viewControllerBeforeViewController的这两种方法viewControllerAfterViewController和UIPageViewControllerDataSource不能告诉您滑动的方向。transitionCompleted委托(delegate)的UIPageViewController方法对我们也没有多大帮助。它只是告诉页面是否被完全刷了。
那么我应该使用哪种方法来准确地检测用户方向(向左还是向右)？
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?
}
最佳答案
您应该同时使用willTransitionToViewControllers:和didFinishAnimating:委托(delegate)方法来确定转换是向前还是向后。在类(class)开始时声明几个索引变量，例如currentIndex和nextIndex(Int)。
在willTransitionToViewControllers方法中，将nextIndex设置为等于未决 View Controller 的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
}
}
END EDIT
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didFinishAnimating中，如果completed为true(因此它完成了向下一个 View Controller 的转换)，请将currentIndex设置为nextIndex，以便您可以在需要指示当前屏幕上页面的任何地方使用currentIndex:编辑
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)，而不是当前代码中的
pageItemController。最后，仅需注意:您引用的枚举(
UIPageViewControllerNavigationDirection)仅在setViewControllers(_, direction:)方法中使用。END EDIT
关于ios - 在UIPageViewController中获取用户滑动方向，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/27931961/