添加顶部和底部约束会导致 UILabel 被压扁
Adding top and bottom constraints causes UILable to be squished
我以编程方式创建了一个自定义 UITableViewCell 并尝试在其中垂直居中放置两个 UILabel。但是 UILabel 最终被压扁了。在 Interface Builder 中使用原型单元执行相同的操作效果很好。我的代码有什么问题?
自定义视图单元格class
import UIKit
class TopViewCell: UITableViewCell {
let df: DateFormatter = {
let df = DateFormatter()
df.dateFormat = NSLocalizedString("DATE_WEEKDAY", comment: "show date and weekday")
return df
}()
var dateLabel: UILabel = {
let label = UILabel()
label.translatesAutoresizingMaskIntoConstraints = false
return label
}()
var costLabel: UILabel = {
let label = UILabel()
label.translatesAutoresizingMaskIntoConstraints = false
return label
}()
override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
super.init(style: style, reuseIdentifier: reuseIdentifier)
let margin = contentView.layoutMarginsGuide
contentView.addSubview(dateLabel)
dateLabel.leadingAnchor.constraint(equalTo: margin.leadingAnchor).isActive = true
dateLabel.topAnchor.constraint(equalTo: margin.topAnchor).isActive = true
dateLabel.bottomAnchor.constraint(equalTo: margin.bottomAnchor).isActive = true
contentView.addSubview(costLabel)
costLabel.trailingAnchor.constraint(equalTo: margin.trailingAnchor).isActive = true
costLabel.topAnchor.constraint(equalTo: dateLabel.topAnchor).isActive = true
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
override func layoutSubviews() {
dateLabel.text = df.string(from: Date())
costLabel.text = "total: five thousand"
}
}
自定义 UITableViewController class
import UIKit
class ItemViewController: UITableViewController {
var itemStore: ItemStore!
override func viewDidLoad() {
super.viewDidLoad()
tableView.register(TopViewCell.self, forCellReuseIdentifier: "top_cell")
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return itemStore.allItems.count + 1
}
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
var cell: UITableViewCell!
if indexPath.row == 0 {
cell = tableView.dequeueReusableCell(withIdentifier: "top_cell", for: indexPath)
} else {
cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath)
cell.textLabel?.text = itemStore.allItems[indexPath.row - 1].name
cell.textLabel?.font = cell.textLabel!.font.withSize(30)
cell.detailTextLabel?.text = "$\(itemStore.allItems[indexPath.row - 1].valueInDolloar)"
}
return cell
}
}
您的 TopViewCell
无法正确自动调整大小,因为您正在 layoutSubviews()
中设置文本。将这两行移动到 init
,它的大小将正确:
override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
super.init(style: style, reuseIdentifier: reuseIdentifier)
let margin = contentView.layoutMarginsGuide
contentView.addSubview(dateLabel)
dateLabel.leadingAnchor.constraint(equalTo: margin.leadingAnchor).isActive = true
dateLabel.topAnchor.constraint(equalTo: margin.topAnchor).isActive = true
dateLabel.bottomAnchor.constraint(equalTo: margin.bottomAnchor).isActive = true
contentView.addSubview(costLabel)
costLabel.trailingAnchor.constraint(equalTo: margin.trailingAnchor).isActive = true
costLabel.topAnchor.constraint(equalTo: dateLabel.topAnchor).isActive = true
// set the text here
dateLabel.text = df.string(from: Date())
costLabel.text = "total: five thousand"
}
作为旁注,您应该在使用 TopViewCell
时指定 class:
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
if indexPath.row == 0 {
let cell = tableView.dequeueReusableCell(withIdentifier: "top_cell", for: indexPath) as! TopViewCell
return cell
}
let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath)
cell.textLabel?.text = itemStore.allItems[indexPath.row - 1].name
cell.textLabel?.font = cell.textLabel!.font.withSize(30)
cell.detailTextLabel?.text = "$\(itemStore.allItems[indexPath.row - 1].valueInDolloar)"
return cell
}
作为另一个旁注...您可以在故事板中创建两个原型单元格。