UITableView API详解
2017-05-26 本文已影响118人
Better_奔
#import <Foundation/Foundation.h>
#import <CoreGraphics/CoreGraphics.h>
#import <UIKit/UIScrollView.h>
#import <UIKit/UISwipeGestureRecognizer.h>
#import <UIKit/UITableViewCell.h>
#import <UIKit/UIKitDefines.h>
NS_ASSUME_NONNULL_BEGIN
//tableView的种类，普通的和组
typedef NS_ENUM(NSInteger, UITableViewStyle) {
UITableViewStylePlain,
UITableViewStyleGrouped
};
//滚动到的位置
typedef NS_ENUM(NSInteger, UITableViewScrollPosition) {
UITableViewScrollPositionNone, //不滚动
UITableViewScrollPositionTop, //头
UITableViewScrollPositionMiddle, //中间
UITableViewScrollPositionBottom //尾
};
//刷新时内置的几种动画，用于删除。新增等
typedef NS_ENUM(NSInteger, UITableViewRowAnimation) {
UITableViewRowAnimationFade,
UITableViewRowAnimationRight,
UITableViewRowAnimationLeft,
UITableViewRowAnimationTop,
UITableViewRowAnimationBottom,
UITableViewRowAnimationNone,
UITableViewRowAnimationMiddle,
UITableViewRowAnimationAutomatic = 100
};
//表格的牵引数组中的放大镜
UIKIT_EXTERN NSString *const UITableViewIndexSearch NS_AVAILABLE_IOS(3_0) __TVOS_PROHIBITED;
//如果约束设置正确，自动计算高度，一般使用方式为tabview.
UIKIT_EXTERN const CGFloat UITableViewAutomaticDimension NS_AVAILABLE_IOS(5_0);
@class UITableView;
@class UINib;
@protocol UITableViewDataSource;
@protocol UITableViewDataSourcePrefetching;
@class UILongPressGestureRecognizer;
@class UITableViewHeaderFooterView;
@class UIRefreshControl;
@class UIVisualEffect;
typedef NS_ENUM(NSInteger, UITableViewRowActionStyle) {
UITableViewRowActionStyleDefault = 0,
UITableViewRowActionStyleDestructive = UITableViewRowActionStyleDefault,
UITableViewRowActionStyleNormal
} NS_ENUM_AVAILABLE_IOS(8_0) __TVOS_PROHIBITED;
//删除按钮等的定制
NS_CLASS_AVAILABLE_IOS(8_0) __TVOS_PROHIBITED @interface UITableViewRowAction : NSObject <NSCopying>
+ (instancetype)rowActionWithStyle:(UITableViewRowActionStyle)style title:(nullable NSString *)title handler:(void (^)(UITableViewRowAction *action, NSIndexPath *indexPath))handler;
@property (nonatomic, readonly) UITableViewRowActionStyle style;
@property (nonatomic, copy, nullable) NSString *title;
@property (nonatomic, copy, nullable) UIColor *backgroundColor; // default background color is dependent on style
@property (nonatomic, copy, nullable) UIVisualEffect* backgroundEffect;
@end
//焦点更新的上下文
NS_CLASS_AVAILABLE_IOS(9_0) @interface UITableViewFocusUpdateContext : UIFocusUpdateContext
@property (nonatomic, strong, readonly, nullable) NSIndexPath *previouslyFocusedIndexPath;
@property (nonatomic, strong, readonly, nullable) NSIndexPath *nextFocusedIndexPath;
@end
// this represents the display and behaviour of the cells.
@protocol UITableViewDelegate<NSObject, UIScrollViewDelegate>
@optional
//将要展示Cell/header/Footer视图回调 可以在其中进行修改
- (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath;
- (void)tableView:(UITableView *)tableView willDisplayHeaderView:(UIView *)view forSection:(NSInteger)section NS_AVAILABLE_IOS(6_0);
- (void)tableView:(UITableView *)tableView willDisplayFooterView:(UIView *)view forSection:(NSInteger)section NS_AVAILABLE_IOS(6_0);
//完成展示Cell/header/Footer视图回调（此时已经展示在了界面上）
- (void)tableView:(UITableView *)tableView didEndDisplayingCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath*)indexPath NS_AVAILABLE_IOS(6_0);
- (void)tableView:(UITableView *)tableView didEndDisplayingHeaderView:(UIView *)view forSection:(NSInteger)section NS_AVAILABLE_IOS(6_0);
- (void)tableView:(UITableView *)tableView didEndDisplayingFooterView:(UIView *)view forSection:(NSInteger)section NS_AVAILABLE_IOS(6_0);
// 每个cell高度的返回(这里高度通过协议返回，是为了table能准确的定位出要显示的Cell-index，从而满足UITableView的重用机制)
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath;
// 每个section-header高度的返回
- (CGFloat)tableView:(UITableView *)tableView heightForHeaderInSection:(NSInteger)section;
// 每个section-footer高度的返回
- (CGFloat)tableView:(UITableView *)tableView heightForFooterInSection:(NSInteger)section;
//性能优化（如果实现），加载的时候使用的是本方法，由于是一个固定的值，不需要计算，所以加载速度回很快，在显示的时候回去调用heightForRowAtIndexPath，真正开始计算。
- (CGFloat)tableView:(UITableView *)tableView estimatedHeightForRowAtIndexPath:(NSIndexPath *)indexPath NS_AVAILABLE_IOS(7_0);
- (CGFloat)tableView:(UITableView *)tableView estimatedHeightForHeaderInSection:(NSInteger)section NS_AVAILABLE_IOS(7_0);
- (CGFloat)tableView:(UITableView *)tableView estimatedHeightForFooterInSection:(NSInteger)section NS_AVAILABLE_IOS(7_0);
//可返回每个section-header的自定义视图
- (nullable UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section;
- (nullable UIView *)tableView:(UITableView *)tableView viewForFooterInSection:(NSInteger)section;
//当cell的accessaryType为UITableViewCellAccessoryDetailDisclosureButton时，
//点击accessaryView将会调用delegate的tableView:accessoryButtonTappedForRowWithIndexPath方法。否则只是didSelectRowAtIndexPath；
- (UITableViewCellAccessoryType)tableView:(UITableView *)tableView accessoryTypeForRowWithIndexPath:(NSIndexPath *)indexPath NS_DEPRECATED_IOS(2_0, 3_0) __TVOS_PROHIBITED;
- (void)tableView:(UITableView *)tableView accessoryButtonTappedForRowWithIndexPath:(NSIndexPath *)indexPath;
//Cell高亮的回调，一般式在选择的时候才高亮
- (BOOL)tableView:(UITableView *)tableView shouldHighlightRowAtIndexPath:(NSIndexPath *)indexPath NS_AVAILABLE_IOS(6_0);
- (void)tableView:(UITableView *)tableView didHighlightRowAtIndexPath:(NSIndexPath *)indexPath NS_AVAILABLE_IOS(6_0);
- (void)tableView:(UITableView *)tableView didUnhighlightRowAtIndexPath:(NSIndexPath *)indexPath NS_AVAILABLE_IOS(6_0);
/* 先点击row1，再点击row2，俩着执行顺序：在下一行将要选中后才取消上一行的选中
willSelectRowAtIndexPath 当前row为:0
didSelectRowAtIndexPath 当前row为:0
willSelectRowAtIndexPath 当前row为:1
willDeselectRowAtIndexPath 当前row为:0
didDeselectRowAtIndexPath 当前row为:0
didSelectRowAtIndexPath 当前row为:1
*/
- (nullable NSIndexPath *)tableView:(UITableView *)tableView willSelectRowAtIndexPath:(NSIndexPath *)indexPath;
- (nullable NSIndexPath *)tableView:(UITableView *)tableView willDeselectRowAtIndexPath:(NSIndexPath *)indexPath NS_AVAILABLE_IOS(3_0);
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath;
- (void)tableView:(UITableView *)tableView didDeselectRowAtIndexPath:(NSIndexPath *)indexPath NS_AVAILABLE_IOS(3_0);
// Editing
//返回编辑的类型1.没有2.删除3.插入
- (UITableViewCellEditingStyle)tableView:(UITableView *)tableView editingStyleForRowAtIndexPath:(NSIndexPath *)indexPath;
//删除提示文本
- (nullable NSString *)tableView:(UITableView *)tableView titleForDeleteConfirmationButtonForRowAtIndexPath:(NSIndexPath *)indexPath NS_AVAILABLE_IOS(3_0) __TVOS_PROHIBITED;
//ios8 出来的左滑小菜单 可以自定义想要的按钮 （要求ios8以上）
- (nullable NSArray<UITableViewRowAction *> *)tableView:(UITableView *)tableView editActionsForRowAtIndexPath:(NSIndexPath *)indexPath NS_AVAILABLE_IOS(8_0) __TVOS_PROHIBITED;
//编辑模式下，不让cell缩进，则使用NO
//只对grouped的TableView有效。
- (BOOL)tableView:(UITableView *)tableView shouldIndentWhileEditingRowAtIndexPath:(NSIndexPath *)indexPath;
//编辑状态发生改变时调用
- (void)tableView:(UITableView *)tableView willBeginEditingRowAtIndexPath:(NSIndexPath *)indexPath __TVOS_PROHIBITED;
- (void)tableView:(UITableView *)tableView didEndEditingRowAtIndexPath:(nullable NSIndexPath *)indexPath __TVOS_PROHIBITED;
//移动row时执行
- (NSIndexPath *)tableView:(UITableView *)tableView targetIndexPathForMoveFromRowAtIndexPath:(NSIndexPath *)sourceIndexPath toProposedIndexPath:(NSIndexPath *)proposedDestinationIndexPath;
//方法用于设置缩进的级别
- (NSInteger)tableView:(UITableView *)tableView indentationLevelForRowAtIndexPath:(NSIndexPath *)indexPath;
//复制的时候三个方法必须被实现
- (BOOL)tableView:(UITableView *)tableView shouldShowMenuForRowAtIndexPath:(NSIndexPath *)indexPath NS_AVAILABLE_IOS(5_0);
- (BOOL)tableView:(UITableView *)tableView canPerformAction:(SEL)action forRowAtIndexPath:(NSIndexPath *)indexPath withSender:(nullable id)sender NS_AVAILABLE_IOS(5_0);
- (void)tableView:(UITableView *)tableView performAction:(SEL)action forRowAtIndexPath:(NSIndexPath *)indexPath withSender:(nullable id)sender NS_AVAILABLE_IOS(5_0);
//使用Apple TV遥控器控制屏幕上的用户界面时使用
- (BOOL)tableView:(UITableView *)tableView canFocusRowAtIndexPath:(NSIndexPath *)indexPath NS_AVAILABLE_IOS(9_0);
- (BOOL)tableView:(UITableView *)tableView shouldUpdateFocusInContext:(UITableViewFocusUpdateContext *)context NS_AVAILABLE_IOS(9_0);
- (void)tableView:(UITableView *)tableView didUpdateFocusInContext:(UITableViewFocusUpdateContext *)context withAnimationCoordinator:(UIFocusAnimationCoordinator *)coordinator NS_AVAILABLE_IOS(9_0);
- (nullable NSIndexPath *)indexPathForPreferredFocusedViewInTableView:(UITableView *)tableView NS_AVAILABLE_IOS(9_0);
@end
//根据 indexPath 以动画的形式取消选中。调用此方法不会造成委托接受tableView:willDeselectRowAtIndexPath和tableView:didDeselectRowAtIndexPath:
//消息；不给UITableViewSelectionDidChangeNotification通知观察者；调用此方法不会产生任何滚动到取消行。
UIKIT_EXTERN NSNotificationName const UITableViewSelectionDidChangeNotification;
NS_CLASS_AVAILABLE_IOS(2_0) @interface UITableView : UIScrollView <NSCoding>
//初始化方法，需要给定frame和样式
- (instancetype)initWithFrame:(CGRect)frame style:(UITableViewStyle)style NS_DESIGNATED_INITIALIZER;
//在stordBoard 中取出时调用
- (nullable instancetype)initWithCoder:(NSCoder *)aDecoder NS_DESIGNATED_INITIALIZER;
//样式，只读
@property (nonatomic, readonly) UITableViewStyle style;
//UITableViewDataSource代理，本身不实现
@property (nonatomic, weak, nullable) id <UITableViewDataSource> dataSource;
//UITableViewDelegate代理，本身实现
@property (nonatomic, weak, nullable) id <UITableViewDelegate> delegate;
//prefetchDataSource代理，本身不实现，预加载处理。
@property (nonatomic, weak) id<UITableViewDataSourcePrefetching> prefetchDataSource NS_AVAILABLE_IOS(10_0);
//行高
@property (nonatomic) CGFloat rowHeight;
//section头高
@property (nonatomic) CGFloat sectionHeaderHeight;
//section尾高
@property (nonatomic) CGFloat sectionFooterHeight;
//优化处理，预计高度
@property (nonatomic) CGFloat estimatedRowHeight NS_AVAILABLE_IOS(7_0);
//优化处理，预计高度 默认0
@property (nonatomic) CGFloat estimatedSectionHeaderHeight NS_AVAILABLE_IOS(7_0);
//优化处理，预计高度 默认0
@property (nonatomic) CGFloat estimatedSectionFooterHeight NS_AVAILABLE_IOS(7_0);
//cell的分割线的偏移。UIEdgeInsets中的right、left起作用
@property (nonatomic) UIEdgeInsets separatorInset NS_AVAILABLE_IOS(7_0)
UI_APPEARANCE_SELECTOR;
//背景色
@property (nonatomic, strong, nullable) UIView *backgroundView NS_AVAILABLE_IOS(3_2);
//根据数据重新加载所有cell，包括全部方法重新调用。
- (void)reloadData;
// 刷新tableView中的section
- (void)reloadSectionIndexTitles NS_AVAILABLE_IOS(3_0);
//Sections个数
@property (nonatomic, readonly) NSInteger numberOfSections;
- (NSInteger)numberOfRowsInSection:(NSInteger)section;
//返回指定section的矩形
- (CGRect)rectForSection:(NSInteger)section;
// // 返回section的header矩形
- (CGRect)rectForHeaderInSection:(NSInteger)section;
// 返回section的footer矩形
- (CGRect)rectForFooterInSection:(NSInteger)section;
// 返回indexPath指定行的矩形
- (CGRect)rectForRowAtIndexPath:(NSIndexPath *)indexPath;
//根据一个几何点返回indexPath,如果超过边界返回nil
- (nullable NSIndexPath *)indexPathForRowAtPoint:(CGPoint)point;
// 通过cell得到这个cell在tableView的位置
- (nullable NSIndexPath *)indexPathForCell:(UITableViewCell *)cell;
// 根据一个几何的矩形返回矩形所覆盖的行,返回是一个indexPath数组
- (nullable NSArray<NSIndexPath *> *)indexPathsForRowsInRect:(CGRect)rect;
//根据indexPath返回cell
- (nullable __kindof UITableViewCell *)cellForRowAtIndexPath:(NSIndexPath *)indexPath;
//返回可见的cells
@property (nonatomic, readonly) NSArray<__kindof UITableViewCell *> *visibleCells;
//返回可见的位置
@property (nonatomic, readonly, nullable) NSArray<NSIndexPath *> *indexPathsForVisibleRows;
//我想在numberOfRowsInSection方法内获取该section的header View。
//须要在使用之前用 tableView 的 registerNib:forHeaderFooterViewReuseIdentifier: 或 registerClass:forHeaderFooterViewReuseIdentifier:。
- (nullable UITableViewHeaderFooterView *)headerViewForSection:(NSInteger)section NS_AVAILABLE_IOS(6_0);
- (nullable UITableViewHeaderFooterView *)footerViewForSection:(NSInteger)section NS_AVAILABLE_IOS(6_0);
// 滚动到指定位置
- (void)scrollToRowAtIndexPath:(NSIndexPath *)indexPath atScrollPosition:(UITableViewScrollPosition)scrollPosition animated:(BOOL)animated;
- (void)scrollToNearestSelectedRowAtScrollPosition:(UITableViewScrollPosition)scrollPosition animated:(BOOL)animated;
//和endUpdates一起用，让插入、删除、选择操作同时动画，没用过
- (void)beginUpdates;
- (void)endUpdates;
//插入sections
- (void)insertSections:(NSIndexSet *)sections withRowAnimation:(UITableViewRowAnimation)animation;
//删除sections
- (void)deleteSections:(NSIndexSet *)sections withRowAnimation:(UITableViewRowAnimation)animation;
//重新加载sections
- (void)reloadSections:(NSIndexSet *)sections withRowAnimation:(UITableViewRowAnimation)animation NS_AVAILABLE_IOS(3_0);
//调换sections位置
- (void)moveSection:(NSInteger)section toSection:(NSInteger)newSection NS_AVAILABLE_IOS(5_0);
//根据indexPath数组插入行
- (void)insertRowsAtIndexPaths:(NSArray<NSIndexPath *> *)indexPaths withRowAnimation:(UITableViewRowAnimation)animation;
//根据indexPath数组删除行
- (void)deleteRowsAtIndexPaths:(NSArray<NSIndexPath *> *)indexPaths withRowAnimation:(UITableViewRowAnimation)animation;
//根据indexPath数组加载行
- (void)reloadRowsAtIndexPaths:(NSArray<NSIndexPath *> *)indexPaths withRowAnimation:(UITableViewRowAnimation)animation NS_AVAILABLE_IOS(3_0);
//根据indexPath调换位置
- (void)moveRowAtIndexPath:(NSIndexPath *)indexPath toIndexPath:(NSIndexPath *)newIndexPath NS_AVAILABLE_IOS(5_0);
//YES进入编辑模式，tableview cell会出现插入、删除、重排序的控件
@property (nonatomic, getter=isEditing) BOOL editing;
//设置进入退出编辑模式 带动画
- (void)setEditing:(BOOL)editing animated:(BOOL)animated;
//是否允许用户选取一行
@property (nonatomic) BOOL allowsSelection NS_AVAILABLE_IOS(3_0);
//编辑模式时是否可选取一行
@property (nonatomic) BOOL allowsSelectionDuringEditing;
//是否允许用户选取多行
@property (nonatomic) BOOL allowsMultipleSelection NS_AVAILABLE_IOS(5_0);
//编辑模式时是否可选取多行
@property (nonatomic) BOOL allowsMultipleSelectionDuringEditing NS_AVAILABLE_IOS(5_0);
// Selection
//返回选定行的indexPath,单行
@property (nonatomic, readonly, nullable) NSIndexPath *indexPathForSelectedRow;
//返回选定行的indexPath,多行
@property (nonatomic, readonly, nullable) NSArray<NSIndexPath *> *indexPathsForSelectedRows NS_AVAILABLE_IOS(5_0);
//滚动到某处选定某行
- (void)selectRowAtIndexPath:(nullable NSIndexPath *)indexPath animated:(BOOL)animated scrollPosition:(UITableViewScrollPosition)scrollPosition;
//取消选定某行
- (void)deselectRowAtIndexPath:(NSIndexPath *)indexPath animated:(BOOL)animated;
//指定当tableView中多少行的时候开始显示IndexList，默认的设置是NSIntegerMax，即默认是不显示indexList的
@property (nonatomic) NSInteger sectionIndexMinimumDisplayRowCount;
// 设置索引号颜色
@property (nonatomic, strong, nullable) UIColor *sectionIndexColor NS_AVAILABLE_IOS(6_0) UI_APPEARANCE_SELECTOR;
// 设置索引号背景颜色
@property (nonatomic, strong, nullable) UIColor *sectionIndexBackgroundColor NS_AVAILABLE_IOS(7_0) UI_APPEARANCE_SELECTOR;
//设置跟踪索引号背景颜色
@property (nonatomic, strong, nullable) UIColor *sectionIndexTrackingBackgroundColor NS_AVAILABLE_IOS(6_0) UI_APPEARANCE_SELECTOR;
//分隔线的样式(默认为UITableViewCellSeparatorStyleSingleLine)
@property (nonatomic) UITableViewCellSeparatorStyle separatorStyle __TVOS_PROHIBITED;
// cell之间的分割线颜色
@property (nonatomic, strong, nullable) UIColor *separatorColor UI_APPEARANCE_SELECTOR __TVOS_PROHIBITED;
// 设置毛玻璃效果
@property (nonatomic, copy, nullable) UIVisualEffect *separatorEffect NS_AVAILABLE_IOS(8_0) UI_APPEARANCE_SELECTOR __TVOS_PROHIBITED;
// 默认是yes，设置为NO则在ios9.0以上不会有偏移
@property (nonatomic) BOOL cellLayoutMarginsFollowReadableWidth NS_AVAILABLE_IOS(9_0);
//设置headerView
@property (nonatomic, strong, nullable) UIView *tableHeaderView;
//设置headerView
@property (nonatomic, strong, nullable) UIView *tableFooterView;
//复用cell取出
- (nullable __kindof UITableViewCell *)dequeueReusableCellWithIdentifier:(NSString *)identifier;
- (__kindof UITableViewCell *)dequeueReusableCellWithIdentifier:(NSString *)identifier forIndexPath:(NSIndexPath *)indexPath NS_AVAILABLE_IOS(6_0);
//复用的header和footer
- (nullable __kindof UITableViewHeaderFooterView *)dequeueReusableHeaderFooterViewWithIdentifier:(NSString *)identifier NS_AVAILABLE_IOS(6_0);
//注册cell和header，footer
- (void)registerNib:(nullable UINib *)nib forCellReuseIdentifier:(NSString *)identifier NS_AVAILABLE_IOS(5_0);
- (void)registerClass:(nullable Class)cellClass forCellReuseIdentifier:(NSString *)identifier NS_AVAILABLE_IOS(6_0);
- (void)registerNib:(nullable UINib *)nib forHeaderFooterViewReuseIdentifier:(NSString *)identifier NS_AVAILABLE_IOS(6_0);
- (void)registerClass:(nullable Class)aClass forHeaderFooterViewReuseIdentifier:(NSString *)identifier NS_AVAILABLE_IOS(6_0);
//记住上次的选择
@property (nonatomic) BOOL remembersLastFocusedIndexPath NS_AVAILABLE_IOS(9_0);
@end
// this protocol represents the data model object. as such, it supplies no information about appearance (including the cells)
@protocol UITableViewDataSource<NSObject>
@required
//每个section下cell的个数（必须实现）
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section;
//通过indexpath返回具体的cell（必须实现）
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath;
@optional
//返回有多少个section（默认是1）
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView;
//每个section上面的标语内容
- (nullable NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section;
//每个section下面的标语内容
- (nullable NSString *)tableView:(UITableView *)tableView titleForFooterInSection:(NSInteger)section;
//是否可编辑
- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath;
// 是否可拖拽
// -tableView:moveRowAtIndexPath:toIndexPath:
- (BOOL)tableView:(UITableView *)tableView canMoveRowAtIndexPath:(NSIndexPath *)indexPath;
// Index
//设置索引号
- (nullable NSArray<NSString *> *)sectionIndexTitlesForTableView:(UITableView *)tableView __TVOS_PROHIBITED;
//点击索引触发
- (NSInteger)tableView:(UITableView *)tableView sectionForSectionIndexTitle:(NSString *)title atIndex:(NSInteger)index __TVOS_PROHIBITED;
// Data manipulation - insert and delete support
//插入/删除指定数据
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath;
// Data manipulation - reorder / moving support
//重新排序/移动数据操作
- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath *)destinationIndexPath;
@end
// this protocol can provide information about cells before they are displayed on screen.
@protocol UITableViewDataSourcePrefetching <NSObject>
@required
//这个新的协议属性是UICollectionView和UITableView都支持的。这个协议其实是用来通知我们，
//当前滑动到某个区域后，根据这次滑动的方向接下去可能还会滑向哪些indexPaths。好让我们做一些数据上的预备或者销毁。
- (void)tableView:(UITableView *)tableView prefetchRowsAtIndexPaths:(NSArray<NSIndexPath *> *)indexPaths;
@optional
// 滑动到某处，相反滑动则调用。
- (void)tableView:(UITableView *)tableView cancelPrefetchingForRowsAtIndexPaths:(NSArray<NSIndexPath *> *)indexPaths;
@end
_______________________________________________________________________________________________________________
@interface NSIndexPath (UITableView)
+ (instancetype)indexPathForRow:(NSInteger)row inSection:(NSInteger)section;
@property (nonatomic, readonly) NSInteger section;
@property (nonatomic, readonly) NSInteger row;
@end
NS_ASSUME_NONNULL_END
