I have a MyCollectionView that has a constraint that is:
BottomLayoutGuide.Top = MyCollectionView.Bottom + 100
In my IB, but this constraint's constant changes according to the height of the keyboard
func keyboardWillShow(notification: NSNotification) {
let keyboardHeight = getKeyboardHeight(notification)
keyboardHeightConstraint.constant = keyboardHeight + 20
self.cardCollectionView.configureCollectionView()
self.cardCollectionView.reloadInputViews()
}
Where configureCollectionView is:
func configureCollectionView() {
self.backgroundColor = UIColor.clearColor()
// Create the layout
let space = 10.0 as CGFloat
let flowLayout = UICollectionViewFlowLayout()
let width = (self.frame.size.width) - 4 * space
let height = (self.frame.size.height)
let edgeInsets = UIEdgeInsetsMake(0, 2 * space, 0, 2 * space)
// Set top and bottom margins if scrolling horizontally, left and right margins if scrolling vertically
flowLayout.minimumLineSpacing = space
flowLayout.minimumInteritemSpacing = 0
// Set horizontal scrolling
flowLayout.scrollDirection = .Horizontal
// Set edge insets
flowLayout.sectionInset = edgeInsets
flowLayout.itemSize = CGSizeMake(width, height)
print(self.frame)
print(flowLayout.itemSize)
self.setCollectionViewLayout(flowLayout, animated: true)
// Always allow it to scroll
self.alwaysBounceHorizontal = true
}
Before the keyboard is shown, everything is fine and these are the values of the frame of MyCollectionView and it's CollectionViewCell
self.frame: (0.0, 75.0, 375.0, 492.0)
flowLayout.itemSize: (335.0, 492.0)
But after the keyboard is shown and configureCollectionView() is called which basically just resets the flowLayout for MyCollectionView everything breaks. And oddly, even though the height of MyCollectionView has decreased the console outputs says that it has actually increased.
self.frame: (0.0, 55.0, 375.0, 512.0)
flowLayout.itemSize: (335.0, 512.0)
Here is a screenshot after the keyboard has appeared:
As you can see, it seems like the CollectionViewCells are being clipped and it has lost it's initial alpha value. Moreover, after randomly scrolling the console outputs:
2016-04-29 09:43:24.012 DeckWheel[15363:2028073] the behavior of the UICollectionViewFlowLayout is not defined because:
2016-04-29 09:43:24.012 DeckWheel[15363:2028073] the item height must be less than the height of the UICollectionView minus the section insets top and bottom values, minus the content insets top and bottom values.
I know that this is due to the height of MyCollectionView changing but, I don't know why it is going wrong as everything works perfectly before the keyboard shows. For example, I can scroll randomly between the cells and if I get to the last cell it will automatically create a new one without any crashes.
I've tried MyCollectionView.invalidateLayout() and then callingconfigureCollectionView() to reset the flowLayout but nothing seems to work. What is the correct way to update MyCollectionView so that this does not happen?
Related
I am using a UICollectionView for chat and using scroll to bottom on load. It's all working good except the first time I scroll manually it bounces up about 50-100 pt. If I continue scrolling it's fine and goes into the safe area and below the screen.
What is causing the initial bounce? It seems that it bounces off the top of the bottom safe area first, and then goes below the safe area fine if you continue scrolling.
What I'm trying to get is a nice smooth scroll initially without the weird bounce.
It seems to be caused by the fact that I am dynamically sizing image heights after they load with invalidateLayout.
I was able to solve this by luck with the following
AutoSizing cells: cell width equal to the CollectionView
// UICollectionViewController
if let layout = collectionView?.collectionViewLayout as? UICollectionViewFlowLayout {
layout.estimatedItemSize = CGSize(width: view.frame.width, height: 100)
}
// UICollectionViewCell
override func preferredLayoutAttributesFitting(_ layoutAttributes: UICollectionViewLayoutAttributes) -> UICollectionViewLayoutAttributes {
let autoLayoutAttributes = super.preferredLayoutAttributesFitting(layoutAttributes)
// Specify you want _full width_
let targetSize = CGSize(width: layoutAttributes.frame.width, height: 200)
// Calculate the size (height) using Auto Layout
let autoLayoutSize = contentView.systemLayoutSizeFitting(targetSize, withHorizontalFittingPriority: UILayoutPriority.required, verticalFittingPriority: UILayoutPriority.defaultLow)
let autoLayoutFrame = CGRect(origin: autoLayoutAttributes.frame.origin, size: autoLayoutSize)
// Assign the new size to the layout attributes
autoLayoutAttributes.frame = autoLayoutFrame
return autoLayoutAttributes
}
Cell contains multiline text so I decided to use text view.
textView.textContainerInset = UIEdgeInsets.zero removes extra padding. Code to center it vertically:
extension UITextView {
func centerVertically() {
var topCorrect = (self.bounds.size.height - self.contentSize.height * self.zoomScale) / 2
topCorrect = topCorrect < 0.0 ? 0.0 : topCorrect;
self.contentInset.top = topCorrect
}
}
This works if I predefine cell height in tableView(_:, heightForRowAt:).
But if I use UITableView.automaticDimension to resize the cell everything becomes broken.
How to solve this issue?
Use auto layout and pin leading, trailing, top and bottom, constraints of textview to the cell.
Disable scrolling in textview
Add a height constraint such that height is greater than or equal to a constant value (this is a min value that will show on the screen) for textview
User .automatic dimension
Try this and let me know if this worked out for you
I have at problem with my cells in a UITableView. I have used the Attribute Inspector to adjust the size. Like this:
But the adjustment only applied on the cells with content. How do I make the separator to be the same size for the whole tableview using Swift or the Attribute Inspector?
For your question, you can try this
tableView.tableFooterView = UIView()
Another way you can do like this.
Then,
In cellForRowAtIndexPath
tableView.separatorStyle = .none
let horizontalGap = 15.0 as CGFloat
// As you want to have equal gaping in left & right side, you have to position the view's origin.x to the constant and have to have the width minus the double of that constant.
let seperatorView = UIView(frame: CGRect(x: horizontalGap, y: cell.frame.size.height - 1, width: cell.frame.size.width - horizontalGap * 2.0, height: 1))
seperatorView.backgroundColor = UIColor.red
cell.addSubview(seperatorView)
In Storyboard
Change Separator as None in Attributes Inspector. Drag UIView and place it inside your cell . Give constraints like, Leading 15, Trailing 15, Bottom 0 and height 1. Change background color to red
I'm looking for a way to replace the native UIPageViewController horizontal paging with a UICollectionView.
so far i did the following:
let layout = UICollectionViewFlowLayout()
layout.scrollDirection = .horizontal
layout.itemSize = collectionView.frame.size
layout.minimumLineSpacing = 0
layout.minimumInteritemSpacing = 10
collectionView.setCollectionViewLayout(layout, animated: false)
collectionView.isPagingEnabled = true
collectionView.alwaysBounceVertical = false
this works fine and i get an horizontal paging effect.
Now i want to add horizontal space between the pages (like u will do with UIPageViewControllerOptionInterPageSpacingKey on UIPageViewController)
so far i couldn't fine a way to add the spaces without damaging the paging effect.
im looking for the same behavior as with the UIPageViewController: the cell should fill the entire screen width, and the space between the cells should only be visible when switching a page.
Solution one:
collectionView.isPagingEnabled = false
add a minimumLineSpacing for the distance between pages
implement targetContentOffsetForProposedContentOffset:withScrollingVelocity: to move the contentOffset to the closest page. You can calculate the page with simple math based on your itemSize and minimumLineSpacing, but it can take a little work to get it right.
Solution Two:
collectionView.isPagingEnabled = true
add a minimumLineSpacing for the distance between pages
the paging size is based on the bounds of the collectionView. So make the collectionView larger then then screenSize. For example, if you have a minimumLineSpacing of 10 then set the frame of the collectionView to be {0,-5, width+10, height}
set a contentInset equal to the minimumLineSpacing to make the first and last item appear correctly.
By default, UICollectionViewFlowLayout's minimumLineSpacing is 10.0, when collectionView's item is horizontally filled (itemSize.width = collectionView.bounds.width) and collectionView is paging enabled, greater than zero 'minimumLineSpacing' will cause an unintended performance: start from second page, every page has a gap which will be accumulated by page number.
It seems that we can expand collectionView's width by 'minimumLineSpacing' to fix this problem. But pratice negates this solution: When there are tow pages or more, collectionView will not give the last one a 'lineSpacing', so it's 'contentSize' is not enough to show this page's content completely, which means if the 'minimumLineSpacing' were 10.0, the last page's end would overstep the collectionView's contentSize by 10.0.
Finally, I use the following simple solution to insert a margin between every item (like UIScrollView's preformance): Expand every collectionViewItem's width by a fixed value 'pageSpacing' (such as 10.0), and expand the collectionView's width by the same value, too. And don't forget that, when layout collevtionViewCell's subviews, there's an additional spacing which is not for diplaying the real content.
Heres the code written in Swift 3.1, I'm sure it's easily understanding for you:
let pageSpacing: CGFloat = 10
class ViewController: UITableViewController {
override func viewDidLoad() {
super.viewDidLoad()
let layout = UICollectionViewFlowLayout()
layout.itemSize = CGSize(width: view.frame.width + pageSpacing, height: view.frame.height)
layout.scrollDirection = .horizontal
layout.minimumInteritemSpacing = 0
layout.minimumLineSpacing = 0
let frame = CGRect(x: 0, y: 0, width: view.frame.width + pageSpacing, height: view.frame.height)
let collectionView = UICollectionView(frame: frame, collectionViewLayout: layout)
view.addSubview(collectionView)
}
}
class MyCell: UICollectionViewCell {
var fullScreenImageView = UIImageView()
override func layoutSubviews() {
super.layoutSubviews()
fullScreenImageView.frame = CGRect(x: 0, y: 0, width: frame.width - pageSpacing, height: frame.height)
}
}
Hope that can help you.
I am using UIScrollView with Auto-layout to change contentSenter code hereize value as following :
UIView
ScrollView
UIView (contentView)
In run time I am adding UITextView & UIImageView to conentView with constraint(Top,Bottom,Left,Right)
but the contentView size is not changing and UIScrollView contentSize also.
So what could be the problem ?
In run time I am adding UITextView & UIImageView to conentView with constraint(Top,Bottom,Left,Right)
Maybe you should add constraint (Top, Left, Height, Width),or (Top, Left, Right, Height)
If you persist in (Top,Bottom,Left,Right), ScrollView will keep the old content size, and make your UITextView & UIImageView (Height = 0, Width = 0).
Here's a neat way of updating scroll view's content size. It's Swift so you'll need a bridging header if you're working in Objective C.
extension UIScrollView {
func updateContentViewSize() {
var newHeight: CGFloat = 0
for view in subviews {
let ref = view.frame.origin.y + view.frame.height
if ref > newHeight {
newHeight = ref
}
}
let oldSize = contentSize
let newSize = CGSize(width: oldSize.width, height: newHeight + 20)
contentSize = newSize
}
}
Just call it on your scroll view's object whenever you add a child view to your scroll view.