Question

将UILabel添加到ViewController时，它显示正常，但是一旦我使用单独的UIView，该控制器就什么也不显示。 ViewController是从TableViewController.didSelectRowAt

推送的

ViewController在didSelectRowAt中被调用

let labelViewController = TempViewController()                
navigationController?.pushViewController(labelViewController, animated: true)

方案1：仅ViewController-显示蓝屏，其文本位于屏幕y中心，如预期的那样

class TempViewController: UIViewController {
    var tempView: UILabel = {
        let label = UILabel()
        label.text = "Please enter your email address"
        label.translatesAutoresizingMaskIntoConstraints = false
        label.backgroundColor = UIColor.blue
        return label
    }()

    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = UIColor.red
        navigationItem.title = "Temp"
        edgesForExtendedLayout = []

        view.addSubview(tempView)
        tempView.topAnchor.constraint(equalTo: view.topAnchor).isActive = true
        tempView.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
        tempView.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
        tempView.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true
    }

方案2：ViewController和视图-显示红色屏幕，没有文本，没有蓝色

class TempViewController: UIViewController {

    var tempView = TempView()

    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = UIColor.red
        navigationItem.title = "Temp"
        edgesForExtendedLayout = []

        view.addSubview(tempView)
        tempView.topAnchor.constraint(equalTo: view.topAnchor).isActive = true
        tempView.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
        tempView.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
        tempView.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true
    }
}

class TempView: UIView {
    var tempView: UILabel = {
        let label = UILabel()
        label.text = "Please enter your email address"
        label.translatesAutoresizingMaskIntoConstraints = false
        label.backgroundColor = UIColor.blue
        return label
    }()

    override init(frame: CGRect) {
        super.init(frame: frame)
        setView()
    }

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

    private func setView() {
        addSubviews()
        setLayout()
    }

    private func addSubviews() {
        addSubview(tempView)
    }

    private func setLayout() {
                tempView.topAnchor.constraint(equalTo: topAnchor).isActive = true
                tempView.leadingAnchor.constraint(equalTo: leadingAnchor).isActive = true
                tempView.trailingAnchor.constraint(equalTo: trailingAnchor).isActive = true
                tempView.bottomAnchor.constraint(equalTo: bottomAnchor).isActive = true
    }
}

我希望两种情况都能产生相同的结果？但是方案2不显示视图吗？

感谢您的帮助

Answer 1

您的视图未显示，因为它过于受限。

您还需要在translatesAutoresizingMaskIntoConstraints = false中为tempView设置viewDidLoad()：

view.addSubview(tempView)
tempView.translatesAutoresizingMaskIntoConstraints = false
tempView.topAnchor.constraint(equalTo: view.topAnchor).isActive = true
tempView.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
tempView.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
tempView.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true

ViewController不显示视图

1 个答案: