xcode - setImageWithUrl 从 Parse.com 到 UICollectionView

Question

我正在使用框架:UIImageView+AFNetworking - 此处代码:http://pastebin.com/cyzSaxsh

这是我从 Parse.com 查询的方式:

func queryFromParse(){
        var query = PFQuery(className: "currentUploads")
        query.orderByDescending("createdAt")
        query.findObjectsInBackgroundWithBlock { (objects:[AnyObject]?, error:NSError?) -> Void in
            if error == nil
            {
                if let newObjects = objects as? [PFObject] {

                    for oneobject in newObjects {
                        let text = oneobject["imageText"] as! String
                        let username = oneobject["username"] as! String
                        let time = oneobject.createdAt!

                        if let userImage = oneobject["imageFile"] as? PFFile {
                            let userImage = oneobject["imageFile"] as! PFFile

                            let imageURL = userImage.url // <- Bruker nå userImage.URL, henter ikke bildefilen med en gang

                            var OneBigObject = Details(username: username, text: text, CreatedAt: time, image: imageURL!)

                            self.arrayOfDetails.append(OneBigObject)

                            dispatch_async(dispatch_get_main_queue()) { self.collectionView.reloadData() }
                        }
                    }
                }
            }
        }
    }

这是我的“cellForItemAtIndexPath”:

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

        cell.layer.borderWidth = 0.5
        cell.layer.cornerRadius = 3
        var myColor : UIColor = UIColor( red: 0.0, green: 0.0, blue:0.0, alpha: 0.15 )
        cell.layer.borderColor = myColor.CGColor

        var post = self.arrayOfDetails[indexPath.row]
        cell.currentUserLabel.text = post.username
        cell.imageText.text = post.text

        cell.uploadedTimeLabel.text = post.CreatedAt.timeAgo

        dispatch_async(dispatch_get_main_queue()) { cell.ImageView.setImageWithUrl(NSURL(string: post.image)!, placeHolderImage: UIImage(named: "Placeholder")) }

        return cell
    }

我有一个问题。加载图像需要 10-20 秒，而我在 Parse 中只有大约 10 张图像。这是 5 秒后的样子:

这里有什么建议吗？

Answer 1

替换这些代码:

dispatch_async(dispatch_get_main_queue()) { self.collectionView.reloadData() }
   }

在 cellForRowAtIndexPath 方法中使用这些代码:

 let request: NSURLRequest = NSURLRequest(URL: imgURL)
 let mainQueue = NSOperationQueue.mainQueue()
 NSURLConnection.sendAsynchronousRequest(request, queue: mainQueue, completionHandler: { (response, data, error) -> Void in
    if error == nil {
        let image = UIImage(data: data)
        // Update the cell
        dispatch_async(dispatch_get_main_queue(), {
            if let cellToUpdate = tableView.cellForRowAtIndexPath(indexPath) {
                cellToUpdate.imageView?.image = image
                    }
                })
            }
            else {
                println("Error: \(error.localizedDescription)")
                 }
            })