I've looked at a lot of examples, but somehow they don't work.
My Code Below.
Objects constraints in a custom cell:
Below is the code in the class:
override func viewDidLoad() {
super.viewDidLoad()
tableView.delegate = self
tableView.dataSource = self
view.addSubview(tableView)
tableView.separatorStyle = .none
tableView.estimatedRowHeight = 200
}
//tableview ->
func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
return 340
}
There a couple of things worth addressing:
1. Do not setup your layout in layoutSubviews()
This method will get triggered multiple times everytime there has been a change to the layout made, meaning all of these constraints will be duplicated, and will eventually cause problems. Try to set them in init of the cell.
2. Do not implement heightForRowAt
When implementing this function:
func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
return 340
}
you are telling tableview to give the cell this exact size. According to documentation:
The value returned by this method takes precedence over the value in the rowHeight property.
Remove this code!
3. Set rowHeight to automatic size value
You have already correctly set the estimatedRowHeight value, but we are going to also need the rowHeight property to be set to UITableView.automaticDimension.
tableView.rowHeight = UITableView.automaticDimension
And now you should be good to go!
Bonus: Scrolling Performance improvements
Table view will benefit from any additional information on the size of the cells and you can supply that information with estimatedHeightForRowAt if you are able to calculate a better approximate than the tableView.estimatedRowHeight value you have set in the initial setup.
func tableView(_ tableView: UITableView, estimatedHeightForRowAt indexPath: IndexPath) -> CGFloat {
// return more accurate value here
}
I am new to swift and I have this app in mind that basically needs to update all the cells based on the data received from one of the cells.
I am using dynamic cells and each one has a textfield inside.
TableViewController.swift:
import UIKit
class MyCells: UITableViewCell{
#IBOutlet weak var value_textfield: UITextField!
}
class TableViewController: UITableViewController {
var units_length: [String] = ["Centimeter", "Meter", "Foot"]
override func viewDidLoad() {
super.viewDidLoad()
units_length = units_length.sorted()
self.tableView.keyboardDismissMode = .onDrag
}
override func numberOfSections(in tableView: UITableView) -> Int {
return 1
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return units_length.count
}
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath)
cell.textLabel?.text = units_length[indexPath.row]
cell.textLabel?.textColor = UIColor.white
cell.textLabel?.font = UIFont(name:"DINAlternate-Bold", size:30)
return cell
}
override func viewWillAppear(_ animated: Bool){
tableView.rowHeight = 100
}
}
Which function should I use to access all the cells with different identifiers and simultaneously update all the textfield inside each cell?
I do have access to the textfield by having another class called MyCells, how should I implement it?
(I will not include the base ViewController class here as there's nothing inside)
Thanks!
Normally you use the function you already showed: cellForRowAt. You update your model data, tell the table to reloadData, cellForRowAt is called for all visible cells, and their values become the new values.
However if you are updating after every character, I would set up a notification broadcast situation and update all visible text fields and the model together without a reload. Just make sure the model and the table stay in sync in case the user scrolls and cellForRow is called.
I have UITableView in a test project that is created this way:
class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {
#IBOutlet weak var tableView: UITableView!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
tableView.delegate = self
tableView.dataSource = self
}
// height?
func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
//return cellHeightWithoutSeparator + cellSeparatorHeight
//print("YES!")
return 80 // arbitrary
}
// table wants a UITableViewCell for each row
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath) as! CustomCell
// customize cell here
return cell
}
// how many rows?
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return 50 // arbitrary
}
}
The structure of the table view is:
So, as you can see the cell contains a button.
I want the button (or any clickable view that is a subview of the cell) to respond immediately to the touch-down event and so I unchecked "Delay Touch Down" in the ScrollView property inspector in the storyboard.
It is my understanding that unchecking that box is equivalent to the code:
tableView.delaysContentTouches = false
According to the docs, this method is supposed to work on IOS 2.0+
But setting this property true or false only works as expected on IOS 11 and 12, but on IOS 10 (and presumably earlier), it is as if the box was never unchecked and touches on the button are still delayed.
I understand that it is still possible to make views "clickable" in the cell, and respond immediately to "touch up inside," (because the touch-up event will cancel the delay on the touch-down), but I still want the touch down event to call immediately (on all iOS versions, not just 11+) because:
1) I want the re-order control to respond immediately.
2) I want to have visual feedback for touch-down be normal/immediate on views in the cell.
I have also consulted this similar, but not the same, question which was written 4 years ago, and I tried applying the answers, but none of those answers seem to apply to whatever the modern day reason for this problem is.
Does anyone know the cause and (preferably Swift) solution to this?
I'm making a chat like application, where the tableView displays dynamic height cells.
The cells have their views&subviews constrained in the right way
So that the AutoLayout can predict the height of the cells
(Top, Bottom, Leading, Trailing)
But still - as you can see in the video - the scroll indicator bar shows that wrong heights were calculated:
It recalculates the heights when a new row is appearing.
Video: https://youtu.be/5ydA5yV2O-Q
(On the second attempt to scroll down everything is fine)
Code:
func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
return UITableView.automaticDimension
}
func tableView(_ tableView: UITableView, estimatedHeightForRowAt indexPath: IndexPath) -> CGFloat {
return UITableView.automaticDimension
}
It is a simple problem. Can someone help me out?
Update 1.0
Added github:
https://github.com/krptia/Test
But still - as you can see in the video - the scroll indicator bar shows that wrong heights were calculated:
So what you want is precise content height.
For that purpose, you cannot use static estimatedRowHeight.
You should implement more correct estimation like below.
...
var sampleCell: WorldMessageCell?
override func viewDidLoad() {
super.viewDidLoad()
tableView.register(UINib(nibName: "WorldMessageCell", bundle: nil), forCellReuseIdentifier: "WorldMessageCell")
sampleCell = UINib(nibName: "WorldMessageCell", bundle: nil).instantiate(withOwner: WorldMessageCell.self, options: nil)[0] as? WorldMessageCell
}
...
func tableView(_ tableView: UITableView, estimatedHeightForRowAt indexPath: IndexPath) -> CGFloat {
if let cell = sampleCell {
let text = self.textForRowAt(indexPath)
// note: this is because of "constrain to margins", which value is actually set after estimation. Do not use them to remove below
let margin = UIEdgeInsets(top: 8, left: 20, bottom: 8, right: 20)
// without "constrain to margins"
// let margin = cell.contentView.layoutMargins
let maxSize = CGSize(width: tableView.frame.size.width - margin.left - margin.right,
height: CGFloat.greatestFiniteMagnitude)
let attributes: [NSAttributedString.Key: Any]? = [NSAttributedString.Key.font: cell.messageLabel.font]
let size: CGRect = (text as NSString).boundingRect(with: maxSize,
options: [.usesLineFragmentOrigin], attributes: attributes, context: nil)
return size.height + margin.top + margin.bottom
}
return 100
}
This is too precise (actually real row height) and maybe slow, but you can do more approximate estimation for optimization.
You need to set tableFooterView to empty.
override func viewDidLoad() {
super.viewDidLoad()
tableView.tableFooterView = UIView()
// your staff
}
According to your answer on my comment that when you set
estimatedHeightForRowAt and heightForRowAt the same values it does
work
I can confirm that you are right and that there is the problem that AutoLayout cannot calculate the right value for estimatedHeightForRowAt. So basically there are two possible things to do:
find alternative layout that will produce better results
make your own calculation for estimatedHeightForRowAt which will produce more accurate results (in general you should be able to tell what is expected height per text length and then add margins to that figure - you need to put a bit of effort to find the proper math, but it should work).
The problem is with your estimatedHeightForRowAt method. As the name implies it gives the estimated height to the table so that it can have some idea about the scrollable content until the actual content will be displayed. The more accurate value will result in a more smooth scrolling and height estimation.
You should set this value to big enough so that it can represent the height of your cell with the maximum content. In your case 650 is working fine.
func tableView(_ tableView: UITableView, estimatedHeightForRowAt indexPath: IndexPath) -> CGFloat {
return 650
}
The result would be far better with this approach.
Also, there is no need to implement delegate method for height until you want a variation on index bases. You can simply set table view property.
tableView.estimatedRowHeight = 650.0
tableView.rowHeight = .automaticDimension
Optimization
One more thing I noticed in your demo project. You've used too many if-else in your cellForRowAtIndexPath which is making it little slower. Try to minimize that. I've done some refinement to this, and it improves the performance.
Define an array which holds your message text.
var messages = ["Lorem ipsum,"many more",.....]
Replace your cellForRowAt indexPath with below:
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
var cell : WorldMessageCell
cell = tableView.dequeueReusableCell(withIdentifier: "WorldMessageCell", for: indexPath) as! WorldMessageCell
if indexPath.row < 14 {
cell.messageLabel.text = messages[indexPath.row]
}
else if indexPath.row >= 14 && indexPath.row != 27 {
cell.messageLabel.text = messages[14]
}
else if indexPath.row == 27 {
cell.messageLabel.text = messages.last
}
return cell
}
Just remove highlighted view from UITableView and it's work like a charm.
Hope it helps.
This is expected behaviour when using coarse cell height estimates (or not providing them at all, as you do). The actual height is computed only when the cells come on screen, so the travel of the scroll bar is adjusted at that time. Expect jumpy insertion/deletion animations too, if you use them.
I hope you heard about this a lot. so take short break and come back on desk and apply 2 - 3 steps for step this.
1) Make sure Autolayouts of label of Cell is setup correct like below.
2) UILabel's number of lines set zero for dynamic height of text.
3) setup automatic dimension height of cell.
func tableView(_ tableView: UITableView, estimatedHeightForRowAt indexPath: IndexPath) -> CGFloat {
return UITableView.automaticDimension
}
func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
return UITableView.automaticDimension
}
and I believe its should be work. see results of my code.
why you add view in table view , it can also work without it. I just delete that view and change some constraints(like bottom constraints change safe area to superview) , and it works fine.
see this video
download storyboard and add it to your project and then check
Configure your tableview with these in viewDidLoad()
tableView.estimatedRowHeight = 100.0
tableView.rowHeight = UITableView.automaticDimension
tableView.tableFooterView = UIView()
And you should remove both height datasource method.
What you want to do is eliminate the extra blank cells. You can do so by setting the tableFooterView to an empty UIView in the viewDidLoad method. I cloned the code from your GitHub and revised the method:
override func viewDidLoad() {
super.viewDidLoad()
tableView.register(UINib(nibName: "WorldMessageCell", bundle: nil), forCellReuseIdentifier: "WorldMessageCell")
tableView.tableFooterView = UIView()
}
setting the tableFooterView to nil worked for me as well
tableView.tableFooterView = nil
I am trying to learn swift which is also my first programming language. I am trying learn by creating an app with table view in it. I have added a table view and table cell(myCell as identifier). Table cell in turn has labels and text field. Also the background color of the table cell is yellow.
The view controller which encapsulates all this is hooked to class showDetailViewController as show below.
class showDetailViewController:UIViewController, UITableViewDataSource, UITableViewDelegate {
override func viewDidLoad() {
super.viewDidLoad()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
//UITableViewDataSource
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return 5
}
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
var cell: TaskCell = tableView.dequeueReusableCellWithIdentifier("myCell") as TaskCell
return cell
}
//UITableViewDelegate
func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
}
}
When I run my application I expect to see my cell replicated 5 times (as number of cells in section returns 5) in table view but upon debug I realized that the no tableview delegate class get invoked and hence the issue.
Can anyone please help me with this issue?
Thanks,
Dev
Add the tableView as an IBOutlet.Then you should set tableView's datasource to viewController. self.tableView.dataSource = self. You can also set tableView's dataSource in Interface bulider.