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。
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;)
我把这个问题的最佳答案的代码包装成一个单一的，可重用的类扩展UIImageView，所以你可以直接在你的故事板中使用异步加载UIImageViews(或从代码中创建它们)。
这是我的班级:
import Foundation
import UIKit
class UIImageViewAsync :UIImageView
{
override init()
{
super.init(frame: CGRect())
}
override init(frame:CGRect)
{
super.init(frame:frame)
}
required init(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
func getDataFromUrl(url:String, completion: ((data: NSData?) -> Void)) {
NSURLSession.sharedSession().dataTaskWithURL(NSURL(string: url)!) { (data, response, error) in
completion(data: NSData(data: data))
}.resume()
}
func downloadImage(url:String){
getDataFromUrl(url) { data in
dispatch_async(dispatch_get_main_queue()) {
self.contentMode = UIViewContentMode.ScaleAspectFill
self.image = UIImage(data: data!)
}
}
}
}
下面是如何使用它:
imageView.downloadImage("http://www.image-server.com/myImage.jpg")
Swift 3错误处理
let url = URL(string: arr[indexPath.row] as! String)
if url != nil {
DispatchQueue.global().async {
let data = try? Data(contentsOf: url!) //make sure your image in this url does exist, otherwise unwrap in a if let check / try-catch
DispatchQueue.main.async {
if data != nil {
cell.imgView.image = UIImage(data:data!)
}else{
cell.imgView.image = UIImage(named: "default.png")
}
}
}
}
与扩展
extension UIImageView {
func setCustomImage(_ imgURLString: String?) {
guard let imageURLString = imgURLString else {
self.image = UIImage(named: "default.png")
return
}
DispatchQueue.global().async { [weak self] in
let data = try? Data(contentsOf: URL(string: imageURLString)!)
DispatchQueue.main.async {
self?.image = data != nil ? UIImage(data: data!) : UIImage(named: "default.png")
}
}
}
}
扩展使用
myImageView. setCustomImage("url")
具有缓存支持
let imageCache = NSCache<NSString, UIImage>()
extension UIImageView {
func loadImageUsingCacheWithURLString(_ URLString: String, placeHolder: UIImage?) {
self.image = nil
if let cachedImage = imageCache.object(forKey: NSString(string: URLString)) {
self.image = cachedImage
return
}
if let url = URL(string: URLString) {
URLSession.shared.dataTask(with: url, completionHandler: { (data, response, error) in
//print("RESPONSE FROM API: \(response)")
if error != nil {
print("ERROR LOADING IMAGES FROM URL: \(String(describing: error))")
DispatchQueue.main.async { [weak self] in
self?.image = placeHolder
}
return
}
DispatchQueue.main.async { [weak self] in
if let data = data {
if let downloadedImage = UIImage(data: data) {
imageCache.setObject(downloadedImage, forKey: NSString(string: URLString))
self?.image = downloadedImage
}
}
}
}).resume()
}
}
}
