iOS:UIView 原点在 iOS 9 上没有改变

Question

我试图在显示键盘时设置我的self.mainView.frame.origin.y。它在 iOS 11 上运行良好，但在 iOS 9 上运行不佳。

这是我的代码:

    func textFieldShouldBeginEditing(_ textField: UITextField) -> Bool {
        print("=== textFieldShouldBeginEditing 1 \(self.mainView.frame.origin.y) ")
        self.mainView.frame.origin.y -= 150
        self.mainView.setNeedsLayout()
        self.mainView.layoutIfNeeded()
        print("=== textFieldShouldBeginEditing 2 \(self.mainView.frame.origin.y) ")
        return true
    }



    internal func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        print("=== textFieldShouldReturn 1 \(self.mainView.frame.origin.y) ")
        self.mainView.frame.origin.y = self.normalMainViewOriginY
        textField.endEditing(true)
        print("=== textFieldShouldReturn 2 \(self.mainView.frame.origin.y) ")
        return true
    }

在viewDidLoad()中:

self.normalMainViewOriginY = self.mainView.frame.origin.y

我也使用 NSNotification 测试了相同的想法，但我在 iOS 9 中遇到了同样的问题

这些是打印输出:

iOS 9:

=== normalMainViewOriginY:243.0(来自viewDidLoad())

=== textFieldShouldBeginEditing 1:208.5

=== textFieldShouldBeginEditing 2:208.5

=== textFieldShouldReturn 1: 208.5

=== textFieldShouldReturn 2: 243.0

iOS 11:

=== normalMainViewOriginY:243.0(来自viewDidLoad())

=== textFieldShouldBeginEditing 1:208.5

=== textFieldShouldBeginEditing 2:58.5

=== textFieldShouldReturn 1: 58.5

=== textFieldShouldReturn 2: 243.0

Answer 1

问题是更改框架不会影响下划线布局约束，因此尝试约束它不会失败，假设您将 mainView 的顶部约束设置为 mainViewTopCon

func textFieldShouldBeginEditing(_ textField: UITextField) -> Bool {
    print("=== textFieldShouldBeginEditing 1 \(self.mainView.frame.origin.y) ")
    self.mainViewTopCon.constant -= 150
    self.mainView.layoutIfNeeded()
    print("=== textFieldShouldBeginEditing 2 \(self.mainView.frame.origin.y) ")
    return true
}

internal func textFieldShouldReturn(_ textField: UITextField) -> Bool {
    print("=== textFieldShouldReturn 1 \(self.mainView.frame.origin.y) ")
    self.mainViewTopCon.constant = 0 // or value in IB that you set initally 
    self.mainView.layoutIfNeeded()
    textField.endEditing(true)
    print("=== textFieldShouldReturn 2 \(self.mainView.frame.origin.y) ")
    return true
}