一旦从firebase接收到数据，如何让uicollectionview重新加载? [英] How to make uicollectionview reload once it receives data from firebase?

问题描述

我想让 UI collectionView 在收到来自 firebase 的数据后自行重新加载.现在它只有在我点击刷新按钮时才能手动工作.

I would like to make a UI collectionView reload itself after it has received data from firebase. Right now it only works manually when I click on the refresh button.

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()
    }
}

这段代码所做的基本上是通过比较两个数组(身份和身份3)来显示用户拥有的奖牌，以确保他们相符，否则它将使数组中不包含的身份图像变灰(身份3)

What this code does is basically display medals a user has by comparing two arrays (identities and identities3) to make sure they tally if not it will greyed out the images of identities no contained in the array (identities3)

数据在 viewDidLoad 中作为来自 firebase 的快照数据接收.我打算让 collectionView 在每次调用 viewWillAppear 时重新加载.

The data is received in viewDidLoad as a snapshot data from firebase. I intend to make it such that the collectionView will reload every time when viewWillAppear is called.

我尝试在 viewDidLoad 和 viewDidAppear 中调用 self.collectionView!.reloadData() 但无济于事.我怀疑这可能是接收数据的延迟导致加载空白数组(identities3).

I've attempted to call self.collectionView!.reloadData() in viewDidLoad and viewDidAppear but to no avail. I suspect it could be the delay in which data is received causing a blank array (identities3) to be loaded instead.

推荐答案

你需要调用 self.collectionView!.reloadData() 在你检索到你的数据并将它存储到你的 数据源.

You need to call self.collectionView!.reloadData() after you have retrieved you data and stored it into your DataSource.

即在您的 Firebase .observeSingleEventOfType

i.e in your completionBlock: of your Firebase .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()
    })

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