我的收藏视图存在问题，在视频出现在屏幕上后，我会在一秒钟内“眨眼”。
可能导致此问题的viewDidLoad或viewDidAppear吗？
这是我目前的Swift代码：
class HomeViewController: UIViewController
{
// MARK: IBOutlets
@IBOutlet weak var backgroundImageView: UIImageView!
@IBOutlet weak var collectionView: UICollectionView!
@IBOutlet weak var currentUserProfileImageButton: UIButton!
@IBOutlet weak var currentUserFullNameButton: UIButton!
// MARK: - UICollectionViewDataSource
private var interests = [Interest]()
override func preferredStatusBarStyle() -> UIStatusBarStyle {
return .LightContent
}
override func viewDidAppear(animated: Bool) {
super.viewDidAppear(animated)
if PFUser.currentUser() == nil {
// the user hasn't logged in yet
showLogin()
} else {
// the user logged in, do something else
fetchInterests()
let center = NSNotificationCenter.defaultCenter()
let queue = NSOperationQueue.mainQueue()
center.addObserverForName("NewInterestCreated", object: nil, queue: queue, usingBlock: { (notification) -> Void in
if let newInterest = notification.userInfo?["newInterestObject"] as? Interest {
if !self.interestWasDisplayed(newInterest) {
self.interests.insert(newInterest, atIndex: 0)
self.collectionView.reloadData()
}
}
})
}
}
func interestWasDisplayed(newInterest: Interest) -> Bool {
for interest in interests {
if interest.objectId! == newInterest.objectId! {
return true
}
}
return false
}
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
if UIScreen.mainScreen().bounds.size.height == 480.0 {
let flowLayout = self.collectionView.collectionViewLayout as! UICollectionViewFlowLayout
flowLayout.itemSize = CGSizeMake(250.0, 300.0)
}
configureUserProfile()
}
func configureUserProfile()
{
// configure image button
currentUserProfileImageButton.contentMode = UIViewContentMode.ScaleAspectFill
currentUserProfileImageButton.layer.cornerRadius = currentUserProfileImageButton.bounds.width / 2
currentUserProfileImageButton.layer.masksToBounds = true
}
private struct Storyboard {
static let CellIdentifier = "Interest Cell"
}
@IBAction func userProfileButtonClicked()
{
PFUser.logOut()
showLogin()
}
// MARK: - Fetch Data From Parse
func fetchInterests()
{
let currentUser = User.currentUser()!
let interestIds = currentUser.interestIds
if interestIds?.count > 0
{
let interestQuery = PFQuery(className: Interest.parseClassName())
interestQuery.orderByDescending("updatedAt")
interestQuery.cachePolicy = PFCachePolicy.NetworkElseCache
interestQuery.whereKey("objectId", containedIn: interestIds)
interestQuery.findObjectsInBackgroundWithBlock({ (objects, error) -> Void in
if error == nil {
if let interestObjects = objects as [PFObject]? {
self.interests.removeAll()
for interestObject in interestObjects {
let interest = interestObject as! Interest
self.interests.append(interest)
}
self.collectionView.reloadData()
}
} else {
print("\(error!.localizedDescription)")
}
})
}
}
// MARK: - Navigation
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "Show Interest" {
let cell = sender as! InterestCollectionViewCell
let interest = cell.interest
let navigationViewController = segue.destinationViewController as! UINavigationController
let interestViewController = navigationViewController.topViewController as! InterestViewController
interestViewController.interest = interest
} else if segue.identifier == "CreateNewInterest" {
_ = segue.destinationViewController as! NewInterestViewController
} else if segue.identifier == "Show Discover" {
_ = segue.destinationViewController as! DiscoverViewController
}
}
func showLogin()
{
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let welcomeNavigationVC = storyboard.instantiateViewControllerWithIdentifier("WelcomeNavigationViewController") as! UINavigationController
self.presentViewController(welcomeNavigationVC, animated: true, completion: nil)
}
}
extension HomeViewController : UICollectionViewDataSource{
func numberOfSectionsInCollectionView(collectionView: UICollectionView) -> Int
{
return 1
}
func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int
{
return interests.count
}
func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell
{
let cell = collectionView.dequeueReusableCellWithReuseIdentifier(Storyboard.CellIdentifier, forIndexPath: indexPath) as! InterestCollectionViewCell
cell.interest = self.interests[indexPath.item]
return cell
}
}
extension HomeViewController : UIScrollViewDelegate{
func scrollViewWillEndDragging(scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>)
{
let layout = self.collectionView?.collectionViewLayout as! UICollectionViewFlowLayout
let cellWidthIncludingSpacing = layout.itemSize.width + layout.minimumLineSpacing
var offset = targetContentOffset.memory
let index = (offset.x + scrollView.contentInset.left) / cellWidthIncludingSpacing
let roundedIndex = round(index)
offset = CGPoint(x: roundedIndex * cellWidthIncludingSpacing - scrollView.contentInset.left, y: -scrollView.contentInset.top)
targetContentOffset.memory = offset
}
}
extension HomeViewController : PFLogInViewControllerDelegate, PFSignUpViewControllerDelegate{
func presentLoginViewController()
{
let logInController = PFLogInViewController()
let signupController = PFSignUpViewController()
signupController.delegate = self
logInController.delegate = self
logInController.fields = [PFLogInFields.UsernameAndPassword, PFLogInFields.LogInButton, PFLogInFields.SignUpButton]
logInController.signUpController = signupController
presentViewController(logInController, animated: true, completion: nil)
}
func logInViewController(logInController: PFLogInViewController, didLogInUser user: PFUser)
{
logInController.dismissViewControllerAnimated(true, completion: nil)
}
func signUpViewController(signUpController: PFSignUpViewController, didSignUpUser user: PFUser)
{
signUpController.dismissViewControllerAnimated(true, completion: nil)
}
}
谢谢你们：）