91 lines
3.8 KiB
Objective-C
91 lines
3.8 KiB
Objective-C
//
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// KBSvipFlowLayout.m
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// keyBoard
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//
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// SVIP 页面自定义布局，支持 Section 背景装饰视图
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//
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#import "KBSvipFlowLayout.h"
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#import "KBSvipBenefitBgView.h"
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static NSString * const kKBSvipDecorationViewKind = @"KBSvipBenefitBgDecoration";
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@interface KBSvipFlowLayout ()
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@property (nonatomic, strong) NSMutableArray<UICollectionViewLayoutAttributes *> *decorationAttributes;
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@end
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@implementation KBSvipFlowLayout
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- (instancetype)init {
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if (self = [super init]) {
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_decorationSection = 1; // 默认 Section 1 需要背景
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[self registerClass:[KBSvipBenefitBgView class] forDecorationViewOfKind:kKBSvipDecorationViewKind];
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}
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return self;
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}
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- (void)prepareLayout {
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[super prepareLayout];
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self.decorationAttributes = [NSMutableArray array];
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NSInteger numberOfSections = [self.collectionView numberOfSections];
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if (self.decorationSection >= numberOfSections) { return; }
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NSInteger numberOfItems = [self.collectionView numberOfItemsInSection:self.decorationSection];
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if (numberOfItems == 0) { return; }
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// 获取 Section Header 的布局属性
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UICollectionViewLayoutAttributes *headerAttr = [self layoutAttributesForSupplementaryViewOfKind:UICollectionElementKindSectionHeader atIndexPath:[NSIndexPath indexPathForItem:0 inSection:self.decorationSection]];
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// 获取第一个和最后一个 item 的布局属性
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UICollectionViewLayoutAttributes *firstItemAttr = [self layoutAttributesForItemAtIndexPath:[NSIndexPath indexPathForItem:0 inSection:self.decorationSection]];
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UICollectionViewLayoutAttributes *lastItemAttr = [self layoutAttributesForItemAtIndexPath:[NSIndexPath indexPathForItem:numberOfItems - 1 inSection:self.decorationSection]];
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if (!firstItemAttr || !lastItemAttr) { return; }
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// 计算背景区域
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UIEdgeInsets sectionInset = self.sectionInset;
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if ([self.collectionView.delegate respondsToSelector:@selector(collectionView:layout:insetForSectionAtIndex:)]) {
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sectionInset = [(id<UICollectionViewDelegateFlowLayout>)self.collectionView.delegate collectionView:self.collectionView layout:self insetForSectionAtIndex:self.decorationSection];
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}
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CGFloat minY = CGRectGetMinY(headerAttr.frame);
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CGFloat maxY = CGRectGetMaxY(lastItemAttr.frame) + 16; // 底部留 16 间距
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CGFloat x = sectionInset.left;
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CGFloat width = self.collectionView.bounds.size.width - sectionInset.left - sectionInset.right;
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CGRect decorationFrame = CGRectMake(x, minY, width, maxY - minY);
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UICollectionViewLayoutAttributes *decorationAttr = [UICollectionViewLayoutAttributes layoutAttributesForDecorationViewOfKind:kKBSvipDecorationViewKind withIndexPath:[NSIndexPath indexPathForItem:0 inSection:self.decorationSection]];
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decorationAttr.frame = decorationFrame;
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decorationAttr.zIndex = -1; // 放在最底层
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[self.decorationAttributes addObject:decorationAttr];
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}
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- (NSArray<__kindof UICollectionViewLayoutAttributes *> *)layoutAttributesForElementsInRect:(CGRect)rect {
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NSMutableArray *attrs = [[super layoutAttributesForElementsInRect:rect] mutableCopy];
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for (UICollectionViewLayoutAttributes *decorationAttr in self.decorationAttributes) {
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if (CGRectIntersectsRect(rect, decorationAttr.frame)) {
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[attrs addObject:decorationAttr];
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}
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}
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return attrs;
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}
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- (UICollectionViewLayoutAttributes *)layoutAttributesForDecorationViewOfKind:(NSString *)elementKind atIndexPath:(NSIndexPath *)indexPath {
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if ([elementKind isEqualToString:kKBSvipDecorationViewKind]) {
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for (UICollectionViewLayoutAttributes *attr in self.decorationAttributes) {
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if (attr.indexPath.section == indexPath.section) {
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return attr;
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}
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}
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}
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return [super layoutAttributesForDecorationViewOfKind:elementKind atIndexPath:indexPath];
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}
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@end
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