使用自动约束使视图居中 - Swift

Question

我正在创建一个 XIB/class 的 datePicker，它在用户点击按钮时通过调用 viewController 以编程方式调用。我如何使用自动约束将此视图立即放置在调用按钮的下方并与调用按钮的中心对齐。我的代码可以纵向工作，但在旋转设备时会失败（datePicker 不会重新居中）。可能是因为我将 CGRect 作为参数传递给视图的初始化，它在旋转时不会改变。我看不到任何其他方法可以覆盖 CGRect 的传递。当我添加自动约束代码时，出现运行次自动格式化错误。

ViewController:

@IBAction func showMyDatePicker(_ sender: Any) {
    showMyDatePicker.isEnabled = false
    let today = Date()
    let minDate = Calendar.current.date(byAdding: .month, value: -3, to: today)
    let maxDate = Calendar.current.date(byAdding: .month, value: 3, to: today)

    let datePickerWidth = 300
    let datePickerHeight = 200

    let datePickerX = Int(showMyDatePicker.center.x - CGFloat(datePickerWidth / 2))
    let datePickerY = Int(showMyDatePicker.center.y + CGFloat(showMyDatePicker.bounds.height / 2))
    let frame = CGRect(x: datePickerX, y: datePickerY, width: datePickerWidth, height: datePickerHeight)

    myDatePicker = MyDatePicker(frame: frame)
    myDatePicker?.setMyDatePicker(date: today, minimumDate: minDate!, maximumDate: maxDate!)
    myDatePicker?.delegate = self
    self.view.addSubview(myDatePicker!)

}

日期选择器类：

class MyDatePicker: UIView {

var delegate: MyDatePickerDelegate?

@IBOutlet var contentView: UIView!

@IBOutlet weak var datePicker: UIDatePicker!
@IBOutlet weak var returnButton: UIButton!

@IBAction func datePickerChanged(_ sender: Any) {
    delegate?.dateFromDatePicker(date: datePicker.date, closeDatePickerView: false)
}

@IBAction func returnButtonTapped(_ sender: Any) {
    delegate?.dateFromDatePicker(date: datePicker.date, closeDatePickerView: true)
}

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

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

private func initView() {//QUESTION: how can I set the datepicker initial values within here
    // Instantiate the view from xib file
    let contentView = Bundle.main.loadNibNamed("MyDatePicker", owner: self, options: nil)?.first as? UIView

    // Check that it's not nil
    guard contentView != nil else {
        return
    }

    // Add the view and set its frame
    addSubview(contentView!)
    contentView?.frame = self.bounds
    contentView?.autoresizingMask = [.flexibleHeight, .flexibleWidth]
}


func setMyDatePicker(date: Date, minimumDate: Date, maximumDate: Date) {
    datePicker.date = date
    datePicker.minimumDate = minimumDate
    datePicker.maximumDate = maximumDate
}

}

Answer 1

只需要在addSubview之后添加需要的约束，并设置TAMIC为false，如下：

@IBAction func showMyDatePicker(_ sender: UIButton) {
    // ...
    view.addSubview(myDatePicker!)
    myDatePicker.translatesAutoresizingMaskIntoConstraints = false
    NSLayoutConstraint.activate([
        myDatePicker.topAnchor.constraint(equalTo: sender.bottomAnchor),
        myDatePicker.centerXAnchor.constraint(equalTo: sender.centerXAnchor)])
}

使用自动约束使视图居中 - Swift

Centering a view with auto constraints - Swift

constraints

swift