我想从我的应用程序中的URL加载图像，所以我首先尝试了Objective-C和它的工作，但是，与Swift，我有一个编译错误:
'imageWithData'不可用:使用对象构造'UIImage(data:)'
我的函数:
@IBOutlet var imageView : UIImageView
override func viewDidLoad() {
super.viewDidLoad()
var url:NSURL = NSURL.URLWithString("http://myURL/ios8.png")
var data:NSData = NSData.dataWithContentsOfURL(url, options: nil, error: nil)
imageView.image = UIImage.imageWithData(data)// Error here
}
在objective - c中:
- (void)viewDidLoad {
[super viewDidLoad];
NSURL *url = [NSURL URLWithString:(@"http://myURL/ios8.png")];
NSData *data = [NSData dataWithContentsOfURL:url];
_imageView.image = [UIImage imageWithData: data];
_labelURL.text = @"http://www.quentinroussat.fr/assets/img/iOS%20icon's%20Style/ios8.png";
}
有人能解释一下为什么imageWithData:不能与Swift一起工作，我该如何解决这个问题。
从服务器加载图像:-
func downloadImage(from url: URL , success:@escaping((_ image:UIImage)->()),failure:@escaping ((_ msg:String)->())){
print("Download Started")
getData(from: url) { data, response, error in
guard let data = data, error == nil else {
failure("Image cant download from G+ or fb server")
return
}
print(response?.suggestedFilename ?? url.lastPathComponent)
print("Download Finished")
DispatchQueue.main.async() {
if let _img = UIImage(data: data){
success(_img)
}
}
}
}
func getData(from url: URL, completion: @escaping (Data?, URLResponse?, Error?) -> ()) {
URLSession.shared.dataTask(with: url, completionHandler: completion).resume()
}
用法:-
if let url = URL(string: "http://www.apple.com/euro/ios/ios8/a/generic/images/og.png") {
self.downloadImage(from:url , success: { (image) in
print(image)
}, failure: { (failureReason) in
print(failureReason)
})
}
一个快速的黑客，如果你想快速检查图像从url
let imageURL = NSURL(string: "https://farm2.staticflickr.com/1591/26078338233_d1466b7da2_m.jpg")
let imagedData = NSData(contentsOfURL: imageURL!)!
imageView?.image = UIImage(data: imagedData)
我在一个tableview中实现了一个只有图像的自定义单元格
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell{
let cell = tableView.dequeueReusableCellWithIdentifier("theCell", forIndexPath: indexPath) as! customTableViewCell
let imageURL = NSURL(string: "https://farm2.staticflickr.com/1591/26078338233_d1466b7da2_m.jpg")
let imagedData = NSData(contentsOfURL: imageURL!)!
cell.imageView?.image = UIImage(data: imagedData)
return cell
}
Swift 4.1我创建了一个函数，只是传递图像url，图像生成后缓存键设置为完成块。
class NetworkManager: NSObject {
private var imageQueue = OperationQueue()
private var imageCache = NSCache<AnyObject, AnyObject>()
func downloadImageWithUrl(imageUrl: String, cacheKey: String, completionBlock: @escaping (_ image: UIImage?)-> Void) {
let downloadedImage = imageCache.object(forKey: cacheKey as AnyObject)
if let _ = downloadedImage as? UIImage {
completionBlock(downloadedImage as? UIImage)
} else {
let blockOperation = BlockOperation()
blockOperation.addExecutionBlock({
let url = URL(string: imageUrl)
do {
let data = try Data(contentsOf: url!)
let newImage = UIImage(data: data)
if newImage != nil {
self.imageCache.setObject(newImage!, forKey: cacheKey as AnyObject)
self.runOnMainThread {
completionBlock(newImage)
}
} else {
completionBlock(nil)
}
} catch {
completionBlock(nil)
}
})
self.imageQueue.addOperation(blockOperation)
blockOperation.completionBlock = {
print("Image downloaded \(cacheKey)")
}
}
}
}
extension NetworkManager {
fileprivate func runOnMainThread(block:@escaping ()->Void) {
if Thread.isMainThread {
block()
} else {
let mainQueue = OperationQueue.main
mainQueue.addOperation({
block()
})
}
}
}
