大多数解决方案都依赖于项目的奇数，这样你就可以把中间的项目放在中间。如果你有偶数个项目想要平均分配呢?这是一个更一般的解。这个类别将沿垂直或水平轴均匀分布任意数量的项目。

在它们的父视图中垂直分布4个标签的示例:

[self.view addConstraints:
     [NSLayoutConstraint constraintsForEvenDistributionOfItems:@[label1, label2, label3, label4]
                                        relativeToCenterOfItem:self.view
                                                    vertically:YES]];

NSLayoutConstraint + EvenDistribution.h

@interface NSLayoutConstraint (EvenDistribution)

/**
 * Returns constraints that will cause a set of views to be evenly distributed horizontally
 * or vertically relative to the center of another item. This is used to maintain an even
 * distribution of subviews even when the superview is resized.
 */
+ (NSArray *) constraintsForEvenDistributionOfItems:(NSArray *)views
                             relativeToCenterOfItem:(id)toView
                                         vertically:(BOOL)vertically;

@end

NSLayoutConstraint + EvenDistribution.m

@implementation NSLayoutConstraint (EvenDistribution)

+(NSArray *)constraintsForEvenDistributionOfItems:(NSArray *)views
                           relativeToCenterOfItem:(id)toView vertically:(BOOL)vertically
{
    NSMutableArray *constraints = [NSMutableArray new];
    NSLayoutAttribute attr = vertically ? NSLayoutAttributeCenterY : NSLayoutAttributeCenterX;

    for (NSUInteger i = 0; i < [views count]; i++) {
        id view = views[i];
        CGFloat multiplier = (2*i + 2) / (CGFloat)([views count] + 1);
        NSLayoutConstraint *constraint = [NSLayoutConstraint constraintWithItem:view
                                                                      attribute:attr
                                                                      relatedBy:NSLayoutRelationEqual
                                                                         toItem:toView
                                                                      attribute:attr
                                                                     multiplier:multiplier
                                                                       constant:0];
        [constraints addObject:constraint];
    }

    return constraints;
}

@end

这里还有另一个答案。我在回答一个类似的问题时看到了这个问题的链接。我没有看到任何与我类似的答案。所以我想写在这里。

  class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = UIColor.whiteColor()
        setupViews()
    }

    var constraints: [NSLayoutConstraint] = []

    func setupViews() {

        let container1 = createButtonContainer(withButtonTitle: "Button 1")
        let container2 = createButtonContainer(withButtonTitle: "Button 2")
        let container3 = createButtonContainer(withButtonTitle: "Button 3")
        let container4 = createButtonContainer(withButtonTitle: "Button 4")

        view.addSubview(container1)
        view.addSubview(container2)
        view.addSubview(container3)
        view.addSubview(container4)

        [

            // left right alignment
            container1.leftAnchor.constraintEqualToAnchor(view.leftAnchor, constant: 20),
            container1.rightAnchor.constraintEqualToAnchor(view.rightAnchor, constant: -20),
            container2.leftAnchor.constraintEqualToAnchor(container1.leftAnchor),
            container2.rightAnchor.constraintEqualToAnchor(container1.rightAnchor),
            container3.leftAnchor.constraintEqualToAnchor(container1.leftAnchor),
            container3.rightAnchor.constraintEqualToAnchor(container1.rightAnchor),
            container4.leftAnchor.constraintEqualToAnchor(container1.leftAnchor),
            container4.rightAnchor.constraintEqualToAnchor(container1.rightAnchor),


            // place containers one after another vertically
            container1.topAnchor.constraintEqualToAnchor(view.topAnchor),
            container2.topAnchor.constraintEqualToAnchor(container1.bottomAnchor),
            container3.topAnchor.constraintEqualToAnchor(container2.bottomAnchor),
            container4.topAnchor.constraintEqualToAnchor(container3.bottomAnchor),
            container4.bottomAnchor.constraintEqualToAnchor(view.bottomAnchor),


            // container height constraints
            container2.heightAnchor.constraintEqualToAnchor(container1.heightAnchor),
            container3.heightAnchor.constraintEqualToAnchor(container1.heightAnchor),
            container4.heightAnchor.constraintEqualToAnchor(container1.heightAnchor)
            ]
            .forEach { $0.active = true }
    }


    func createButtonContainer(withButtonTitle title: String) -> UIView {
        let view = UIView(frame: .zero)
        view.translatesAutoresizingMaskIntoConstraints = false

        let button = UIButton(type: .System)
        button.translatesAutoresizingMaskIntoConstraints = false
        button.setTitle(title, forState: .Normal)
        view.addSubview(button)

        [button.centerYAnchor.constraintEqualToAnchor(view.centerYAnchor),
            button.leftAnchor.constraintEqualToAnchor(view.leftAnchor),
            button.rightAnchor.constraintEqualToAnchor(view.rightAnchor)].forEach { $0.active = true }

        return view
    }
}

同样，这也可以用iOS9 UIStackViews很容易做到。

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = UIColor.greenColor()
        setupViews()
    }

    var constraints: [NSLayoutConstraint] = []

    func setupViews() {

        let container1 = createButtonContainer(withButtonTitle: "Button 1")
        let container2 = createButtonContainer(withButtonTitle: "Button 2")
        let container3 = createButtonContainer(withButtonTitle: "Button 3")
        let container4 = createButtonContainer(withButtonTitle: "Button 4")

        let stackView = UIStackView(arrangedSubviews: [container1, container2, container3, container4])
        stackView.translatesAutoresizingMaskIntoConstraints = false
        stackView.axis = .Vertical
        stackView.distribution = .FillEqually
        view.addSubview(stackView)

        [stackView.topAnchor.constraintEqualToAnchor(view.topAnchor),
            stackView.bottomAnchor.constraintEqualToAnchor(view.bottomAnchor),
            stackView.leftAnchor.constraintEqualToAnchor(view.leftAnchor, constant: 20),
            stackView.rightAnchor.constraintEqualToAnchor(view.rightAnchor, constant: -20)].forEach { $0.active = true }
    }


    func createButtonContainer(withButtonTitle title: String) -> UIView {
        let button = UIButton(type: .Custom)
        button.translatesAutoresizingMaskIntoConstraints = false
        button.backgroundColor = UIColor.redColor()
        button.setTitleColor(UIColor.whiteColor(), forState: .Normal)
        button.setTitle(title, forState: .Normal)
        let buttonContainer = UIStackView(arrangedSubviews: [button])
        buttonContainer.distribution = .EqualCentering
        buttonContainer.alignment = .Center
        buttonContainer.translatesAutoresizingMaskIntoConstraints = false
        return buttonContainer
    }
}

注意，这与上面的方法完全相同。它添加了四个容器视图，这些视图都是均等填充的，每个堆栈视图都添加了一个视图，并在中间对齐。但是，这个版本的UIStackView减少了一些代码，看起来不错。

我的方法允许你在接口构建器中做这个。你要做的是创建“间隔视图”，你已经设置为匹配高度相等。然后在标签上添加顶部和底部约束(见截图)。

更具体地说，我在“Spacer View 1”上有一个顶部约束，以优先级低于1000的高度约束来superview，并且高度等于所有其他的“Spacer views”。'Spacer View 4'有一个用于superview的底部空间约束。每个标签都有各自的顶部和底部约束到其最近的“间隔视图”。

注意:确保你的标签上没有额外的顶部/底部空间限制;只有那些“空间视图”。这是可以满足的，因为顶部和底部的约束分别在'Space View 1'和'Spacer View 4'上。

废话1:我复制了我的视图，只是把它设置为横向模式，这样你就可以看到它工作了。

废话2:“间隔视图”本可以是透明的。

废话3:这种方法可以横向应用。

Swift 3版本

let _redView = UIView()
        _redView.backgroundColor = UIColor.red
        _redView.translatesAutoresizingMaskIntoConstraints = false

        let _yellowView = UIView()
        _yellowView.backgroundColor = UIColor.yellow
        _yellowView.translatesAutoresizingMaskIntoConstraints = false

        let _blueView = UIView()
        _blueView.backgroundColor = UIColor.blue
        _blueView.translatesAutoresizingMaskIntoConstraints = false

        self.view.addSubview(_redView)
        self.view.addSubview(_yellowView)
        self.view.addSubview(_blueView)

        var views = ["_redView": _redView, "_yellowView": _yellowView, "_blueView":_blueView]

        var nslayoutConstraint_H = NSLayoutConstraint.constraints(withVisualFormat: "|->=0-[_redView(40)]->=0-[_yellowView(40)]->=0-[_blueView(40)]->=0-|", options: [.alignAllTop, .alignAllBottom], metrics: nil, views: views)
        self.view.addConstraints(nslayoutConstraint_H)

        var nslayoutConstraint_V = NSLayoutConstraint.constraints(withVisualFormat: "V:[_redView(60)]", options: NSLayoutFormatOptions.init(rawValue: 0), metrics: nil, views: views)
        self.view.addConstraints(nslayoutConstraint_V)


        let constraint_red = NSLayoutConstraint.init(item: self.view, attribute: .centerY, relatedBy: .equal, toItem: _redView, attribute: .centerY, multiplier: 1, constant: 0)
        self.view.addConstraint(constraint_red)

        let constraint_yellow = NSLayoutConstraint.init(item: self.view, attribute: .centerX, relatedBy: .equal, toItem: _yellowView, attribute: .centerX, multiplier: 1, constant: 0)
        self.view.addConstraint(constraint_yellow)

        let constraint_yellow1 = NSLayoutConstraint.init(item: _redView, attribute: .centerX, relatedBy: .equal, toItem: _yellowView, attribute: .leading, multiplier: 0.5, constant: 0)
        self.view.addConstraint(constraint_yellow1)

        let constraint_yellow2 = NSLayoutConstraint.init(item: _blueView, attribute: .centerX, relatedBy: .equal, toItem: _yellowView, attribute: .leading, multiplier: 1.5, constant: 40)
        self.view.addConstraint(constraint_yellow2)

我一直在坐过山车，爱自动布局和讨厌它。喜欢它的关键似乎是接受以下几点:

接口构建器的编辑和“有帮助的”自动创建约束在大多数情况下几乎无用 创建类别来简化常见操作是一种拯救，因为代码是如此重复和冗长。

也就是说，你正在尝试的不是直接的，在接口构建器中很难实现。这在代码中很简单。这段代码，在viewDidLoad，创建和定位三个标签，你需要他们:

// Create three labels, turning off the default constraints applied to views created in code
UILabel *label1 = [UILabel new];
label1.translatesAutoresizingMaskIntoConstraints = NO;
label1.text = @"Label 1";

UILabel *label2 = [UILabel new];
label2.translatesAutoresizingMaskIntoConstraints = NO;
label2.text = @"Label 2";

UILabel *label3 = [UILabel new];
label3.translatesAutoresizingMaskIntoConstraints = NO;
label3.text = @"Label 3";

// Add them all to the view
[self.view addSubview:label1];
[self.view addSubview:label2];
[self.view addSubview:label3];

// Center them all horizontally
[self.view addConstraint:[NSLayoutConstraint constraintWithItem:label1 attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterX multiplier:1.0 constant:0]];

[self.view addConstraint:[NSLayoutConstraint constraintWithItem:label2 attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterX multiplier:1.0 constant:0]];

[self.view addConstraint:[NSLayoutConstraint constraintWithItem:label3 attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterX multiplier:1.0 constant:0]];

// Center the middle one vertically
[self.view addConstraint:[NSLayoutConstraint constraintWithItem:label2 attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterY multiplier:1.0 constant:0]];

// Position the top one half way up
[self.view addConstraint:[NSLayoutConstraint constraintWithItem:label1 attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:label2 attribute:NSLayoutAttributeCenterY multiplier:0.5 constant:0]];

// Position the bottom one half way down
[self.view addConstraint:[NSLayoutConstraint constraintWithItem:label3 attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:label2 attribute:NSLayoutAttributeCenterY multiplier:1.5 constant:0]];

我说过，这段代码通过UIView中的一些类别方法简化了很多，但为了清晰起见，这里我做了很多。

对于感兴趣的人来说，这个类别在这里，它有一个方法，可以沿着特定的轴均匀地间隔一个视图数组。

对于标签，这至少是可行的:

@“H: | -15 -(第一(第二)= =]-[二(= =第三)](第三(= =))-15 - |

如果第一个和第二个有相同的宽度，第二个和第三个有相同的宽度，第三个和第一个有相同的宽度……你可以做水平(H)和垂直(V)。