如果图像在ios swift中很大，如何非常快速地加载图像

Question

我有大图像它来自 Api 然后如何快速加载它。加载需要太多时间

  let data = NSData(contentsOf: NSURL(string: self.imageFile)! as URL)
            if data == nil{
            }
            else{
                DispatchQueue.main.async() {
        self.imageShow.image = UIImage(data: data! as Data)
                }
            }

这是我的代码，任何人都可以建议我

Answer 1

您可以使用此代码异步下载映像。

    if let url = self.imageFile{
    let url = URL(string: self.imageFile)
        let task = URLSession.shared.dataTask(with: url!) { data, response, error in
            guard let data = data, error == nil else { return }
            /**CHECK 404 HERE*/
            if let httpResponse = response as? HTTPURLResponse {
                if httpResponse.statusCode == 400 {
                    //YOUR CODE HERE
                return
                }
            }

            DispatchQueue.main.async() {    // execute on main thread
                self.imageShow.image = UIImage(data: data)
            }
        }
    task.resume()
    }else{
        DispatchQueue.main.async() {    // execute on main thread
         self.viewImageType.isHidden = true
        }
    }

最好不要依赖第三方库

Answer 2

您可以使用

NSOperationQueue在后台线程上加载图像，然后在主线程上的图像视图上加载图像。您可以通过以下方式实现此目的：

    let myQueue = OperationQueue()
    myQueue.addOperation { // Load image on background thread
        if let urlString = URL(string: self.imageFile) {
            do {
                let data = try Data(contentsOf: urlString)
                DispatchQueue.main.async { // Load image on main thread
                    self.imageShow.image = UIImage(data: data)
                }
            } catch {
                print("not able to load image")
            }
        }
    }