IBPCollectionViewCompositionalLayout

Fix different behavior with above iOS 13 when set UIScrollViewContentInsetAdjustmentNever #150

Backport of UICollectionViewCompositionalLayout to earlier iOS 12.

A new UICollectionViewCompositionalLayout class has been added to UIKit to make it incredibly easier to create custom complex collection view layout. You can use new excellent APIs immediately without maintaining two different code bases until iOS 13 would be widely adopted.

Note: that this library is still currently under active development. Please file all bugs, issues, and suggestions as an Issue in the GitHub repository.

What is Collection View Compositional Layouts?

At the WWDC 2019, Apple introduced a new form of UICollectionViewLayout. A new UICollectionViewCompositionalLayout class has been added to UIKit to make it easier to create compositional layouts without requiring a custom UICollectionViewLayout.

In iOS 12 and earlier, we need subclassing of UICollectionViewLayout to do that. We have to override lots of methods correctly, and it is error-prone.

With Collection View Compositional Layouts, you can make very complex layout even nested collection views with independently scrolling sections just within few lines of code.

Screenshots

Nested Group	Orthogonal Scroll	Orthogonal Scroll

List	Grid	Inset Grid	Column

Distinct Sections	Badges	Nested Groups

Mosaic	Tile Grid	Banner Tile Grid	Portlait Tile Grid

Usage

Copy IBPCollectionViewCompositionalLayout/IBPCollectionViewCompositionalLayoutInteroperability.swift file to your project. It tricks the compiler to make the same code base available for iOS 13 and earlier than iOS 12.

Import IBPCollectionViewCompositionalLayout.

Then you can use Collection View Compositonal Layouts API as-is.

import IBPCollectionViewCompositionalLayout

let itemSize = NSCollectionLayoutSize(widthDimension: .fractionalWidth(1),
                                     heightDimension: .fractionalHeight(1))
let item = NSCollectionLayoutItem(layoutSize: itemSize)

let groupSize = NSCollectionLayoutSize(widthDimension: .fractionalWidth(1),
                                      heightDimension: .absolute(44))
let group = NSCollectionLayoutGroup.horizontal(layoutSize: groupSize, subitems: [item])

let section = NSCollectionLayoutSection(group: group)

let layout = UICollectionViewCompositionalLayout(section: section)

let collectionView = UICollectionView(frame: .zero, collectionViewLayout: layout)
...