mirror of
https://github.com/Instagram/IGListKit
synced 2026-05-06 15:08:50 +00:00
e2c2d3dcec
Summary: Working on porting our collection view layout to IGListKit. I'm doing this because its a solid layout, and we just finished preparing it to work with inline sections. It is designed to work in tandem with IGListKit, so we're adding it. This is still a WIP as I add more tests, but I'd love as much feedback as possible. Aside from the glob of header documentation, this has the following features: - Infinite sections that each have infinite items. Sections and items can fall inline. When they break the width of their container they will fall on the next row. - Sections can have their own insets, line spacing, and interitem spacing. - Sticky header support! When you use headers, it will always newline the section. - Maximum width with a border decoration view - Use this to pinch in your content on larger devices Followup to #423 - [ ] ~~Move decoration view support to delegate~~ removed - [x] Unit test changing [top y sticky inset](https://coveralls.io/builds/9977284/source?filen Closes https://github.com/Instagram/IGListKit/pull/484 Differential Revision: D4547760 Pulled By: rnystrom fbshipit-source-id: 879e2da16eb78bb6a90967e77d9ad0bbf7c69594
103 lines
4.2 KiB
Objective-C
103 lines
4.2 KiB
Objective-C
/**
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* Copyright (c) 2016-present, Facebook, Inc.
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* All rights reserved.
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*
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* This source code is licensed under the BSD-style license found in the
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* LICENSE file in the root directory of this source tree. An additional grant
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* of patent rights can be found in the PATENTS file in the same directory.
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*/
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#import <UIKit/UIKit.h>
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#import <IGListKit/IGListMacros.h>
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NS_ASSUME_NONNULL_BEGIN
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/**
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This UICollectionViewLayout subclass is for vertically-scrolling lists of data with variable widths and heights. It
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supports an infinite number of sections and items. All work is done on the main thread, and while extremely efficient,
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care must be taken not to stall the main thread in sizing delegate methods.
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This layout piggybacks on the mechanics of UICollectionViewFlowLayout in that:
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- Your UICollectionView data source must also conform to UICollectionViewDelegateFlowLayout
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- Header support given via UICollectionElementKindSectionHeader
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All UICollectionViewDelegateFlowLayout methods are required and used by this layout:
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```
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- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath;
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- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout insetForSectionAtIndex:(NSInteger)section;
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- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section;
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- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section;
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- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section;
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```
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Sections and items are put into the same horizontal row until the max-x position of an item extends beyond the width
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of the collection view. When that happens, the item is "newlined" to the next row. The y position of that row is
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deteremined by the maximum height (including section insets) of the section/item of the previous row.
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Ex. of a section (2,0) with a large width causing a newline.
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```
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|[ 0,0 ][ 1,0 ] |
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|[ 2,0 ]|
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```
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A section with a non-zero height header will always cause that section to newline. Headers are always stretched to the
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width of the collection view, pinched with the section insets.
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Ex. of a section (2,0) with a header inset on the left/right.
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```
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|[ 0,0 ][ 1,0 ] |
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| >======header=======< |
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| [ 2,0 ] |
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```
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Section insets apply to items in the section no matter if they begin on a new row or are on the same row as a previous
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section.
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Ex. of a section (2) with multiple items and a left inset.
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```
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|[ 0,0 ][ 1,0 ] >[ 2,0 ]|
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| >[ 2,1 ][ 2,2 ][ 2,3 ]|
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```
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Interitem spacing applies to items and sections within the same row. Line spacing only applies to items within the same
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section.
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Please see the unit tests for more configuration examples and expected output.
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*/
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IGLK_SUBCLASSING_RESTRICTED
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@interface IGListCollectionViewLayout : UICollectionViewLayout
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/**
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Set this to adjust the offset of the sticky headers. Can be used to change the sticky header position as UI like the
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navigation bar is scrolled offscreen. Changing this to the height of the navigation bar will give the effect of the
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headers sticking to the nav as it is collapsed.
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@discussion Changing the value on this method will invalidate the layout every time.
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*/
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@property (nonatomic, assign) CGFloat stickyHeaderOriginYAdjustment;
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/**
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Create and return a new collection view layout.
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@param stickyHeaders Set to `YES` to stick section headers to the top of the bounds while scrolling.
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@param topContentInset The top content inset used to offset the sticky headers. Ignored if stickyHeaders is `NO`.
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@return A new collection view layout.
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*/
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- (instancetype)initWithStickyHeaders:(BOOL)stickyHeaders
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topContentInset:(CGFloat)topContentInset NS_DESIGNATED_INITIALIZER;
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/**
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:nodoc:
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*/
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- (instancetype)init NS_UNAVAILABLE;
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/**
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:nodoc:
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*/
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+ (instancetype)new NS_UNAVAILABLE;
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@end
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NS_ASSUME_NONNULL_END
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