如何使uicollectionview在从Firebase接收数据后重新加载？

Question

我想让一个UI collectionView在它从Firebase接收到数据后重新加载自己。现在只有当我点击刷新按钮时它才能手动工作。

class MedalsViewController: UICollectionViewController { 

    var imagesArray = [String]() 
    var identities = [String]() 
    var identities2 = [String]() //Creates an empty array 
    var imagesArrayGreyed = [String]() 
    var identities3 = [String]() 
    let databaseRef = FIRDatabase.database().reference() 
    let userID = FIRAuth.auth()?.currentUser?.uid 

    override func viewDidLoad() { 
     super.viewDidLoad() 


     let userID = FIRAuth.auth()?.currentUser?.uid 
     let databaseRef = FIRDatabase.database().reference() 
     databaseRef.child("users").child(userID!).child("medals").observeSingleEventOfType(.Value, withBlock: { (snapshot) in 
      // Get user medals 
      self.identities3 = snapshot.value as! [String] 
      print (self.identities3) 
     }) 


     imagesArray = ["1", "2", "3"] //Add all the medal images here 
     identities = ["Shield", "Tie", "Star"] //Add all the identities here 
     identities2 = ["Shield", "Tie"] //Choose what medals the user has. 
     imagesArrayGreyed = ["1Greyed","2Greyed","3Greyed"] //Add all the greyed images here 

    } 

    override func didReceiveMemoryWarning() { 
     super.didReceiveMemoryWarning() 
     // Dispose of any resources that can be recreated. 
    } 

    override func viewWillAppear(animated: Bool) { 

     self.tabBarController?.tabBar.hidden = false 
     // Attempt at getting medals array from firebase database 

    } 



    override func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell { 
     let cell = collectionView.dequeueReusableCellWithReuseIdentifier("cell", forIndexPath: indexPath) 

     let imageView = cell.viewWithTag(1) as! UIImageView 

     // Identites2 is the medals you currently own, so it'll check back to see if you own the medal and if not a question mark will be displayed. 
     // Time to check to see if it can update in real time. Check out firebase and try to link it here 
     // Also see if can add a progress bar to only show for those greyed out medals 


     // Get ready to edit this to identities3 which is directly taken from firebase database 
     if (identities3.contains(identities[indexPath.row])) { 
      imageView.image = UIImage(named: imagesArray[indexPath.row]) 

     } 
     else { 
      imageView.image = UIImage(named: imagesArrayGreyed[indexPath.row]) //Set default image not in identities2 
     } 

     return cell 

    } 

    override func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int { 
     return imagesArray.count 
    } 

    override func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) { 
     let vc = identities[indexPath.row] 
     let viewController = storyboard?.instantiateViewControllerWithIdentifier(vc) 
     self.navigationController?.pushViewController(viewController!, animated: true) 
     viewController?.title = self.identities[indexPath.row] 
    } 


    // Send a fake medal from the array of identities2 
    @IBAction func sendFakeMedalandReload(sender: UIBarButtonItem) { 
     let databaseRef = FIRDatabase.database().reference() 
     databaseRef.child("users/\(FIRAuth.auth()!.currentUser!.uid)/medals").setValue(identities2) 
     self.collectionView!.reloadData() 
    } 
} 

通过比较两个数组这段代码的含义基本上是显示奖牌用户有（身份和identities3），以确保它们相符，如果不是会变灰不包含在数组中的身份的图像（identities3）

数据在viewDidLoad中作为firebase的快照数据接收。我打算这样做，使得每次调用viewWillAppear时，collectionView都会重新加载。

我试图在viewDidLoad和viewDidAppear中调用self.collectionView！.reloadData（），但无济于事。我怀疑这可能是数据收到时导致空数组（identities3）被加载的延迟。

Answer 1

您需要拨打self.collectionView!.reloadData()，您需要检索您的数据并将其存入您的DataSource。

即在你的completionBlock:你的火力地堡.observeSingleEventOfType

databaseRef.child("users").child(userID!).child("medals").observeSingleEventOfType(.Value, withBlock: { (snapshot) in 
     // Get user medals 
     self.identities3 = snapshot.value as! [String] 
     self.collectionView!.reloadData() 
    })