//通過一個(gè)布局策略初識(shí)化CollectionView
- (instancetype)initWithFrame:(CGRect)frame collectionViewLayout:(UICollectionViewLayout *)layout;
 
//獲取和設(shè)置collection的layout
@property (nonatomic, strong) UICollectionViewLayout *collectionViewLayout;
 
//數(shù)據(jù)源和代理
@property (nonatomic, weak, nullable) id <UICollectionViewDelegate> delegate;
@property (nonatomic, weak, nullable) id <UICollectionViewDataSource> dataSource;
 
//從一個(gè)class或者xib文件進(jìn)行cell(item)的注冊(cè)
- (void)registerClass:(nullable Class)cellClass forCellWithReuseIdentifier:(NSString *)identifier;
- (void)registerNib:(nullable UINib *)nib forCellWithReuseIdentifier:(NSString *)identifier;
 
//下面兩個(gè)方法與上面相似拉馋，這里注冊(cè)的是頭視圖或者尾視圖的類
//其中第二個(gè)參數(shù)是設(shè)置 頭視圖或者尾視圖 系統(tǒng)為我們定義好了這兩個(gè)字符串
//UIKIT_EXTERN NSString *const UICollectionElementKindSectionHeader NS_AVAILABLE_IOS(6_0);
//UIKIT_EXTERN NSString *const UICollectionElementKindSectionFooter NS_AVAILABLE_IOS(6_0);
- (void)registerClass:(nullable Class)viewClass forSupplementaryViewOfKind:(NSString *)elementKind withReuseIdentifier:(NSString *)identifier;
- (void)registerNib:(nullable UINib *)nib forSupplementaryViewOfKind:(NSString *)kind withReuseIdentifier:(NSString *)identifier;
 
//這兩個(gè)方法是從復(fù)用池中取出cell或者頭尾視圖
- (__kindof UICollectionViewCell *)dequeueReusableCellWithReuseIdentifier:(NSString *)identifier forIndexPath:(NSIndexPath *)indexPath;
- (__kindof UICollectionReusableView *)dequeueReusableSupplementaryViewOfKind:(NSString *)elementKind withReuseIdentifier:(NSString *)identifier forIndexPath:(NSIndexPath *)indexPath;
 
//設(shè)置是否允許選中 默認(rèn)YES
@property (nonatomic) BOOL allowsSelection;
 
//設(shè)置是否允許多選 默認(rèn)NO
@property (nonatomic) BOOL allowsMultipleSelection;
 
//獲取所有選中的item的位置信息
- (nullable NSArray<NSIndexPath *> *)indexPathsForSelectedItems; 
 
//設(shè)置選中某一item台谍，并使視圖滑動(dòng)到相應(yīng)位置，scrollPosition是滑動(dòng)位置的相關(guān)參數(shù)，如下：
/*
typedef NS_OPTIONS(NSUInteger, UICollectionViewScrollPosition) {
    //無
    UICollectionViewScrollPositionNone                 = 0,
    //垂直布局時(shí)使用的 對(duì)應(yīng)上中下
    UICollectionViewScrollPositionTop                  = 1 << 0,
    UICollectionViewScrollPositionCenteredVertically   = 1 << 1,
    UICollectionViewScrollPositionBottom               = 1 << 2,
    //水平布局時(shí)使用的  對(duì)應(yīng)左中右
    UICollectionViewScrollPositionLeft                 = 1 << 3,
    UICollectionViewScrollPositionCenteredHorizontally = 1 << 4,
    UICollectionViewScrollPositionRight                = 1 << 5
};
*/
- (void)selectItemAtIndexPath:(nullable NSIndexPath *)indexPath animated:(BOOL)animated scrollPosition:(UICollectionViewScrollPosition)scrollPosition;
 
//將某一item取消選中
- (void)deselectItemAtIndexPath:(NSIndexPath *)indexPath animated:(BOOL)animated;
 
//重新加載數(shù)據(jù)
- (void)reloadData;
 
//下面這兩個(gè)方法散罕，可以重新設(shè)置collection的布局，后面的方法多了一個(gè)布局完成后的回調(diào)维哈，iOS7后可以用
//使用這兩個(gè)方法可以產(chǎn)生非常炫酷的動(dòng)畫效果
- (void)setCollectionViewLayout:(UICollectionViewLayout *)layout animated:(BOOL)animated;
- (void)setCollectionViewLayout:(UICollectionViewLayout *)layout animated:(BOOL)animated completion:(void (^ __nullable)(BOOL finished))completion NS_AVAILABLE_IOS(7_0);
 
//下面這些方法更加強(qiáng)大雄驹，我們可以對(duì)布局更改后的動(dòng)畫進(jìn)行設(shè)置
//這個(gè)方法傳入一個(gè)布局策略layout，系統(tǒng)會(huì)開始進(jìn)行布局渲染，返回一個(gè)UICollectionViewTransitionLayout對(duì)象
//這個(gè)UICollectionViewTransitionLayout對(duì)象管理動(dòng)畫的相關(guān)屬性床未，我們可以進(jìn)行設(shè)置
- (UICollectionViewTransitionLayout *)startInteractiveTransitionToCollectionViewLayout:(UICollectionViewLayout *)layout completion:(nullable UICollectionViewLayoutInteractiveTransitionCompletion)completion NS_AVAILABLE_IOS(7_0);
//準(zhǔn)備好動(dòng)畫設(shè)置后褂乍，我們需要調(diào)用下面的方法進(jìn)行布局動(dòng)畫的展示，之后會(huì)調(diào)用上面方法的block回調(diào)
- (void)finishInteractiveTransition NS_AVAILABLE_IOS(7_0);
//調(diào)用這個(gè)方法取消上面的布局動(dòng)畫設(shè)置即硼，之后也會(huì)進(jìn)行上面方法的block回調(diào)
- (void)cancelInteractiveTransition NS_AVAILABLE_IOS(7_0);
 
//獲取分區(qū)數(shù)
- (NSInteger)numberOfSections;
 
//獲取某一分區(qū)的item數(shù)
- (NSInteger)numberOfItemsInSection:(NSInteger)section;
 
//下面兩個(gè)方法獲取item或者頭尾視圖的layout屬性逃片，這個(gè)UICollectionViewLayoutAttributes對(duì)象
//存放著布局的相關(guān)數(shù)據(jù)，可以用來做完全自定義布局只酥，后面博客會(huì)介紹
- (nullable UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath;
- (nullable UICollectionViewLayoutAttributes *)layoutAttributesForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath;
 
//獲取某一點(diǎn)所在的indexpath位置
- (nullable NSIndexPath *)indexPathForItemAtPoint:(CGPoint)point;
 
//獲取某個(gè)cell所在的indexPath
- (nullable NSIndexPath *)indexPathForCell:(UICollectionViewCell *)cell;
 
//根據(jù)indexPath獲取cell
- (nullable UICollectionViewCell *)cellForItemAtIndexPath:(NSIndexPath *)indexPath;
 
//獲取所有可見cell的數(shù)組
- (NSArray<__kindof UICollectionViewCell *> *)visibleCells;
 
//獲取所有可見cell的位置數(shù)組
- (NSArray<NSIndexPath *> *)indexPathsForVisibleItems;
 
//下面三個(gè)方法是iOS9中新添加的方法褥实，用于獲取頭尾視圖
- (UICollectionReusableView *)supplementaryViewForElementKind:(NSString *)elementKind atIndexPath:(NSIndexPath *)indexPath NS_AVAILABLE_IOS(9_0);
- (NSArray<UICollectionReusableView *> *)visibleSupplementaryViewsOfKind:(NSString *)elementKind NS_AVAILABLE_IOS(9_0);
- (NSArray<NSIndexPath *> *)indexPathsForVisibleSupplementaryElementsOfKind:(NSString *)elementKind NS_AVAILABLE_IOS(9_0);
 
//使視圖滑動(dòng)到某一位置，可以帶動(dòng)畫效果
- (void)scrollToItemAtIndexPath:(NSIndexPath *)indexPath atScrollPosition:(UICollectionViewScrollPosition)scrollPosition animated:(BOOL)animated;
 
//下面這些方法用于動(dòng)態(tài)添加裂允，刪除损离，移動(dòng)某些分區(qū)獲取items
- (void)insertSections:(NSIndexSet *)sections;
- (void)deleteSections:(NSIndexSet *)sections;
- (void)reloadSections:(NSIndexSet *)sections;
- (void)moveSection:(NSInteger)section toSection:(NSInteger)newSection;
 
- (void)insertItemsAtIndexPaths:(NSArray<NSIndexPath *> *)indexPaths;
- (void)deleteItemsAtIndexPaths:(NSArray<NSIndexPath *> *)indexPaths;
- (void)reloadItemsAtIndexPaths:(NSArray<NSIndexPath *> *)indexPaths;
- (void)moveItemAtIndexPath:(NSIndexPath *)indexPath toIndexPath:(NSIndexPath *)newIndexPath;