swift - 布局不会在 keyboardWillHide 方法上更新

Question

我已经能够使用 keyboardWillShow 方法更新我的 scrollView 的布局约束。但是，当尝试在 keyboardWillHide 方法中执行相同操作时，布局不会更新(导致 scrollView 在键盘用于启动的位置被切断)。关于如何解决这个问题的任何提示？谢谢!!

@objc func keyboardWillShow(notification: NSNotification) {
    let info = notification.userInfo!
    let keyboardFrame: CGRect = (info[UIKeyboardFrameEndUserInfoKey] as! NSValue).cgRectValue
    keyboardHeightSubtraction = keyboardFrame.size.height
    scrollView.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -keyboardHeightSubtraction).isActive = true
    UIView.animate(withDuration: 0.3, animations: { () -> Void in
        self.view.layoutIfNeeded()
    })
}


@objc func keyboardWillHide(notification: NSNotification) {
    scrollView.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
    UIView.animate(withDuration: 0.3, animations: { () -> Void in
        self.view.layoutIfNeeded()
    })
}

Answer 1

问题是您当前在约束中创建了冲突，因此在 viewDidLoad 中创建一次，并像这样在 2 个函数中管理它的常量\

var botCon:NSLayoutConstraint!

//

botCon = scrollView.bottomAnchor.constraint(equalTo: view.bottomAnchor)
botcon.isActive = true

//

@objc func keyboardWillShow(notification: NSNotification) {
    let info = notification.userInfo!
    let keyboardFrame: CGRect = (info[UIKeyboardFrameEndUserInfoKey] as! NSValue).cgRectValue
    botCon.constant = -1 * keyboardHeightSubtraction 
    UIView.animate(withDuration: 0.3, animations: { () -> Void in
        self.view.layoutIfNeeded()
    })
}


@objc func keyboardWillHide(notification: NSNotification) {
    botCon.constant = 0
    UIView.animate(withDuration: 0.3, animations: { () -> Void in
        self.view.layoutIfNeeded()
    })
}