不使用静态数据时 UIPageViewController 崩溃
UIPageViewController crashing when not using static data
我有一个可用的页面视图控制器系统（只是要粘贴所有内容，很确定问题出在顶部附近的我的 firebase 观察中）：
class IndividualPeopleVC: UIViewController, UIPageViewControllerDataSource {
var pageViewController: UIPageViewController!
var pageTitles : [String]!
var imageURLS: NSArray!
let currentUser = FIRAuth.auth()?.currentUser?.uid
override func viewDidLoad()
{
super.viewDidLoad()
self.pageTitles = []
self.pageTitles = ["1", "2", "3", "4'"]
DataService.ds.REF_INTERESTS.child(passedInterest).child("rooms").child(passedRoom).child("users").observeSingleEventOfType(.Value) { (snapshot: FIRDataSnapshot) in
print(snapshot.value)
if let snapshots = snapshot.children.allObjects as? [FIRDataSnapshot] {
for snap in snapshots {
let name = snap.key
let uid = snap.value as! String
let person = Person(name: name, bio: "", UID: uid)
if person.UID != self.currentUser {
self.pageTitles.append(uid)
}
}
}
self.pageViewController = self.storyboard?.instantiateViewControllerWithIdentifier("PageViewController") as! UIPageViewController
self.pageViewController.dataSource = self
let startVC = self.viewControllerAtIndex(0) as ContentViewController
let viewControllers = NSArray(object: startVC)
self.pageViewController.setViewControllers(viewControllers as? [UIViewController], direction: .Forward, animated: true, completion: nil)
self.pageViewController.view.frame = CGRectMake(0, 30, self.view.frame.width, self.view.frame.size.height - 60)
self.addChildViewController(self.pageViewController)
self.view.addSubview(self.pageViewController.view)
self.pageViewController.didMoveToParentViewController(self)
}
func viewControllerAtIndex(index: Int) -> ContentViewController
{
if ((self.pageTitles.count == 0) || (index >= self.pageTitles.count)) {
return ContentViewController()
}
var vc: ContentViewController = self.storyboard?.instantiateViewControllerWithIdentifier("ContentViewController") as! ContentViewController
vc.titleText = self.pageTitles[index] as! String
vc.imageFile = self.pageImages[index] as! String
vc.pageIndex = index
return vc
}
func pageViewController(pageViewController: UIPageViewController, viewControllerBeforeViewController viewController: UIViewController) -> UIViewController?
{
var vc = viewController as! ContentViewController
var index = vc.pageIndex as Int
if (index == 0 || index == NSNotFound)
{
return nil
}
index--
return self.viewControllerAtIndex(index)
}
func pageViewController(pageViewController: UIPageViewController, viewControllerAfterViewController viewController: UIViewController) -> UIViewController? {
var vc = viewController as! ContentViewController
var index = vc.pageIndex as Int
if (index == NSNotFound) {
return nil
}
index++
if (index == self.pageTitles.count){
return nil
}
return self.viewControllerAtIndex(index)
}
func presentationCountForPageViewController(pageViewController: UIPageViewController) -> Int{
return self.pageTitles.count
}
func presentationIndexForPageViewController(pageViewController: UIPageViewController) -> Int{
return 0
}
}
所以基本上大部分只是 copy-pasted 来自另一个来源并且它有效。它从滚动的 pageTitles 数组创建 4 个页面，在另一个 VC 我传递 1、2、3 和 4 并且标签显示数组中的所有内容，滚动视图应该如此。
当我尝试不 hard-code pageTitles 而是从 firebase 中提取它时，问题就来了。
当我注释掉我在 hard-coding pageTitles 数组的位置时，我在发送标题的 ContentViewController 上得到了一个意外的 nil 值，我喜欢 titleLabel.text =（什么已发送过来）。
我想也许用 if/let 来保护它，让 firebase 有时间加载东西会有所帮助，所以我做了
if let title = (what was sent over) {
titleLabel.text = title
}
发生这种情况时屏幕上没有任何显示，然后如果我向左或向右滚动，我会收到 pagebefore/pageafters 中索引向下的错误。
我感觉这个应该超级简单，很像tableview吧？从 firebase 加载数据，用信息填充数组，使用 if/lets 让 firebase 有时间加载，然后根据数组更新 UI。
我认为您的 DataService 是异步的。数据准备好后，您必须创建 pageviewcontroller。试试这个修改后的 viewDidLoad 方法。
重写 func viewDidLoad()
{
super.viewDidLoad()
self.pageTitles = []
// self.pageTitles = ["1", "2", "3", "4'"]
DataService.ds.REF_INTERESTS.child(passedInterest).child("rooms").child(passedRoom).child("users").observeSingleEventOfType(.Value) {（快照：FIRDataSnapshot）在
print(snapshot.value)
if let snapshots = snapshot.children.allObjects as? [FIRDataSnapshot] {
for snap in snapshots {
let name = snap.key
let uid = snap.value as! String
let person = Person(name: name, bio: "", UID: uid)
if person.UID != self.currentUser {
self.pageTitles.append(uid)
}
}
self.pageViewController = self.storyboard?.instantiateViewControllerWithIdentifier("PageViewController") as! UIPageViewController
self.pageViewController.dataSource = self
let startVC = self.viewControllerAtIndex(0) as ContentViewController
let viewControllers = NSArray(object: startVC)
self.pageViewController.setViewControllers(viewControllers as? [UIViewController], direction: .Forward, animated: true, completion: nil)
self.pageViewController.view.frame = CGRectMake(0, 30, self.view.frame.width, self.view.frame.size.height - 60)
self.addChildViewController(self.pageViewController)
self.view.addSubview(self.pageViewController.view)
self.pageViewController.didMoveToParentViewController(self)
}
}
我有一个可用的页面视图控制器系统（只是要粘贴所有内容，很确定问题出在顶部附近的我的 firebase 观察中）：
class IndividualPeopleVC: UIViewController, UIPageViewControllerDataSource {
var pageViewController: UIPageViewController!
var pageTitles : [String]!
var imageURLS: NSArray!
let currentUser = FIRAuth.auth()?.currentUser?.uid
override func viewDidLoad()
{
super.viewDidLoad()
self.pageTitles = []
self.pageTitles = ["1", "2", "3", "4'"]
DataService.ds.REF_INTERESTS.child(passedInterest).child("rooms").child(passedRoom).child("users").observeSingleEventOfType(.Value) { (snapshot: FIRDataSnapshot) in
print(snapshot.value)
if let snapshots = snapshot.children.allObjects as? [FIRDataSnapshot] {
for snap in snapshots {
let name = snap.key
let uid = snap.value as! String
let person = Person(name: name, bio: "", UID: uid)
if person.UID != self.currentUser {
self.pageTitles.append(uid)
}
}
}
self.pageViewController = self.storyboard?.instantiateViewControllerWithIdentifier("PageViewController") as! UIPageViewController
self.pageViewController.dataSource = self
let startVC = self.viewControllerAtIndex(0) as ContentViewController
let viewControllers = NSArray(object: startVC)
self.pageViewController.setViewControllers(viewControllers as? [UIViewController], direction: .Forward, animated: true, completion: nil)
self.pageViewController.view.frame = CGRectMake(0, 30, self.view.frame.width, self.view.frame.size.height - 60)
self.addChildViewController(self.pageViewController)
self.view.addSubview(self.pageViewController.view)
self.pageViewController.didMoveToParentViewController(self)
}
func viewControllerAtIndex(index: Int) -> ContentViewController
{
if ((self.pageTitles.count == 0) || (index >= self.pageTitles.count)) {
return ContentViewController()
}
var vc: ContentViewController = self.storyboard?.instantiateViewControllerWithIdentifier("ContentViewController") as! ContentViewController
vc.titleText = self.pageTitles[index] as! String
vc.imageFile = self.pageImages[index] as! String
vc.pageIndex = index
return vc
}
func pageViewController(pageViewController: UIPageViewController, viewControllerBeforeViewController viewController: UIViewController) -> UIViewController?
{
var vc = viewController as! ContentViewController
var index = vc.pageIndex as Int
if (index == 0 || index == NSNotFound)
{
return nil
}
index--
return self.viewControllerAtIndex(index)
}
func pageViewController(pageViewController: UIPageViewController, viewControllerAfterViewController viewController: UIViewController) -> UIViewController? {
var vc = viewController as! ContentViewController
var index = vc.pageIndex as Int
if (index == NSNotFound) {
return nil
}
index++
if (index == self.pageTitles.count){
return nil
}
return self.viewControllerAtIndex(index)
}
func presentationCountForPageViewController(pageViewController: UIPageViewController) -> Int{
return self.pageTitles.count
}
func presentationIndexForPageViewController(pageViewController: UIPageViewController) -> Int{
return 0
}
}
所以基本上大部分只是 copy-pasted 来自另一个来源并且它有效。它从滚动的 pageTitles 数组创建 4 个页面，在另一个 VC 我传递 1、2、3 和 4 并且标签显示数组中的所有内容，滚动视图应该如此。
当我尝试不 hard-code pageTitles 而是从 firebase 中提取它时，问题就来了。
当我注释掉我在 hard-coding pageTitles 数组的位置时，我在发送标题的 ContentViewController 上得到了一个意外的 nil 值，我喜欢 titleLabel.text =（什么已发送过来）。
我想也许用 if/let 来保护它，让 firebase 有时间加载东西会有所帮助，所以我做了
if let title = (what was sent over) {
titleLabel.text = title
}
发生这种情况时屏幕上没有任何显示，然后如果我向左或向右滚动，我会收到 pagebefore/pageafters 中索引向下的错误。
我感觉这个应该超级简单，很像tableview吧？从 firebase 加载数据，用信息填充数组，使用 if/lets 让 firebase 有时间加载，然后根据数组更新 UI。
我认为您的 DataService 是异步的。数据准备好后，您必须创建 pageviewcontroller。试试这个修改后的 viewDidLoad 方法。
重写 func viewDidLoad()
{
super.viewDidLoad()
self.pageTitles = []
// self.pageTitles = ["1", "2", "3", "4'"] DataService.ds.REF_INTERESTS.child(passedInterest).child("rooms").child(passedRoom).child("users").observeSingleEventOfType(.Value) {（快照：FIRDataSnapshot）在
print(snapshot.value)
if let snapshots = snapshot.children.allObjects as? [FIRDataSnapshot] {
for snap in snapshots {
let name = snap.key
let uid = snap.value as! String
let person = Person(name: name, bio: "", UID: uid)
if person.UID != self.currentUser {
self.pageTitles.append(uid)
}
}
self.pageViewController = self.storyboard?.instantiateViewControllerWithIdentifier("PageViewController") as! UIPageViewController
self.pageViewController.dataSource = self
let startVC = self.viewControllerAtIndex(0) as ContentViewController
let viewControllers = NSArray(object: startVC)
self.pageViewController.setViewControllers(viewControllers as? [UIViewController], direction: .Forward, animated: true, completion: nil)
self.pageViewController.view.frame = CGRectMake(0, 30, self.view.frame.width, self.view.frame.size.height - 60)
self.addChildViewController(self.pageViewController)
self.view.addSubview(self.pageViewController.view)
self.pageViewController.didMoveToParentViewController(self)
}
}