具有动态高度和宽度的 UITableView 单元格无法正确重用
UITableView Cell with dynamic height and width not getting reused properly
我有一个具有动态高度和宽度的 UITableView 单元格。最初，它工作正常，但是当重新使用旧单元格时，约束设置不正确。我正在停用所有旧约束并再次激活它们。我还调用了 setNeedsLayout() 和 layoutIfNeeded()。但这并没有帮助。
自动高度设置：（我认为这是一个问题）
discussionTableView.rowHeight = UITableViewAutomaticDimension
discussionTableView.estimatedRowHeight = 10
我的 table 查看单元格：
class DiscussionChatMessageCell: UITableViewCell {
private let messageLabel: UILabel
private let senderNameLabel: UILabel
private let messageBubble: UIView
let screenWidth: CGFloat
override init(style: UITableViewCellStyle, reuseIdentifier: String?) {
messageLabel = UILabel()
senderNameLabel = UILabel()
screenWidth = UIScreen.main.bounds.size.width
messageBubble = UIView()
super.init(style: style, reuseIdentifier: reuseIdentifier)
// self.contentView.backgroundColor = .clear
self.contentView.addSubview(messageBubble)
messageBubble.translatesAutoresizingMaskIntoConstraints = false
messageBubble.addSubview(senderNameLabel)
senderNameLabel.translatesAutoresizingMaskIntoConstraints = false
senderNameLabel.numberOfLines = 0
senderNameLabel.lineBreakMode = .byCharWrapping
senderNameLabel.font = UIFont.boldSystemFont(ofSize: 15)
senderNameLabel.textColor = .white
messageBubble.addSubview(messageLabel)
messageLabel.translatesAutoresizingMaskIntoConstraints = false
messageLabel.numberOfLines = 0
messageLabel.lineBreakMode = .byWordWrapping
messageLabel.font = UIFont.systemFont(ofSize: 13)
messageLabel.textColor = .white
NSLayoutConstraint.activate([
messageBubble.topAnchor.constraint(equalTo: self.contentView.topAnchor, constant: 10),
messageBubble.bottomAnchor.constraint(equalTo: self.contentView.bottomAnchor, constant: -10),
messageBubble.widthAnchor.constraint(lessThanOrEqualToConstant: screenWidth - 100),
senderNameLabel.topAnchor.constraint(equalTo: messageBubble.topAnchor, constant: 10),
senderNameLabel.leadingAnchor.constraint(equalTo: messageBubble.leadingAnchor, constant: 10),
senderNameLabel.trailingAnchor.constraint(equalTo: messageBubble.trailingAnchor, constant: -10),
messageLabel.topAnchor.constraint(equalTo: senderNameLabel.bottomAnchor, constant: 10),
messageLabel.leadingAnchor.constraint(equalTo: messageBubble.leadingAnchor, constant: 10),
messageLabel.trailingAnchor.constraint(equalTo: messageBubble.trailingAnchor, constant: -10),
messageLabel.bottomAnchor.constraint(equalTo: messageBubble.bottomAnchor, constant: -10),
])
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
func configureCell(message: String, isSender: Bool) {
senderNameLabel.text = "Default Sender"
messageLabel.text = message
for constraint in messageBubble.constraints {
// messageBubble.removeConstraint(constraint)
constraint.isActive = false
}
for constraint in messageLabel.constraints {
// messageLabel.removeConstraint(constraint)
constraint.isActive = false
}
for constraint in senderNameLabel.constraints {
//senderNameLabel.removeConstraint(constraint)
constraint.isActive = false
}
NSLayoutConstraint.deactivate([
messageBubble.trailingAnchor.constraint(equalTo: self.contentView.trailingAnchor, constant: -10),
messageBubble.leadingAnchor.constraint(equalTo: self.contentView.leadingAnchor, constant: 10)
])
NSLayoutConstraint.activate([
messageBubble.topAnchor.constraint(equalTo: self.contentView.topAnchor, constant: 10),
messageBubble.bottomAnchor.constraint(equalTo: self.contentView.bottomAnchor, constant: -10),
messageBubble.widthAnchor.constraint(lessThanOrEqualToConstant: screenWidth - 100),
senderNameLabel.topAnchor.constraint(equalTo: messageBubble.topAnchor, constant: 10),
senderNameLabel.leadingAnchor.constraint(equalTo: messageBubble.leadingAnchor, constant: 10),
senderNameLabel.trailingAnchor.constraint(equalTo: messageBubble.trailingAnchor, constant: -10),
messageLabel.topAnchor.constraint(equalTo: senderNameLabel.bottomAnchor, constant: 10),
messageLabel.leadingAnchor.constraint(equalTo: messageBubble.leadingAnchor, constant: 10),
messageLabel.trailingAnchor.constraint(equalTo: messageBubble.trailingAnchor, constant: -10),
messageLabel.bottomAnchor.constraint(equalTo: messageBubble.bottomAnchor, constant: -10),
])
messageBubble.backgroundColor = isSender ? accentColor : .gray
if isSender {
NSLayoutConstraint.activate([
messageBubble.trailingAnchor.constraint(equalTo: self.contentView.trailingAnchor, constant: -10)
])
// let corners: UIRectCorner = [.topLeft, .topRight, .bottomLeft]
// roundCorners(corners: corners, isSender: isSender)
} else {
NSLayoutConstraint.activate([
messageBubble.leadingAnchor.constraint(equalTo: self.contentView.leadingAnchor, constant: 10)
])
// let corners: UIRectCorner = [.topLeft, .topRight, .bottomRight]
// roundCorners(corners: corners, isSender: isSender)
}
}
重复使用单元格：
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
guard let discussionChatMessageCell = tableView.dequeueReusableCell(withIdentifier: discussionChatId, for: indexPath) as? DiscussionChatMessageCell else { return UITableViewCell()}
discussionChatMessageCell.configureCell(message: messages[indexPath.row], isSender: isSender[indexPath.row])
discussionChatMessageCell.setNeedsLayout()
discussionChatMessageCell.layoutIfNeeded()
return discussionChatMessageCell
}
重新使用单元格之前：
重复使用单元格后：
编辑
当使用 UITextView 而不是 UILabel 作为 messageLabel 时，约束的工作方式非常不同，table 视图需要 2-3 秒才能加载。
更改了 textView 的设置
// messageLabel.numberOfLines = 0
// messageLabel.lineBreakMode = .byWordWrapping
messageLabel.isEditable = false
messageLabel.dataDetectorTypes = .all
messageLabel.textContainer.lineBreakMode = .byWordWrapping
messageLabel.setContentCompressionResistancePriority(.required, for: .vertical)
messageLabel.setContentHuggingPriority(.required, for: .vertical)
输出：
这是更新单元格的代码，我还在其中添加了时间标签。所以需要的是
UILable，UITextView，UILabel。现在这是 UILabel，UILabel，UILabel。
class DiscussionChatMessageCell: UITableViewCell {
private let messageLabel: UILabel
private let senderNameLabel: UILabel
private let messageSentTimeLabel: UILabel
private let messageBubble: UIView
private var bubbleLeadingConstraint: NSLayoutConstraint!
private var bubbleTrailingConstraint: NSLayoutConstraint!
override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
messageLabel = UILabel()
senderNameLabel = UILabel()
messageSentTimeLabel = UILabel()
messageBubble = UIView()
super.init(style: style, reuseIdentifier: reuseIdentifier)
self.contentView.addSubview(messageBubble)
messageBubble.translatesAutoresizingMaskIntoConstraints = false
messageBubble.addSubview(senderNameLabel)
senderNameLabel.translatesAutoresizingMaskIntoConstraints = false
senderNameLabel.numberOfLines = 0
senderNameLabel.lineBreakMode = .byCharWrapping
senderNameLabel.font = UIFont.boldSystemFont(ofSize: 15)
senderNameLabel.textColor = .white
messageBubble.addSubview(messageLabel)
messageLabel.translatesAutoresizingMaskIntoConstraints = false
// messageLabel.isEditable = false
// messageLabel.dataDetectorTypes = .all
// messageLabel.textContainer.lineBreakMode = .byWordWrapping
messageLabel.numberOfLines = 0
messageLabel.lineBreakMode = .byWordWrapping
messageLabel.font = UIFont(name: "Helvetica Neue", size: 13)!
messageBubble.addSubview(messageSentTimeLabel)
messageSentTimeLabel.translatesAutoresizingMaskIntoConstraints = false
messageSentTimeLabel.lineBreakMode = .byCharWrapping
messageSentTimeLabel.numberOfLines = 0
messageSentTimeLabel.font = UIFont(name: "HelveticaNeue-Italic", size: 11)!
// set hugging and compression resistance for Name label
senderNameLabel.setContentCompressionResistancePriority(.required, for: .vertical)
senderNameLabel.setContentHuggingPriority(.required, for: .vertical)
// messageLabel.setContentCompressionResistancePriority(.required, for: .vertical)
// messageLabel.setContentHuggingPriority(.required, for: .vertical)
// create bubble Leading and Trailing constraints
bubbleLeadingConstraint = messageBubble.leadingAnchor.constraint(equalTo: self.contentView.leadingAnchor, constant: 10)
bubbleTrailingConstraint = messageBubble.trailingAnchor.constraint(equalTo: self.contentView.trailingAnchor, constant: -10)
// priority will be changed in configureCell()
bubbleLeadingConstraint.priority = .defaultHigh
bubbleTrailingConstraint.priority = .defaultLow
NSLayoutConstraint.activate([
bubbleLeadingConstraint,
bubbleTrailingConstraint,
messageBubble.topAnchor.constraint(equalTo: self.contentView.topAnchor, constant: 10),
messageBubble.bottomAnchor.constraint(equalTo: self.contentView.bottomAnchor, constant: -10),
messageBubble.widthAnchor.constraint(lessThanOrEqualTo: self.contentView.widthAnchor, constant: -100),
senderNameLabel.topAnchor.constraint(equalTo: messageBubble.topAnchor, constant: 10),
senderNameLabel.leadingAnchor.constraint(equalTo: messageBubble.leadingAnchor, constant: 10),
senderNameLabel.trailingAnchor.constraint(equalTo: messageBubble.trailingAnchor, constant: -10),
messageLabel.topAnchor.constraint(equalTo: senderNameLabel.bottomAnchor, constant: 10),
messageLabel.leadingAnchor.constraint(equalTo: messageBubble.leadingAnchor, constant: 10),
messageLabel.trailingAnchor.constraint(equalTo: messageBubble.trailingAnchor, constant: -10),
messageLabel.bottomAnchor.constraint(equalTo: messageSentTimeLabel.topAnchor, constant: -10),
messageSentTimeLabel.leadingAnchor.constraint(equalTo: messageBubble.leadingAnchor, constant: 10),
messageSentTimeLabel.trailingAnchor.constraint(equalTo: messageBubble.trailingAnchor, constant: -10),
messageSentTimeLabel.bottomAnchor.constraint(equalTo: messageBubble.bottomAnchor, constant: -10),
])
// corners will have radius: 10
messageBubble.layer.cornerRadius = 10
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
func configureCell(message: DiscussionMessage, isSender: Bool) {
senderNameLabel.text = message.userName + " " + message.userCountryEmoji
let date = Date(timeIntervalSince1970: message.messageTimestamp)
let dayTimePeriodFormatter = DateFormatter()
dayTimePeriodFormatter.timeZone = .current
dayTimePeriodFormatter.dateFormat = "hh:mm a"
let dateString = dayTimePeriodFormatter.string(from: date)
messageLabel.text = message.message
messageSentTimeLabel.text = dateString
messageLabel.textColor = isSender ? .black : .white
senderNameLabel.textColor = isSender ? .black : .white
messageSentTimeLabel.textColor = isSender ? .black : .white
messageSentTimeLabel.textAlignment = isSender ? .right : .left
bubbleLeadingConstraint.priority = isSender ? .defaultLow : .defaultHigh
bubbleTrailingConstraint.priority = isSender ? .defaultHigh : .defaultLow
messageBubble.backgroundColor = isSender ? accentColor : .gray
let senderCorners: CACornerMask = [.layerMinXMinYCorner, .layerMaxXMinYCorner, .layerMinXMaxYCorner]
let nonSenderCorners: CACornerMask = [.layerMinXMinYCorner, .layerMaxXMinYCorner, .layerMaxXMaxYCorner]
if #available(iOS 11.0, *) {
messageBubble.layer.maskedCorners = isSender ?
// topLeft, topRight, bottomRight
senderCorners
:
// topLeft, topRight, bottomLeft
nonSenderCorners
} else {
// Fallback on earlier versions
// All corners will be rounded
}
}
}
发件人姓名标签和消息标签中添加了时间标签的当前输出：
我更改了您的代码设置 messageBuble 相对于单元格而不是内容视图的约束：
messageBubble.topAnchor.constraint(equalTo: self.topAnchor, constant: 10),
messageBubble.bottomAnchor.constraint(equalTo: self.bottomAnchor, constant: -10)
刚刚调用 layoutIfNeeded():
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
guard let discussionChatMessageCell = tableView.dequeueReusableCell(withIdentifier: discussionChatId, for: indexPath) as? DiscussionChatMessageCell else { return UITableViewCell()}
discussionChatMessageCell.configureCell(message: messages[indexPath.row], isSender: isSender[indexPath.row])
discussionChatMessageCell.layoutIfNeeded()
return discussionChatMessageCell
}
您多次添加子视图，但它是可重用的。不要忘记它。
在 .addSubview(....
之前添加下一个代码
contentView.subviews.forEach { [=10=].removeFromSuperview() }
或者只改变视图值，不要每次都添加
您修改约束的方式超出了您的需要。
更好的方法是为您的“气泡”同时创建前导和尾随约束 --- 并更改它们的优先级以确定使用哪一个。
因此，如果是“已收到”消息，我们将前导约束优先级设置为高，将尾随约束优先级设置为低。如果是“已发送”消息，我们执行相反的操作。
试一试：
class DiscussionChatMessageCell: UITableViewCell {
let accentColor: UIColor = .systemYellow
private let messageLabel: UILabel
private let senderNameLabel: UILabel
private let messageBubble: UIView
private var bubbleLeadingConstraint: NSLayoutConstraint!
private var bubbleTrailingConstraint: NSLayoutConstraint!
// not needed
//let screenWidth: CGFloat
// wrong signature
//override init(style: UITableViewCellStyle, reuseIdentifier: String?) {
override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
messageLabel = UILabel()
senderNameLabel = UILabel()
messageBubble = UIView()
super.init(style: style, reuseIdentifier: reuseIdentifier)
// self.contentView.backgroundColor = .clear
self.contentView.addSubview(messageBubble)
messageBubble.translatesAutoresizingMaskIntoConstraints = false
messageBubble.addSubview(senderNameLabel)
senderNameLabel.translatesAutoresizingMaskIntoConstraints = false
senderNameLabel.numberOfLines = 0
senderNameLabel.lineBreakMode = .byCharWrapping
senderNameLabel.font = UIFont.boldSystemFont(ofSize: 15)
senderNameLabel.textColor = .white
messageBubble.addSubview(messageLabel)
messageLabel.translatesAutoresizingMaskIntoConstraints = false
messageLabel.numberOfLines = 0
messageLabel.lineBreakMode = .byWordWrapping
messageLabel.font = UIFont.systemFont(ofSize: 13)
messageLabel.textColor = .white
// set hugging and compression resistance for Name label
senderNameLabel.setContentCompressionResistancePriority(.required, for: .vertical)
senderNameLabel.setContentHuggingPriority(.required, for: .vertical)
// create bubble Leading and Trailing constraints
bubbleLeadingConstraint = messageBubble.leadingAnchor.constraint(equalTo: self.contentView.leadingAnchor, constant: 10)
bubbleTrailingConstraint = messageBubble.trailingAnchor.constraint(equalTo: self.contentView.trailingAnchor, constant: -10)
// priority will be changed in configureCell()
bubbleLeadingConstraint.priority = .defaultHigh
bubbleTrailingConstraint.priority = .defaultLow
NSLayoutConstraint.activate([
bubbleLeadingConstraint,
bubbleTrailingConstraint,
messageBubble.topAnchor.constraint(equalTo: self.contentView.topAnchor, constant: 10),
messageBubble.bottomAnchor.constraint(equalTo: self.contentView.bottomAnchor, constant: -10),
messageBubble.widthAnchor.constraint(lessThanOrEqualTo: self.contentView.widthAnchor, constant: -100),
senderNameLabel.topAnchor.constraint(equalTo: messageBubble.topAnchor, constant: 10),
senderNameLabel.leadingAnchor.constraint(equalTo: messageBubble.leadingAnchor, constant: 10),
senderNameLabel.trailingAnchor.constraint(equalTo: messageBubble.trailingAnchor, constant: -10),
messageLabel.topAnchor.constraint(equalTo: senderNameLabel.bottomAnchor, constant: 10),
messageLabel.leadingAnchor.constraint(equalTo: messageBubble.leadingAnchor, constant: 10),
messageLabel.trailingAnchor.constraint(equalTo: messageBubble.trailingAnchor, constant: -10),
messageLabel.bottomAnchor.constraint(equalTo: messageBubble.bottomAnchor, constant: -10),
])
// corners will have radius: 10
messageBubble.layer.cornerRadius = 10
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
func configureCell(message: String, isSender: Bool) {
senderNameLabel.text = "Default Sender"
messageLabel.text = message
bubbleLeadingConstraint.priority = isSender ? .defaultHigh : .defaultLow
bubbleTrailingConstraint.priority = isSender ? .defaultLow : .defaultHigh
messageBubble.backgroundColor = isSender ? accentColor : .gray
messageBubble.layer.maskedCorners = isSender ?
// topLeft, topRight, bottomRight
[.layerMinXMinYCorner, .layerMaxXMinYCorner, .layerMaxXMaxYCorner]
:
// topLeft, topRight, bottomLeft
[.layerMinXMinYCorner, .layerMaxXMinYCorner, .layerMinXMaxYCorner]
}
}
旁注：cellForRowAt:
中不需要这两行
//discussionChatMessageCell.setNeedsLayout()
//discussionChatMessageCell.layoutIfNeeded()
编辑 - 如果你真的想在 11 之前支持 iOS...
我建议您像这样子类化“BubbleView”：
class BubbleView: UIView {
var radius: CGFloat = 0
var corners: UIRectCorner = []
var color: UIColor = .clear
lazy var shapeLayer: CAShapeLayer = self.layer as! CAShapeLayer
override class var layerClass: AnyClass {
return CAShapeLayer.self
}
override func layoutSubviews() {
super.layoutSubviews()
let path = UIBezierPath(roundedRect: self.bounds, byRoundingCorners: corners, cornerRadii: CGSize(width: radius, height: radius))
shapeLayer.path = path.cgPath
shapeLayer.fillColor = color.cgColor
}
}
然后像这样使用它：
class DiscussionChatMessageCell: UITableViewCell {
let accentColor: UIColor = .systemYellow
private let messageLabel: UILabel
private let senderNameLabel: UILabel
// use custom BubbleView class instead of standard UIView
private let messageBubble: BubbleView
private var bubbleLeadingConstraint: NSLayoutConstraint!
private var bubbleTrailingConstraint: NSLayoutConstraint!
// wrong signature - I beliee as of Swift 4.2
// 'UITableViewCellStyle' has been renamed to 'UITableViewCell.CellStyle'
//override init(style: UITableViewCellStyle, reuseIdentifier: String?) {
override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
messageLabel = UILabel()
senderNameLabel = UILabel()
messageBubble = BubbleView()
super.init(style: style, reuseIdentifier: reuseIdentifier)
self.contentView.addSubview(messageBubble)
messageBubble.translatesAutoresizingMaskIntoConstraints = false
messageBubble.addSubview(senderNameLabel)
senderNameLabel.translatesAutoresizingMaskIntoConstraints = false
senderNameLabel.numberOfLines = 0
senderNameLabel.lineBreakMode = .byCharWrapping
senderNameLabel.font = UIFont.boldSystemFont(ofSize: 15)
senderNameLabel.textColor = .white
messageBubble.addSubview(messageLabel)
messageLabel.translatesAutoresizingMaskIntoConstraints = false
messageLabel.numberOfLines = 0
messageLabel.lineBreakMode = .byWordWrapping
messageLabel.font = UIFont.systemFont(ofSize: 13)
messageLabel.textColor = .white
// set hugging and compression resistance for Name label
senderNameLabel.setContentCompressionResistancePriority(.required, for: .vertical)
senderNameLabel.setContentHuggingPriority(.required, for: .vertical)
// create bubble Leading and Trailing constraints
bubbleLeadingConstraint = messageBubble.leadingAnchor.constraint(equalTo: self.contentView.leadingAnchor, constant: 10)
bubbleTrailingConstraint = messageBubble.trailingAnchor.constraint(equalTo: self.contentView.trailingAnchor, constant: -10)
// priority will be changed in configureCell()
bubbleLeadingConstraint.priority = .defaultHigh
bubbleTrailingConstraint.priority = .defaultLow
NSLayoutConstraint.activate([
bubbleLeadingConstraint,
bubbleTrailingConstraint,
messageBubble.topAnchor.constraint(equalTo: self.contentView.topAnchor, constant: 10),
messageBubble.bottomAnchor.constraint(equalTo: self.contentView.bottomAnchor, constant: -10),
messageBubble.widthAnchor.constraint(lessThanOrEqualTo: self.contentView.widthAnchor, constant: -100),
senderNameLabel.topAnchor.constraint(equalTo: messageBubble.topAnchor, constant: 10),
senderNameLabel.leadingAnchor.constraint(equalTo: messageBubble.leadingAnchor, constant: 10),
senderNameLabel.trailingAnchor.constraint(equalTo: messageBubble.trailingAnchor, constant: -10),
messageLabel.topAnchor.constraint(equalTo: senderNameLabel.bottomAnchor, constant: 10),
messageLabel.leadingAnchor.constraint(equalTo: messageBubble.leadingAnchor, constant: 10),
messageLabel.trailingAnchor.constraint(equalTo: messageBubble.trailingAnchor, constant: -10),
messageLabel.bottomAnchor.constraint(equalTo: messageBubble.bottomAnchor, constant: -10),
])
// corners will have radius: 10
messageBubble.radius = 10
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
func configureCell(message: String, isSender: Bool) {
senderNameLabel.text = "Default Sender"
messageLabel.text = message
bubbleLeadingConstraint.priority = isSender ? .defaultHigh : .defaultLow
bubbleTrailingConstraint.priority = isSender ? .defaultLow : .defaultHigh
messageBubble.color = isSender ? accentColor : .gray
let senderCorners: UIRectCorner = [.topLeft, .topRight, .bottomRight]
let nonSenderCorners: UIRectCorner = [.topLeft, .topRight, .bottomLeft]
messageBubble.corners = isSender ? senderCorners : nonSenderCorners
}
}
这将保持“气泡”视图的形状和大小，即使单元格发生变化（例如旋转设备时）也是如此。
我有一个具有动态高度和宽度的 UITableView 单元格。最初，它工作正常，但是当重新使用旧单元格时，约束设置不正确。我正在停用所有旧约束并再次激活它们。我还调用了 setNeedsLayout() 和 layoutIfNeeded()。但这并没有帮助。
自动高度设置：（我认为这是一个问题）
discussionTableView.rowHeight = UITableViewAutomaticDimension
discussionTableView.estimatedRowHeight = 10
我的 table 查看单元格：
class DiscussionChatMessageCell: UITableViewCell {
private let messageLabel: UILabel
private let senderNameLabel: UILabel
private let messageBubble: UIView
let screenWidth: CGFloat
override init(style: UITableViewCellStyle, reuseIdentifier: String?) {
messageLabel = UILabel()
senderNameLabel = UILabel()
screenWidth = UIScreen.main.bounds.size.width
messageBubble = UIView()
super.init(style: style, reuseIdentifier: reuseIdentifier)
// self.contentView.backgroundColor = .clear
self.contentView.addSubview(messageBubble)
messageBubble.translatesAutoresizingMaskIntoConstraints = false
messageBubble.addSubview(senderNameLabel)
senderNameLabel.translatesAutoresizingMaskIntoConstraints = false
senderNameLabel.numberOfLines = 0
senderNameLabel.lineBreakMode = .byCharWrapping
senderNameLabel.font = UIFont.boldSystemFont(ofSize: 15)
senderNameLabel.textColor = .white
messageBubble.addSubview(messageLabel)
messageLabel.translatesAutoresizingMaskIntoConstraints = false
messageLabel.numberOfLines = 0
messageLabel.lineBreakMode = .byWordWrapping
messageLabel.font = UIFont.systemFont(ofSize: 13)
messageLabel.textColor = .white
NSLayoutConstraint.activate([
messageBubble.topAnchor.constraint(equalTo: self.contentView.topAnchor, constant: 10),
messageBubble.bottomAnchor.constraint(equalTo: self.contentView.bottomAnchor, constant: -10),
messageBubble.widthAnchor.constraint(lessThanOrEqualToConstant: screenWidth - 100),
senderNameLabel.topAnchor.constraint(equalTo: messageBubble.topAnchor, constant: 10),
senderNameLabel.leadingAnchor.constraint(equalTo: messageBubble.leadingAnchor, constant: 10),
senderNameLabel.trailingAnchor.constraint(equalTo: messageBubble.trailingAnchor, constant: -10),
messageLabel.topAnchor.constraint(equalTo: senderNameLabel.bottomAnchor, constant: 10),
messageLabel.leadingAnchor.constraint(equalTo: messageBubble.leadingAnchor, constant: 10),
messageLabel.trailingAnchor.constraint(equalTo: messageBubble.trailingAnchor, constant: -10),
messageLabel.bottomAnchor.constraint(equalTo: messageBubble.bottomAnchor, constant: -10),
])
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
func configureCell(message: String, isSender: Bool) {
senderNameLabel.text = "Default Sender"
messageLabel.text = message
for constraint in messageBubble.constraints {
// messageBubble.removeConstraint(constraint)
constraint.isActive = false
}
for constraint in messageLabel.constraints {
// messageLabel.removeConstraint(constraint)
constraint.isActive = false
}
for constraint in senderNameLabel.constraints {
//senderNameLabel.removeConstraint(constraint)
constraint.isActive = false
}
NSLayoutConstraint.deactivate([
messageBubble.trailingAnchor.constraint(equalTo: self.contentView.trailingAnchor, constant: -10),
messageBubble.leadingAnchor.constraint(equalTo: self.contentView.leadingAnchor, constant: 10)
])
NSLayoutConstraint.activate([
messageBubble.topAnchor.constraint(equalTo: self.contentView.topAnchor, constant: 10),
messageBubble.bottomAnchor.constraint(equalTo: self.contentView.bottomAnchor, constant: -10),
messageBubble.widthAnchor.constraint(lessThanOrEqualToConstant: screenWidth - 100),
senderNameLabel.topAnchor.constraint(equalTo: messageBubble.topAnchor, constant: 10),
senderNameLabel.leadingAnchor.constraint(equalTo: messageBubble.leadingAnchor, constant: 10),
senderNameLabel.trailingAnchor.constraint(equalTo: messageBubble.trailingAnchor, constant: -10),
messageLabel.topAnchor.constraint(equalTo: senderNameLabel.bottomAnchor, constant: 10),
messageLabel.leadingAnchor.constraint(equalTo: messageBubble.leadingAnchor, constant: 10),
messageLabel.trailingAnchor.constraint(equalTo: messageBubble.trailingAnchor, constant: -10),
messageLabel.bottomAnchor.constraint(equalTo: messageBubble.bottomAnchor, constant: -10),
])
messageBubble.backgroundColor = isSender ? accentColor : .gray
if isSender {
NSLayoutConstraint.activate([
messageBubble.trailingAnchor.constraint(equalTo: self.contentView.trailingAnchor, constant: -10)
])
// let corners: UIRectCorner = [.topLeft, .topRight, .bottomLeft]
// roundCorners(corners: corners, isSender: isSender)
} else {
NSLayoutConstraint.activate([
messageBubble.leadingAnchor.constraint(equalTo: self.contentView.leadingAnchor, constant: 10)
])
// let corners: UIRectCorner = [.topLeft, .topRight, .bottomRight]
// roundCorners(corners: corners, isSender: isSender)
}
}
重复使用单元格：
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
guard let discussionChatMessageCell = tableView.dequeueReusableCell(withIdentifier: discussionChatId, for: indexPath) as? DiscussionChatMessageCell else { return UITableViewCell()}
discussionChatMessageCell.configureCell(message: messages[indexPath.row], isSender: isSender[indexPath.row])
discussionChatMessageCell.setNeedsLayout()
discussionChatMessageCell.layoutIfNeeded()
return discussionChatMessageCell
}
重新使用单元格之前：
重复使用单元格后：
编辑
当使用 UITextView 而不是 UILabel 作为 messageLabel 时，约束的工作方式非常不同，table 视图需要 2-3 秒才能加载。
更改了 textView 的设置
// messageLabel.numberOfLines = 0
// messageLabel.lineBreakMode = .byWordWrapping
messageLabel.isEditable = false
messageLabel.dataDetectorTypes = .all
messageLabel.textContainer.lineBreakMode = .byWordWrapping
messageLabel.setContentCompressionResistancePriority(.required, for: .vertical)
messageLabel.setContentHuggingPriority(.required, for: .vertical)
输出：
这是更新单元格的代码，我还在其中添加了时间标签。所以需要的是 UILable，UITextView，UILabel。现在这是 UILabel，UILabel，UILabel。
class DiscussionChatMessageCell: UITableViewCell {
private let messageLabel: UILabel
private let senderNameLabel: UILabel
private let messageSentTimeLabel: UILabel
private let messageBubble: UIView
private var bubbleLeadingConstraint: NSLayoutConstraint!
private var bubbleTrailingConstraint: NSLayoutConstraint!
override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
messageLabel = UILabel()
senderNameLabel = UILabel()
messageSentTimeLabel = UILabel()
messageBubble = UIView()
super.init(style: style, reuseIdentifier: reuseIdentifier)
self.contentView.addSubview(messageBubble)
messageBubble.translatesAutoresizingMaskIntoConstraints = false
messageBubble.addSubview(senderNameLabel)
senderNameLabel.translatesAutoresizingMaskIntoConstraints = false
senderNameLabel.numberOfLines = 0
senderNameLabel.lineBreakMode = .byCharWrapping
senderNameLabel.font = UIFont.boldSystemFont(ofSize: 15)
senderNameLabel.textColor = .white
messageBubble.addSubview(messageLabel)
messageLabel.translatesAutoresizingMaskIntoConstraints = false
// messageLabel.isEditable = false
// messageLabel.dataDetectorTypes = .all
// messageLabel.textContainer.lineBreakMode = .byWordWrapping
messageLabel.numberOfLines = 0
messageLabel.lineBreakMode = .byWordWrapping
messageLabel.font = UIFont(name: "Helvetica Neue", size: 13)!
messageBubble.addSubview(messageSentTimeLabel)
messageSentTimeLabel.translatesAutoresizingMaskIntoConstraints = false
messageSentTimeLabel.lineBreakMode = .byCharWrapping
messageSentTimeLabel.numberOfLines = 0
messageSentTimeLabel.font = UIFont(name: "HelveticaNeue-Italic", size: 11)!
// set hugging and compression resistance for Name label
senderNameLabel.setContentCompressionResistancePriority(.required, for: .vertical)
senderNameLabel.setContentHuggingPriority(.required, for: .vertical)
// messageLabel.setContentCompressionResistancePriority(.required, for: .vertical)
// messageLabel.setContentHuggingPriority(.required, for: .vertical)
// create bubble Leading and Trailing constraints
bubbleLeadingConstraint = messageBubble.leadingAnchor.constraint(equalTo: self.contentView.leadingAnchor, constant: 10)
bubbleTrailingConstraint = messageBubble.trailingAnchor.constraint(equalTo: self.contentView.trailingAnchor, constant: -10)
// priority will be changed in configureCell()
bubbleLeadingConstraint.priority = .defaultHigh
bubbleTrailingConstraint.priority = .defaultLow
NSLayoutConstraint.activate([
bubbleLeadingConstraint,
bubbleTrailingConstraint,
messageBubble.topAnchor.constraint(equalTo: self.contentView.topAnchor, constant: 10),
messageBubble.bottomAnchor.constraint(equalTo: self.contentView.bottomAnchor, constant: -10),
messageBubble.widthAnchor.constraint(lessThanOrEqualTo: self.contentView.widthAnchor, constant: -100),
senderNameLabel.topAnchor.constraint(equalTo: messageBubble.topAnchor, constant: 10),
senderNameLabel.leadingAnchor.constraint(equalTo: messageBubble.leadingAnchor, constant: 10),
senderNameLabel.trailingAnchor.constraint(equalTo: messageBubble.trailingAnchor, constant: -10),
messageLabel.topAnchor.constraint(equalTo: senderNameLabel.bottomAnchor, constant: 10),
messageLabel.leadingAnchor.constraint(equalTo: messageBubble.leadingAnchor, constant: 10),
messageLabel.trailingAnchor.constraint(equalTo: messageBubble.trailingAnchor, constant: -10),
messageLabel.bottomAnchor.constraint(equalTo: messageSentTimeLabel.topAnchor, constant: -10),
messageSentTimeLabel.leadingAnchor.constraint(equalTo: messageBubble.leadingAnchor, constant: 10),
messageSentTimeLabel.trailingAnchor.constraint(equalTo: messageBubble.trailingAnchor, constant: -10),
messageSentTimeLabel.bottomAnchor.constraint(equalTo: messageBubble.bottomAnchor, constant: -10),
])
// corners will have radius: 10
messageBubble.layer.cornerRadius = 10
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
func configureCell(message: DiscussionMessage, isSender: Bool) {
senderNameLabel.text = message.userName + " " + message.userCountryEmoji
let date = Date(timeIntervalSince1970: message.messageTimestamp)
let dayTimePeriodFormatter = DateFormatter()
dayTimePeriodFormatter.timeZone = .current
dayTimePeriodFormatter.dateFormat = "hh:mm a"
let dateString = dayTimePeriodFormatter.string(from: date)
messageLabel.text = message.message
messageSentTimeLabel.text = dateString
messageLabel.textColor = isSender ? .black : .white
senderNameLabel.textColor = isSender ? .black : .white
messageSentTimeLabel.textColor = isSender ? .black : .white
messageSentTimeLabel.textAlignment = isSender ? .right : .left
bubbleLeadingConstraint.priority = isSender ? .defaultLow : .defaultHigh
bubbleTrailingConstraint.priority = isSender ? .defaultHigh : .defaultLow
messageBubble.backgroundColor = isSender ? accentColor : .gray
let senderCorners: CACornerMask = [.layerMinXMinYCorner, .layerMaxXMinYCorner, .layerMinXMaxYCorner]
let nonSenderCorners: CACornerMask = [.layerMinXMinYCorner, .layerMaxXMinYCorner, .layerMaxXMaxYCorner]
if #available(iOS 11.0, *) {
messageBubble.layer.maskedCorners = isSender ?
// topLeft, topRight, bottomRight
senderCorners
:
// topLeft, topRight, bottomLeft
nonSenderCorners
} else {
// Fallback on earlier versions
// All corners will be rounded
}
}
}
发件人姓名标签和消息标签中添加了时间标签的当前输出：
我更改了您的代码设置 messageBuble 相对于单元格而不是内容视图的约束：
messageBubble.topAnchor.constraint(equalTo: self.topAnchor, constant: 10),
messageBubble.bottomAnchor.constraint(equalTo: self.bottomAnchor, constant: -10)
刚刚调用 layoutIfNeeded():
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
guard let discussionChatMessageCell = tableView.dequeueReusableCell(withIdentifier: discussionChatId, for: indexPath) as? DiscussionChatMessageCell else { return UITableViewCell()}
discussionChatMessageCell.configureCell(message: messages[indexPath.row], isSender: isSender[indexPath.row])
discussionChatMessageCell.layoutIfNeeded()
return discussionChatMessageCell
}
您多次添加子视图，但它是可重用的。不要忘记它。 在 .addSubview(....
之前添加下一个代码contentView.subviews.forEach { [=10=].removeFromSuperview() }
或者只改变视图值，不要每次都添加
您修改约束的方式超出了您的需要。
更好的方法是为您的“气泡”同时创建前导和尾随约束 --- 并更改它们的优先级以确定使用哪一个。
因此，如果是“已收到”消息，我们将前导约束优先级设置为高，将尾随约束优先级设置为低。如果是“已发送”消息，我们执行相反的操作。
试一试：
class DiscussionChatMessageCell: UITableViewCell {
let accentColor: UIColor = .systemYellow
private let messageLabel: UILabel
private let senderNameLabel: UILabel
private let messageBubble: UIView
private var bubbleLeadingConstraint: NSLayoutConstraint!
private var bubbleTrailingConstraint: NSLayoutConstraint!
// not needed
//let screenWidth: CGFloat
// wrong signature
//override init(style: UITableViewCellStyle, reuseIdentifier: String?) {
override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
messageLabel = UILabel()
senderNameLabel = UILabel()
messageBubble = UIView()
super.init(style: style, reuseIdentifier: reuseIdentifier)
// self.contentView.backgroundColor = .clear
self.contentView.addSubview(messageBubble)
messageBubble.translatesAutoresizingMaskIntoConstraints = false
messageBubble.addSubview(senderNameLabel)
senderNameLabel.translatesAutoresizingMaskIntoConstraints = false
senderNameLabel.numberOfLines = 0
senderNameLabel.lineBreakMode = .byCharWrapping
senderNameLabel.font = UIFont.boldSystemFont(ofSize: 15)
senderNameLabel.textColor = .white
messageBubble.addSubview(messageLabel)
messageLabel.translatesAutoresizingMaskIntoConstraints = false
messageLabel.numberOfLines = 0
messageLabel.lineBreakMode = .byWordWrapping
messageLabel.font = UIFont.systemFont(ofSize: 13)
messageLabel.textColor = .white
// set hugging and compression resistance for Name label
senderNameLabel.setContentCompressionResistancePriority(.required, for: .vertical)
senderNameLabel.setContentHuggingPriority(.required, for: .vertical)
// create bubble Leading and Trailing constraints
bubbleLeadingConstraint = messageBubble.leadingAnchor.constraint(equalTo: self.contentView.leadingAnchor, constant: 10)
bubbleTrailingConstraint = messageBubble.trailingAnchor.constraint(equalTo: self.contentView.trailingAnchor, constant: -10)
// priority will be changed in configureCell()
bubbleLeadingConstraint.priority = .defaultHigh
bubbleTrailingConstraint.priority = .defaultLow
NSLayoutConstraint.activate([
bubbleLeadingConstraint,
bubbleTrailingConstraint,
messageBubble.topAnchor.constraint(equalTo: self.contentView.topAnchor, constant: 10),
messageBubble.bottomAnchor.constraint(equalTo: self.contentView.bottomAnchor, constant: -10),
messageBubble.widthAnchor.constraint(lessThanOrEqualTo: self.contentView.widthAnchor, constant: -100),
senderNameLabel.topAnchor.constraint(equalTo: messageBubble.topAnchor, constant: 10),
senderNameLabel.leadingAnchor.constraint(equalTo: messageBubble.leadingAnchor, constant: 10),
senderNameLabel.trailingAnchor.constraint(equalTo: messageBubble.trailingAnchor, constant: -10),
messageLabel.topAnchor.constraint(equalTo: senderNameLabel.bottomAnchor, constant: 10),
messageLabel.leadingAnchor.constraint(equalTo: messageBubble.leadingAnchor, constant: 10),
messageLabel.trailingAnchor.constraint(equalTo: messageBubble.trailingAnchor, constant: -10),
messageLabel.bottomAnchor.constraint(equalTo: messageBubble.bottomAnchor, constant: -10),
])
// corners will have radius: 10
messageBubble.layer.cornerRadius = 10
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
func configureCell(message: String, isSender: Bool) {
senderNameLabel.text = "Default Sender"
messageLabel.text = message
bubbleLeadingConstraint.priority = isSender ? .defaultHigh : .defaultLow
bubbleTrailingConstraint.priority = isSender ? .defaultLow : .defaultHigh
messageBubble.backgroundColor = isSender ? accentColor : .gray
messageBubble.layer.maskedCorners = isSender ?
// topLeft, topRight, bottomRight
[.layerMinXMinYCorner, .layerMaxXMinYCorner, .layerMaxXMaxYCorner]
:
// topLeft, topRight, bottomLeft
[.layerMinXMinYCorner, .layerMaxXMinYCorner, .layerMinXMaxYCorner]
}
}
旁注：cellForRowAt:
//discussionChatMessageCell.setNeedsLayout()
//discussionChatMessageCell.layoutIfNeeded()
编辑 - 如果你真的想在 11 之前支持 iOS...
我建议您像这样子类化“BubbleView”：
class BubbleView: UIView {
var radius: CGFloat = 0
var corners: UIRectCorner = []
var color: UIColor = .clear
lazy var shapeLayer: CAShapeLayer = self.layer as! CAShapeLayer
override class var layerClass: AnyClass {
return CAShapeLayer.self
}
override func layoutSubviews() {
super.layoutSubviews()
let path = UIBezierPath(roundedRect: self.bounds, byRoundingCorners: corners, cornerRadii: CGSize(width: radius, height: radius))
shapeLayer.path = path.cgPath
shapeLayer.fillColor = color.cgColor
}
}
然后像这样使用它：
class DiscussionChatMessageCell: UITableViewCell {
let accentColor: UIColor = .systemYellow
private let messageLabel: UILabel
private let senderNameLabel: UILabel
// use custom BubbleView class instead of standard UIView
private let messageBubble: BubbleView
private var bubbleLeadingConstraint: NSLayoutConstraint!
private var bubbleTrailingConstraint: NSLayoutConstraint!
// wrong signature - I beliee as of Swift 4.2
// 'UITableViewCellStyle' has been renamed to 'UITableViewCell.CellStyle'
//override init(style: UITableViewCellStyle, reuseIdentifier: String?) {
override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
messageLabel = UILabel()
senderNameLabel = UILabel()
messageBubble = BubbleView()
super.init(style: style, reuseIdentifier: reuseIdentifier)
self.contentView.addSubview(messageBubble)
messageBubble.translatesAutoresizingMaskIntoConstraints = false
messageBubble.addSubview(senderNameLabel)
senderNameLabel.translatesAutoresizingMaskIntoConstraints = false
senderNameLabel.numberOfLines = 0
senderNameLabel.lineBreakMode = .byCharWrapping
senderNameLabel.font = UIFont.boldSystemFont(ofSize: 15)
senderNameLabel.textColor = .white
messageBubble.addSubview(messageLabel)
messageLabel.translatesAutoresizingMaskIntoConstraints = false
messageLabel.numberOfLines = 0
messageLabel.lineBreakMode = .byWordWrapping
messageLabel.font = UIFont.systemFont(ofSize: 13)
messageLabel.textColor = .white
// set hugging and compression resistance for Name label
senderNameLabel.setContentCompressionResistancePriority(.required, for: .vertical)
senderNameLabel.setContentHuggingPriority(.required, for: .vertical)
// create bubble Leading and Trailing constraints
bubbleLeadingConstraint = messageBubble.leadingAnchor.constraint(equalTo: self.contentView.leadingAnchor, constant: 10)
bubbleTrailingConstraint = messageBubble.trailingAnchor.constraint(equalTo: self.contentView.trailingAnchor, constant: -10)
// priority will be changed in configureCell()
bubbleLeadingConstraint.priority = .defaultHigh
bubbleTrailingConstraint.priority = .defaultLow
NSLayoutConstraint.activate([
bubbleLeadingConstraint,
bubbleTrailingConstraint,
messageBubble.topAnchor.constraint(equalTo: self.contentView.topAnchor, constant: 10),
messageBubble.bottomAnchor.constraint(equalTo: self.contentView.bottomAnchor, constant: -10),
messageBubble.widthAnchor.constraint(lessThanOrEqualTo: self.contentView.widthAnchor, constant: -100),
senderNameLabel.topAnchor.constraint(equalTo: messageBubble.topAnchor, constant: 10),
senderNameLabel.leadingAnchor.constraint(equalTo: messageBubble.leadingAnchor, constant: 10),
senderNameLabel.trailingAnchor.constraint(equalTo: messageBubble.trailingAnchor, constant: -10),
messageLabel.topAnchor.constraint(equalTo: senderNameLabel.bottomAnchor, constant: 10),
messageLabel.leadingAnchor.constraint(equalTo: messageBubble.leadingAnchor, constant: 10),
messageLabel.trailingAnchor.constraint(equalTo: messageBubble.trailingAnchor, constant: -10),
messageLabel.bottomAnchor.constraint(equalTo: messageBubble.bottomAnchor, constant: -10),
])
// corners will have radius: 10
messageBubble.radius = 10
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
func configureCell(message: String, isSender: Bool) {
senderNameLabel.text = "Default Sender"
messageLabel.text = message
bubbleLeadingConstraint.priority = isSender ? .defaultHigh : .defaultLow
bubbleTrailingConstraint.priority = isSender ? .defaultLow : .defaultHigh
messageBubble.color = isSender ? accentColor : .gray
let senderCorners: UIRectCorner = [.topLeft, .topRight, .bottomRight]
let nonSenderCorners: UIRectCorner = [.topLeft, .topRight, .bottomLeft]
messageBubble.corners = isSender ? senderCorners : nonSenderCorners
}
}
这将保持“气泡”视图的形状和大小，即使单元格发生变化（例如旋转设备时）也是如此。