Swift异步加载映像 [英] Swift async load image

问题描述

我正在处理来自url异步的显示图像.我试图创建一个用于下载图像的新线程，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
        }

    }
}

当我尝试调试时，涉及dispatch_async(downloadQueue)时，它会跳出功能.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+更新的代码:(获得了 jamesrochabrun 的帮助链接

Swift 5.0+ updated Code :( took help from jamesrochabrun Link https://github.com/jamesrochabrun/JSONTutorialFinal )

extension UIImageView {

    let imageCache = NSCache<NSString, UIImage>()

        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 cachedImage = imageCache.object(forKey: NSString(string: imageServerUrl)) {
            self.image = cachedImage
            return
        }

        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) {
                            imageCache.setObject(downloadedImage, forKey: NSString(string: imageServerUrl))
                            self.image = downloadedImage
                        }
                    }
                }
            }).resume()
        }
    }
}

快速3更新代码:

extension UIImageView {
    public func imageFromServerURL(urlString: String) {
        self.image = nil
        URLSession.shared.dataTask(with: NSURL(string: urlString)! as URL, completionHandler: { (data, response, error) -> Void in

            if error != nil {
                print(error)
                return
            }
            DispatchQueue.main.async(execute: { () -> Void in
                let image = UIImage(data: data!)
                self.image = image
            })

        }).resume()
    }}

Swift 2.2代码:

 extension UIImageView {
        public func imageFromServerURL(urlString: String) {
    self.image = nil
            NSURLSession.sharedSession().dataTaskWithURL(NSURL(string: urlString)!, completionHandler: { (data, response, error) -> Void in

                if error != nil {
                    print(error)
                    return
                }
                dispatch_async(dispatch_get_main_queue(), { () -> Void in
                    let image = UIImage(data: data!)
                    self.image = image
                })

            }).resume()
        }}

现在，无论您需要什么地方，都只需执行此操作即可从服务器url加载图像:

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

1. 使用占位符图像的swift 3.0 +更新代码: UIImageView.imageFromServerURL(URLString:此处服务器url"，placeHolder:uiimage格式的占位符图像)

1. Using swift 3.0 + updated code using placeholder image : UIImageView.imageFromServerURL(URLString:"here server url",placeHolder: placeholder image in uiimage format)

Swfit 3以下: UIImageView.imageFromServerURL(此处服务器网址")

Swfit 3 or less : UIImageView.imageFromServerURL("here server url")

简单！

这篇关于Swift异步加载映像的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！