I would like to understand why setting clipsToBounds/masksToBounds to False have no impact on UICollectionViewCell subviews (in my case its UILabel).
I tried any possible solution with clipsToBounds/masksToBounds (although I think under the hood they behave/do the same).
override open func layoutSubviews() {
super.layoutSubviews()
super.clipsToBounds = false
super.layer.masksToBounds = false
self.clipsToBounds = false
self.layer.masksToBounds = false
self.contentView.clipsToBounds = false
self.contentView.layer.masksToBounds = false
self.contentView.superview?.clipsToBounds = false
self.contentView.superview?.layer.masksToBounds = false
self.endTime.layer.masksToBounds = false
self.endTime.clipsToBounds = false
self.endTime.layer.zPosition = CGFloat(FLT_MAX)
}
I do override UICollectionViewLayout according to Custom layout from raywenderlich
override public func prepare() {
if cache.isEmpty {
let columnWidth = contentWidth / CGFloat(numberOfColumns)
var xOffset = [CGFloat]()
for column in 0 ..< numberOfColumns {
xOffset.append(CGFloat(column) * columnWidth )
}
let column = 0
var yOffset = [CGFloat](repeating: 0, count: numberOfColumns)
for item in 0 ..< collectionView!.numberOfItems(inSection: 0) {
let indexPath = NSIndexPath(row: item, section:0)
let frame = CGRect(x: xOffset[column], y: yOffset[column], width: cellSize.width, height: cellSize.height)
let insetFrame = frame.insetBy(dx: cellPaddingX, dy: cellPaddingY)
let attributes = UICollectionViewLayoutAttributes(forCellWith: indexPath as IndexPath)
attributes.frame = insetFrame
cache.append(attributes)
contentHeight = max(contentHeight, frame.maxY)
yOffset[column] = yOffset[column] + cellSize.height + minimumLineSpacing
}
}
}
public override var collectionViewContentSize: CGSize {
return CGSize(width: contentWidth, height: contentHeight)
}
override open func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
var layoutAttributes = [UICollectionViewLayoutAttributes]()
for attributes in cache {
if attributes.frame.intersects(rect) {
layoutAttributes.append(attributes)
}
}
return layoutAttributes
}
Result:
The red vertical line indicates "Unavailable" its starts from one cell and may finish in another (depends on time duration).
From the UI Debug its seems that each next cell always on the top of previous one.(The 21:00 cell is the only one that looks as I want)
Possible Duplicates:
A
B
Related
I used the Pinterest layout file provided from Ray Wenderlich and I implemented the desired layout for cells perfectly, however on a CollectionViewController where I am adding a custom header, I want to add the Pinterest layer below the custom header.
But the Pinterest layer is overriding the custom header and I can no longer find the custom header.
Any suggestion on how I can solve this would be greatly appreciated.
The Pinterest Layout file is below:
import UIKit
protocol CustomLayoutDelegate: class {
// 1. Method to ask the delegate for the height of the image
func collectionView(_ collectionView:UICollectionView, heightForPhotoAtIndexPath indexPath:IndexPath) -> CGFloat
}
class CustomLayout: UICollectionViewFlowLayout {
//1. Pinterest Layout Delegate
weak var delegate: CustomLayoutDelegate!
//2. Configurable properties
fileprivate var numberOfColumns = 2
fileprivate var cellPadding: CGFloat = 5
//3. Array to keep a cache of attributes.
fileprivate var cache = [UICollectionViewLayoutAttributes]()
//4. Content height and size
fileprivate var contentHeight: CGFloat = 0
fileprivate var contentWidth: CGFloat {
guard let collectionView = collectionView else {
return 0
}
let insets = collectionView.contentInset
return collectionView.bounds.width - (insets.left + insets.right)
}
override var collectionViewContentSize: CGSize {
return CGSize(width: contentWidth, height: contentHeight)
}
override func prepare() {
// 1. Only calculate once
guard cache.isEmpty == true, let collectionView = collectionView else {
return
}
// 2. Pre-Calculates the X Offset for every column and adds an array to increment the currently max Y Offset for each column
let columnWidth = contentWidth / CGFloat(numberOfColumns)
var xOffset = [CGFloat]()
for column in 0 ..< numberOfColumns {
xOffset.append(CGFloat(column) * columnWidth)
}
var column = 0
var yOffset = [CGFloat](repeating: 0, count: numberOfColumns)
// 3. Iterates through the list of items in the first section
for item in 0 ..< collectionView.numberOfItems(inSection: 0) {
let indexPath = IndexPath(item: item, section: 0)
// 4. Asks the delegate for the height of the picture and the annotation and calculates the cell frame.
let photoHeight = delegate.collectionView(collectionView, heightForPhotoAtIndexPath: indexPath)
let height = cellPadding * 2 + photoHeight
let frame = CGRect(x: xOffset[column], y: yOffset[column], width: columnWidth, height: height)
let insetFrame = frame.insetBy(dx: cellPadding, dy: cellPadding)
// 5. Creates an UICollectionViewLayoutItem with the frame and add it to the cache
let attributes = UICollectionViewLayoutAttributes(forCellWith: indexPath)
attributes.frame = insetFrame
cache.append(attributes)
// 6. Updates the collection view content height
contentHeight = max(contentHeight, frame.maxY)
yOffset[column] = yOffset[column] + height
column = column < (numberOfColumns - 1) ? (column + 1) : 0
}
}
override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
var visibleLayoutAttributes = [UICollectionViewLayoutAttributes]()
// Loop through the cache and look for items in the rect
for attributes in cache {
if attributes.frame.intersects(rect) {
visibleLayoutAttributes.append(attributes)
}
}
return visibleLayoutAttributes
}
override func layoutAttributesForItem(at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
return cache[indexPath.item]
}
}
You have to append an attributes for your header before append the first item
Beside that set the yOffset first start from your Header Height
var yOffset = [yourHeaderHeight, yourHeaderHeight]
Add this code between section after the indexPath in section 3
if item == 0 {
let headerAttributes = UICollectionViewLayoutAttributes(forSupplementaryViewOfKind: UICollectionElementKindSectionHeader, with: indexPath)
headerAttributes.frame = CGRect(x: 0, y: 0, width: yourHeaderWidth, height: yourHeaderHeight)
cache.append(headerAttributes)
}
I followed this tutorial: https://www.raywenderlich.com/164608/uicollectionview-custom-layout-tutorial-pinterest-2
and came up with the following code.
My question is now, how I can center the items of my collection view. Every item has a different height. (I have vertical scrolling enabled.)
class DynamicLayout: UICollectionViewFlowLayout {
var delegate: DynamicLayoutDelegate?
var numberOfColumns = 2
fileprivate var cellPadding: CGFloat = 6
fileprivate var contentHeight: CGFloat = 0
var xOffset = 0
fileprivate var contentWidth: CGFloat {
guard let c = collectionView else { return 0 }
return c.bounds.width - (c.contentInset.left + c.contentInset.right)
}
fileprivate var cache = [UICollectionViewLayoutAttributes]()
override func shouldInvalidateLayout(forBoundsChange newBounds: CGRect) -> Bool {
return true
}
override func prepare() {
guard cache.isEmpty == true, let collectionView = collectionView else { return }
// let columnWidth = contentWidth / CGFloat(numberOfColumns)
let columnWidth = CGFloat(310)
var xOffset = [CGFloat]()
for column in 0 ..< numberOfColumns {
xOffset.append(CGFloat(column) * columnWidth)
}
var column = 0
var yOffset = [CGFloat](repeating: 0, count: numberOfColumns)
// 3. Iterates through the list of items in the first section
for item in 0 ..< collectionView.numberOfItems(inSection: 0) {
let indexPath = IndexPath(item: item, section: 0)
// 4. Asks the delegate for the height of the picture and the annotation and calculates the cell frame.
let cellHeight = delegate?.collectionView(collectionView, heightFor: indexPath)
let height = cellPadding * 2 + cellHeight!
let frame = CGRect(x: xOffset[column], y: yOffset[column], width: columnWidth, height: height)
// let totalCellWidth = CGFloat(310 * numberOfColumns)
// let totalSpacingWidth = cellPadding * CGFloat(numberOfColumns - 1)
// let leftInset = (collectionView.frame.width - CGFloat(totalCellWidth + totalSpacingWidth)) / 2
// let leftInset = collectionView.frame.width - 310 / 2
let insetFrame = frame.insetBy(dx: cellPadding, dy: cellPadding)
// 5. Creates an UICollectionViewLayoutItem with the frame and add it to the cache
let attributes = UICollectionViewLayoutAttributes(forCellWith: indexPath)
attributes.frame = insetFrame
cache.append(attributes)
// 6. Updates the collection view content height
contentHeight = max(contentHeight, frame.maxY)
yOffset[column] = yOffset[column] + height
column = column < (numberOfColumns - 1) ? (column + 1) : 0
}
}
override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
var visibleLayoutAttributes = [UICollectionViewLayoutAttributes]()
// Loop through the cache and look for items in the rect
for attributes in cache {
if attributes.frame.intersects(rect) {
visibleLayoutAttributes.append(attributes)
}
}
return visibleLayoutAttributes
}
override func layoutAttributesForItem(at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
return cache[indexPath.item] }
}
protocol DynamicLayoutDelegate: class {
func collectionView(_ collectionView:UICollectionView, heightFor indexPath:IndexPath) -> CGFloat
}
The problem is, that I don't want to have empty space below and above smaller cells.
Screenshot of the problem:
I'm trying to create a custom UICollectionViewFlowLayout where items can be displayed either vertically or horizontally (see below)
Vertical:
|S|S|S|
|1|4|7|
|2|5|8|
|3|6|9|
Horizontal:
|S|1|2|3|
|S|4|5|6|
|S|7|8|9|
However, I cannot seem to get the vertical layout to work properly. The horizontal layout works just fine but every time I want to use the vertical layout it just crashes with the following error:
*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'UICollectionView received layout attributes for a cell with an index path that does not exist: <NSIndexPath: 0x7ffcf597fa60> {length = 2, path = 1 - 6}'
When I use the same data and force it to use the horizontal layout it works just fine which leads me to believe I'm doing something wrong with the layout attributes.
My custom flow layout class:
import UIKit
class CustomCollectionViewLayout: UICollectionViewFlowLayout {
var horizontalInset = 0.0 as CGFloat
var verticalInset = 0.0 as CGFloat
var minimumItemWidth = 0.0 as CGFloat
var maximumItemWidth = 0.0 as CGFloat
var itemHeight = 0.0 as CGFloat
var itemWidth = 0.0 as CGFloat
var initialItemSizeSet: Bool = false
var _layoutAttributes = Dictionary<String, UICollectionViewLayoutAttributes>()
var _contentSize = CGSize.zero
var transposed: Bool
init(transposed: Bool) {
self.transposed = transposed
super.init()
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
override func prepare() {
super.prepare()
_layoutAttributes = Dictionary<String, UICollectionViewLayoutAttributes>()
_layoutAttributes.removeAll()
let path = IndexPath(item: 0, section: 0)
let attributes = UICollectionViewLayoutAttributes(forSupplementaryViewOfKind: UICollectionElementKindSectionHeader, with: path)
let headerHeight = CGFloat(self.itemHeight / 4)
attributes.frame = CGRect(x: 0, y: 0, width: self.collectionView!.frame.size.width, height: headerHeight)
let headerKey = layoutKeyForHeaderAtIndexPath(path)
_layoutAttributes[headerKey] = attributes
let numberOfSections = (self.collectionView!.numberOfSections)-1
var yOffset = headerHeight
var xOffset = self.horizontalInset
var largestNumberOfItems = 0
for section in 0...numberOfSections {
let numberOfItems = self.collectionView!.numberOfItems(inSection: section)
if(numberOfItems > largestNumberOfItems){
largestNumberOfItems = numberOfItems
}
for item in 0...numberOfItems {
let indexPath = IndexPath(item: item, section: section)
let attributes = UICollectionViewLayoutAttributes(forCellWith: indexPath)
var itemSize = CGSize.zero
//Every cell has a fixed size
if(!initialItemSizeSet){
self.itemWidth = 75
self.itemHeight = 75
initialItemSizeSet = true
}
itemSize.width = itemWidth
itemSize.height = itemHeight
attributes.frame = CGRect(x: xOffset, y: yOffset, width: itemSize.width, height: itemSize.height).integral
print("Created frame with xOffset \(xOffset), yOffset \(yOffset), width \(itemSize.width) and height \(itemSize.height)")
let key = layoutKeyForIndexPath(indexPath)
print("Attached indexPath key: \(key)")
_layoutAttributes[key] = attributes
if transposed {
yOffset += itemSize.height
yOffset += self.verticalInset
}else {
xOffset += itemSize.width
xOffset += self.horizontalInset
}
}
//After going through all items in section, check if current section is not the last section
if !(section == numberOfSections) {
if transposed {
//Increase xOffset for correct horizontal placement
xOffset += self.horizontalInset
xOffset += self.itemWidth
//Reset yOffset for correct spacing between cells
yOffset = self.verticalInset
}else {
//Increase yOffset for correct vertical placement
yOffset += self.verticalInset
yOffset += self.itemHeight
//Reset xOffset for correct spacing between cells
xOffset = self.horizontalInset
}
print("Finished adding items in section \(section), xOffset: \(xOffset), yOffset: \(yOffset)")
}else{
if transposed {
yOffset = self.verticalInset
}else {
xOffset = self.horizontalInset
}
}
}
if transposed {
xOffset += self.itemWidth
}else {
yOffset += self.itemHeight
}
//Calculate size of content based on largest number of items in the sections
print("xOffset: \(xOffset), yOffset: \(yOffset)")
if transposed {
_contentSize = CGSize(width: xOffset + self.horizontalInset, height: (CGFloat(largestNumberOfItems) * (itemHeight + yOffset)))
}else {
_contentSize = CGSize(width: (CGFloat(largestNumberOfItems) * (itemWidth + xOffset)), height: yOffset + self.verticalInset)
}
print("content size :\(_contentSize)")
}
func changeItemSize(_ newWidth: CGFloat, newHeight: CGFloat){
self.itemHeight = newHeight
self.itemWidth = newWidth
}
func changeInset(_ newHorizontalInset: CGFloat, newVerticalInset: CGFloat){
self.horizontalInset = newHorizontalInset
self.verticalInset = newVerticalInset
}
func layoutKeyForIndexPath(_ indexPath : IndexPath) -> String {
return "\(indexPath.section)_\(indexPath.row)"
}
func layoutKeyForHeaderAtIndexPath(_ indexPath : IndexPath) -> String {
return "s_\(indexPath.section)_\(indexPath.row)"
}
override var collectionViewContentSize : CGSize {
return _contentSize
}
override func layoutAttributesForSupplementaryView(ofKind elementKind: String, at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
let headerKey = layoutKeyForIndexPath(indexPath)
return _layoutAttributes[headerKey]
}
override func layoutAttributesForItem(at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
let key = layoutKeyForIndexPath(indexPath)
return _layoutAttributes[key]
}
override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
let predicate = NSPredicate { [unowned self] (evaluatedObject, bindings) -> Bool in
let layoutAttribute = self._layoutAttributes[evaluatedObject as! String]
return rect.intersects(layoutAttribute!.frame)
}
let dict = _layoutAttributes as NSDictionary
let keys = dict.allKeys as NSArray
let matchingKeys = keys.filtered(using: predicate)
return dict.objects(forKeys: matchingKeys, notFoundMarker: NSNull()) as? [UICollectionViewLayoutAttributes]
}
}
So it turns out that the cause of the crash was me forgetting that the number of items returned by the collectionview's numberOfItems(inSection) was not zero-based. I didn't think to look there because the horizontal layout handled this inconsistency fine for some unknown reason.
I'm trying to implement a horizontal aligned CollectionView with centered cells and I'm using a custom UICollectionViewFlowLayout. I found several solutions with UICollectionViewDelegateFlowLayout but the delegate is not called, if you use a custom UICollectionViewFlowLayout.
Here is my UICollectionViewFlowLayout. Any ideas what to do?
class MyFlowLayout: UICollectionViewFlowLayout {
var numberOfRows = 1
var cellPadding: CGFloat = 15.0
var availableSize = CGSize.zero
fileprivate var cache = [UICollectionViewLayoutAttributes]()
fileprivate var contentWidth: CGFloat = 0.0
fileprivate var contentHeight: CGFloat {
var collectionViewHeight = collectionView!.bounds.height
if availableSize.height > 0{
collectionViewHeight = availableSize.height
}
let insets = collectionView!.contentInset
return collectionViewHeight - (insets.top + insets.bottom)
}
func reInit(_ newSize: CGSize){
availableSize = newSize
cache.removeAll()
}
override func prepare() {
if cache.isEmpty {
let rowHeight = contentHeight / CGFloat(numberOfRows)
var yOffset = [CGFloat]()
for row in 0 ..< numberOfRows {
yOffset.append(CGFloat(row) * rowHeight )
}
var row = 0
var xOffset = [CGFloat](repeating: 0, count: numberOfRows)
for item in 0 ..< collectionView!.numberOfItems(inSection: 0) {
let indexPath = IndexPath(item: item, section: 0)
let height = rowHeight
let width = CGFloat(height / 1.27)
let frame = CGRect(x: xOffset[row], y: yOffset[row], width: width, height: height)
let insetFrame = frame.insetBy(dx: cellPadding * 2, dy: cellPadding)
let attributes = UICollectionViewLayoutAttributes(forCellWith: indexPath)
attributes.frame = insetFrame
cache.append(attributes)
contentWidth = max(contentWidth, frame.maxX)
xOffset[row] = xOffset[row] + width
row = row >= (numberOfRows - 1) ? 0 : (row + 1)
}
}
}
override var collectionViewContentSize : CGSize {
return CGSize(width: contentWidth, height: contentHeight)
}
override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
var layoutAttributes = [UICollectionViewLayoutAttributes]()
for attributes in cache {
if attributes.frame.intersects(rect) {
layoutAttributes.append(attributes)
}
}
return layoutAttributes
}
}
The layout is connected this way:
collectionView.collectionViewLayout = MyFlowLayout()
collectionView.register(MyCell.self, forCellWithReuseIdentifier: MyCell.identifier)
collectionView.dataSource = self
Prepare in MyFlowLayout is called.
I've created a custom data grid. It's based on collection view with custom layout. The layout modifies the first section and row attributes making them sticky, so when the user scrolls other rows and sections should go under the sticky ones. The idea for this layout is not mine, I've just adopted it. (I can't give the credits for the real creator, in my research I found so many variations of the layout that I'm not sure which is the original one).
Unfortunately I'm facing a problem with it. I'm getting a crash when scrolling:
*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'no
UICollectionViewLayoutAttributes instance for
-layoutAttributesForItemAtIndexPath:
Despite the message I think that the real problem is in layoutAttributesForElements method. I've read some threads with a similar problem, but the only working solution is to return all cached attributes, no matter of the passed rectangle. I just don't like quick and dirty solutions like this. I would really appreciate any ideas/solutions you can give me.
The whole project is here. However the most important is the layout so for convenience here it is:
class GridViewLayout: UICollectionViewLayout {
//MARK: - Setup
private var isInitialized: Bool = false
//MARK: - Attributes
var attributesList: [[UICollectionViewLayoutAttributes]] = []
//MARK: - Size
private static let defaultGridViewItemHeight: CGFloat = 47
private static let defaultGridViewItemWidth: CGFloat = 160
static let defaultGridViewRowHeaderWidth: CGFloat = 200
static let defaultGridViewColumnHeaderHeight: CGFloat = 80
static let defaultGridViewItemSize: CGSize =
CGSize(width: defaultGridViewItemWidth, height: defaultGridViewItemHeight)
// This is regular cell size
var itemSize: CGSize = defaultGridViewItemSize
// Row Header Size
var rowHeaderSize: CGSize =
CGSize(width: defaultGridViewRowHeaderWidth, height: defaultGridViewItemHeight)
// Column Header Size
var columnHeaderSize: CGSize =
CGSize(width: defaultGridViewItemWidth, height: defaultGridViewColumnHeaderHeight)
var contentSize : CGSize!
//MARK: - Layout
private var columnsCount: Int = 0
private var rowsCount: Int = 0
private var includesRowHeader: Bool = false
private var includesColumnHeader: Bool = false
override func prepare() {
super.prepare()
rowsCount = collectionView!.numberOfSections
if rowsCount == 0 { return }
columnsCount = collectionView!.numberOfItems(inSection: 0)
// make header row and header column sticky if needed
if self.attributesList.count > 0 {
for section in 0..<rowsCount {
for index in 0..<columnsCount {
if section != 0 && index != 0 {
continue
}
let attributes : UICollectionViewLayoutAttributes =
layoutAttributesForItem(at: IndexPath(forRow: section, inColumn: index))!
if includesColumnHeader && section == 0 {
var frame = attributes.frame
frame.origin.y = collectionView!.contentOffset.y
attributes.frame = frame
}
if includesRowHeader && index == 0 {
var frame = attributes.frame
frame.origin.x = collectionView!.contentOffset.x
attributes.frame = frame
}
}
}
return // no need for futher calculations
}
// Read once from delegate
if !isInitialized {
if let delegate = collectionView!.delegate as? UICollectionViewDelegateGridLayout {
// Calculate Item Sizes
let indexPath = IndexPath(forRow: 0, inColumn: 0)
let _itemSize = delegate.collectionView(collectionView!,
layout: self,
sizeForItemAt: indexPath)
let width = delegate.rowHeaderWidth(in: collectionView!,
layout: self)
let _rowHeaderSize = CGSize(width: width, height: _itemSize.height)
let height = delegate.columnHeaderHeight(in: collectionView!,
layout: self)
let _columnHeaderSize = CGSize(width: _itemSize.width, height: height)
if !__CGSizeEqualToSize(_itemSize, itemSize) {
itemSize = _itemSize
}
if !__CGSizeEqualToSize(_rowHeaderSize, rowHeaderSize) {
rowHeaderSize = _rowHeaderSize
}
if !__CGSizeEqualToSize(_columnHeaderSize, columnHeaderSize) {
columnHeaderSize = _columnHeaderSize
}
// Should enable sticky row and column headers
includesRowHeader = delegate.shouldIncludeHeaderRow(in: collectionView!)
includesColumnHeader = delegate.shouldIncludeHeaderColumn(in: collectionView!)
}
isInitialized = true
}
var column = 0
var xOffset : CGFloat = 0
var yOffset : CGFloat = 0
var contentWidth : CGFloat = 0
var contentHeight : CGFloat = 0
for section in 0..<rowsCount {
var sectionAttributes: [UICollectionViewLayoutAttributes] = []
for index in 0..<columnsCount {
var _itemSize: CGSize = .zero
switch (section, index) {
case (0, 0):
switch (includesRowHeader, includesColumnHeader) {
case (true, true):
_itemSize = CGSize(width: rowHeaderSize.width, height: columnHeaderSize.height)
case (false, true): _itemSize = columnHeaderSize
case (true, false): _itemSize = rowHeaderSize
default: _itemSize = itemSize
}
case (0, _):
if includesColumnHeader {
_itemSize = columnHeaderSize
} else {
_itemSize = itemSize
}
case (_, 0):
if includesRowHeader {
_itemSize = rowHeaderSize
} else {
_itemSize = itemSize
}
default: _itemSize = itemSize
}
let indexPath = IndexPath(forRow: section, inColumn: index)
let attributes = UICollectionViewLayoutAttributes(forCellWith: indexPath)
attributes.frame = CGRect(x: xOffset,
y: yOffset,
width: _itemSize.width,
height: _itemSize.height).integral
// allow others cells to go under
if section == 0 && index == 0 { // top-left cell
attributes.zIndex = 1024
} else if section == 0 || index == 0 {
attributes.zIndex = 1023 // any ohter header cell
}
// sticky part - probably just in case here
if includesColumnHeader && section == 0 {
var frame = attributes.frame
frame.origin.y = collectionView!.contentOffset.y
attributes.frame = frame
}
if includesRowHeader && index == 0 {
var frame = attributes.frame
frame.origin.x = collectionView!.contentOffset.x
attributes.frame = frame
}
sectionAttributes.append(attributes)
xOffset += _itemSize.width
column += 1
if column == columnsCount {
if xOffset > contentWidth {
contentWidth = xOffset
}
column = 0
xOffset = 0
yOffset += _itemSize.height
}
}
attributesList.append(sectionAttributes)
}
let attributes = self.attributesList.last!.last!
contentHeight = attributes.frame.origin.y + attributes.frame.size.height
self.contentSize = CGSize(width: contentWidth,
height: contentHeight)
}
override var collectionViewContentSize: CGSize {
return self.contentSize
}
override func layoutAttributesForItem(at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
var curLayoutAttribute: UICollectionViewLayoutAttributes? = nil
if indexPath.section < self.attributesList.count {
let sectionAttributes = self.attributesList[indexPath.section]
if indexPath.row < sectionAttributes.count {
curLayoutAttribute = sectionAttributes[indexPath.row]
}
}
return curLayoutAttribute
}
override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
var attributes: [UICollectionViewLayoutAttributes] = []
for section in self.attributesList {
let filteredArray = section.filter({ (evaluatedObject) -> Bool in
return rect.intersects(evaluatedObject.frame)
})
attributes.append(contentsOf: filteredArray)
}
return attributes
}
override func shouldInvalidateLayout(forBoundsChange newBounds: CGRect) -> Bool {
return true
}
//MARK: - Moving
override func layoutAttributesForInteractivelyMovingItem(at indexPath: IndexPath,
withTargetPosition position: CGPoint) -> UICollectionViewLayoutAttributes {
guard let dest = super.layoutAttributesForItem(at: indexPath as IndexPath)?.copy() as? UICollectionViewLayoutAttributes else { return UICollectionViewLayoutAttributes() }
dest.transform = CGAffineTransform(scaleX: 1.4, y: 1.4)
dest.alpha = 0.8
dest.center = position
return dest
}
override func invalidationContext(forInteractivelyMovingItems targetIndexPaths: [IndexPath],
withTargetPosition targetPosition: CGPoint,
previousIndexPaths: [IndexPath],
previousPosition: CGPoint) -> UICollectionViewLayoutInvalidationContext {
let context = super.invalidationContext(forInteractivelyMovingItems: targetIndexPaths,
withTargetPosition: targetPosition,
previousIndexPaths: previousIndexPaths,
previousPosition: previousPosition)
collectionView!.dataSource?.collectionView?(collectionView!,
moveItemAt: previousIndexPaths[0],
to: targetIndexPaths[0])
return context
}
}
Implement layoutAttributesForItemAtIndexPath. As per the documentation, "Subclasses must override this method and use it to return layout information for items in the collection view. ".
In my experience this method is normally not called when running in the simulator but can be called on the device. YMMV.