Should I set cell.bound / cell.frame in UITableView's datasource method?
override func collectionView(collectionView: UICollectionView!, cellForItemAtIndexPath indexPath: NSIndexPath!) -> UICollectionViewCell! {
let cell = collectionView.dequeueReusableCellWithReuseIdentifier("", forIndexPath: indexPath) as CompoundStatementCollectionViewCell
cell.bounds = ..
or implementing sizeForItemAtIndexPath indicates the needed cell size?
You should not set bounds/frame in cellForItemAtIndexPath: the right place to set up the size of the cell is sizeForItemAtIndexPath, you can also use it with insetForSectionAtIndex if you want to set up spacing between cell, header and footer.
Related
I am trying to create simple educational app about movies, and I need to create movie frames horizontal scroller.
I create collection view for that:
But if I build it for another target (iPhone 6s Plus for example), I have this:
How to solve this problem?
My scene controller code (Swift 3):
public func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 4
}
public func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath)
cell.backgroundColor = UIColor.black
// Configure the cell
return cell
}
override func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
return UITableViewAutomaticDimension
}
I think that you can try to implement the method of UICollectionView delegate:
func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
return CGSizeMake(yourHeight, self.view.frame.size.width)
}
in this way, your collectionView-cell inside in tableView will appear as big as the screen.
First I want to say something about UITableViewAutomaticDimension you use, in case you not exactly understand how it works.
Your expectations probably are, that UITableViewAutomaticDimension will infer tableView to make a cell with size of entire tableView, but it doesn't work this way.
UITableViewAutomaticDimension is just infers tableView, that inner size of your cell will be used as a returned here; so if you add some constraints, views with constraints, or whatever inside your tV, its size will be used.
and second - your comment doesn't make sense at all for me, because your posted code isn't related to cell of collectionView and I can't comment anything related to size of its cells
EDITED:
to make all cells with width of your screen, return correct size from delegate method of collectionViewFlowLayout - sizeForItem
I have a weird issue with UICollectionView and UITabBarController. Inside the UITabBarController i have references to two different ViewControllers. If i put View Controller that has UICollectionView as a first page of UITabBarController then my list with cells (UICollectionView) is loading normally like this:
But if i put it as a second View Controller when i open the tab it is like UIImageView and UILabel are disappearing from the cells:
I have checked collectionView method that is getting the cells and there is always data printed for the Label and Image. Here is a code of the methods for DataSource and Delagate
// tell the collection view how many cells to make
func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return self.items.count
}
// make a cell for each cell index path
func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
// get a reference to our storyboard cell
let cell = collectionView.dequeueReusableCellWithReuseIdentifier(reuseIdentifier, forIndexPath: indexPath) as! AdsCollectionViewCell
// Use the outlet in our custom class to get a reference to the UILabel in the cell
cell.myLabel.text = self.items[indexPath.item]
cell.backgroundColor = UIColor.whiteColor() // make cell more visible in our
cell.layer.borderColor = UIColor.grayColor().CGColor
cell.layer.borderWidth = 1
cell.layer.cornerRadius = 8
cell.layoutIfNeeded()
return cell
}
func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
let width = collectionView.frame.width - 22;
return CGSize(width: width/2, height: width/2);
}
// MARK: - UICollectionViewDelegate protocol
func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
// handle tap events
print("You selected cell #\(indexPath.item)!")
}
Is there someone that had problem like this? How can it be solved?
I am trying to make my cell height size fit with label. The thing is that the label text is set in the cellForItemAtIndexPath, and if i have understood correct, sizeForItemAtIndexPath runs before the cellForItemAtIndexPath. This is something i have tried so far:
func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell
{
let imageCell = collectionView.dequeueReusableCellWithReuseIdentifier("imageCell", forIndexPath: indexPath) as? CollectionViewCell
imageCell!.imageText.text = post.text // This set the UICollectionView Cell text
imageCell!.frame.size.height = (imageCell!.frame.size.height) + (imageCell!.imageText.frame.size.height)
return imageCell!
}
I am not using Auto Layout.
Any suggestions why the cell height not changes depending on the label?
This used to be an annoying problem to solve, but it gets substantially easier if you're able to use Auto Layout. See this answer for a thorough walkthrough.
Even if sizeForItemAtIndexPath runs first, that's the place to set the size of the cell. cellForItemAtIndexPath cannot change the size.
In sizeForItemAtIndexPath you need to find out the image size for each cell, then return that size.
Something like this:
func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
let imageCell = collectionView.cellForItemAtIndexPath(indexPath) as! CollectionViewCell
let size = CGSize(width: imageCell.frame.width, height: imageCell.frame.size.height + imageCell.imageText.frame.size.height)
return size
}
Here is an design issue in the app that uses AutoLayout, UICollectionView and UICollectionViewCell that has automatically resizable width & height depending on AutoLayout constraints and its content (some text).
It is a UITableView list like, with each cell that has it's own width & height calculated separately for each row dependant on its content. It is more like iOS Messages build in app (or WhatsUp).
It is obvious that app should make use of func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize.
Issue is that within that method, app cannot call func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell nor dequeueReusableCellWithReuseIdentifier(identifier: String, forIndexPath indexPath: NSIndexPath!) -> AnyObject to instantiate cell, populate it with specific content and calculate its width & height. Trying to do that will result in an indefinite recursion calls or some other type of app crash (at least in iOS 8.3).
The closest way to fix this situation seems to copy definition of the cell into view hierarchy to let Auto-layout resize "cell" automatically (like cell to have the same width as parent collection view), so app can configure cell with specific content and calculate its size. This should definitely not be the only way to fix it because of duplicated resources.
All of that is connected with setting UILabel.preferredMaxLayoutWidth to some value that should be Auto-Layout controllable (not hardcoded) that could depend on screen width & height or at least setup by Auto-layout constraint definition, so app can get multiline UILabel intrinsic size calculated.
I would not like to instantiate cells from XIB file since Storyboards should be today's industry standard and I would like to have as less intervention in code.
EDIT:
The basic code that cannot be run is listed bellow. So only instantiating variable cellProbe (not used) crashes the app. Without that call, app runs smoothly.
var onceToken: dispatch_once_t = 0
class ViewController: UICollectionViewController, UICollectionViewDelegateFlowLayout {
override func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 1
}
func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
dispatch_once(&onceToken) {
let cellProbe = collectionView.dequeueReusableCellWithReuseIdentifier("first", forIndexPath: NSIndexPath(forRow: 0, inSection: 0)) as! UICollectionViewCell
}
return CGSize(width: 200,height: 50)
}
override func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCellWithReuseIdentifier("first", forIndexPath: NSIndexPath(forRow: 0, inSection: 0)) as! UICollectionViewCell
return cell
}
}
If you are using constraints, you don't need to set a size per cell. So you should remove your delegate method func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize
Instead you need to set a size in estimatedItemSize by setting this to a value other than CGSizeZero you are telling the layout that you don't know the exact size yet. The layout will then ask each cell for it's size and it should be calculated when it's required.
let layout = collectionView.collectionViewLayout as! UICollectionViewFlowLayout
layout.estimatedItemSize = someReasonableEstimatedSize()
Just like when dynamically size Table View Cell height using Auto Layout you don't need call
func tableView(_ tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell
in
optional func tableView(_ tableView: UITableView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat
the proper way is create a local static cell for height calculation like a class method of the custom cell
+ (CGFloat)cellHeightForContent:(id)content tableView:(UITableView *)tableView {
static CustomCell *cell;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
cell = [tableView dequeueReusableCellWithIdentifier:[CustomCell cellIdentifier]];
});
Item *item = (Item *)content;
configureBasicCell(cell, item);
[cell setNeedsLayout];
[cell layoutIfNeeded];
CGSize size = [cell.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize];
return size.height + 1.0f; // Add 1.0f for the cell separator height
}
and I seriously doubt storyboard is some industry standard. xib is the best way to create custom cell like view including tableViewCell and CollectionViewCell
To calculate the CollectionView cell's size dynamically, just set the flow layout property to any arbitrary value:
let flowLayout = collectionView.collectionViewLayout as! UICollectionViewFlowLayout
flowLayout.estimatedItemSize = CGSize(width: 0, height: 0)
I've set the width of a cell(UICollectionViewCell) to be equal to the width of the UICollectionView and I'm trying to do exactly the same thing with the UILabel that is included inside that cell. I think the code below explains exactly what I'm trying to achieve. So i've read some question here in SO and also a couple of tutorials but I'm still not sure how I can achieve this.
In a couple of questions it was saying about using collectionViewLayout but I'm really struggling on how to use it within my code. Any ideas? Thank you!
func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
var cell = collectionView.dequeueReusableCellWithReuseIdentifier("myCell", forIndexPath: indexPath) as LocationViewCell
cell.locationLabel.text = "Hello there!"
// Set cell & label width to 100%
let collectionViewWidth = self.collectionView.bounds.size.width
cell.frame.size.width = collectionViewWidth // Works
cell.locationLabel.frame.size.width = collectionViewWidth // Does NOT
Update 1
So I added the following:
func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
// Set cell width to 100%
let collectionViewWidth = self.collectionView.bounds.size.width
return CGSize(width: collectionViewWidth, height: 35)
}
What happens is that when the view is loaded the UILabel's width is still small. If I go to another view and then return back then it's 100%. So I have to do something in the viewDidLoad() right? I'm already using self.collectionView.reloadData() but I guess that's only for data.
Update 2
func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
var cell = collectionView.dequeueReusableCellWithReuseIdentifier("locationCell", forIndexPath: indexPath) as LocationViewCell
cell.locationLabel.text = "Hello UILabel"
// Set cell width to 100%
let collectionViewWidth = self.collectionView.bounds.size.width
cell.frame.size.width = collectionViewWidth
cell.locationLabel.frame.size.width = collectionViewWidth
return cell
}
It doesn't work because by the time this method is called, the collection view already knows how big the cell should be because it has got it from the flow delegate method:
optional func collectionView(_ collectionView: UICollectionView,
layout collectionViewLayout: UICollectionViewLayout,
sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize
This is where you should be setting the size of your cells.