UIImageView不顯示UICollectionViewCell中的下載圖像

我有一個應顯示照片的集合視圖。UIImageView不顯示UICollectionViewCell中的下載圖像

當我從Assets.xcassets顯示臨時圖像時，一切正常，但是當我從互聯網上下載圖像時，它不顯示任何內容。

CollectionViewController.swift

class CollectionViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate, UICollectionViewDelegateFlowLayout { 
    @IBOutlet var collectionView: UICollectionView! 

    var currentCategory:PhotoCategory! 

    func numberOfSections(in collectionView: UICollectionView) -> Int { 
     return 1 
    } 

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

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell { 
     let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "GalleryItemCollectionViewCell", for: indexPath) as! GalleryItemCollectionViewCell 

     cell.setGalleryItem(imageURL: currentCategory.images[indexPath.row].image) 
     return cell 
    } 

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize { 
     let picDimension = self.view.frame.size.width/4.0 
     return CGSize(width: picDimension, height: picDimension) 
    } 

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets { 
     let leftRightInset = self.view.frame.size.width/20.0 
     return UIEdgeInsetsMake(0, leftRightInset, 0, leftRightInset) 
    } 
}

GalleryItemCollectionViewCell.swift

class GalleryItemCollectionViewCell: UICollectionViewCell { 
    @IBOutlet var itemImageView: UIImageView! 

    func setGalleryItem(imageURL:String) { 
     //itemImageView.image = #imageLiteral(resourceName: "tempImage2") 
     let url = URL(string: imageURL) 
     DispatchQueue.global(qos: DispatchQoS.QoSClass.default).async { 
      let data = try? Data(contentsOf: url!) 
      DispatchQueue.main.async(execute: { 
       if let imageData = data { 
        if let image = UIImage(data: imageData) { 
         print("We do have the image") 
         self.itemImageView = UIImageView(image: image) 
        } 
       } 
      }); 
     } 
    } 
}

我確實看到「我們確實有形象」的輸出，所以下載完成，數據是一個UIImage。

如果我取消對該行：

//itemImageView.image = #imageLiteral(resourceName: "tempImage2")

並刪除以下異步，一切正常。

當我在ViewController中使用下載代碼來顯示一個正常的UiImageView它確實有效。

更新：

我最終加入了擴展的UIImageView到項目：

extension UIImageView { 
    func downloadedFrom(link:String, contentMode mode: UIViewContentMode) { 
     guard 
      let url = NSURL(string: link) 
      else {return} 
     contentMode = mode 
     URLSession.shared.dataTask(with: url as URL, completionHandler: { (data, response, error) -> Void in 
      guard 
       let httpURLResponse = response as? HTTPURLResponse, httpURLResponse.statusCode == 200, 
       let mimeType = response?.mimeType, mimeType.hasPrefix("image"), 
       let data = data, error == nil, 
       let image = UIImage(data: data) 
       else { return } 
      DispatchQueue.main.async(execute: { 
       self.image = image 
      }); 
     }).resume() 
    } 
}

，我將照片添加像這樣cellForItemAt：

cell.itemImageView.downloadedFrom(link: cell.photo.image, contentMode: .scaleAspectFill)

來源

2016-11-27 Walter

if let image = UIImage(data: imageData) { 
        print("We do have the image") 
        self.itemImageView = UIImageView(image: image) 
       }

更改爲

if let image = UIImage(data: imageData) { 
        print("We do have the image") 
        self.itemImageView.image = image 
       }

來源

2016-11-27 12:41:57

UIImageView不顯示UICollectionViewCell中的下載圖像

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