编程布局：UIStackView 对齐似乎不起作用

Question

我创建了一个 UIViewController，其中 UIStackView（垂直轴）包裹在 UIScrollView 中，通过自动布局固定到根 View 的边缘约束。

我还生成了一些 UIButton 并添加到 UIStackView 的 arranged subviews 中。

我尝试将 UIButtons 居中对齐到 UIStackView 中，但没有成功。

我不确定我做错了什么。

代码如下：

import UIKit

class ViewController: UIViewController {
var scrollView: UIScrollView!
var stackView: UIStackView!

override func viewDidLoad() {
    super.viewDidLoad()

    view.backgroundColor = UIColor.whiteColor()

    scrollView = UIScrollView()
    scrollView.translatesAutoresizingMaskIntoConstraints = false
    view.addSubview(scrollView)

    view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:|[scrollView]|", options: .AlignAllCenterX, metrics: nil, views: ["scrollView": scrollView]))
    view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:|[scrollView]|", options: .AlignAllCenterX, metrics: nil, views: ["scrollView": scrollView]))


    stackView = UIStackView()
    stackView.translatesAutoresizingMaskIntoConstraints = false
    stackView.axis = .Vertical
    stackView.alignment = .Center
    scrollView.addSubview(stackView)

    scrollView.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:|[stackView]|", options: NSLayoutFormatOptions.AlignAllCenterX, metrics: nil, views: ["stackView": stackView]))
    scrollView.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:|[stackView]|", options: NSLayoutFormatOptions.AlignAllCenterX, metrics: nil, views: ["stackView": stackView]))

    for _ in 1 ..< 100 {
        let vw = UIButton(type: UIButtonType.System)
        vw.setTitle("Button", forState: .Normal)
        stackView.addArrangedSubview(vw)
    }
}

}

Answer 1

怎么样：

stackView.Alignment = UIStackViewAlignment.Center

?

Answer 2

scrollView 和 stackView 之间需要一个额外的等宽约束。像这样：

scrollView.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:[stackView(==scrollView)]", options: .AlignAllCenterX, metrics: nil, views: ["stackView": stackView, "scrollView": scrollView]))

这对我有用。

编程布局：UIStackView 对齐似乎不起作用

Programmatic layout : UIStackView alignment doesn't seem to work

swift

ios-autolayout

uistackview