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git-subtree-dir: submodules/AsyncDisplayKit git-subtree-mainline: d06f423e0ed3df1fed9bd10d79ee312a9179b632 git-subtree-split: 02bedc12816e251ad71777f9d2578329b6d2bef6
97 lines
3.5 KiB
Objective-C
97 lines
3.5 KiB
Objective-C
//
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// ASPagerFlowLayout.m
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// AsyncDisplayKit
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//
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// Created by Levi McCallum on 2/12/16.
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//
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// Copyright (c) 2014-present, Facebook, Inc. All rights reserved.
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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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#ifndef MINIMAL_ASDK
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#import <AsyncDisplayKit/ASPagerFlowLayout.h>
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@interface ASPagerFlowLayout () {
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BOOL _didRotate;
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CGRect _cachedCollectionViewBounds;
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NSIndexPath *_currentIndexPath;
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}
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@end
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@implementation ASPagerFlowLayout
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- (CGPoint)targetContentOffsetForProposedContentOffset:(CGPoint)proposedContentOffset withScrollingVelocity:(CGPoint)velocity
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{
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NSInteger currentPage = ceil(proposedContentOffset.x / self.collectionView.bounds.size.width);
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_currentIndexPath = [NSIndexPath indexPathForItem:currentPage inSection:0];
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return [super targetContentOffsetForProposedContentOffset:proposedContentOffset withScrollingVelocity:velocity];
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}
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- (void)prepareForAnimatedBoundsChange:(CGRect)oldBounds
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{
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// Cache the current page if a rotation did happen. This happens before the rotation animation
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// is occuring and the bounds changed so we use this as an opportunity to cache the current index path
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if (_cachedCollectionViewBounds.size.width != self.collectionView.bounds.size.width) {
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_cachedCollectionViewBounds = self.collectionView.bounds;
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// Figurring out current page based on the old bounds visible space
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CGRect visibleRect = oldBounds;
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CGFloat visibleXCenter = CGRectGetMidX(visibleRect);
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NSArray<UICollectionViewLayoutAttributes *> *layoutAttributes = [self layoutAttributesForElementsInRect:visibleRect];
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for (UICollectionViewLayoutAttributes *attributes in layoutAttributes) {
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if ([attributes representedElementCategory] == UICollectionElementCategoryCell && attributes.center.x == visibleXCenter) {
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_currentIndexPath = attributes.indexPath;
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break;
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}
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}
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_didRotate = YES;
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}
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[super prepareForAnimatedBoundsChange:oldBounds];
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}
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- (CGPoint)targetContentOffsetForProposedContentOffset:(CGPoint)proposedContentOffset
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{
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// Don't mess around if the user is interacting with the page node. Although if just a rotation happened we should
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// try to use the current index path to not end up setting the target content offset to something in between pages
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if (_didRotate || (!self.collectionView.isDecelerating && !self.collectionView.isTracking)) {
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_didRotate = NO;
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if (_currentIndexPath) {
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return [self _targetContentOffsetForItemAtIndexPath:_currentIndexPath proposedContentOffset:proposedContentOffset];
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}
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}
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return [super targetContentOffsetForProposedContentOffset:proposedContentOffset];
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}
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- (CGPoint)_targetContentOffsetForItemAtIndexPath:(NSIndexPath *)indexPath proposedContentOffset:(CGPoint)proposedContentOffset
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{
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if ([self _dataSourceIsEmpty]) {
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return proposedContentOffset;
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}
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UICollectionViewLayoutAttributes *attributes = [self layoutAttributesForItemAtIndexPath:_currentIndexPath];
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if (attributes == nil) {
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return proposedContentOffset;
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}
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CGFloat xOffset = (CGRectGetWidth(self.collectionView.bounds) - CGRectGetWidth(attributes.frame)) / 2.0;
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return CGPointMake(attributes.frame.origin.x - xOffset, proposedContentOffset.y);
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}
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- (BOOL)_dataSourceIsEmpty
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{
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return ([self.collectionView numberOfSections] == 0 ||
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[self.collectionView numberOfItemsInSection:0] == 0);
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}
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@end
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#endif
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