UICollectionView自定义layout
发布时间
阅读量：
阅读量
当我们使用Objective-C语言开发iOS应用时 可能会遇到这样的场景：当frame发生变更时相应的cell会随之调整 这种情况既可能因受parent view boundaries的影响而发生 也可能通过复杂且富有创意的方式进行处理 频繁调用reloading数据可能导致性能问题 因此这时我们可以自定义布局并直接编写代码实现
#import "CustomLayout.h"
#define MainCell @"MainCell"
@interface CustomLayout ()
@property (nonatomic, strong) NSMutableDictionary *layoutInfo;
@end
@implementation CustomLayout
- (NSMutableDictionary *)layoutInfo
{
if (!_layoutInfo) {
_layoutInfo = [NSMutableDictionary dictionary];
}
return _layoutInfo;
}
- (void)prepareLayout
{
NSMutableDictionary *cellLayoutInfo = [NSMutableDictionary dictionary];
NSIndexPath *indexPath;
CGFloat itemWidth;
CGFloat itemSpacing;
CGFloat widthWithoutSpacing = [self collectionViewContentSize].width / ([self.collectionView numberOfItemsInSection:0]);
if (widthWithoutSpacing > [self collectionViewContentSize].height) {
itemWidth = [self collectionViewContentSize].height;
itemSpacing = ([self collectionViewContentSize].width - itemWidth*[self.collectionView numberOfItemsInSection:0])/
([self.collectionView numberOfItemsInSection:0]+1);
}
else {
itemWidth = widthWithoutSpacing;
itemSpacing = 0;
}
CGFloat xPosition = itemSpacing;
for (NSInteger section = 0; section < [self.collectionView numberOfSections]; section++) {
for (NSInteger index = 0 ; index < [self.collectionView numberOfItemsInSection:section] ; index++) {
indexPath = [NSIndexPath indexPathForItem:index inSection:section];
UICollectionViewLayoutAttributes *itemAttributes = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:indexPath];
CGRect currentFrame=itemAttributes.frame;
currentFrame.origin.x = xPosition;
currentFrame.size.width = itemWidth;
currentFrame.size.height = itemWidth;
itemAttributes.frame=currentFrame;
cellLayoutInfo[indexPath] = itemAttributes;
xPosition += itemWidth + itemSpacing;
}
}
self.layoutInfo[MainCell] = cellLayoutInfo;
}
- (BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds
{
return YES;
}
- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect
{
NSMutableArray *allAttributes = [NSMutableArray arrayWithCapacity:self.layoutInfo.count];
[self.layoutInfo enumerateKeysAndObjectsUsingBlock:^(NSString *elementIdentifier, NSDictionary *elementsInfo, BOOL *stop) {
[elementsInfo enumerateKeysAndObjectsUsingBlock:^(NSIndexPath *indexPath, UICollectionViewLayoutAttributes *attributes, BOOL *innerStop) {
if (CGRectIntersectsRect(rect, attributes.frame)) {
[allAttributes addObject:attributes];
}
}];
}];
return allAttributes;
}
- (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath
{
return self.layoutInfo[MainCell][indexPath];
}
- (CGSize) collectionViewContentSize
{
return self.collectionView.frame.size;
}
@end
代码解读全部评论 (0)
还没有任何评论哟~