这两种方法viewControllerBeforeViewController以及viewControllerAfterViewController的两种方法UIPageViewControllerDataSource都不会告诉您滑动的方向。
viewControllerBeforeViewController
viewControllerAfterViewController
UIPageViewControllerDataSource
该方法transitionCompleted的的UIPageViewController委托不帮助我们,所以尽管。它只是告诉页面是否被完全刷了。
transitionCompleted
UIPageViewController
那么我应该使用哪种方法来准确地检测用户方向(左或右)?
这两个属性可能会有所帮助:
let directionForward = UIPageViewControllerNavigationDirection.Forward let directionReverse = UIPageViewControllerNavigationDirection.Reverse
我的代码如下所示:
import UIKit class ProView: UIViewController, UIPageViewControllerDataSource, UIPageViewControllerDelegate { var pageViewController: UIPageViewController? let characterImages = ["character1", "character2", "character1", "character2", "character1", "character2", "character1", "character2"] override func viewDidLoad() { super.viewDidLoad() createPageViewController() setupPageControl() character = 1 } override func didReceiveMemoryWarning() { super.didReceiveMemoryWarning() } // Forward, check if this IS NOT the last controller func pageViewController(pageViewController: UIPageViewController, viewControllerAfterViewController ProView: UIViewController) -> UIViewController? { let itemController = ProView as PageItemController // Check if there is another view if itemController.itemIndex+1 < characterImages.count { return getItemController(itemController.itemIndex+1) } return nil } // Check if this IS NOT the first controller func pageViewController(pageViewController: UIPageViewController, viewControllerBeforeViewController ProView: UIViewController) -> UIViewController? { let itemController = ProView as PageItemController if itemController.itemIndex < 0 { return getItemController(itemController.itemIndex-1) } return nil } private func getItemController(itemIndex: Int) -> PageItemController? { if itemIndex < characterImages.count { let pageItemController = self.storyboard!.instantiateViewControllerWithIdentifier("ItemController") as PageItemController pageItemController.itemIndex = itemIndex pageItemController.imageName = characterImages[itemIndex] return pageItemController } return nil } func createPageViewController() { let pageController = self.storyboard!.instantiateViewControllerWithIdentifier("PageController") as UIPageViewController pageController.dataSource = self pageController.delegate = self if characterImages.count > 0 { let firstController = getItemController(0)! let startingViewControllers: NSArray = [firstController] pageController.setViewControllers(startingViewControllers, direction: UIPageViewControllerNavigationDirection.Forward, animated: false, completion: nil) } pageViewController = pageController addChildViewController(pageViewController!) self.view.addSubview(pageViewController!.view) pageViewController?.didMoveToParentViewController(self) } func setupPageControl() { let appearance = UIPageControl.appearance() appearance.pageIndicatorTintColor = UIColor.grayColor() appearance.currentPageIndicatorTintColor = UIColor.whiteColor() } func presentationCountForPageViewController(pageViewController: UIPageViewController) -> Int { return characterImages.count } func presentationIndexForPageViewController(pageViewController: UIPageViewController) -> Int { } // BETA func pageViewController(PageItemController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers pageViewController: [AnyObject], transitionCompleted completed: Bool) { if (!completed) { // You do nothing because whatever page you thought // the book was on before the gesture started is still the correct page return; } // This is where you would know the page number changed and handle it appropriately character = workaround } } class PageItemController: UIViewController { @IBOutlet weak var imageCharacterChoose: UIImageView! var itemIndex: Int = 0 var imageName: String = "" { didSet { if let imageView = imageCharacterChoose {imageCharacterChoose.image = UIImage(named: imageName) } } } }
根据pbasdf所说,
var currentIndex: Int = 0 var nextIndex: Int = 0 func pageViewController(PageItemController: UIPageViewController, willTransitionToViewControllers pageViewController: [AnyObject]) { // pageViewController is the pending View Controller nextIndex = currentIndex // pageViewController...... how do I get its index? }
您应该同时使用willTransitionToViewControllers:和didFinishAnimating:委托方法来确定转换是向前还是向后。在课程开始时声明几个索引变量,例如currentIndex和nextIndex(均为Int)。
willTransitionToViewControllers:
didFinishAnimating:
currentIndex
nextIndex
Int
在该willTransitionToViewControllers方法中,将nextIndex等于itemIndex挂起的视图控制器的:
willTransitionToViewControllers
itemIndex
编辑
func pageViewController(pageViewController: UIPageViewController, willTransitionToViewControllers pendingViewControllers: [AnyObject]) { // the page view controller is about to transition to a new page, so take note // of the index of the page it will display. (We can't update our currentIndex // yet, because the transition might not be completed - we will check in didFinishAnimating:) if let itemController = pendingViewControllers[0] as? PageItemController { nextIndex = itemController.itemIndex } }
结束编辑
您可以在此时确定转换是前进还是后退:如果nextIndex> currentIndex,则前进;如果nextIndex< currentIndex则向后。然后在中didFinishAnimating,如果completed为true(因此它完成了向下一个视图控制器的转换),请将其设置currentIndex为,nextIndex以便您可以currentIndex在需要指示屏幕上当前页面的任何位置使用:
didFinishAnimating
completed
func pageViewController(pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [AnyObject], transitionCompleted completed: Bool) { if (completed) { // the page view controller has successfully transitioned to the next view // controller, so we can update our currentIndex to the value we obtained // in the willTransitionToViewControllers method: currentIndex = nextIndex } }
请注意,这些方法的第一个参数是pageViewController(UIPageViewController的实例),而不是pageItemController当前代码中的那个。
pageItemController
最后,仅需注意:您引用(UIPageViewControllerNavigationDirection)的枚举仅在setViewControllers(_, direction:)方法中使用。
UIPageViewControllerNavigationDirection
setViewControllers(_, direction:)