I have a collectionView with horizontal UICollectionViewFlowLayout.
I am trying to achieve:
If a device orientation is portrait, UIImageView width will be qual to view.width and let the height be calculated automatically (like it usually happens with Auto Layout). And the same for the landscape mode. Example - standard photo app on the Iphone.
Unfortunately i don't see how to achieve it with autoLayout. I set constraints on UIImageView for it to be equal in size to the cell. But looks like the sell itself cannot be pinned to the Parent View.
After reading similar questions looks like cells must be resized programmatically using
func collectionView(collectionView: UICollectionView,
layout collectionViewLayout: UICollectionViewLayout,
sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
return CGSize(width: width, height: height)
}
And here i am stuck because i know the width of the screen but don't know how to calculate the height dynamically.
About image height:
I have my image declared like this:
var pageImages = [UIImage]()
override func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
let cell: ImageDetailViewCell = collectionView.dequeueReusableCellWithReuseIdentifier(reuseIdentifier, forIndexPath: indexPath) as! ImageDetailViewCell
let curr = indexPath.row
let imgName = data[albumNumber][curr]["image"]
cell.DetailImageView.image = UIImage(named: imgName!)
return cell
}
If you use the proper UIImageView resize setting (say, aspect fit/fill), then you just need to set the cell's height to your collectionView's (you get a pointer to it as one of the ...sizeForItemAtIndexPath... method parameters) height. You also should call the - layoutIfNeeded method on your cell afterwards.
You can use sizeForItemAtIndexPath: to change the size of collection view cell.
func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
var numberOfCellInRow : Int = 3
var padding : Int = 5
var collectionCellWidth : CGFloat = (self.view.frame.size.width/CGFloat(numberOfCellInRow)) - CGFloat(padding)
return CGSize(width: collectionCellWidth , height: collectionCellWidth)
}
You can get the size of cell via :
((UICollectionViewFlowLayout) self.collectionViewName).itemSize.height)
You can get the image size via :
let sizeOfImage = image.size
let height = image.height
If you want to change the height then change it manually by return CGSize(width: collectionCellWidth , height: cellheight)
Related
I have a horizontal collection view.
Each cell has a label and an image.
The problem that I am facing is that when label renders data from the server, sometimes the text is too big and overlaps the image because the width of each cell is fixed.
How can I change the width of the collection View view cell according to the data it contains so that the label does not overlap the image?
CollectionView does have a delegate method which returns cell size.
Please inherit UICollectionViewDelegateFlowLayout and implement the following method.
func collectionView(_ collectionView: UICollectionView,layout collectionViewLayout: UICollectionViewLayout,sizeForItemAt indexPath: IndexPath) -> CGSize {
return CGSize(width: 30, height: 30)
}
You can calculate your label width and return it to the function.
Hope this will help.
Calculate the width of the label text first with the font associated with the text.
extension String {
func size(with font: UIFont) -> CGSize {
let fontAttribute = [NSAttributedString.Key.font: font]
let size = self.size(withAttributes: fontAttribute)
return size
}
}
Return the calculated width along with collectionView height in collectionView(_, collectionViewLayout:_, sizeForItemAt)
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
// Note: Margins are spaces around the cell
// model[indexPath.row].text is the text of label to be shown
let newWidth = model[indexPath.row].text.size(with: labelFont!).width + margins + imageView.width
return CGSize(width: newWidth, height: collectionView.bounds.height)
}
Note:
Don't forgot to confirm your viewController to UICollectionViewDataSource, UICollectionViewDelegateFlowLayout.
I need a collection view which displays cells in a grid. So a standard flow layout is fine for me. However, I want to tell how many cells to show per row, while the cell height should be determined by the autolayout constraints that I put on the cell. Here is my cell layout:
It is quite simple - an image view and two labels below it. Now the image view has an aspect ratio constraint (1:1) which means whenever the width is known for the cell the height should automatically be known by the auto layout rules (there are vertical constraints going through: celltop-image-label1-label2-cellbottom).
Now, since I don't know any other good way to tell the collection view to show 2 items per row, I have overridden UICollectionViewDelegateFlowLayout methods:
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
let availableWidth = collectionView.frame.width - padding
let widthPerItem = availableWidth / itemsPerRow
return CGSize(width: widthPerItem, height: widthPerItem)
}
As you can see, since I don't know the item height I return the same thing as the width, hoping that the autolayout will fix it later. I also set the estimatedItemSize in order the whole mechanism to start working.
The results are quite strange - it seems like the collection view doesn't event take into account the width I return there, mostly depending on the label lengths:
I have seen some other answers where people recommend manually calculating the cell size for width, like telling "layout yourself, then measure yourself, then give me your size for this width", and even though it would still run the autolayout rules under the hood, I would like to know if there is a way of doing this without manually messing with the sizes.
You can easily find out the height of your collectionView cell in the storyboard's Size inspector, as shown below:
Now, just pick up this height from here, and pass it to the overridden UICollectionViewDelegateFlowLayout method:
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
let availableWidth = collectionView.frame.width - padding
let widthPerItem = availableWidth / itemsPerRow
return CGSize(width: widthPerItem, height: **114**)
}
And you will get the desired output.
I ended up implementing a trick to move everything to autolayout. I completely removed the delegate method func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize and added a width constraint for my cell content in the interface builder (set the initial value to something, that's not important). Then, I created an outlet for that constraint in the custom cell class:
class MyCell: UICollectionViewCell {
#IBOutlet weak var cellContentWidth: NSLayoutConstraint!
func updateCellWidth(width: CGFloat) {
cellContentWidth.constant = width
}
}
Later, when the cell is created, I update the width constraint to the precalculated value according to the number of cells that I want per row:
private var cellWidth: CGFloat {
let paddingSpace = itemSpacing * (itemsPerRow - 1) + sectionInsets.left + sectionInsets.right
let availableWidth = collectionView.frame.width - paddingSpace
return availableWidth / itemsPerRow
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "MyCell", for: indexPath) as! MyCell
...
cell.updateCellWidth(width: cellWidth)
return cell
}
And this, together with autolayout cell sizing enabled, will lay out the cells correctly.
I have a collectionview covering the whole screen. I want to use the collectionview so that all cells are visible at the same time which means that the height gets set dynamically. And as a plus: It should work in portrait and landscape.
In the past I solved it like this:
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize
{
let heightOffset = (UIDevice.current.orientation.isPortrait) ? CGFloat(30) : CGFloat(0)
let width = UIScreen.main.bounds.width
let height = UIScreen.main.bounds.height - heightOffset
return CGSize(width: width, height: height / CGFloat(mainScreenItems.count))
}
But on iPhoneX I get problems, because the offset is not correct. Even if I take the height of the collectionview frame it doesn't work correctly.
I want to use collection view for show user's instagram photos like Tinder. I placed a collectionview and enabled paging. But i don't know how to show 6 photos for each page. How can i do this?
This is what i want:
First page:
Second Page:
I used all spacing settings zero because setting spacing from storyboard problem for different screen sizes.
My collection view's settings and result:
Result:
So i want to show 6 photos per page. How to achive this?
To show the specific number of cells you want, you have to calculate the size of the cells. Something like this:
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
let numberOfRows = 2
let numberOfColumns = 3
let height = collectionView.frame.size.height / numberOfRows
let width = collectionView.frame.size.width / numberOfColumns
let cellSize = CGSize(width: width, height: height)
return cellSize
}
Since your layout configuration is static you can calculate it just once to make it faster:
class MyVC: UIViewController {
private let cellSize: CGSize = CGSize(width: collectionView.frame.width/numberOfColumns, height: collectionView.frame.height/numberOfRows) // or create a computed property
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return cellSize
}
}
This code is untested, maybe you have to add some padding but you get the idea. Another option would be to implement your own UICollectionViewLayout subclass
Im currently attempting to calculate the height of a UICollectionViewCell dynamically but using a UILabel (the dynamic property) and the current height of the cell. The height is calculated by getting height for sizeThatFits of the label within the cell and adding that value to the original height of the cell. For some reason this always returns 0 in sizeForItemAt. I'm pretty sure the problem is the size is being calculated before the cell is created thus will always return 0. Is there anyway around this? (The UI for the cell is created within the class itself, not at celllForItemAt could that also be a problem?)
var descHeight: CGFloat = 0
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "desc", for: indexPath) as! ImageDescCell
descHeight = cell.descriptionLbl.sizeThatFits(cell.frame.size).height + cell.bounds.height
return cell
}
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
let w = collectionView.bounds.width
return CGSize(width: w, height: descHeight)
}
NSAttributedString can tell you how big an instance is, given a bound. So assuming you know how wide the label is and you know what the text is and what its attributes are you can get the size without ever creating a label:
let width = CGFloat(200)
let attributedString = NSAttributedString(string: "Test", attributes: [NSFontAttributeName : UIFont(name: "Helvetica", size: 18)!])
let boundingRect = attributedString.boundingRect(with: CGSize(width: width, height: CGFloat.greatestFiniteMagnitude), options: [.usesLineFragmentOrigin, .usesFontLeading], context: nil)
swift-3.0
func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize
{
let width = self.collectionView.frame.size.width
let Height = self.view.frame.size.height - 64 // 64 is a navigation bar height minus.
let cellSize:CGSize = CGSize(width: width, height: Height )
return cellSize
}