问题
I have a UIView which is reusable via a nib/xib-file. I want to load this and fill a UITableViewCell which is to be used in a self-resizing UITableView. All with auto-layout.
Most works good, but It seems as the loaded UIView uses the added constraints around it to shrink the UITableViewCell's contentView. This is good for the height, but I don't want this for the width.
Ignore the grey cell below, this is just a selected cell.
public func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell
{
let cellId = "RowView0002"
var cell = tableView.dequeueReusableCell(withIdentifier: cellId)
if cell == nil {
cell = UITableViewCell(style: UITableViewCellStyle.default, reuseIdentifier: cellId)
let subView = RowView(frame: cell!.frame)
cell!.contentView.attachViewWithConstraints(subView)
let _ = subView.viewLoadedFromNibAttached(name: cellId)
}
return cell!
}
override public func viewDidLoad() {
super.viewDidLoad()
tableView.delegate = self
tableView.dataSource = self
tableView.estimatedRowHeight = 40.0
tableView.rowHeight = UITableViewAutomaticDimension
}
extension UIView
{
public func attachViewWithConstraints(_ view:UIView)
{
addSubview(view)
view.translatesAutoresizingMaskIntoConstraints = false
view.layoutAttachAll(to: self)
}
@discardableResult
public func viewLoadedFromNibAttached<T : UIView>(name:String) -> T? {
guard let view = Bundle.main.loadNibNamed(name, owner: self, options: nil)?[0] as? T else {
return nil
}
attachViewWithConstraints(view)
return view
}
public func layoutAttachAll(to childView:UIView)
{
var constraints = [NSLayoutConstraint]()
childView.translatesAutoresizingMaskIntoConstraints = false
constraints.append(NSLayoutConstraint(item: childView, attribute: .left, relatedBy: .equal, toItem: self, attribute: .left, multiplier: 1.0, constant: 0))
constraints.append(NSLayoutConstraint(item: childView, attribute: .right, relatedBy: .equal, toItem: self, attribute: .right, multiplier: 1.0, constant: 0))
constraints.append(NSLayoutConstraint(item: childView, attribute: .top, relatedBy: .equal, toItem: self, attribute: .top, multiplier: 1.0, constant: 0))
constraints.append(NSLayoutConstraint(item: childView, attribute: .bottom, relatedBy: .equal, toItem: self, attribute: .bottom, multiplier: 1.0, constant: 0))
childView.addConstraints(constraints)
}
In RowView0002.xib I have set the rootviews background to red, added a UILabel with 4 constraints to it's sides with some margin as you can see. I both tried to set the rootView to the class RowView as well as it's File's Owner. Both "works".
Any idea how to get the contentView to match the UITableView?
*Edit 1: The green is the background of the UILabel. The red is the background of the nib-file. After running the app the View heirarcy is: UITableViewCell > ContentView > RowView > NibFileView (red) > UILabel (green)
Inspecting the view hierarchy shows that all constraints is setup as expected. However the UITableViewContentView have constraints that match the total size seen (wrong):
self.width = 156.5 @ 1000
回答1:
A full implementation of layoutAttachAll is below.
Some usage examples first:
// pin all edge to superview
myView.layoutAttachAll()
// pin all edges (to superview) with margin:
myView.layoutAttachAll(margin: 8.0)
// for child views: pin leading edge to superview's leading edge:
myView.layoutAttachLeading()
// for sibling views: pin leading edge to siblingView's trailing edge:
myView.layoutAttachLeading(to: siblingView)
// for sibling views: pin top edge to siblingView's bottom edge:
myView.layoutAttachTop(to: siblingView)
Note: myView must be added as a subview before attaching to superview using these methods. Also, all participating views must be set with translatesAutoresizingMaskIntoConstraints = false.
The full implementation:
import UIKit
extension UIView {
/// attaches all sides of the receiver to its parent view
func layoutAttachAll(margin : CGFloat = 0.0) {
let view = superview
layoutAttachTop(to: view, margin: margin)
layoutAttachBottom(to: view, margin: margin)
layoutAttachLeading(to: view, margin: margin)
layoutAttachTrailing(to: view, margin: margin)
}
/// attaches the top of the current view to the given view's top if it's a superview of the current view, or to it's bottom if it's not (assuming this is then a sibling view).
/// if view is not provided, the current view's super view is used
@discardableResult
func layoutAttachTop(to: UIView? = nil, margin : CGFloat = 0.0) -> NSLayoutConstraint {
let view: UIView? = to ?? superview
let isSuperview = view == superview
let constraint = NSLayoutConstraint(item: self, attribute: .top, relatedBy: .equal, toItem: view, attribute: isSuperview ? .top : .bottom, multiplier: 1.0, constant: margin)
superview?.addConstraint(constraint)
return constraint
}
/// attaches the bottom of the current view to the given view
@discardableResult
func layoutAttachBottom(to: UIView? = nil, margin : CGFloat = 0.0, priority: UILayoutPriority? = nil) -> NSLayoutConstraint {
let view: UIView? = to ?? superview
let isSuperview = (view == superview) || false
let constraint = NSLayoutConstraint(item: self, attribute: .bottom, relatedBy: .equal, toItem: view, attribute: isSuperview ? .bottom : .top, multiplier: 1.0, constant: -margin)
if let priority = priority {
constraint.priority = priority
}
superview?.addConstraint(constraint)
return constraint
}
/// attaches the leading edge of the current view to the given view
@discardableResult
func layoutAttachLeading(to: UIView? = nil, margin : CGFloat = 0.0) -> NSLayoutConstraint {
let view: UIView? = to ?? superview
let isSuperview = (view == superview) || false
let constraint = NSLayoutConstraint(item: self, attribute: .leading, relatedBy: .equal, toItem: view, attribute: isSuperview ? .leading : .trailing, multiplier: 1.0, constant: margin)
superview?.addConstraint(constraint)
return constraint
}
/// attaches the trailing edge of the current view to the given view
@discardableResult
func layoutAttachTrailing(to: UIView? = nil, margin : CGFloat = 0.0, priority: UILayoutPriority? = nil) -> NSLayoutConstraint {
let view: UIView? = to ?? superview
let isSuperview = (view == superview) || false
let constraint = NSLayoutConstraint(item: self, attribute: .trailing, relatedBy: .equal, toItem: view, attribute: isSuperview ? .trailing : .leading, multiplier: 1.0, constant: -margin)
if let priority = priority {
constraint.priority = priority
}
superview?.addConstraint(constraint)
return constraint
}
}
回答2:
It looks like the problem is that the cell created with UITableViewCell(style: UITableViewCellStyle.default, reuseIdentifier: cellId) has no information about the width of the table view, so it is sizing itself based on the width of the label. Apparently the table view / cell don't force the cell's content view to take its width.
You probably want to rework some of this cell-handling code.
If you want to load your cell from a xib, you can skip everything with constraints. Just implement:
override func viewDidLoad() {
//...
let nib = UINib(nibName: "RowView0002", bundle: NSBundle.main)
tableView.reigsterNib(nib, forCellReuseIdentifier: "RowView0002")
}
Very important: The first top level item in the .xib file must be a UITableViewCell. Nibs are UIViews by default, delete the view in IB and drag a UITableViewCell from the object library in the lower-right of IB. Then if necessary set its subclass to a UITableViewCell subclass that you created. (You might also need to set the reuseIdentifier in IB.)
Then in tableView(_:cellForRowAt IndexPath:):
guard let cell = tableView.dequeueResuableCell(withIdentifier: "RowView0002", for: indexPath) as? TheNibUITableViewSubclass else { //something went wrong, probably crash }
cell.label.text = //...
return cell
You probably will want to put that "RowView0002" in a constant somewhere.
If the "RowView0002" and the RowView class both need to be views, you should probably create a subclass of UITableViewCell. Override just init(style:resueIdentifier:) and after callingsuper` add your subviews in the code above. Hope this helps!
回答3:
I solved it by also adding a width constraint matching the tableViews width. This is code from CustomTableViewCell:
public override func layoutSubviews() {
super.layoutSubviews()
if let width = tableView()?.frame.width, !haveAddedWidthConstraint {
haveAddedWidthConstraint = true
rowView.addWidthConstraint(width: width)
}
}
UIViewExtension:
public func addWidthConstraint(width: CGFloat) {
let widthConstraint = NSLayoutConstraint(item: self, attribute: .width, relatedBy: .greaterThanOrEqual, toItem: nil, attribute: .notAnAttribute, multiplier: 1.0, constant: width)
widthConstraint.priority = 1000
addConstraint(widthConstraint)
}
UITableViewCellExtension:
func tableView() -> UITableView? {
var currentView: UIView = self
while let superView = currentView.superview {
if superView is UITableView {
return (superView as! UITableView)
}
currentView = superView
}
return nil
}
来源：https://stackoverflow.com/questions/41851892/nib-file-loaded-uiview-in-uitableviewcell-does-not-stretch