如何在 .interactive keyboardDismissMode 集合视图的“向下拖动”键盘中间调整底部约束？

Question

我希望实现键盘和视图调整大小的行为，如 iOS 消息中所示。它看起来像

https://i.imgur.com/92rvHpo.mp4

我尝试以下方法

步骤 1

这确保了当我们的向下滚动手势触及键盘区域时，键盘将随着我们的手势动作向下滚动。

collectionView.keyboardDismissMode = .interactive

---

第二步

调整底部约束，以确保我们的集合视图不会被键盘在视觉上阻挡。当键盘完成隐藏或键盘显示完成时，我们调整底部约束。

override func viewDidLoad() {
    super.viewDidLoad()
    
    initKeyboardNotifications()
}

//
// https://stackoverflow.com/a/41808338/72437
//
func initKeyboardNotifications() {
    // If your app targets iOS 9.0 and later or macOS 10.11 and later, you do not need to unregister an observer
    // that you created with this function.
    
    NotificationCenter.default.addObserver(self,
        selector: #selector(keyboardWillShow),
        name: UIResponder.keyboardWillShowNotification,
        object: nil)
    NotificationCenter.default.addObserver(self,
        selector: #selector(keyboardWillHide),
        name: UIResponder.keyboardWillHideNotification,
        object: nil)
}

@objc private func keyboardWillShow(sender: NSNotification) {
    let i = sender.userInfo!
    let s: TimeInterval = (i[UIResponder.keyboardAnimationDurationUserInfoKey] as! NSNumber).doubleValue
    let k = (i[UIResponder.keyboardFrameEndUserInfoKey] as! NSValue).cgRectValue.height
    bottomLayoutConstraint.constant = -k
    
    UIView.animate(withDuration: s) { self.view.layoutIfNeeded() }
}

@objc private func keyboardWillHide(sender: NSNotification) {
    let info = sender.userInfo!
    let s: TimeInterval = (info[UIResponder.keyboardAnimationDurationUserInfoKey] as! NSNumber).doubleValue
    bottomLayoutConstraint.constant = 0
    UIView.animate(withDuration: s) { self.view.layoutIfNeeded() }
}

---

到目前为止，这是我们不完美的结果。

我想，当键盘被拖动时，我需要实时调整底部约束。但是，我不知道从哪里可以得到键盘高度信息，当它被拖动时。

您知道如何在拖动键盘时实时调整底部约束吗？

Answer 1

您可以尝试添加观察者以获取更多通知以观察键盘高度变化。

UIResponder.keyboardDidChangeFrameNotification

然后您将获得当前的键盘高度，并可以相应地调整您的布局。

---

更新

keyboardWillChangeFrameNotification 和 keyboardDidChangeFrameNotification 在“下拉”期间都不会收到通知。

您可以尝试将inputAccessoryView 添加到您的文本字段中，这可以帮助您观察键盘框架的变化。

import UIKit

class FrameObservingInputAccessoryView: UIView {
    var onFrameChange: ((_ frame: CGRect) -> Void)?
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        self.commonSetUp()
    }

    required init?(coder: NSCoder) {
        super.init(coder: coder)
        self.commonSetUp()
    }
    
    private var frameObservation: NSKeyValueObservation?
    override func willMove(toSuperview newSuperview: UIView?) {
        frameObservation?.invalidate()
        frameObservation = newSuperview?.observe(\.frame, changeHandler: { [weak self] (_, _) in
            guard let self = self, let superview = self.superview else { return }
            self.onFrameChange?(superview.frame)
        })
        super.willMove(toSuperview: newSuperview)
    }
    
    deinit {
        frameObservation?.invalidate()
    }
    
    private func commonSetUp() {
        self.isUserInteractionEnabled = false
    }
}

用法

class MyCollectionViewCell: UICollectionViewCell, UITextFieldDelegate {
    var onShouldBeginEditing: ((_ textField: UITextField) -> Void)?
    
    func textFieldShouldBeginEditing(_ textField: UITextField) -> Bool {
        onShouldBeginEditing?(textField)
        return true
    }
}

class ViewController: UIViewController, UICollectionViewDataSource {
    lazy var frameObservingView: FrameObservingInputAccessoryView = {
        let frameObservingView = FrameObservingInputAccessoryView(frame: .zero)
        frameObservingView.onFrameChange = { [weak self] (frame) in
            // update your constraint
        }
        return frameObservingView
    }()
    
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        5
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "MyCollectionViewCell", for: indexPath) as! MyCollectionViewCell
        cell.onShouldBeginEditing = { [weak self] (textField) in
            textField.inputAccessoryView = self?.frameObservingView
        }
        return cell
    }
}

Answer 2

当键盘显示/隐藏时，您应该调整collectionView 的contentInset.bottom，而不是更改bottomConstraint：

@objc private func keyboardWillShow(sender: NSNotification) {
    let i = sender.userInfo!
    let s: TimeInterval = (i[UIResponder.keyboardAnimationDurationUserInfoKey] as! NSNumber).doubleValue
    let k = (i[UIResponder.keyboardFrameEndUserInfoKey] as! NSValue).cgRectValue.height
    collectionView.contentInset.bottom = k
    UIView.animate(withDuration: s) { self.view.layoutIfNeeded() }
}

@objc private func keyboardWillHide(sender: NSNotification) {
    let info = sender.userInfo!
    let s: TimeInterval = (info[UIResponder.keyboardAnimationDurationUserInfoKey] as! NSNumber).doubleValue
    collectionView.contentInset.bottom = 0
    UIView.animate(withDuration: s) { self.view.layoutIfNeeded() }
}