[英]loading tableView images asynchronously in swift
我的代码从网上下载图像并将它们设置为tableView单元格imageView。 它工作正常,除了我需要点击一个单元格来刷新单元格的内容并加载图像。 我希望这些图像在加载后立即显示。 我尝试在cellToUpdate下添加reloadData(),但应用程序最终陷入无限循环并崩溃。 这是我的代码:
let request: NSURLRequest = NSURLRequest(URL: imgURL)
let getImage: NSURLSessionDataTask = session.dataTaskWithRequest(request, completionHandler: { (data: NSData!, response: NSURLResponse!, error: NSError!) -> Void in
if error == nil {
image = UIImage(data: data)
// Store the image in to our cache
self.imageCache[urlString] = image
dispatch_async(dispatch_get_main_queue(), {
if let cellToUpdate = tableView.cellForRowAtIndexPath(indexPath) {
cellToUpdate.imageView?.image = image
}
})
}
else {
println("Error: \(error.localizedDescription)")
}
})
getImage.resume()
使用以下类:
class ImageLoadingWithCache {
var imageCache = [String:UIImage]()
func getImage(url: String, imageView: UIImageView, defaultImage: String) {
if let img = imageCache[url] {
imageView.image = img
} else {
let request: NSURLRequest = NSURLRequest(URL: NSURL(string: url)!)
let mainQueue = NSOperationQueue.mainQueue()
NSURLConnection.sendAsynchronousRequest(request, queue: mainQueue, completionHandler: { (response, data, error) -> Void in
if error == nil {
let image = UIImage(data: data)
self.imageCache[url] = image
dispatch_async(dispatch_get_main_queue(), {
imageView.image = image
})
}
else {
imageView.image = UIImage(named: defaultImage)
}
})
}
}
}
用法:
var cache = ImageLoadingWithCache()
cache.getImage(YOUR_URL, imageView: YOUR_IMAGEVIEW, defaultImage: "DEFAULT_IMAGE_NAME")
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