Swift:如何在UICollectionViewCell中不断调整UITextView的高度

下午好。

我已经为我的iOS应用程序的这个"功能"挣扎了几个小时，我需要一些帮助。

问题：我应该如何实现，以便当用户键入UITextView时，大小会增加(只有底部边距(，同时单元格会增加高度以动态适应UITextView？我不知道该怎么处理。

研究：经过一番搜索，我发现了Dynamicly change cell'；键入文本时的高度，并重新加载包含的表视图以调整大小，以及选中时是否可以在UITableViewCell上设置高度更改的动画？我也读过https://developer.apple.com/documentation/uikit/uicollectionview但到目前为止，我觉得我的快速知识不如这些职位上的预期。

换句话说，我不知道如何为我的UICollectionView实现它。

我现在的代码看起来是这样的(我在EventsCell中有更多的UI元素，但为了节省空间，我把它们删掉了，所以我只想更改UITextView的底部边距(。我已经将我的UITextView的RootCell设置为delegate，然后我打算在编辑时获取textView高度，以获得我想要的高度，但它不起作用。

细胞类别：

class EventsCell: UICollectionViewCell {
override init(frame: CGRect) {
super.init(frame: frame)
backgroundColor = UIColor.white
setupViews()

}
let textView: GrowingTextView = { // GrowingTextView is a cocoapod extending UITextView
let rootCellDelegate = RootCell()
let tv = GrowingTextView()
tv.backgroundColor = .clear
tv.allowsEditingTextAttributes = true
tv.isScrollEnabled = false
tv.font = UIFont(name: "Didot", size: 16)
tv.textColor = .black
tv.textContainerInset = UIEdgeInsetsMake(4, 4, 4, 6)
tv.placeholder = "Write your event text here"
tv.placeholderColor = UIColor.lightGray
tv.autoresizingMask = .flexibleHeight
tv.isUserInteractionEnabled = false
tv.delegate = rootCellDelegate
return tv
}()
let eventPlaceholderMarkImage: UIButton = {
let iv = UIButton()
let image = UIImage(named: "placeHolderEventTitleMark")
iv.setImage(image, for: .normal)
return iv
}()
func setupViews() {

//MARK: - Constraints for EventsCell
//horizontal
addConstraintsWithFormat(format: "H:|-16-[v0((frame.width - 32))]-16-|", views: textView)
addConstraintsWithFormat(format: "V:|-47-[v0]-16-|", views: textView)
addConstraint(NSLayoutConstraint(item: eventPlaceholderMarkImage, attribute: .bottom, relatedBy: .equal, toItem: textView, attribute: .top, multiplier: 1, constant: -7))
addConstraint(NSLayoutConstraint(item: eventPlaceholderMarkImage, attribute: .height, relatedBy: .equal, toItem: self, attribute: .height, multiplier: 0, constant: 20))
addConstraintsWithFormat(format: "H:|-12-[v0(27)]-(cellWidth - 39)-|", views: eventPlaceholderMarkImage)
}
}

UICollectionView类：

class RootCell: BaseCell, UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
var textViewHeight : CGFloat?
func textViewDidChange(_ textView: UITextView) {
textViewHeight = textView.textContainer.size.height + 63
collectionView.reloadInputViews()
collectionView.reloadData()
collectionView.layoutSubviews()

}
lazy var collectionView: UICollectionView = {
let layout = UICollectionViewFlowLayout()
let cv = UICollectionView(frame: .zero, collectionViewLayout: layout)
cv.backgroundColor = UIColor.white
cv.delegate = self
cv.dataSource = self
return cv
}()
override func setupViews() {
super.setupViews()
addSubview(collectionView)
addConstraintsWithFormat(format: "H:|[v0]|", views: collectionView)
addConstraintsWithFormat(format: "V:|[v0]|", views: collectionView)
collectionView.register(EventsCell.self, forCellWithReuseIdentifier: EventCellID)
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 10
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: EventCellID, for: indexPath)
return cell
}

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
let height = textViewHeight ?? frame.width * 1/3
let width = frame.width - 8
return CGSize(width: width, height: height)
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
return 0
}
//MARK: - Design selected cells background
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
if let cell = collectionView.cellForItem(at: indexPath) as? EventsCell {
cell.textView.isUserInteractionEnabled = true
cell.eventTitleLabel.isUserInteractionEnabled = true
cell.layer.borderColor = UIColor.flatBlack.cgColor
cell.layer.borderWidth = 2
cell.layer.cornerRadius = 7
cell.backgroundColor = GradientColor(.topToBottom, frame: cell.frame, colors: [UIColor.flatRed.withAlphaComponent(0.2), UIColor.white])

} else {return}
}
func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {
if let cell = collectionView.cellForItem(at: indexPath) {
cell.layer.borderColor = UIColor.clear.cgColor
cell.layer.borderWidth = 0
cell.layer.cornerRadius = 0
cell.backgroundColor = .white
} else {return}
}
}

第一次回答后的尝试：

class RootCell: BaseCell, UITextViewDelegate, UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
var textViewText : String?
func textViewDidChange(_ textView: UITextView) {
textViewText = textView.text
DispatchQueue.main.async {
self.collectionView.reloadInputViews()
self.collectionView.reloadData()
}

}
func heightWithConstrainedWidth(width: CGFloat, font: UIFont) -> CGFloat {
let constraintRect = CGSize(width: width, height: CGFloat.greatestFiniteMagnitude)
guard let boundingBox = textViewText?.boundingRect(with: constraintRect, options: [NSStringDrawingOptions.usesLineFragmentOrigin], attributes: [NSAttributedStringKey.font: font], context: nil) else {return frame.width * 1/3}
return boundingBox.height
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
let width = frame.width - 8
let height = heightWithConstrainedWidth(width: width, font: UIFont(name: "Didot", size: 16)!)
return CGSize(width: width, height: height)
}

感谢您阅读我的帖子！

重新加载集合视图或单个单元格会使单元格闪烁，用户在键入时会失去对TextView的关注。如果用户失去了焦点，他们必须再次单击UITextView以继续键入。

当您检测到UITextView需要调整大小时，您可以使集合视图的布局无效-如果您的自动布局参数都正确，则会导致单元格调整大小。参见以下示例：

我有一个UICollectionCell，里面只有UITextView，并且禁用了在UITextView上滚动。使用AutoLayout将UITextView正确地约束到单元的所有边。最后，单元格也是UITextView的委托，如下所示：

class MyCollectionCell: UICollectionViewCell {
@IBOutlet private weak var myTextView: UITextView!
//this local variable will be used to determine if the intrinsic content size has changed or not
private var textViewHeight: CGFloat = .zero
...
...
override func awakeFromNib() {
super.awakeFromNib()
myTextView.delegate = self
}
...
...
}

使此单元格符合UITextViewDelegate

extension MyCollectionCell: UITextViewDelegate { 
func textViewShouldBeginEditing(_ textView: UITextView) -> Bool {
//this assumes that collection view already correctly laid out the cell
//to the correct height for the contents of the UITextView
//textViewHeight simply needs to catch up to it before user starts typing
let fittingSize = textView.sizeThatFits(CGSize(width: myTextView.frame.width, height: CGFloat.greatestFiniteMagnitude))
textViewHeight = fittingSize.height
return true
}
func textViewDidChange(_ textView: UITextView) {
//flag to determine whether textview's size is changing
var shouldResize = false
//calculate fitting size after the content has changed
let fittingSize = textView.sizeThatFits(CGSize(width: myTextView.frame.width, height: CGFloat.greatestFiniteMagnitude))
//if the current height is not equal to the fitting height
//save the new fitting height to our local variable and inform the delegate 
//that collection view needs resizing
if textViewHeight != fittingSize.height {
shouldResize = true
//save the new height 
textViewHeight = fittingSize.height
}
//notify the cell's delegate (most likely a UIViewController) 
//that UITextView's intrinsic content size has changed
//perhaps with a protocol such as this:
delegate?.textViewDidChange(newText: textView.text, alsoRequiresResize: shouldResize)
}

然后，当代表收到通知时，可能会保存更新后的文本并更新布局，例如：
```
myCollectionView.collectionViewLayout.invalidateLayout()
```

此解决方案的最佳部分是不必调用collectionView(_:layout:sizeForItemAt:(。

干杯！

首先将textView文本存储在某个变量中，然后通过这种方法可以获得文本的高度

func heightWithConstrainedWidth(width: CGFloat, font: UIFont) -> CGFloat {
let constraintRect = CGSize(width: width, height: CGFloat.greatestFiniteMagnitude)
let boundingBox = self.boundingRect(with: constraintRect, options: [NSStringDrawingOptions.usesLineFragmentOrigin], attributes: [NSAttributedStringKey.font: font], context: nil)
return boundingBox.height
}

然后把这个高度传给cell+你的围场当用户输入时，不要忘记重新加载collectionView

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