第十三篇、OC_UICollectionView的基本配置

- (UICollectionView *) categoryCollectionView
{
    if (! _categoryCollectionView) {

        // 创建布局
        UICollectionViewFlowLayout *layout = [[UICollectionViewFlowLayout alloc]init];
        layout.itemSize = CGSizeMake(KItemWidth,KItemHeight);
        layout.minimumInteritemSpacing = KSpace;
        layout.minimumLineSpacing = KSpace;
        layout.headerReferenceSize = CGSizeMake(KScreentW,KProductHeaderCellH);

        _categoryCollectionView = [[UICollectionView alloc]initWithFrame:self.view.bounds collectionViewLayout:layout];
        _categoryCollectionView.dataSource = self;
        _categoryCollectionView.delegate = self;
        _categoryCollectionView.backgroundColor = [UIColor colorWithRed:234.0/ green:234.0/ blue:234.0/ alpha:];

        // 注册
        [_categoryCollectionView registerNib:[UINib nibWithNibName:@"GFBCategoryCollectionViewCell" bundle:nil] forCellWithReuseIdentifier:KProductCell];
        [_categoryCollectionView registerNib:[UINib nibWithNibName:@"GFBCategoryCollectionReusableView" bundle:nil] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:KProductHeaderCell];

        // 设置内边距，添加轮播图
        _categoryCollectionView.contentInset = UIEdgeInsetsMake(KBanerH, , , );

    }
    return _categoryCollectionView;
}