#import "MyFlowLayout.h"
@implementation MyFlowLayout
#define kWidth self.collectionView.frame.size.width
- (instancetype)init
{
if (self = [super init]) {
// 设置item估计值
self.estimatedItemSize = CGSizeMake(300, 100);
// 全局配置item尺寸,单独定义调用协议方法[sizeForItemAtIndexPath]
self.itemSize = CGSizeMake(300, 100);
// 全局配置每行之间的间距,单独定义可调用协议方法[minimumLineSpacingForSectionAtIndex]
self.minimumLineSpacing = 10;
// 全局配置每行内部item的间距,单独定义可调用协议方法[minimumInteritemSpacingForSectionAtIndex]
self.minimumInteritemSpacing = 0;
// 设置滚动方向
// UICollectionViewScrollDirectionVertical
// UICollectionViewScrollDirectionHorizontal
self.scrollDirection = UICollectionViewScrollDirectionVertical;
// 设置是否当元素超出屏幕之后固定头部视图位置，默认NO；
self.sectionHeadersPinToVisibleBounds = YES;
// 设置是否当元素超出屏幕之后固定尾部视图位置，默认NO；
self.sectionFootersPinToVisibleBounds = YES;
}
return self;
}
- (NSArray<UICollectionViewLayoutAttributes *> *)layoutAttributesForElementsInRect:(CGRect)rect
{
// 拿到可见区域布局属性
NSArray *arr = [super layoutAttributesForElementsInRect:rect];
// 处理当前可见区内的布局属性吸顶
[arr enumerateObjectsUsingBlock:^(id _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
[self recomputeCellAttribute:obj];
}];
return arr;
}
- (void)recomputeCellAttribute:(UICollectionViewLayoutAttributes *)attrib
{
// 获得悬停的Y值
CGFloat minY = CGRectGetMinY(self.collectionView.bounds) + self.collectionView.contentInset.top;
//拿到布局属性应该出现的位置
CGFloat finalY = MAX(minY, attrib.frame.origin.y);
CGPoint point = attrib.frame.origin;
point.y = finalY;
attrib.frame = (CGRect){point,attrib.frame.size};
//根据IndexPath设置zIndex能确立顶部悬停的cell被后来的cell覆盖的层级关系
attrib.zIndex = attrib.indexPath.row;
}
- (NSArray<NSString *>*)arrStr
{
return @[@"f",@1];
}
- (BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds
{
return YES;
}
@end