这有点棘手...

我们需要允许“点行”（水平堆栈视图）居中，而不是拉伸主堆栈视图的宽度。

我们还需要实际计算点的宽度，而不是使用点宽度，.fillEqually这样我们就不会最终得出局部点的大小。

例如：

• 主堆栈宽度为75
• 间距为1点
• 3个水平点

可用宽度是堆栈视图宽度减去“空格”数x间距：

75 - 2 = 73
73 / 3 = 24.333333...

在@2x缩放设备上，这三个视图的实际宽度将是：

24.5 : 24 : 24.5

仅用3个“点”不是很明显，但是当我们到达一个1, 3, 5, 7, 9, 8, 7, 6, 5模式时，它将变得非常明显。

.fillEqually 在左侧，在右侧计算出的整数点大小：

这是一些示例代码：

class DotsViewController: UIViewController {
    
    let patterns: [[Int]] = [
        [3, 3, 3],
        [3],
        [1, 2, 3],
        [1, 3, 5, 4, 3],
        [1, 3, 5, 7, 9, 8, 7, 6, 5],
    ]
    
    let mainStack: UIStackView = {
        let v = UIStackView()
        v.translatesAutoresizingMaskIntoConstraints = false
        v.axis = .vertical
        v.alignment = .fill
        v.distribution = .equalSpacing
        return v
    }()
    
    // space between dots
    let dotSpacing: CGFloat = 1
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        view.addSubview(mainStack)
        
        let g = view.safeAreaLayoutGuide
        
        NSLayoutConstraint.activate([
            // constrain main stack view 20-pts from top / leading / bottom
            mainStack.topAnchor.constraint(equalTo: g.topAnchor, constant: 20.0),
            mainStack.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 20.0),
            mainStack.bottomAnchor.constraint(equalTo: g.bottomAnchor, constant: -20.0),
            
            // width: 75
            mainStack.widthAnchor.constraint(equalToConstant: 75.0),
        ])
        
        patterns.forEach { a in
            // create a vertical stack view
            //  to hold the "rows" of horizontal stack views (containing the dots)
            let vBlockStack = UIStackView()
            vBlockStack.axis = .vertical
            vBlockStack.alignment = .center
            vBlockStack.distribution = .fill
            vBlockStack.spacing = dotSpacing
            // add it to the main stack view
            mainStack.addArrangedSubview(vBlockStack)

            // calculate dot size
            //  needs to be a whole number so we don't get
            //  half-point sizes
            let maxDots:CGFloat = CGFloat(a.max()!)
            let availableWidth:CGFloat = 75.0 - ((maxDots - 1) * dotSpacing)
            let w:CGFloat = floor(availableWidth / maxDots)
            
            a.forEach { numDots in
                // create a horizontal stack view
                let hDotStack = UIStackView()
                hDotStack.axis = .horizontal
                hDotStack.alignment = .fill
                hDotStack.distribution = .fill
                hDotStack.spacing = dotSpacing
                // add it to the vertical block stack view
                vBlockStack.addArrangedSubview(hDotStack)
                for _ in 0..<numDots {
                    let v = UIImageView()
                    v.contentMode = .scaleAspectFit
                    v.image = UIImage(systemName: "circle.fill")
                    v.tintColor = .red
                    // add view to dot stack view
                    hDotStack.addArrangedSubview(v)
                    // set dots image view size constraints
                    v.widthAnchor.constraint(equalToConstant: w).isActive = true
                    v.heightAnchor.constraint(equalTo: v.widthAnchor).isActive = true
                }
            }
            
        }
        
    }

}

产生以下输出：