ios - 来自网络服务的图像在 UITableview 中刷新

Question

我试图将图像从网络服务加载到我的表格 View 中。但是图像被刷新并且相同的图像在每个单元格中旋转。我认为问题是由于没有以正确的方式实现缓存。我尝试了很多东西。但是没有运气..

导入 UIKit 类 NewsTableViewController: UITableViewController {

var SLAFImages = [String]()
var SLAFHeading = [String]()
var SLAFText = [String]()
var SLAFCount = [Int]()

@IBOutlet weak var btnAction: UIBarButtonItem!

override func viewDidLoad() {
    super.viewDidLoad()

    let reposURL = NSURL(string: "https://www.helitours.lk/test.html")
    // 2
    do{
        if let JSONData = NSData(contentsOfURL: reposURL!) {
            // 3
            if let json = try NSJSONSerialization.JSONObjectWithData(JSONData, options: NSJSONReadingOptions.MutableContainers) as? NSDictionary {
                // 4
                if let reposArray = json["items"] as? [NSDictionary] {
                    // 5
                    for item in reposArray {
                       if let name = item.valueForKey("title") {

                           SLAFHeading.append(name as! String)
                        }

                        if let Imgname = item.valueForKey("main_image") {
                            let urlimg=("http://airforce.lk/"+(Imgname as! String)) as String;
                             SLAFImages.append(urlimg)
                                                       }
                                              }
                }
            }
        }

    }catch{}

    let infoImage = UIImage(named: "crest png.png")
    let imgWidth = infoImage?.size.width
    let imgHeight = infoImage?.size.height
    let button:UIButton = UIButton(frame: CGRect(x: 0,y: 0,width: imgWidth!, height: imgHeight!))
    button.setBackgroundImage(infoImage, forState: .Normal)
     //button.addTarget(self, action: Selector("openInfo"), forControlEvents: UIControlEvents.TouchUpInside)
    SLAFCount=[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]
    SLAFText = ["While they like to munch on underwater plants, you might ",
        "While they like to munch on underwater plants, you might ",
        "While they like to munch on underwater plants, you might "]

    //SLAFImages = ["Img1.jpg","Img2.jpg","Img3.jpg"]


    // Uncomment the following line to preserve selection between presentations
    // self.clearsSelectionOnViewWillAppear = false

    // Uncomment the following line to display an Edit button in the navigation bar for this view controller.
    // self.navigationItem.rightBarButtonItem = self.editButtonItem()
}

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

// MARK: - Table view data source

override func numberOfSectionsInTableView(tableView: UITableView) -> Int {

    return 1
}

override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    // #warning Incomplete implementation, return the number of rows
    return SLAFHeading.count
}


override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
    let cell =
    self.tableView.dequeueReusableCellWithIdentifier(
        "NewsTableCell", forIndexPath: indexPath)
        as! NewsTableViewCell

    let row = indexPath.row
    cell.NewsHeading.font =
        UIFont.preferredFontForTextStyle(UIFontTextStyleHeadline)
    cell.NewsHeading.text = SLAFHeading[row]
    if let url = NSURL(string: SLAFImages[row]) {
        let task = NSURLSession.sharedSession().dataTaskWithURL(url) { (data, NSHTTPURLResponse, error) -> Void in

            if error != nil {
                print("thers an error in the log")
            } else {

                dispatch_async(dispatch_get_main_queue()) {
                    cell.NewsImage.image = UIImage(data: data!)

                }
            }

        }

        task.resume()
    }
    cell.NewsCount.text=String(SLAFCount[row])
    cell.layoutIfNeeded()
    return cell
}

Answer 1

在表格 View 单元格中下载图像

更好的方法 此代码不会增加应用程序的更多内存使用。

//Initialize your catch variable 
  var cache = NSCache()
    
// MARK: - Private   Image Download Block here
                private func downloadPhoto(url: NSURL, completion: (url: NSURL, image: UIImage) -> Void) {
                    dispatch_async(downloadQueue, { () -> Void in
                        if let data = NSData(contentsOfURL: url) {
                            if let image = UIImage(data: data) {
                                dispatch_async(dispatch_get_main_queue(), { () -> Void in
                                    cache.setObject(image, forKey: url)
                                    completion(url: url, image: image)
                                })
                            }
                        }
                    })
                }
    


//Call this Function from Table view 
 //Step 1
 // Checking here Image inside Catch
           let imageurl = NSURL(string:”Image URL here”)
               let myimage = cache.objectForKey(imageurl!) as? UIImage
    
            //Step 2
            // Downloading here Promotion image
            if myimage == nil {
           downloadPhoto(imageurl!, completion: { (url, image) -> Void in
                    let indexPath_ = self.tblView.indexPathForCell(cell)
                            if indexPath.isEqual(indexPath_) {
                                cell.myImageView.image = image
                            }
                            
                        })
                        
                    }

希望对您有所帮助。