Swift 异步加载图像 [英] Swift async load image

问题描述

我正在处理来自 url 异步的显示图像.我试图为下载图像创建一个新线程，然后在 main thread 上刷新.

I am working on show image from url async. I have tried to create a new thread for download image and then refresh on main thread.

func asyncLoadImg(product:Product,imageView:UIImageView){
    let downloadQueue = dispatch_queue_create("com.myApp.processdownload", nil)
    dispatch_async(downloadQueue){
        let data = NSData(contentsOfURL: NSURL(string: product.productImage)!)
        var image:UIImage?
        if data != nil{
            image = UIImage(data: data!)
        }
        dispatch_async(dispatch_get_main_queue()){
            imageView.image = image
        }

    }
}

当我试图调试它时，当涉及到 dispatch_async(downloadQueue) 时，它跳出了 func.有什么建议吗?谢谢

When I was trying to debug that, when it comes to dispatch_async(downloadQueue), it jumps out the func. Any suggestion? Thx

推荐答案

**Swift 5.0+ 更新代码:

**Swift 5.0+ updated Code :

extension UIImageView {

    
        func imageFromServerURL(_ URLString: String, placeHolder: UIImage?) {

        self.image = nil
        //If imageurl's imagename has space then this line going to work for this
        let imageServerUrl = URLString.addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed) ?? ""
        

        if let url = URL(string: imageServerUrl) {
            URLSession.shared.dataTask(with: url, completionHandler: { (data, response, error) in

                //print("RESPONSE FROM API: (response)")
                if error != nil {
                    print("ERROR LOADING IMAGES FROM URL: (error)")
                    DispatchQueue.main.async {
                        self.image = placeHolder
                    }
                    return
                }
                DispatchQueue.main.async {
                    if let data = data {
                        if let downloadedImage = UIImage(data: data) {
                       
                            self.image = downloadedImage
                        }
                    }
                }
            }).resume()
        }
    }
}

现在只要你需要这样做就可以从服务器 url 加载图像:

Now wherever you required just do this to load image from server url :

1. 使用 swift 5.0 + 使用占位符图像的更新代码:UIImageView.imageFromServerURL(URLString:here server url",placeHolder: uiimage 格式的占位符图片)

简单！

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