UIPageViewController电子书翻页效果

     /*
     UIPageViewController 为我们提供了2种翻页样式，一种是拟真，一种是滚动
     UIPageViewControllerTransitionStylePageCurl//拟真
     UIPageViewControllerTransitionStyleScroll//滚动
    翻页的方向
     UIPageViewControllerNavigationOrientationHoriz//横向
     UIPageViewControllerNavigationOrientationVertical//纵向
     */
    UIPageViewController * pageVC = [[UIPageViewController alloc] initWithTransitionStyle:UIPageViewControllerTransitionStylePageCurl navigationOrientation:UIPageViewControllerNavigationOrientationHorizontal options:nil];
    pageVC.delegate = self;
    pageVC.dataSource = self;
    [self addChildViewController:pageVC];
    [self.view addSubview:pageVC.view];

   //UIPageViewControllerNavigationDirectionForward,//横向，像书一样
   //UIPageViewControllerNavigationDirectionReverse//纵向，像日历一样
   TextViewController *readerController = [TextViewController alloc] init];//需要展示内容的控制器
   [pageVC setViewControllers:@[ readerController ]
                                  direction:UIPageViewControllerNavigationDirectionForward
                                   animated:YES
                                 completion:nil];

  #pragma mark -- UIPageViewControllerDelegate,UIPageViewControllerDataSource
/*
 * 参数ViewController为当前正在显示的VC控制器
  return 的ViewController为将要显示的VC控制器
 */
  //向前翻页执行
  - (nullable UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController *)viewController{}
  //向后翻页时执行
  - (nullable UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController{}
//在动画执行完毕后被调用，在controller切换完成后，我们可以在这个代理中进行一些后续操作
  - (void)pageViewController:(UIPageViewController *)pageViewController didFinishAnimating:(BOOL)finished previousViewControllers:(nonnull NSArray<UIViewController *> *)previousViewControllers transitionCompleted:(BOOL)completed{  }