Handling keyboard with bottom constraint

问题

I'm building a chat app with a regular design and UI of a chat app.

I have a "toolbar" that my app needs (0,0 375x66) and I want it to stay where it is when the keyboard is shown. It has 4 constraints: top: 0, leading: 0, trailing: 0, aspect-ratio: 125:22

I have a UICollectionView (0,66 375x530) that I want to be scrolled like any other chat app when the keyboard is shown. It has 4 constraints: top (to the toolbar): 0, leading: 0, trailing: 0, bottom (to the newMessageView I'll explain shortly): 0

I have a UIView that has a UITextField inside it. let's call it newMessageView (0,596 375x71) and it has 4 constraints: bottom: 0, leading: 0, trailing: 0, aspect-ratio: 375:71

Now, I'm trying to bring the newMessageView app when the keyboard is shown. I'm trying to to it like this:

@objc func keyboardWillShow(notification: NSNotification) {
    if let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
        if self.view.frame.origin.y == 0{
            self.newMessageViewBottomConstraint.constant += keyboardSize.height
        }
    }
}

@objc func keyboardWillHide(notification: NSNotification) {
    if let keyboardSize = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
        if self.view.frame.origin.y != 0{
            self.newMessageViewBottomConstraint.constant -= keyboardSize.height
        }
    }
}

but it completly doesn't work. The view jumps and hides and I really can't understand why.

Am I doing it right? Can anyone help me and guide me with this?

回答1:

You have to use self.view.layoutIfNeeded() after Update constraint

i write complete solution for you

 class ViewController: UIViewController {

        override func viewDidLoad() {
            super.viewDidLoad()

            NotificationCenter.default.addObserver(self, selector: #selector(self.keyboardWillShow), name: NSNotification.Name.UIKeyboardWillShow, object: nil)
            NotificationCenter.default.addObserver(self, selector: #selector(self.keyboardWillHide), name: NSNotification.Name.UIKeyboardWillHide, object: nil)

        }

        @objc func keyboardWillShow(notification: Notification) {
            self.keyboardControl(notification, isShowing: true)
        }

        @objc func keyboardWillHide(notification: Notification) {
            self.keyboardControl(notification, isShowing: false)
        }


        private func keyboardControl(_ notification: Notification, isShowing: Bool) {


            /* Handle the Keyboard property of Default*/

            var userInfo = notification.userInfo!
            let keyboardRect = (userInfo[UIKeyboardFrameEndUserInfoKey]! as AnyObject).cgRectValue
            let curve = (userInfo[UIKeyboardAnimationCurveUserInfoKey]! as AnyObject).uint32Value

            let convertedFrame = self.view.convert(keyboardRect!, from: nil)
            let heightOffset = self.view.bounds.size.height - convertedFrame.origin.y
            let options = UIViewAnimationOptions(rawValue: UInt(curve!) << 16 | UIViewAnimationOptions.beginFromCurrentState.rawValue)
            let duration = (userInfo[UIKeyboardAnimationDurationUserInfoKey]! as AnyObject).doubleValue



            var  pureheightOffset : CGFloat = -heightOffset

            if isShowing { /// Wite space of save area in iphonex ios 11
                if #available(iOS 11.0, *) {
                    pureheightOffset = pureheightOffset + view.safeAreaInsets.bottom
                }
            }

            // Here change you Consrant
         //   self.actionBarPaddingBottomConstranit?.update(offset:pureheightOffset)

            UIView.animate(
                withDuration: duration!,
                delay: 0,
                options: options,
                animations: {
                    self.view.layoutIfNeeded()
            },
                completion: { bool in

            })

        }

来源：https://stackoverflow.com/questions/50171955/handling-keyboard-with-bottom-constraint