint(item: emptyView, attribute: .centerX, relatedBy: .equal, toItem: self.view, attribute: .centerX, multiplier: 1, constant: 0)
        let centerYConstraint = NSLayoutConstraint(item: emptyView, attribute: .centerY, relatedBy: .equal, toItem: self.view, attribute: .centerY, multiplier: 1, constant: 0)
        let widthConstraint = NSLayoutConstraint(item: emptyView, attribute: NSLayoutAttribute.width, relatedBy: NSLayoutRelation.equal, toItem: nil, attribute: NSLayoutAttribute.notAnAttribute, multiplier: 1, constant: 100)
        let heightConstraint = NSLayoutConstraint(item: emptyView, attribute: NSLayoutAttribute.height, relatedBy: NSLayoutRelation.equal, toItem: nil, attribute: NSLayoutAttribute.notAnAttribute, multiplier: 1, constant: 100)

        self.view.addConstraints([centerXConstraint, centerYConstraint, widthConstraint, heightConstraint])
        self.view.layoutIfNeeded()
    }
}

如果您使用的是标签、按钮或任何其他具有固有大小的视图，则不需要高度和宽度约束

ViewController界面：


输出：

这是代码

import UIKit

class ViewController: UIViewController
{
    @IBOutlet weak var emptyView: UIView!

    override func viewDidLoad()
    {
        super.viewDidLoad()
        self.emptyView.translatesAutoresizingMaskIntoConstraints = false
        let centerXConstraint = NSLayoutConstraint(item: emptyView, attribute: .centerX, relatedBy: .equal, toItem: self.view, attribute: .centerX, multiplier: 1, constant: 0)
        let centerYConstraint = NSLayoutConstraint(item: emptyView, attribute: .centerY, relatedBy: .equal, toItem: self.view, attribute: .centerY, multiplier: 1, constant: 0)
        let widthConstraint = NSLayoutConstraint(item: emptyView, attribute: NSLayoutAttribute.width, relatedBy: NSLayoutRelation.equal, toItem: nil, attribute: NSLayoutAttribute.notAnAttribute, multiplier: 1, constant: 100)
        let heightConstraint = NSLayoutConstraint(item: emptyView, attribute: NSLayoutAttribute.height, relatedBy: NSLayoutRelation.equal, toItem: nil, attribute: NSLayoutAttribute.notAnAttribute, multiplier: 1, constant: 100)

        self.view.addConstraints([centerXConstraint, centerYConstraint, widthConstraint, heightConstraint])
        self.view.layoutIfNeeded()
    }
}

如果您使用的是标签、按钮或任何其他具有固有大小的视图，则不需要高度和宽度约束

ViewController界面：


输出：

view.addConstraints
？验证应用程序崩溃原因：**由于未捕获的异常“nsInternalInconConsistencyException”终止应用程序，原因：“无法设置布局，视图层次结构未为约束做好准备。”您在哪里编写此代码来设置约束？此异常意味着视图未完成布局ely和Outlet未设置，因此无法对其应用约束。我想应该是这样的顺序：
emptyView.translatesAutoResizezingmaskintoConstraints=false
view.addSubview（emptyView）
view.addConstraints（）
正如@PGDev所建议的，这意味着可能没有添加您的
清空视图。
查看。添加约束
？Sesquatch应用程序崩溃：**由于未捕获的异常“nsinternalinconsistenceexception”终止应用程序，原因是：“无法设置布局，视图层次结构未为约束做好准备。”用于设置约束？此异常意味着视图未完全布局且未设置出口，因此无法对其应用约束。我想应该是这样的顺序：
emptyView.translatesAutoResistinggmaskintoConstraints=false
视图。addSubview（emptyView）
视图。addConstraints（）
正如@PGDev所建议的，这意味着您的
emptyView
可能没有添加。