我正在嘗試使用行高和單元格的Autolayout組合來製作可擴展單元格。爲了讓事情變得簡單,我開始用下面簡單的代碼,我預期工作:使用Autolayout的可擴展UITableView單元格導致UIViewAlertForUnsatisiableConstraints
import UIKit
class ViewController: UITableViewController {
let cells = [Cell(), Cell(), Cell()]
override func viewDidLoad() {
super.viewDidLoad()
tableView.rowHeight = UITableViewAutomaticDimension
tableView.estimatedRowHeight = 50
for cell in cells {
cell.tableView = tableView
}
}
override func numberOfSections(in tableView: UITableView) -> Int {
return 1
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return 3
}
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
return cells[indexPath.row]
}
}
class Cell: UITableViewCell {
var cons: NSLayoutConstraint?
var tableView: UITableView?
init() {
super.init(style: .default, reuseIdentifier: nil)
let button = UIButton()
contentView.addSubview(button)
button.addTarget(self, action: #selector(Cell.tapped(_:)), for: .touchUpInside)
button.setTitle("Press me", for: .normal)
button.setTitleColor(.red, for: .normal)
button.translatesAutoresizingMaskIntoConstraints = false
// constraining the button to the view, so that buttons height would define cell height
let constraints = [
button.topAnchor.constraint(equalTo: contentView.topAnchor),
button.rightAnchor.constraint(equalTo: contentView.rightAnchor),
button.bottomAnchor.constraint(equalTo: contentView.bottomAnchor),
button.leftAnchor.constraint(equalTo: contentView.leftAnchor),
]
NSLayoutConstraint.activate(constraints)
cons = button.heightAnchor.constraint(equalToConstant: 100)
cons?.isActive = true
}
func tapped(_ sender: UIButton) {
// change the height of the button, thus of the contentView too (since the button is constrained to the contentView)
if cons?.constant == 100 {
cons?.constant = 200
} else {
cons?.constant = 100
}
// tell the tableView to redraw itself to apply the change
tableView?.beginUpdates()
tableView?.setNeedsDisplay()
tableView?.endUpdates()
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
}
現在,這似乎不過是工作,我還是做得到UIViewAlertForUnsatisfiableConstraints
以下消息警告:
(
"<NSLayoutConstraint:0x17408c7b0 V:|-(0)-[UIButton:0x109e10290'Press me'] (active, names: '|':UITableViewCellContentView:0x109e0fd90)>",
"<NSLayoutConstraint:0x17408c8a0 UIButton:0x109e10290'Press me'.bottom == UITableViewCellContentView:0x109e0fd90.bottom (active)>",
"<NSLayoutConstraint:0x17408c990 UIButton:0x109e10290'Press me'.height == 200 (active)>",
"<NSLayoutConstraint:0x17408db10 'UIView-Encapsulated-Layout-Height' UITableViewCellContentView:0x109e0fd90.height == 100 (active)>"
)
Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x17408c990 UIButton:0x109e10290'Press me'.height == 200 (active)>
似乎估計(或當前)行高與我提供的自動佈局約束相沖突。不過,令人耳目一新使用下面的代碼將顯示爲預期的tableView:
tableView?.beginUpdates()
tableView?.setNeedsDisplay()
tableView?.endUpdates()
如何刪除警告?
我知道簡單的改變高度限制爲999會刪除該警告的優先級,但在我看來,作爲一個黑客刪除它,而不是作爲一種解決方案。如果我錯了,請解釋。謝謝。
變化prority到的高度約束下 –