UIPageViewController 中的相同 UIViewController
Same UIViewControllers in UIPageViewController
我需要一个 UIPageViewController 来显示与数组中可用数据一样多的 UIViewController。
假设我有一个 Int 数组,对于每个 Int,我希望 UIViewController 在 UILabel 中显示其中一个。
为此,我在主故事板中创建了 UIPageViewController 和 UIViewController 及其 UILabel。
这是我为 UIPageViewController 编写的代码:
import UIKit
import RealmSwift
class PageViewController: UIPageViewController, UIPageViewControllerDataSource {
lazy var subViewControllers: [UIViewController] = {
return [
self.createNewVC(withName: "CounterViewController"),
self.createNewVC(withName: "CounterViewController"),
self.createNewVC(withName: "CounterViewController")
]
}()
var dataArray: [Int] = [30, 134, 345]
override func viewDidLoad() {
super.viewDidLoad()
self.dataSource = self
setViewControllers([subViewControllers[0]], direction: .forward, animated: true, completion: nil)
}
// Creates a new ViewController
func createNewVC(withName name: String) -> UIViewController {
return UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: name)
}
// Returns the previous ViewController
func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
let currentIndex: Int = subViewControllers.index(of: viewController) ?? 0
if (currentIndex <= 0) {
return nil
}
if let previous = subViewControllers[currentIndex - 1] as? CounterViewController {
previous.daysLeftLabel.text = String(dataArray[currentIndex])
return previous
} else {
return nil
}
}
// Returns the next ViewController
func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
let currentIndex: Int = subViewControllers.index(of: viewController) ?? 0
if (currentIndex >= subViewControllers.count - 1) {
return nil
}
if let next = subViewControllers[currentIndex + 1] as? CounterViewController {
next.daysLeftLabel.text = "0"
return next
} else {
return nil
}
}
}
这是 UIViewController 的代码
import UIKit
class CounterViewController: UIViewController {
@IBOutlet weak var daysLeftLabel: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
注意:"CounterViewController" 也是 UIViewController StoryBoardID
问题是,当我第一次向右滚动时,应用程序在这一行崩溃 next.daysLeftLabel.text = "0"
说它在展开 Optional 时发现了一个 nil 值。
我做错了什么?
也想借此机会问一问。
在这种情况下,正如您可能已经猜到的那样,我使用的是 UIPageViewController,它拥有相同的 UIViewController,但显示的数据不同,这是实现此目的的最佳方式吗?我做得对吗?还是有更简单、更简洁的方法?
此行崩溃
next.daysLeftLabel.text = "0"
因为 daysLeftLabel
在 VC 加载之前为零,您需要
class CounterViewController: UIViewController {
@IBOutlet weak var daysLeftLabel: UILabel!
var sendedText = ""
override func viewDidLoad() {
super.viewDidLoad()
daysLeftLabel.text = sendedText
// Do any additional setup after loading the view.
}
}
然后使用
next.sendedText = "0"
我需要一个 UIPageViewController 来显示与数组中可用数据一样多的 UIViewController。 假设我有一个 Int 数组,对于每个 Int,我希望 UIViewController 在 UILabel 中显示其中一个。 为此,我在主故事板中创建了 UIPageViewController 和 UIViewController 及其 UILabel。
这是我为 UIPageViewController 编写的代码:
import UIKit
import RealmSwift
class PageViewController: UIPageViewController, UIPageViewControllerDataSource {
lazy var subViewControllers: [UIViewController] = {
return [
self.createNewVC(withName: "CounterViewController"),
self.createNewVC(withName: "CounterViewController"),
self.createNewVC(withName: "CounterViewController")
]
}()
var dataArray: [Int] = [30, 134, 345]
override func viewDidLoad() {
super.viewDidLoad()
self.dataSource = self
setViewControllers([subViewControllers[0]], direction: .forward, animated: true, completion: nil)
}
// Creates a new ViewController
func createNewVC(withName name: String) -> UIViewController {
return UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: name)
}
// Returns the previous ViewController
func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
let currentIndex: Int = subViewControllers.index(of: viewController) ?? 0
if (currentIndex <= 0) {
return nil
}
if let previous = subViewControllers[currentIndex - 1] as? CounterViewController {
previous.daysLeftLabel.text = String(dataArray[currentIndex])
return previous
} else {
return nil
}
}
// Returns the next ViewController
func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
let currentIndex: Int = subViewControllers.index(of: viewController) ?? 0
if (currentIndex >= subViewControllers.count - 1) {
return nil
}
if let next = subViewControllers[currentIndex + 1] as? CounterViewController {
next.daysLeftLabel.text = "0"
return next
} else {
return nil
}
}
}
这是 UIViewController 的代码
import UIKit
class CounterViewController: UIViewController {
@IBOutlet weak var daysLeftLabel: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
注意:"CounterViewController" 也是 UIViewController StoryBoardID
问题是,当我第一次向右滚动时,应用程序在这一行崩溃 next.daysLeftLabel.text = "0"
说它在展开 Optional 时发现了一个 nil 值。
我做错了什么?
也想借此机会问一问。 在这种情况下,正如您可能已经猜到的那样,我使用的是 UIPageViewController,它拥有相同的 UIViewController,但显示的数据不同,这是实现此目的的最佳方式吗?我做得对吗?还是有更简单、更简洁的方法?
此行崩溃
next.daysLeftLabel.text = "0"
因为 daysLeftLabel
在 VC 加载之前为零,您需要
class CounterViewController: UIViewController {
@IBOutlet weak var daysLeftLabel: UILabel!
var sendedText = ""
override func viewDidLoad() {
super.viewDidLoad()
daysLeftLabel.text = sendedText
// Do any additional setup after loading the view.
}
}
然后使用
next.sendedText = "0"