问题
Good afternoon.
I've struggled with this "feature" for my iOS app for some hours now and I'm in need of some help.
Question: How should I implement so that when a user types in the UITextView increases in size (only the bottom margin) and the cell increases its height to fit the UITextView dynamically meanwhile? I can't figure out how to tackle it.
Research: After some searching I came upon Dynamically change cell's height while typing text, and reload the containing tableview for resize as well as Can you animate a height change on a UITableViewCell when selected? I've also read https://developer.apple.com/documentation/uikit/uicollectionview but I feel my swift knowledge so far is inferior to whats expected in these posts.
In other words I cant figure out how to implement it for my UICollectionView.
My code at moment looks like this (I have more UI elements in the EventsCell but cut them out to save space, thus its only the bottom margin of the UITextView I want to change). I have set the RootCell as delegate for my UITextView and then i intend to grab the textView height as it is edited in order to get the height I want, but it isn't working.
Cell class:
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 class:
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}
}
}
Attempt after first answer:
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)
}
Thank you for reading my post!
回答1:
First store textView text in some variable then you can get height of your text by this method
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
}
then pass this in height for cell + your paddings
and don't forget to reload your collectionView when user enters something
来源：https://stackoverflow.com/questions/51642331/swift-how-to-continuously-adapt-a-uicollectionviewcell-height-to-a-uitextview-w