Question

我有一个ViewController类，它有一个textField变量，已配置当它在viewDidLoad的{{1}}方法中设置时。

ViewController

一组自动布局约束被添加到视图中。我想要这个文本字段以中间（class ViewController: UIViewController { weak var textField: UITextField! { didSet { textField.delegate = self textField.placeholder = "Enter Text" view.addSubview(textField) view.addConstraint(NSLayoutConstraint(item: textField, attribute: .Width, relatedBy: .Equal, toItem: view, attribute: .Width, multiplier: 0.80, constant: 0)) view.addConstraint(NSLayoutConstraint(item: textField, attribute: .Height, relatedBy: .Equal, toItem: view, attribute: .Height, multiplier: 0.05, constant: 0)) view.addConstraint(NSLayoutConstraint(item: textField, attribute: .CenterX, relatedBy: .Equal, toItem: view, attribute: .CenterX, multiplier: 1, constant: 0)) view.addConstraint(NSLayoutConstraint(item: textField, attribute: .CenterY, relatedBy: .Equal, toItem: view, attribute: .CenterY, multiplier: 1, constant: 0)) } } override func viewDidLoad() { super.viewDidLoad() textField = UITextField() } }和.CenterX）为中心，宽度（高度）为80％（5％）在人像模式下计算的.CenterY＆n; ViewController。

如果将设备的方向（view）旋转到横向方向，或从横向方向呈现，我想要宽度（高度）与纵向方向保持一致。

更改UIDevice.currentDevice().orientation的{{1}}：

attribute

为：

toItem

没有做到这一点，因为我猜在设备切换方向时view.addConstraint(NSLayoutConstraint(item: textField, attribute: .Height, relatedBy: .Equal, toItem: view, attribute: .Height, multiplier: 0.05, constant: 0))没有得到（重新）设置。此外，对于Swift来说，这个检查似乎有些笨拙。我错过了自动布局的技巧吗？

Answer 1

实际上代码中的问题是您没有将textField的translatesAutoresizingMaskIntoConstraints设置为false，无论何时您想使用自动布局约束，您都必须将视图的translatesAutoresizingMaskIntoConstraints设置为false。

我已更新您的代码，看看它的工作正常。

class ViewController: UIViewController, UITextFieldDelegate {    
    weak var textField: UITextField! {
        didSet {
            textField.delegate = self
            textField.placeholder = "Enter Text"
            view.addSubview(textField)
            // to see the size of textField
            textField.backgroundColor = UIColor.purpleColor()

            textField.translatesAutoresizingMaskIntoConstraints = false

            view.addConstraint(NSLayoutConstraint(item: textField, attribute: .Width, relatedBy: .Equal, toItem: view, attribute: .Width, multiplier: 0.80, constant: 0))
            view.addConstraint(NSLayoutConstraint(item: textField, attribute: .Height, relatedBy: .Equal, toItem: view, attribute: .Height, multiplier: 0.05, constant: 0))
            view.addConstraint(NSLayoutConstraint(item: textField, attribute: .CenterX, relatedBy: .Equal, toItem: view, attribute: .CenterX, multiplier: 1, constant: 0))
            view.addConstraint(NSLayoutConstraint(item: textField, attribute: .CenterY, relatedBy: .Equal, toItem: view, attribute: .CenterY, multiplier: 1, constant: 0))
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        textField = UITextField()

    }
}

Answer 2

一种解决方案是获取屏幕的固定坐标范围（iOS> = 8）并适当调整前两个约束：

class ViewController: UIViewController, UITextFieldDelegate {

    override func viewDidLoad() {
        super.viewDidLoad()

        let textField = UITextField()
        textField.translatesAutoresizingMaskIntoConstraints = false
        textField.delegate = self
        textField.placeholder = "Enter Text"
        view.addSubview(textField)

        textField.backgroundColor = UIColor.redColor()
        textField.textAlignment = .Center

        let fixedScreenBounds = UIScreen.mainScreen().fixedCoordinateSpace.bounds

        NSLayoutConstraint.activateConstraints([
            NSLayoutConstraint(item: textField, attribute: .Width, relatedBy: .Equal, toItem: nil, attribute: .NotAnAttribute, multiplier: 0, constant: 0.8*fixedScreenBounds.width),
            NSLayoutConstraint(item: textField, attribute: .Height, relatedBy: .Equal, toItem: nil, attribute: .NotAnAttribute, multiplier: 0, constant: 0.05*fixedScreenBounds.height),
            NSLayoutConstraint(item: textField, attribute: .CenterX, relatedBy: .Equal, toItem: view, attribute: .CenterX, multiplier: 1, constant: 0),
            NSLayoutConstraint(item: textField, attribute: .CenterY, relatedBy: .Equal, toItem: view, attribute: .CenterY, multiplier: 1, constant: 0)
            ])
    }
}

另外，请注意，由于您要在代码中创建文本字段并且要使用autolayout，因此必须将其translatesAutoresizingMaskIntoConstraints设置为false。

根据方向更新自动布局约束

2 个答案: