UITableView在更改出现排队后影响单元格高度的约束时发生UITableView,最终以破坏的约束结束
此代码块试图解决问题的核心问题。如果在将一个单元格出队后(通过configure
)更改了约束条件,以便更改单元格高度,那么最终会出现损坏的约束警告(Unable to simultaneously satisfy constraints
...)。但是,它显示正确。UITableView在更改出现排队后影响单元格高度的约束时发生UITableView,最终以破坏的约束结束
import UIKit
class ViewController: UIViewController {
@IBOutlet var tableView: UITableView!
override func viewDidLoad() {
super.viewDidLoad()
tableView.delegate = self
tableView.dataSource = self
tableView.registerClass(Cell.self, forCellReuseIdentifier: "cell")
tableView.estimatedRowHeight = 55.0
tableView.rowHeight = UITableViewAutomaticDimension
}
}
extension ViewController: UITableViewDelegate, UITableViewDataSource {
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return array.count
}
func numberOfSectionsInTableView(tableView: UITableView) -> Int {
return 1
}
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("cell") as! Cell
cell.configure(array[indexPath.row])
return cell
}
func tableView(tableView: UITableView, willDisplayCell cell: UITableViewCell, forRowAtIndexPath indexPath: NSIndexPath) {
}
}
enum Position {
case Top
case Middle
case Bottom
}
class Cell: UITableViewCell {
private var topConstraint: NSLayoutConstraint!
private var bottomConstraint: NSLayoutConstraint!
private let label = UILabel()
private var previous: Position?
override init(style: UITableViewCellStyle, reuseIdentifier: String?) {
super.init(style: style, reuseIdentifier: reuseIdentifier)
label.backgroundColor = UIColor.redColor().colorWithAlphaComponent(0.5)
label.textColor = UIColor.blackColor()
label.translatesAutoresizingMaskIntoConstraints = false
contentView.addSubview(label)
label.leadingAnchor.constraintEqualToAnchor(contentView.leadingAnchor, constant: 30).active = true
label.trailingAnchor.constraintEqualToAnchor(contentView.trailingAnchor, constant: -30).active = true
topConstraint = label.topAnchor.constraintEqualToAnchor(contentView.topAnchor)
topConstraint.active = true
bottomConstraint = label.bottomAnchor.constraintEqualToAnchor(contentView.bottomAnchor)
bottomConstraint.active = true
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
func configure(position: Position) {
if previous != nil {print("previous \(previous!) new \(position)")}
topConstraint.constant = position == .Top ? 30 : 0
bottomConstraint.constant = position == .Bottom ? -30 : 0
label.text = String(position)
previous = position
}
}
let array: [Position] = [.Top, .Middle, .Middle, .Middle, .Bottom,
.Top, .Middle, .Middle, .Middle, .Middle, .Bottom,
.Top, .Middle, .Middle, .Bottom,
.Top, .Middle, .Middle, .Middle, .Middle, .Middle, .Middle, .Bottom,
.Top, .Middle, .Middle, .Middle, .Bottom,
.Top, .Bottom,
.Top, .Middle, .Middle, .Middle, .Middle, .Middle, .Middle, .Bottom,
.Top, .Middle, .Middle, .Middle, .Bottom,
.Top, .Middle, .Middle, .Bottom,
.Top, .Middle, .Middle, .Middle, .Middle, .Middle, .Middle, .Bottom,
]
错误消息是...
2016-04-28 22:56:29.831 test-constraint-change[51059:3776208] Unable to simultaneously satisfy constraints.
Probably at least one of the constraints in the following list is one you don't want.
Try this:
(1) look at each constraint and try to figure out which you don't expect;
(2) find the code that added the unwanted constraint or constraints and fix it.
(
"<NSLayoutConstraint:0x7c117c70 V:|-(30)-[UILabel:0x7c148770'Middle'] (Names: '|':UITableViewCellContentView:0x7c149b70)>",
"<NSLayoutConstraint:0x7c115bd0 UILabel:0x7c148770'Middle'.bottom == UITableViewCellContentView:0x7c149b70.bottom>",
"<NSLayoutConstraint:0x7c14a3f0 'UIView-Encapsulated-Layout-Height' V:[UITableViewCellContentView:0x7c149b70(20.5)]>"
)
Will attempt to recover by breaking constraint <NSLayoutConstraint:0x7c115bd0 UILabel:0x7c148770'Middle'.bottom == UITableViewCellContentView:0x7c149b70.bottom>
Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.
设置你的约束优先级999就像现在,它会正确显示。
感谢您的回复......我确信这会做到这一点。但感觉有点哈克。希望找到一个干净的方式来做到这一点。 (我也可以忽略这些警告) –
这是您最干净的解决方案,并且与自动布局的工作方式有关。使用自动调整表格单元格,系统隐式添加高度约束('UIView-Encapsulated-Layout-Height')。设置优先级允许自动布局优雅地解决这些冲突。请参阅:https://www.raywenderlich.com/87975/dynamic-table-view-cell-height-ios-8-swift –
好的,我认为这只与动态高度有关。我们也注意到与宽度完全相同的问题(不同的场景)。尽可能多的解决方案,仍然感觉像一个自动布局的错误。你怎么看? –
你得到的错误是什么?请向我们展示确切的堆栈跟踪和错误消息。 – ozgur
完成,但3个约束没有任何技术上的错误。当时,他们应该强制细胞高度变大(细胞高度是动态的)。该单元正在从“中”向“顶”类型发展。 –