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。
编辑为最新更改2021年9月
// It's better to use extension
extension UIImageView {
func downloadImage(from URLString: String, with completion: @escaping (_ response: (status: Bool, image: UIImage? ) ) -> Void) {
guard let url = URL(string: URLString) else {
completion((status: false, image: nil))
return
}
URLSession.shared.dataTask(with: url) { data, response, error in
guard error == nil else {
completion((status: false, image: nil))
return
}
guard let httpURLResponse = response as? HTTPURLResponse,
httpURLResponse.statusCode == 200,
let data = data else {
completion((status: false, image: nil))
return
}
let image = UIImage(data: data)
completion((status: true, image: image))
}.resume()
}
}
快乐的鳕鱼。欢呼:)
斯威夫特 2.2 ||Xcode 7.3
我得到了惊人的成绩!!使用AlamofireImage swift库
它提供了多种功能，如:
异步下载
自动清除图像缓存，如果内存警告发生的应用程序
图像URL缓存
图像缓存
避免重复下载
在你的应用中很容易实现
步骤1安装吊舱
Alamofire 3 x 3。
宾夕法尼亚州’Alamofire’
AlamofireImage 2。4 . x
宾夕法尼亚州’AlamofireImage’
步骤2导入并使用
import Alamofire
import AlamofireImage
let downloadURL = NSURL(string: "http://cdn.sstatic.net/Sites/stackoverflow/company/Img/photos/big/6.jpg?v=f4b7c5fee820")!
imageView.af_setImageWithURL(downloadURL)
就是这样! !它会照顾好一切
非常感谢Alamofire的伙计们，让iDevelopers的生活变得简单了;)
斯威夫特2。x答案下载图像到文件(与Leo Dabus的答案相反，它将图像存储在内存中)。根据Leo Dabus的回答和Rob的回答，从完成处理程序的NSURLSession DownloadTaskWithRequest中获取数据:
// Set download vars
let downloadURL = NSURL() // URL to download from
let localFilename = "foobar.png" // Filename for storing locally
// Create download request
let task = NSURLSession.sharedSession().downloadTaskWithURL(downloadURL) { location, response, error in
guard location != nil && error == nil else {
print("Error downloading message: \(error)")
return
}
// If here, no errors so save message to permanent location
let fileManager = NSFileManager.defaultManager()
do {
let documents = try fileManager.URLForDirectory(.DocumentDirectory, inDomain: .UserDomainMask, appropriateForURL: nil, create: false)
let fileURL = documents.URLByAppendingPathComponent(localFilename)
try fileManager.moveItemAtURL(location!, toURL: fileURL)
self.doFileDownloaded(fileURL, localFilename: localFilename)
print("Downloaded message @ \(localFilename)")
} catch {
print("Error downloading message: \(error)")
}
}
// Start download
print("Starting download @ \(downloadURL)")
task.resume()
// Helper function called after file successfully downloaded
private func doFileDownloaded(fileURL: NSURL, localFilename: String) {
// Do stuff with downloaded image
}
