collectionView - flowLayout

//定义每个UICollectionView 的大小

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath{    return [self getCollectionCellSize_180x180];}- (CGSize)getCollectionCellSize_180x180{ return CGSizeMake((self.frame.size.width - 11)/3, (self.frame.size.width - 11)/3);}

//缩进 设置collection view 的每个section与上下左右的距离

- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section{        return UIEdgeInsetsMake(0, 0, 0, 0);}