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。
干净的方式:
extension URL {
var favIcon16: UIImage? { getFav(ofSize: .s) }
var favIcon32: UIImage? { getFav(ofSize: .m) }
var favIcon64: UIImage? { getFav(ofSize: .l) }
var favIcon128: UIImage? { getFav(ofSize: .xl) }
var favIcon256: UIImage? { getFav(ofSize: .xxl) }
var favIcon512: UIImage? { getFav(ofSize: .xxxl) }
private func getFav(ofSize s: FavSize) -> UIImage? {
guard UIApplication.shared.canOpenURL(self),
let favUrl = URL(string: "https://www.google.com/s2/favicons?sz=\(s.rawValue)&domain=\(self.absoluteURL)"),
let data = try? Data(contentsOf: favUrl)
else { return nil }
return UIImage(data: data)
}
private enum FavSize: Int, CaseIterable { case s = 16, m = 32, l = 64, xl = 128, xxl = 256, xxxl = 512 }
}
和用法:
let myUrl = URL(string: "http://facebook.com")
myImgView.image = myUrl.favIcon16
翠鸟是一个最好的库加载图像到URL。
Github URL - https://github.com/onevcat/Kingfisher
// If you want to use Activity Indicator.
imageview_pic.kf.indicatorType = .activity
imageview_pic.kf.setImage(with: URL(string: "Give your url string"))
// If you want to use custom placeholder image.
imageview_pic.kf.setImage(with: URL(string: "Give your url string"), placeholder: UIImage(named: "placeholder image name"), options: nil, progressBlock: nil, completionHandler: nil)
斯威夫特4
这个方法将从一个网站异步下载图像并缓存它:
func getImageFromWeb(_ urlString: String, closure: @escaping (UIImage?) -> ()) {
guard let url = URL(string: urlString) else {
return closure(nil)
}
let task = URLSession(configuration: .default).dataTask(with: url) { (data, response, error) in
guard error == nil else {
print("error: \(String(describing: error))")
return closure(nil)
}
guard response != nil else {
print("no response")
return closure(nil)
}
guard data != nil else {
print("no data")
return closure(nil)
}
DispatchQueue.main.async {
closure(UIImage(data: data!))
}
}; task.resume()
}
在使用:
getImageFromWeb("http://www.apple.com/euro/ios/ios8/a/generic/images/og.png") { (image) in
if let image = image {
let imageView = UIImageView(frame: CGRect(x: 0, y: 0, width: 200, height: 200))
imageView.image = image
self.view.addSubview(imageView)
} // if you use an Else statement, it will be in background
}
