系统自带的网格布局
UICollectionViewFlowLayout * flowLayout = [[UICollectionViewFlowLayout alloc] init];
NSInteger itemWidth = (CGRectGetWidth(self.view.frame) - 4 * kMargin) / 3;
//设置单元格大小
flowLayout.itemSize = CGSizeMake(itemWidth, itemWidth / 0.618);
//最小行间距（默认10）
flowLayout.minimumLineSpacing = 10;
//最小cell间距 （默认10）
flowLayout.minimumInteritemSpacing = 10;
//设置section的内边距
flowLayout.sectionInset = UIEdgeInsetsMake(kMargin, kMargin, kMargin, kMargin);
设置UICollectionView的滑动方向
flowLayout.scrollDirection = UICollectionViewScrollDirectionVertical;
//sectionHeader的大小,如果是竖向滚动，只需设置Y值。如果是横向，只需设置X值。
flowLayout.headerReferenceSize = CGSizeMake(0, 200);
//网格布局
UICollectionView * collectionView = [[UICollectionView alloc] initWithFrame:self.view.bounds collectionViewLayout:flowLayout];
//设置数据源代理
collectionView.dataSource = self;
//注册cell
[collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:cellID];
//注册sectionHeader
[collectionView registerClass:[UICollectionReusableView class] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:headerID];
//多少分组
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
return 2;
}
//每一个分组里有多少个item
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
return 200;
}
// The cell that is returned must be retrieved from a call to -dequeueReusableCellWithReuseIdentifier:forIndexPath:
//创建UICollectionViewCell的方法
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
//根据identifier从缓冲池里取cell
UICollectionViewCell * cell = [collectionView dequeueReusableCellWithReuseIdentifier:cellID forIndexPath:indexPath];
cell.backgroundColor = [UIColor orangeColor];
return cell;
}
//创建sectionHeader的方法
- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath {
//kind:种类，一共两种，一种是header,一种是footer
if (kind == UICollectionElementKindSectionHeader) {
UICollectionReusableView * reusable = [collectionView dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:headerID forIndexPath:indexPath];
reusable.backgroundColor = [UIColor yellowColor];
return reusable;
}
return nil;
}
3、#pragma mark - UICollectionViewDelegate
//点击cell的方法 cell == item
- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath {
NSLog(@"section - %@ , row - %@",@(indexPath.section),@(indexPath.row));
}
4、#pragma mark - UICollectionViewDelegateFlowLayout
设置itemSize,代理优先级高于属性
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
if (indexPath.section == 0) {
return CGSizeMake(20, 20);
}
return CGSizeMake(10, 10);
return CGSizeMake(arc4random_uniform(100), arc4random_uniform(100));
}
设置sectionInset
- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section {
if (section == 0) {
return UIEdgeInsetsMake(20, 30, 40, 50);
}
return UIEdgeInsetsMake(kMargin, kMargin, kMargin, kMargin);
}
设置minimumLineSpacing最小行间距
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section {
if (section == 0) {
return 20;
}
return 2;
}
设置headersize
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section {
if (section == 0) {
return CGSizeMake(0, 500);
}
return CGSizeMake(0, 100);
}