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 }
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)
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)
})
}
