Question

我正在弄乱this以编程方式创建的滚动视图和堆栈视图的示例，我决定尝试将UIButtons更改为UILabels。我用以下代码替换了for循环中的代码：

let label = UILabel()
label.text = "Label"
stackView.addArrangedSubview(label)

然而，当我重新运行应用程序时，我发现滚动视图无法再滚动。调试后，我发现堆栈视图的frame零宽度和零高度，我认为这是问题的根源。我一直无法弄清楚为什么堆栈视图没有宽度或高度，或者如何再次滚动滚动视图。

这里是全视图控制器，我修改为Swift 4编译它，使用UILabel，并打印帧大小：

import UIKit

class ViewController: UIViewController {

    var scrollView: UIScrollView!
    var stackView: UIStackView!

    override func viewDidLoad() {
        super.viewDidLoad()

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

        view.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:|[scrollView]|", options: .alignAllCenterX, metrics: nil, views: ["scrollView": scrollView]))
        view.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:|[scrollView]|", options: .alignAllCenterX, metrics: nil, views: ["scrollView": scrollView]))


        stackView = UIStackView()
        stackView.translatesAutoresizingMaskIntoConstraints = false
        stackView.axis = .vertical
        scrollView.addSubview(stackView)

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

        for _ in 1 ..< 100 {
            let label = UILabel()
            label.text = "Label"
            label.sizeToFit()
            stackView.addArrangedSubview(label)

//            let vw = UIButton(type: UIButtonType.system)
//            vw.setTitle("Button", for: .normal)
//            stackView.addArrangedSubview(vw)
        }
    }

    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        scrollView.contentSize = CGSize(width: stackView.frame.width, height: stackView.frame.height)
        print("stack view frame: \(stackView.frame)")
    }

}

Answer 1

你应该：

•通过更新上一个VFL约束，将stackView的底部固定到scrollView的内容底边：

scrollView.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:|[stackView]|", options: NSLayoutFormatOptions.alignAllCenterX, metrics: nil, views: ["stackView": stackView]))

•避免将自动布局与“手动”布局混合并删除该行：

scrollView.contentSize = CGSize(width: stackView.frame.width, height: stackView.frame.height)

以编程方式创建一堆UILabel

1 个答案: