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。
这是从URL加载/下载图像的工作代码。NSCache自动和显示占位符图像下载和加载实际图像(Swift 4 | Swift 5代码)。
func NKPlaceholderImage(image:UIImage?, imageView:UIImageView?,imgUrl:String,compate:@escaping (UIImage?) -> Void){
if image != nil && imageView != nil {
imageView!.image = image!
}
var urlcatch = imgUrl.replacingOccurrences(of: "/", with: "#")
let documentpath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0]
urlcatch = documentpath + "/" + "\(urlcatch)"
let image = UIImage(contentsOfFile:urlcatch)
if image != nil && imageView != nil
{
imageView!.image = image!
compate(image)
}else{
if let url = URL(string: imgUrl){
DispatchQueue.global(qos: .background).async {
() -> Void in
let imgdata = NSData(contentsOf: url)
DispatchQueue.main.async {
() -> Void in
imgdata?.write(toFile: urlcatch, atomically: true)
let image = UIImage(contentsOfFile:urlcatch)
compate(image)
if image != nil {
if imageView != nil {
imageView!.image = image!
}
}
}
}
}
}
}
像这样使用:
// Here imgPicture = your imageView
// UIImage(named: "placeholder") is Display image brfore download and load actual image.
NKPlaceholderImage(image: UIImage(named: "placeholder"), imageView: imgPicture, imgUrl: "Put Here your server image Url Sting") { (image) in }
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4::
这将在加载图像时显示加载器。
你可以使用NSCache临时存储图像
let imageCache = NSCache<NSString, UIImage>()
extension UIImageView {
func loadImageUsingCache(withUrl urlString : String) {
let url = URL(string: urlString)
if url == nil {return}
self.image = nil
// check cached image
if let cachedImage = imageCache.object(forKey: urlString as NSString) {
self.image = cachedImage
return
}
let activityIndicator: UIActivityIndicatorView = UIActivityIndicatorView.init(activityIndicatorStyle: .gray)
addSubview(activityIndicator)
activityIndicator.startAnimating()
activityIndicator.center = self.center
// if not, download image from url
URLSession.shared.dataTask(with: url!, completionHandler: { (data, response, error) in
if error != nil {
print(error!)
return
}
DispatchQueue.main.async {
if let image = UIImage(data: data!) {
imageCache.setObject(image, forKey: urlString as NSString)
self.image = image
activityIndicator.removeFromSuperview()
}
}
}).resume()
}
}
用法:-
truckImageView.loadImageUsingCache(withUrl: currentTruck.logoString)
