Can you get a UITableView's intrinsic content size to update based on the number of rows shown if scrolling is disabled? - swift

Question

We have a portion of our UI which is a small list of labels with color swatches next to them. The design I'm taking over has six of these hard-coded in the layout even though the actual data is dynamic, meaning if we only need to show three, we have to explicitly hide three, which also throws off the balance of the page. Making matters worse is each one of those 'items' is actually made up of several sub-views so a screen with six hard-coded items has eighteen IBOutlets.
What I'm trying to do is to instead use a UITableView to represent this small portion of the screen, and since it won't scroll, I was wondering if you can use AutoLayout to configure the intrinsic content height of the UITableView to be based on the number of rows.
Currently I have a test page with a UITableView vertically constrained to the center, but without a height constraint because I am hoping to have the table's intrinsic content size reflect the visible rows. I have also disabled scrolling on the table. When I reload the table, I call updateConstraints. But the table still does not resize.
Note: We can't use a UIStackView (which would have been perfect for this) because we have to target iOS8 and that wasn't introduced until iOS9, hence this solution.
Has anyone been able to do something similar to our needs?

Answer 1

Ok, so unlike UITextView, it doesn't look like UITableView ever returns an intrinsic size based on the visible rows. But that's not that big a deal to implement via a subclass, especially if there's a single section, no headers or footers, and the rows are of a fixed height.
class AutoSizingUiTableView : UITableView
{
override func intrinsicContentSize() -> CGSize
{
let requiredHeight = rowCount * rowHeight
return CGSize(width: UIView.noIntrinsicMetric, height: CGFloat(requiredHeight))
}
}
I'll leave it up to the reader to figure out how to get their own rowCount. The same if you have variable heights, multiple sections, etc. You just need more logic.
By doing this, it works great with AutoLayout. I just wish it handled this automatically.

Answer 2

// Define this puppy:
class AutoTableView: UITableView {
override func layoutSubviews() {
super.layoutSubviews()
self.invalidateIntrinsicContentSize()
}
override var intrinsicContentSize: CGSize {
get {
var height:CGFloat = 0;
for s in 0..<self.numberOfSections {
let nRowsSection = self.numberOfRows(inSection: s)
for r in 0..<nRowsSection {
height += self.rectForRow(at: IndexPath(row: r, section: s)).size.height;
}
}
return CGSize(width: UIView.noIntrinsicMetric, height: height)
}
set {
}
}
}
and make it your class in IB.
obs: this is if your class is only cells and shit. if it has header, footer or some other thign, dunno. it'll not work. for my purposes it works
peace

Answer 3

This can be done, please see below for a very simple (and rough - rotation does not work properly!) example, which allows you to update the size of the table view by entering a number in the text field and resetting with a button.
import UIKit
class ViewController: UIViewController {
var tableViewController : FlexibleTableViewController!
var textView : UITextView!
var button : UIButton!
var count : Int! {
didSet {
self.refreshDataSource()
}
}
var dataSource : [Int]!
let rowHeight : CGFloat = 50
override func viewDidLoad() {
super.viewDidLoad()
// Configure
self.tableViewController = FlexibleTableViewController(style: UITableViewStyle.plain)
self.count = 10
self.tableViewController.tableView.backgroundColor = UIColor.red
self.textView = UITextView()
self.textView.textAlignment = NSTextAlignment.center
self.textView.textColor = UIColor.white
self.textView.backgroundColor = UIColor.blue
self.button = UIButton()
self.button.setTitle("Reset", for: UIControlState.normal)
self.button.setTitleColor(UIColor.white, for: UIControlState.normal)
self.button.backgroundColor = UIColor.red
self.button.addTarget(self, action: #selector(self.updateTable), for: UIControlEvents.touchUpInside)
self.layoutFrames()
// Assemble
self.view.addSubview(self.tableViewController.tableView)
self.view.addSubview(self.textView)
self.view.addSubview(self.button)
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
func refreshDataSource() -> Void {
if let _ = self.dataSource {
if !self.dataSource.isEmpty {
self.dataSource.removeAll()
}
}
else
{
self.dataSource = [Int]()
}
for count in 0..<self.count {
self.dataSource.append(count)
}
self.tableViewController.dataSource = self.dataSource
self.tableViewController.tableView.reloadData()
if let _ = self.view {
self.layoutFrames()
self.view.setNeedsDisplay()
}
}
func updateTable() -> Void {
guard let _ = self.textView.text else { return }
guard let validNumber = Int(self.textView.text!) else { return }
self.count = validNumber
}
func layoutFrames() -> Void {
if self.tableViewController.tableView != nil {
self.tableViewController.tableView.frame = CGRect(origin: CGPoint(x: self.view.frame.width / 2 - 100, y: 100), size: CGSize(width: 200, height: CGFloat(self.dataSource.count) * self.rowHeight))
NSLog("\(self.tableViewController.tableView.frame)")
}
if self.textView != nil {
self.textView.frame = CGRect(origin: CGPoint(x: 50, y: 100), size: CGSize(width: 100, height: 100))
}
if self.button != nil {
self.button.frame = CGRect(origin: CGPoint(x: 50, y: 150), size: CGSize(width: 100, height: 100))
}
}
}
class FlexibleTableViewController : UITableViewController {
var dataSource : [Int]!
override init(style: UITableViewStyle) {
super.init(style: style)
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
override func numberOfSections(in tableView: UITableView) -> Int {
return 1
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return self.dataSource.count
}
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
self.tableView.register(UITableViewCell.self, forCellReuseIdentifier: "cell")
let cell = tableView.dequeueReusableCell(withIdentifier: "cell") ?? UITableViewCell()
cell.frame = CGRect(origin: CGPoint(x: 10, y: 5), size: CGSize(width: 180, height : 40))
cell.backgroundColor = UIColor.green
return cell
}
}
Whether it is a good idea or not, is, as has been pointed out, another question! Hope that helps!

Answer 4

Version from no_ripcord accounting for header and footer height
final // until proven otherwise
class IntrinsicallySizedTableView: UITableView {
override func layoutSubviews() {
super.layoutSubviews()
self.invalidateIntrinsicContentSize()
}
override var intrinsicContentSize: CGSize {
guard let dataSource = self.dataSource else {
return super.intrinsicContentSize
}
var height: CGFloat = (tableHeaderView?.intrinsicContentSize.height ?? 0)
+ contentInset.top + contentInset.bottom
if let footer = tableFooterView {
height += footer.intrinsicContentSize.height
}
let nsections = dataSource.numberOfSections?(in: self) ?? self.numberOfSections
for section in 0..<nsections {
let sectionheader = rectForHeader(inSection: section)
height += sectionheader.height
let sectionfooter = rectForFooter(inSection: section)
height += sectionfooter.height
let nRowsSection = self.numberOfRows(inSection: section)
for row in 0..<nRowsSection {
height += self.rectForRow(at: IndexPath(row: row, section: section)).size.height
}
}
return CGSize(width: UIView.noIntrinsicMetric, height: height)
}
}