ios - 为什么 reloadData() 在我的应用程序中不起作用？

Question

我正在尝试从 Parse.com 下载一组图像到 UICollectionView 中。除 reloadData() 函数外，一切正常。在应用程序中，我可以点击后退按钮并重新进入 UICollectionView，所有图像都在那里。我只是不知道我在使用 reloadData() 函数时做错了什么。

var images = [UIImage]()
var imageFiles = [PFFile]()

class CollectionCollectionViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource {

@IBAction func xy1Button(sender: AnyObject) {

}

@IBAction func xy2Button(sender: AnyObject) {

        var downloadImages = PFQuery(className: "XY2")
        downloadImages.whereKey("Expansion", equalTo: "XY2")
        downloadImages.findObjectsInBackgroundWithBlock {
            (objects: [AnyObject]?, error: NSError?) -> Void in
            if error == nil {
                println("Successfully retrieved \(objects!.count) cards.")
                if let objects = objects as? [PFObject] {
                    for object in objects {
                        imageFiles.append(object["Image"] as! PFFile)
                        dispatch_async(dispatch_get_main_queue() ^{
                            self.collectionView.reloadData()
                            });
                        //ERROR BREAKPOINT HERE:'Thread 1: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)'
                    }
                }
            } else {
                println("Error: \(error!) \(error!.userInfo!)")
            }    
      }
}   
override func viewDidLoad() {
    super.viewDidLoad()
  }

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

func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {

    let cell: CardsCollectionViewCell = collectionView.dequeueReusableCellWithReuseIdentifier("Cell", forIndexPath: indexPath) as! CardsCollectionViewCell
    //cell.cardsImg.image = UIImage(named: cards[indexPath.row] as String)
    //return cell
    imageFiles[indexPath.row].getDataInBackgroundWithBlock{
        (imageData: NSData?, error: NSError?) -> Void in

        if error == nil {

            let image = UIImage(data: imageData!)

            cell.cardsImg.image = image
        }


    }
    return cell
}
}

Answer 1

需要在主线程中执行reloadData 来更新UI。你可以试试这个

dispatch_async(dispatch_get_main_queue(), ^{
            self.collectionView.reloadData()
}); 

正如@Grimxn 所建议的，您应该检查您的 collectionView IBOutlet 是否已连接到 Storyboard或 xib 文件中。