Adding views programmatically into tableView cells making scroll jerky and slow. I am adding views programmatically into cell in the delegate function "CellForRowAt". I tried it through delegate function "WillDisplay" but the results are the same.
What is the best possible solution to achieve this?
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier:
"cell", for: indexPath) as! CustomCell
addViewsInCell(cell: cell, indexPath: indexPath)
return cell
}
func addViewsInCell(cell: CustomCell, indexPath: IndexPath) {
//here i am adding some views programmatically
for i in 0..<3 {
let customView: CustomView = Bundle.main.loadNibNamed("CustomView", owner: self, options: nil)![0] as! customView
cell.customViewPlacement.addSubview(customView)
}
}
Cell views are reused. Adding a subview every time in cellForRowAt indexPath: you end up with multiple copies of the same subview. Instead you should check whether that subview is already added. You could mark your subview with a tag and then use the viewWithTag method to test its presence.
Don't add any subviews/custom views inside tableView: cellForRowAt indexPath:. This will cause those subviews to be added repeatedly whenever that cell loaded by the table view. Instead create a subclass of UITableViewCell and create your subviews inside that subclass if you are working programmatically. Or else if you are working with storyboards, you can create a dynamic prototype cell.
Related
I have a UITableView that uses a cell that has 3 expandable and collapsable subviews in them. I would prefer to maintain the state of these views in my UITableViewCell class itself (states as in collapsed or expanded)
Since they are reusable cells, currently, if I expand view 1 in cell A, and then scroll down to cell B, it's view 1 will be expanded. I don't want this. I want it collapsed. But, if I scroll back up to cell A, I want it to still be expanded.
Other than storing all of these states in an array or dictionary
var expandedViewOneCells: [Int] = []
var expandedViewTwoCells: [Int] = []
etc.
I would prefer to have the cells essentially of act individually and maintain their own state... But how would I do this when cells are reused? Keep in mind, I will always only have at most 3 of these kinds of cells, so can I set something like only reuse after 3 cells.
Would it be wise to keep an array of the cells I load, and then on cellForRowAt load the cell from that array based on the index and return it?
In your func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell function try not to deque a cell but create a new instance of your cell
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = MyCustomCell()
return cell
}
If you are loading your cell from a xib file you need a way to create your custom cell from that nib. Add the following method to your CustomCell class
static func loadFromNib() -> RequestTableViewCell {
let nib = UINib(nibName: "\(MyCustomCell.self)", bundle: Bundle.main)
let cell = nib.instantiate(withOwner: self, options: nil)[0] as! MyCustomCell
return cell
}
Then in your func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell this will create a new cell for every row and not reuse a cell when scrolling
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = MyCustomCell.loadFromNib()
return cell
}
A solution like this may not be optimal if your table view has a lot of rows but for a SMALL amount of rows this should be okay
I see 2 solutions to your problem:
Use 3 View Controllers. They should never get destroyed, and add / remove the corresponding VC's view on top of the .contentView of the cell as it appears or goes off-screen. See the solution here http://khanlou.com/2015/04/view-controllers-in-cells/ The Custom Cell itself is just a view, shouldn't really be concerned with the state, but if we move that logic to a View Controller - we should be fine, an we are not violating MVC. Plus, the View Controller can keep track of the height of the view, based on the state, and heightForRow(at:) can ask it for that
I'd use a Stack View as this is a perfect scenario for it. I'd probably represent the Cell itself as another stack view. Not sure exactly what the views look like and how they change, but it may end up as simple as hiding / unhiding the second view from the Stack View that represent a "cell".
public func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = UITableViewCell(style: UITableViewCellStyle.default, reuseIdentifier: "approve_cell");
let event = self.events[indexPath.row];
cell.textLabel?.text = event.name;
return cell;
}
I placed 2 images and a label in tableviewcell. When i run the app, images are not visible. What could be the reason?
Check that you are not using the basic style of the UITableViewCell because if you are then that style only includes labels.. no image views. Change it to subtitle or one of the details.
For reference, see: https://developer.apple.com/library/content/documentation/UserExperience/Conceptual/TableView_iPhone/TableViewCells/TableViewCells.html
You probably forgot to set AutoLayoutConstraints of your image view. You could either add constraints to that image view through storyboard or through code. The other method is setting the frame of your image view in -(void)viewDidLayoutSubviews, because when you're using auto-layout, the layout of those views will be undefined if its constraints doesn't fulfill system's computing need. So you should either set right constraints or give a specific frame to those undefined views after all of the others has-constraints-views are arranged.
You creat cell in storyboard but you never use this cell created from storyboard. instead you manually creat it by UITableViewCell's designated initializer without override layout method of it.
public func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "approve_cell", for: indexPath)
let event = self.events[indexPath.row];
cell.textLabel?.text = event.name;
return cell;
}
You need to set either Autolayout or used Autoresizing. For autolayout just pinned the proper leading, trailing, top and bottom constraint.
I created two ViewControllers and two TableViews. Then i added prototype cell to one TableView, set it up according to my needs, copied it to the other TableView, changed its class and identifier and linked it up in ViewController that is datasource and delegate for each one.
The problem is, FEEDING one is behaving good, having constraints as expected, and the WALKING one is not, but i have no idea why since they have all same properties in each one's:
ViewControllers:
FEEDING
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = myFeedingTableView.dequeueReusableCellWithIdentifier("feedingcell", forIndexPath: indexPath) as! FeedingCell
cell.time.text = self.vremena[indexPath.row]
return cell
}
WALKING
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = myWalkingTableView.dequeueReusableCellWithIdentifier("walkingcell", forIndexPath: indexPath) as! WalkingCell
cell.time.text = self.vremena[indexPath.row]
return cell
}
CustomCell files
each one is connected to its class
FeedingCell is class of feeding prototype cell
WalkingCell is class of feeding prototype cell
Constraints
and the constraints are same, as you can see on the picture.
Here is the image providing different results and constraints:
image
Solved by changing rowHeight settings in TableView. Thanks #SilentLupin
Cells Overlapping
I used custom class for UITableViewCell. It look fine
but the debug view Hierarchy cells is overlapping as image above.
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier(self.reuseIdentify, forIndexPath: indexPath) as! ContactViewCell
cell.lbContactName.text = self.dataSource[indexPath.row]
return cell
}
Please check the custom UITableviewCell Clip Subviews property.
Having a UITableViewControllerand using:
override func tableView(tableView: UITableView, cellForRowAtIndexPath
indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("reuseIdentifier", forIndexPath: indexPath) as! UITableViewCell
return cell
}
Using dequeueReusableCellWithIdentifier:forIndexPath:'' instead ofdequeueReusableCellWithIdentifier`` how can I determine if a cell is a new one or a reused one?
Create your own custom cell class to use for the reuse identifier. Then, inside that cell, implement awakeFromNib and make your changes to the cell. This will only be called once when your cell is loaded from its NIB file.
Any other changes that need to be made when the cell is reused can be made in prepareForReuse.