UICollectionView详解之基础使用介绍

UICollectionView简介

UICollectionView在iOS6.0以后引进,与UITableView比较相似。但是UICollectionView将布局完全交给UICollectionViewLayout，而且允许用户自定义layout来进行布局。使其功能比UITableView更加强大、布局更加灵活，迅速在各大APP广泛使用。

本篇将对UICollectionView的使用进行简单介绍，主要包括UICollectionView的视图组成、数据源、常用代理方法以及UICollectionViewFlowLayout的使用。下一遍将会详细讲解UICollectionViewLayout的自定义布局。

UICollectionView的视图组成：

UICollectionView由cell视图、Supplementary View和Decoration View三部分组成。

cell视图

这个大家应该都很清楚，UICollectionView主要内容展示的视图

Supplementary View

对于每组section的信息视图，类似于UITableView的header或者footer

Decoration View

装饰视图，好像很少使用

cell视图跟Supplementary View使用是需要先进行注册以便实现复用：

注册cell的方法，第一个是代码创建，第二个是xib创建
- (void)registerClass:(nullable Class)cellClass forCellWithReuseIdentifier:(NSString *)identifier;
- (void)registerNib:(nullable UINib *)nib forCellWithReuseIdentifier:(NSString *)identifier;

注册Supplementary View的方法，第一个是代码创建，第二个是xib创建
- (void)registerClass:(nullable Class)viewClass forSupplementaryViewOfKind:(NSString *)elementKind withReuseIdentifier:(NSString *)identifier;
- (void)registerNib:(nullable UINib *)nib forSupplementaryViewOfKind:(NSString *)kind withReuseIdentifier:(NSString *)identifier;

在数据源回调中复用的方法：
- (__kindof UICollectionViewCell *)dequeueReusableCellWithReuseIdentifier:(NSString *)identifier forIndexPath:(NSIndexPath *)indexPath;
- (__kindof UICollectionReusableView *)dequeueReusableSupplementaryViewOfKind:(NSString *)elementKind withReuseIdentifier:(NSString *)identifier forIndexPath:(NSIndexPath *)indexPath;

***上面方法的的kind和elementKind参数用来区分是头部视图还是尾部视图
           

UICollectionView的数据源代理方法：

//必须实现的数据源代理
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section;
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath;


//可选数据源代理
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView;
- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath;
处理移动相关（详细使用看demo）
- (BOOL)collectionView:(UICollectionView *)collectionView canMoveItemAtIndexPath:(NSIndexPath *)indexPath NS_AVAILABLE_IOS(_0);
- (void)collectionView:(UICollectionView *)collectionView moveItemAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath*)destinationIndexPath NS_AVAILABLE_IOS(_0);
           

UICollectionView的常用代理方法：

//点击cell高亮相关
- (BOOL)collectionView:(UICollectionView *)collectionView shouldHighlightItemAtIndexPath:(NSIndexPath *)indexPath;
- (void)collectionView:(UICollectionView *)collectionView didHighlightItemAtIndexPath:(NSIndexPath *)indexPath;
- (void)collectionView:(UICollectionView *)collectionView didUnhighlightItemAtIndexPath:(NSIndexPath *)indexPath;


//cell选中相关
- (BOOL)collectionView:(UICollectionView *)collectionView shouldSelectItemAtIndexPath:(NSIndexPath *)indexPath;
- (BOOL)collectionView:(UICollectionView *)collectionView shouldDeselectItemAtIndexPath:(NSIndexPath *)indexPath; // called when the user taps on an already-selected item in multi-select mode
- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath;
- (void)collectionView:(UICollectionView *)collectionView didDeselectItemAtIndexPath:(NSIndexPath *)indexPath;


//cell以及Supplementary View绘制相关
- (void)collectionView:(UICollectionView *)collectionView willDisplayCell:(UICollectionViewCell *)cell forItemAtIndexPath:(NSIndexPath *)indexPath NS_AVAILABLE_IOS(_0);
- (void)collectionView:(UICollectionView *)collectionView willDisplaySupplementaryView:(UICollectionReusableView *)view forElementKind:(NSString *)elementKind atIndexPath:(NSIndexPath *)indexPath NS_AVAILABLE_IOS(_0);
- (void)collectionView:(UICollectionView *)collectionView didEndDisplayingCell:(UICollectionViewCell *)cell forItemAtIndexPath:(NSIndexPath *)indexPath;
- (void)collectionView:(UICollectionView *)collectionView didEndDisplayingSupplementaryView:(UICollectionReusableView *)view forElementOfKind:(NSString *)elementKind atIndexPath:(NSIndexPath *)indexPath;
***这几个方法可以添加简易的动画,例如添加如下几句代码，cell加载的时候将会有放缩等效果。
- (void)collectionView:(UICollectionView *)collectionView willDisplayCell:(UICollectionViewCell *)cell forItemAtIndexPath:(NSIndexPath *)indexPath NS_AVAILABLE_IOS(_0)
{
    cell.contentView.alpha = ;
    cell.transform = CGAffineTransformRotate(CGAffineTransformMakeScale(, ), );

    [UIView animateKeyframesWithDuration: delay: options: animations:^{

        /**
         *  分步动画   第一个参数是该动画开始的百分比时间  第二个参数是该动画持续的百分比时间
         */
        [UIView addKeyframeWithRelativeStartTime: relativeDuration: animations:^{
            cell.contentView.alpha = ;
            cell.transform = CGAffineTransformRotate(CGAffineTransformMakeScale(, ), );
        }];
        [UIView addKeyframeWithRelativeStartTime: relativeDuration: animations:^{
            cell.contentView.alpha = ;
            cell.transform = CGAffineTransformRotate(CGAffineTransformMakeScale(, ), );

        }];

    } completion:^(BOOL finished) {

    }];
}

//长按显示菜单相关：(demo中有详细使用)
- (BOOL)collectionView:(UICollectionView *)collectionView shouldShowMenuForItemAtIndexPath:(NSIndexPath *)indexPath;
- (BOOL)collectionView:(UICollectionView *)collectionView canPerformAction:(SEL)action forItemAtIndexPath:(NSIndexPath *)indexPath withSender:(nullable id)sender;
- (void)collectionView:(UICollectionView *)collectionView performAction:(SEL)action forItemAtIndexPath:(NSIndexPath *)indexPath withSender:(nullable id)sender;

//转场相关（下一篇会讲解）
- (nonnull UICollectionViewTransitionLayout *)collectionView:(UICollectionView *)collectionView transitionLayoutForOldLayout:(UICollectionViewLayout *)fromLayout newLayout:(UICollectionViewLayout *)toLayout;
           

UICollectionViewFlowLayout && UICollectionViewLayout：

UICollectionView之所以比UITableView强大，主要在于其精髓UICollectionViewLayout的布局。它通过 UICollectionViewLayoutAttributes 类来管理 cell 、 Supplementary View 和 Decoration View 的 位置 、 transform 、 alpha 、 hidden 等等。先看看系统为我们提供的UICollectionViewFlowLayout布局的使用吧。

UICollectionViewFlowLayout 的常用属性

//决定了每行的间隔
@property (nonatomic) CGFloat minimumLineSpacing;
//决定了Item之间的间隔
@property (nonatomic) CGFloat minimumInteritemSpacing;
//cell的大小（如果实现的代理该设置无效）
@property (nonatomic) CGSize itemSize;
//cell大小的预计算
@property (nonatomic) CGSize estimatedItemSize NS_AVAILABLE_IOS(_0); // defaults to CGSizeZero - setting a non-zero size enables cells that self-size via -preferredLayoutAttributesFittingAttributes:
//布局的方向
@property (nonatomic) UICollectionViewScrollDirection scrollDirection; // default is UICollectionViewScrollDirectionVertical
//头视图跟尾视图的大小（横向的时候，headerReferenceSize.width有效，headerReferenceSize.height无效。纵向时相反）
@property (nonatomic) CGSize headerReferenceSize;
@property (nonatomic) CGSize footerReferenceSize;
//间距
@property (nonatomic) UIEdgeInsets sectionInset;

// Set these properties to YES to get headers that pin to the top of the screen and footers that pin to the bottom while scrolling (similar to UITableView).
@property (nonatomic) BOOL sectionHeadersPinToVisibleBounds NS_AVAILABLE_IOS(_0);
@property (nonatomic) BOOL sectionFootersPinToVisibleBounds NS_AVAILABLE_IOS(_0);
           

UICollectionViewFlowLayout 的代理方法

//基本就是上面的属性通过代理的方法返回
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath;
- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section;
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section;
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section;
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section;
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForFooterInSection:(NSInteger)section;
           

文／阿聪o（简书作者）

原文链接：http://www.jianshu.com/p/b0d03c40fd65

著作权归作者所有，转载请联系作者获得授权，并标注“简书作者”。