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2023-08-04 10:00:02

如何使用Swift以编程方式添加约束

从上周开始，我就一直在想办法解决这个问题。好的，所以我需要在Swift中使用以下代码应用一些约束到UIView:

var new_view:UIView! = UIView(frame: CGRectMake(0, 0, 100, 100));
new_view.backgroundColor = UIColor.redColor();
view.addSubview(new_view);

var constX:NSLayoutConstraint = NSLayoutConstraint(item: new_view, attribute: NSLayoutAttribute.CenterX, relatedBy: NSLayoutRelation.Equal, toItem: self.view, attribute: NSLayoutAttribute.CenterX, multiplier: 1, constant: 0);
self.view.addConstraint(constX);

var constY:NSLayoutConstraint = NSLayoutConstraint(item: new_view, attribute: NSLayoutAttribute.CenterY, relatedBy: NSLayoutRelation.Equal, toItem: self.view, attribute: NSLayoutAttribute.CenterY, multiplier: 1, constant: 0);
self.view.addConstraint(constY);

var constW:NSLayoutConstraint = NSLayoutConstraint(item: new_view, attribute: NSLayoutAttribute.Width, relatedBy: NSLayoutRelation.Equal, toItem: new_view, attribute: NSLayoutAttribute.Width, multiplier: 1, constant: 0);
self.view.addConstraint(constW);

var constH:NSLayoutConstraint = NSLayoutConstraint(item: new_view, attribute: NSLayoutAttribute.Height, relatedBy: NSLayoutRelation.Equal, toItem: new_view, attribute: NSLayoutAttribute.Height, multiplier: 1, constant: 0);
self.view.addConstraint(constH);

但是Xcode返回了这个奇怪的输出:

2014-10-03 09:48:12.657 Test[35088:2454916] Unable to simultaneously satisfy constraints.  Probably at least one of the constraints in the following list is one you don't want. Try this: (1) look at each constraint and try to figure out which you don't expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints) 
(
"<NSLayoutConstraint:0x7fa4ea446830 UIView:0x7fa4ea429290.centerX == UIView:0x7fa4ea4470f0.centerX>",
"<NSAutoresizingMaskLayoutConstraint:0x7fa4ea4516c0 h=--& v=--& UIView:0x7fa4ea429290.midX == + 50>",
"<NSLayoutConstraint:0x7fa4ea452830 'UIView-Encapsulated-Layout-Width' H:[UIView:0x7fa4ea4470f0(375)]>",
"<NSAutoresizingMaskLayoutConstraint:0x7fa4ea446db0 h=-&- v=-&- 'UIView-Encapsulated-Layout-Left' H:|-(0)-[UIView:0x7fa4ea4470f0]   (Names: '|':UIWindow:0x7fa4ea444b20 )>"
)

Will attempt to recover by breaking constraint <NSLayoutConstraint:0x7fa4ea446830 UIView:0x7fa4ea429290.centerX == UIView:0x7fa4ea4470f0.centerX>

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger. The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in
<UIKit/UIView.h> may also be helpful.

2014-10-03 09:48:12.658 Test[35088:2454916] Unable to simultaneously satisfy constraints.  Probably at least one of the constraints in the following list is one you don't want. Try this: (1) look at each constraint and try to figure out which you don't expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints)
(
"<NSLayoutConstraint:0x7fa4ea44d160 UIView:0x7fa4ea429290.centerY == UIView:0x7fa4ea4470f0.centerY>",
"<NSAutoresizingMaskLayoutConstraint:0x7fa4ea451b30 h=--& v=--& UIView:0x7fa4ea429290.midY == + 50>",
"<NSLayoutConstraint:0x7fa4ea44cf00 'UIView-Encapsulated-Layout-Height' V:[UIView:0x7fa4ea4470f0(667)]>",
"<NSAutoresizingMaskLayoutConstraint:0x7fa4ea452700 h=-&- v=-&- 'UIView-Encapsulated-Layout-Top' V:|-(0)-[UIView:0x7fa4ea4470f0]  (Names: '|':UIWindow:0x7fa4ea444b20 )>"
)

Will attempt to recover by breaking constraint <NSLayoutConstraint:0x7fa4ea44d160 UIView:0x7fa4ea429290.centerY == UIView:0x7fa4ea4470f0.centerY>

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger. The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.

你能帮我吗? 非常感谢

当前回答

您正在向self添加所有已定义的约束。视图的宽度和高度限制应该添加到你的newView。

另外，据我所知，你想要设置恒定的宽度和高度100:100。 在这种情况下，您应该将代码更改为:

var constW = NSLayoutConstraint(item: newView, 
    attribute: .Width, 
    relatedBy: .Equal, 
    toItem: nil, 
    attribute: .NotAnAttribute, 
    multiplier: 1, 
    constant: 100)
newView.addConstraint(constW)

var constH = NSLayoutConstraint(item: newView, 
    attribute: .Height, 
    relatedBy: .Equal, 
    toItem: nil, 
    attribute: .NotAnAttribute, 
    multiplier: 1, 
    constant: 100)
newView.addConstraint(constH)
2016-09-14 11:11:50

其他回答

如果你觉得上面的内容很难看。您应该考虑使用DSL进行约束。比如SnapKit 使约束API更加用户友好

view.snp.makeConstraints { make in
    make.edges.equalToSuperview()
}
2017-11-29 15:59:10

在xcode 7.3.1中略有不同。这是我想到的

   // creating the view
        let newView = UIView()
        newView.backgroundColor = UIColor.redColor()
        newView.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(newView)

        // creating the constraint 

        // attribute and relation cannot be set directyl you need to create a cariable of them
        let layout11 = NSLayoutAttribute.CenterX
        let layout21 = NSLayoutRelation.Equal
        let layout31 = NSLayoutAttribute.CenterY
        let layout41 = NSLayoutAttribute.Width
        let layout51 = NSLayoutAttribute.Height
        let layout61 = NSLayoutAttribute.NotAnAttribute

        // defining all the constraint
        let horizontalConstraint = NSLayoutConstraint(item: newView, attribute: layout11, relatedBy: layout21, toItem: view, attribute: layout11, multiplier: 1, constant: 0)
        let verticalConstraint = NSLayoutConstraint(item: newView, attribute: layout31, relatedBy: layout21, toItem: view, attribute: layout31, multiplier: 1, constant: 0)
        let widthConstraint = NSLayoutConstraint(item: newView, attribute: layout41, relatedBy: layout21, toItem: nil, attribute: layout61, multiplier: 1, constant: 100)
        let heightConstraint = NSLayoutConstraint(item: newView, attribute: layout51, relatedBy: layout21, toItem: nil, attribute: layout61, multiplier: 1, constant: 100)

        // adding all the constraint
        NSLayoutConstraint.activateConstraints([horizontalConstraint,verticalConstraint,widthConstraint,heightConstraint])
2016-10-10 18:35:27

如果你想要填充你的超级视图，那么我建议快速的方法:

view.translatesAutoresizingMaskIntoConstraints = false
let attributes: [NSLayoutAttribute] = [.top, .bottom, .right, .left]
NSLayoutConstraint.activate(attributes.map {
    NSLayoutConstraint(item: view, attribute: $0, relatedBy: .equal, toItem: view.superview, attribute: $0, multiplier: 1, constant: 0)
})

否则，如果你需要非相等的约束检查NSLayoutAnchor作为iOS 9。使用NSLayoutConstraint直接读取通常要容易得多:

view.translatesAutoresizingMaskIntoConstraints = false
view.topAnchor.constraint(equalTo: view.superview!.topAnchor).isActive = true
view.bottomAnchor.constraint(equalTo: view.superview!.bottomAnchor).isActive = true
view.leadingAnchor.constraint(equalTo: view.superview!.leadingAnchor, constant: 10).isActive = true
view.trailingAnchor.constraint(equalTo: view.superview!.trailingAnchor, constant: 10).isActive = true
2016-10-21 19:31:51

Swift 3更新

import UIKit

class ViewController: UIViewController {

let redView: UIView = {

    let view = UIView()
    view.translatesAutoresizingMaskIntoConstraints = false
    view.backgroundColor = .red
    return view
}()

override func viewDidLoad() {
    super.viewDidLoad()

    setupViews()
    setupAutoLayout()
}

func setupViews() {

    view.backgroundColor = .white
    view.addSubview(redView)
}

func setupAutoLayout() {

    // Available from iOS 9 commonly known as Anchoring System for AutoLayout...
    redView.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 20).isActive = true
    redView.rightAnchor.constraint(equalTo: view.rightAnchor, constant: -20).isActive = true

    redView.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
    redView.heightAnchor.constraint(equalToConstant: 300).isActive = true

    // You can also modified above last two lines as follows by commenting above & uncommenting below lines...
    // redView.topAnchor.constraint(equalTo: view.topAnchor, constant: 20).isActive = true
    // redView.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
 }
}

约束的类型

 /*
// regular use
1.leftAnchor
2.rightAnchor
3.topAnchor
// intermediate use
4.widthAnchor
5.heightAnchor
6.bottomAnchor
7.centerXAnchor
8.centerYAnchor
// rare use
9.leadingAnchor
10.trailingAnchor
etc. (note: very project to project)
*/
2017-08-11 03:44:24

你计划在UIViewController的UIView中有一个宽度为100和高度为100的平方UIView吗?如果是这样，你可以尝试以下6种自动布局风格之一(Swift 5 / iOS 12.2):

1. 使用NSLayoutConstraint初始化器

override func viewDidLoad() {
    let newView = UIView()
    newView.backgroundColor = UIColor.red
    view.addSubview(newView)

    newView.translatesAutoresizingMaskIntoConstraints = false
    let horizontalConstraint = NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.centerX, relatedBy: NSLayoutConstraint.Relation.equal, toItem: view, attribute: NSLayoutConstraint.Attribute.centerX, multiplier: 1, constant: 0)
    let verticalConstraint = NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.centerY, relatedBy: NSLayoutConstraint.Relation.equal, toItem: view, attribute: NSLayoutConstraint.Attribute.centerY, multiplier: 1, constant: 0)
    let widthConstraint = NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.width, relatedBy: NSLayoutConstraint.Relation.equal, toItem: nil, attribute: NSLayoutConstraint.Attribute.notAnAttribute, multiplier: 1, constant: 100)
    let heightConstraint = NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.height, relatedBy: NSLayoutConstraint.Relation.equal, toItem: nil, attribute: NSLayoutConstraint.Attribute.notAnAttribute, multiplier: 1, constant: 100)
    view.addConstraints([horizontalConstraint, verticalConstraint, widthConstraint, heightConstraint])
}

override func viewDidLoad() {
    let newView = UIView()
    newView.backgroundColor = UIColor.red
    view.addSubview(newView)

    newView.translatesAutoresizingMaskIntoConstraints = false
    let horizontalConstraint = NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.centerX, relatedBy: NSLayoutConstraint.Relation.equal, toItem: view, attribute: NSLayoutConstraint.Attribute.centerX, multiplier: 1, constant: 0)
    let verticalConstraint = NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.centerY, relatedBy: NSLayoutConstraint.Relation.equal, toItem: view, attribute: NSLayoutConstraint.Attribute.centerY, multiplier: 1, constant: 0)
    let widthConstraint = NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.width, relatedBy: NSLayoutConstraint.Relation.equal, toItem: nil, attribute: NSLayoutConstraint.Attribute.notAnAttribute, multiplier: 1, constant: 100)
    let heightConstraint = NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.height, relatedBy: NSLayoutConstraint.Relation.equal, toItem: nil, attribute: NSLayoutConstraint.Attribute.notAnAttribute, multiplier: 1, constant: 100)
    NSLayoutConstraint.activate([horizontalConstraint, verticalConstraint, widthConstraint, heightConstraint])
}

override func viewDidLoad() {
    let newView = UIView()
    newView.backgroundColor = UIColor.red
    view.addSubview(newView)

    newView.translatesAutoresizingMaskIntoConstraints = false
    NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.centerX, relatedBy: NSLayoutConstraint.Relation.equal, toItem: view, attribute: NSLayoutConstraint.Attribute.centerX, multiplier: 1, constant: 0).isActive = true
    NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.centerY, relatedBy: NSLayoutConstraint.Relation.equal, toItem: view, attribute: NSLayoutConstraint.Attribute.centerY, multiplier: 1, constant: 0).isActive = true
    NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.width, relatedBy: NSLayoutConstraint.Relation.equal, toItem: nil, attribute: NSLayoutConstraint.Attribute.notAnAttribute, multiplier: 1, constant: 100).isActive = true
    NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.height, relatedBy: NSLayoutConstraint.Relation.equal, toItem: nil, attribute: NSLayoutConstraint.Attribute.notAnAttribute, multiplier: 1, constant: 100).isActive = true
}

2. 使用可视化格式语言

override func viewDidLoad() {
    let newView = UIView()
    newView.backgroundColor = UIColor.red
    view.addSubview(newView)

    newView.translatesAutoresizingMaskIntoConstraints = false
    let views = ["view": view!, "newView": newView]
    let horizontalConstraints = NSLayoutConstraint.constraints(withVisualFormat: "H:[view]-(<=0)-[newView(100)]", options: NSLayoutConstraint.FormatOptions.alignAllCenterY, metrics: nil, views: views)
    let verticalConstraints = NSLayoutConstraint.constraints(withVisualFormat: "V:[view]-(<=0)-[newView(100)]", options: NSLayoutConstraint.FormatOptions.alignAllCenterX, metrics: nil, views: views)
    view.addConstraints(horizontalConstraints)
    view.addConstraints(verticalConstraints)
}

override func viewDidLoad() {
    let newView = UIView()
    newView.backgroundColor = UIColor.red
    view.addSubview(newView)

    newView.translatesAutoresizingMaskIntoConstraints = false
    let views = ["view": view!, "newView": newView]
    let horizontalConstraints = NSLayoutConstraint.constraints(withVisualFormat: "H:[view]-(<=0)-[newView(100)]", options: NSLayoutConstraint.FormatOptions.alignAllCenterY, metrics: nil, views: views)
    let verticalConstraints = NSLayoutConstraint.constraints(withVisualFormat: "V:[view]-(<=0)-[newView(100)]", options: NSLayoutConstraint.FormatOptions.alignAllCenterX, metrics: nil, views: views)
    NSLayoutConstraint.activate(horizontalConstraints)
    NSLayoutConstraint.activate(verticalConstraints)
}

3.混合使用NSLayoutConstraint初始化器和可视格式语言

override func viewDidLoad() {
    let newView = UIView()
    newView.backgroundColor = UIColor.red
    view.addSubview(newView)

    newView.translatesAutoresizingMaskIntoConstraints = false
    let views = ["newView": newView]
    let widthConstraints = NSLayoutConstraint.constraints(withVisualFormat: "H:[newView(100)]", options: NSLayoutConstraint.FormatOptions(rawValue: 0), metrics: nil, views: views)
    let heightConstraints = NSLayoutConstraint.constraints(withVisualFormat: "V:[newView(100)]", options: NSLayoutConstraint.FormatOptions(rawValue: 0), metrics: nil, views: views)
    let horizontalConstraint = NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.centerX, relatedBy: NSLayoutConstraint.Relation.equal, toItem: view, attribute: NSLayoutConstraint.Attribute.centerX, multiplier: 1, constant: 0)
    let verticalConstraint = NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.centerY, relatedBy: NSLayoutConstraint.Relation.equal, toItem: view, attribute: NSLayoutConstraint.Attribute.centerY, multiplier: 1, constant: 0)
    view.addConstraints(widthConstraints)
    view.addConstraints(heightConstraints)
    view.addConstraints([horizontalConstraint, verticalConstraint])
}

override func viewDidLoad() {
    let newView = UIView()
    newView.backgroundColor = UIColor.red
    view.addSubview(newView)

    newView.translatesAutoresizingMaskIntoConstraints = false
    let views = ["newView": newView]
    let widthConstraints = NSLayoutConstraint.constraints(withVisualFormat: "H:[newView(100)]", options: NSLayoutConstraint.FormatOptions(rawValue: 0), metrics: nil, views: views)
    let heightConstraints = NSLayoutConstraint.constraints(withVisualFormat: "V:[newView(100)]", options: NSLayoutConstraint.FormatOptions(rawValue: 0), metrics: nil, views: views)
    let horizontalConstraint = NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.centerX, relatedBy: NSLayoutConstraint.Relation.equal, toItem: view, attribute: NSLayoutConstraint.Attribute.centerX, multiplier: 1, constant: 0)
    let verticalConstraint = NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.centerY, relatedBy: NSLayoutConstraint.Relation.equal, toItem: view, attribute: NSLayoutConstraint.Attribute.centerY, multiplier: 1, constant: 0)
    NSLayoutConstraint.activate(widthConstraints)
    NSLayoutConstraint.activate(heightConstraints)
    NSLayoutConstraint.activate([horizontalConstraint, verticalConstraint])
}

override func viewDidLoad() {
    let newView = UIView()
    newView.backgroundColor = UIColor.red
    view.addSubview(newView)

    newView.translatesAutoresizingMaskIntoConstraints = false
    let views = ["newView": newView]
    let widthConstraints = NSLayoutConstraint.constraints(withVisualFormat: "H:[newView(100)]", options: NSLayoutConstraint.FormatOptions(rawValue: 0), metrics: nil, views: views)
    let heightConstraints = NSLayoutConstraint.constraints(withVisualFormat: "V:[newView(100)]", options: NSLayoutConstraint.FormatOptions(rawValue: 0), metrics: nil, views: views)
    NSLayoutConstraint.activate(widthConstraints)
    NSLayoutConstraint.activate(heightConstraints)
    NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.centerX, relatedBy: NSLayoutConstraint.Relation.equal, toItem: view, attribute: NSLayoutConstraint.Attribute.centerX, multiplier: 1, constant: 0).isActive = true
    NSLayoutConstraint(item: newView, attribute: NSLayoutConstraint.Attribute.centerY, relatedBy: NSLayoutConstraint.Relation.equal, toItem: view, attribute: NSLayoutConstraint.Attribute.centerY, multiplier: 1, constant: 0).isActive = true
}

4. 使用UIView。AutoresizingMask

注意:spring和Struts将在运行时转换为相应的自动布局约束。

override func viewDidLoad() {
    let newView = UIView(frame: CGRect(x: 0, y: 0, width: 100, height: 100))
    newView.backgroundColor = UIColor.red
    view.addSubview(newView)

    newView.translatesAutoresizingMaskIntoConstraints = true
    newView.center = CGPoint(x: view.bounds.midX, y: view.bounds.midY)
    newView.autoresizingMask = [UIView.AutoresizingMask.flexibleLeftMargin, UIView.AutoresizingMask.flexibleRightMargin, UIView.AutoresizingMask.flexibleTopMargin, UIView.AutoresizingMask.flexibleBottomMargin]
}

5. 使用NSLayoutAnchor

override func viewDidLoad() {
    let newView = UIView()
    newView.backgroundColor = UIColor.red
    view.addSubview(newView)
    
    newView.translatesAutoresizingMaskIntoConstraints = false
    let horizontalConstraint = newView.centerXAnchor.constraint(equalTo: view.centerXAnchor)
    let verticalConstraint = newView.centerYAnchor.constraint(equalTo: view.centerYAnchor)
    let widthConstraint = newView.widthAnchor.constraint(equalToConstant: 100)
    let heightConstraint = newView.heightAnchor.constraint(equalToConstant: 100)
    view.addConstraints([horizontalConstraint, verticalConstraint, widthConstraint, heightConstraint])
}

override func viewDidLoad() {
    let newView = UIView()
    newView.backgroundColor = UIColor.red
    view.addSubview(newView)
    
    newView.translatesAutoresizingMaskIntoConstraints = false
    let horizontalConstraint = newView.centerXAnchor.constraint(equalTo: view.centerXAnchor)
    let verticalConstraint = newView.centerYAnchor.constraint(equalTo: view.centerYAnchor)
    let widthConstraint = newView.widthAnchor.constraint(equalToConstant: 100)
    let heightConstraint = newView.heightAnchor.constraint(equalToConstant: 100)
    NSLayoutConstraint.activate([horizontalConstraint, verticalConstraint, widthConstraint, heightConstraint])
}

override func viewDidLoad() {
    let newView = UIView()
    newView.backgroundColor = UIColor.red
    view.addSubview(newView)
    
    newView.translatesAutoresizingMaskIntoConstraints = false
    newView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
    newView.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
    newView.widthAnchor.constraint(equalToConstant: 100).isActive = true
    newView.heightAnchor.constraint(equalToConstant: 100).isActive = true
}

6. 使用intrinsicContentSize和NSLayoutAnchor

import UIKit

class CustomView: UIView {
    
    override var intrinsicContentSize: CGSize {
        return CGSize(width: 100, height: 100)
    }
    
}

class ViewController: UIViewController {
    
    override func viewDidLoad() {
        let newView = CustomView()
        newView.backgroundColor = UIColor.red
        view.addSubview(newView)
        
        newView.translatesAutoresizingMaskIntoConstraints = false
        let horizontalConstraint = newView.centerXAnchor.constraint(equalTo: view.centerXAnchor)
        let verticalConstraint = newView.centerYAnchor.constraint(equalTo: view.centerYAnchor)
        NSLayoutConstraint.activate([horizontalConstraint, verticalConstraint])
    }
    
}

结果:

2014-10-03 15:27:12

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