UICollectionViewFlowLayout 默认值测试

最简单的流水布局: 
在iPhone6屏幕上, 默认尺寸如下: 

UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc] init];

NSLog(@"%f, %f, %f, %f, %f",PJWITCH, flowLayout.itemSize.width, flowLayout.itemSize.height, flowLayout.minimumLineSpacing, flowLayout.minimumInteritemSpacing);
UICollectionView[1461:98531] 375.000000, 50.000000, 50.000000, 10.000000, 10.000000
    
NSLog(@"%f, %f, %f, %f", flowLayout.headerReferenceSize.width, flowLayout.headerReferenceSize.height, flowLayout.footerReferenceSize.width, flowLayout.footerReferenceSize.height);

UICollectionView[1461:98531] 0.000000, 0.000000, 0.000000, 0.000000

flowLayout.sectionInset默认全部为0.

flowLayout.scrollDirection =UICollectionViewScrollDirectionHorizontal;//每个item按照横向的方向开始摆放

flowLayout.scrollDirection =UICollectionViewScrollDirectionVertical; //每个item按照竖向的方向开始摆放

每一列的最小间距

    layout.minimumInteritemSpacing = 10;

每一行的最小间距

    layout.minimumLineSpacing = 10;

    //
设置UICollectionViewFlowLayout与CollectionView边缘的间距

    layout.sectionInset =
UIEdgeInsetsMake(lineSpacing, interitemSpacing, lineSpacing, interitemSpacing);

layout.sectionInset = UIEdgeInsets(top: 0, left: kItemMargin, bottom:
0, right: kItemMargin)

layout.headerReferenceSize = CGSize(width: WIDTH, height: kHeaderViewH)

colltionView.contentInset = UIEdgeInsets(top: kCycleViewH + kGameViewH, left:
0, bottom: 0, right:
0)