无法以编程方式将标签添加到xib

Question

这是我为标签添加标签的无尽追求。我唯一能够显示标签的方法是使用框架对其进行初始化。但是，如果这样做，标签将完全忽略我尝试施加的任何约束。

这是我的xib，具有标准设置：

这是xib的代码：

import UIKit

class TestSheet: UIView {

    @IBOutlet weak var testStackView: UIStackView!

    override init(frame: CGRect) {
        super.init(frame: frame)
        let subView: UIView = loadViewFromNib()
        subView.frame = self.bounds
        addSubview(subView)
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }

    func loadViewFromNib() -> UIView {
        let view: UIView = UINib(nibName: "TestSheet", bundle: nil).instantiate(withOwner: nil, options: nil)[0] as! UIView
        return view
    }
}

下面，我实例化XIB，创建标签，然后尝试将其居中：

func makeTestPage() {

    let testView = UINib(nibName: "TestSheet", bundle: nil).instantiate(withOwner: nil, options: nil)[0] as? TestSheet

    let centerLabel = UILabel()

    //The line below will show a label, but it won't obey constraints:
    //let centerLabel = UILabel(frame: CGRect(x: 0, y: 0, width: 100, height: 100))

    centerLabel.translatesAutoresizingMaskIntoConstraints = false

    centerLabel.text = "Hello middle of the view"
    testView?.addSubview(centerLabel)

    NSLayoutConstraint.activate([
      centerLabel.centerXAnchor.constraint(
        equalTo: testView!.centerXAnchor, constant: 0),
      centerLabel.centerYAnchor.constraint(
        equalTo: testView!.centerYAnchor, constant: 0)
      ])
    pdfPages.append(testView!)
}

这就是什么都没出现的样子...

Answer 1

您忘了为标签说translatesAutoresizingMaskIntoConstraints = false。当您这样做时，它们的行为会好得多。