swift - 使用按钮更改 PageViewController 会使最后一页上的应用程序崩溃

Question

我正在使用按钮来更改页面控制，它发生了变化，但是当它到达最后一页时，问题就出现了，应用程序崩溃了。这是我更改页面的代码

func backBtnClicked() {
        if currentIndex > 0 {
            currentIndex -= 1
        }
        if currentIndex < 1 {
            backBtn.isHidden = true
        }
        if currentIndex >= 0 {
            nextBtn.setTitle("Next", for: .normal)
            let startingViewController: TableVC? = viewControllerAtIndex(index: currentIndex)
            let viewControllers = [startingViewController]
            pageController?.setViewControllers(viewControllers as? [UIViewController], direction: .reverse, animated: false)
        }

    }

    @objc func nextBtnClicked() {
        if currentIndex != NSNotFound {
            currentIndex += 1
        }

        if currentIndex == pg.count - 1 {
            //Navigate Outside Pageview controller
            log("lastt")
        } else {


            let startingViewController: TableVC? = viewControllerAtIndex(index: currentIndex)
            let viewControllers = [startingViewController]
            pageController?.setViewControllers(viewControllers as? [UIViewController], direction: .forward, animated: false)
        }

    }

这是我遇到的错误

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'The number of view controllers provided (0) doesn't match the number required (1) for the requested transition'

任何帮助

Answer 1

替换

pageController?.setViewControllers(viewControllers as? [UIViewController], direction: .forward, animated: false)

与

pageController?.setViewControllers(viewControllers, direction: .forward, animated: false)

成为

let startingViewController = viewControllerAtIndex(index: currentIndex)!
pageController?.setViewControllers([startingViewController], direction: .forward, animated: false)

<小时/>

按后退

guard currentIndex - 1 >= 0 else { return }
currentIndex -= 1
// get the vc 

下一次按下

guard currentIndex + 1 < pg.count else { return }
currentIndex  += 1
// get the vc

在您当前的代码中，似乎这个 let runningViewController: TableVC? 在某个时刻返回 nil，这使得这个 viewControllers as? [UIViewController] 为空数组