我的场景:
我异步调用下载器对象函数来尝试下载文件。
在下载器的函数中,它异步启动下载连接。
即便如此,我也无法与我的 UI 元素进行交互。
例如,在下载过程中我无法编辑我的文本字段。
我希望能够在下载时与我的 UI 元素进行交互。
我错过了哪里?我应该怎么办?我真的很感谢你的帮助!
ViewController 的异步下载片段
//relevant UI elements I am referring to
@IBOutlet var renderButton: UIButton!
@IBOutlet var urlField: UITextField!
func handleOpenURL(url: NSURL){
var downloader: aDownloader = aDownloader(url: url)
//I try to put download to background thread
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), {() -> Void in
//This function initiates a connection call in an attempt to download the file
downloader.executeConnection({
(dataURL:NSURL!,error:NSError!) -> Void in
dispatch_async(dispatch_get_main_queue(), { () -> Void in
self.imageView.image = UIImage(data:NSData(contentsOfURL: url)!)
})
//rest are nonsense
}, progress: { (percentage:Double) -> Void in
//nonsense
}
)
})
}
aDownloader.swift 的相关代码片段
class aDownloader: NSObject, allOtherProtocols {
unowned var url: NSURL
//this block reports the progress as a % number
var progressBlock : ((Double)->Void)?
//this block will return either the destinationFileURL after download finishes,
//or return error of any sort
var dataBlock: ((NSURL!,NSError!)->Void)?
init(url: NSURL) {
self.url = url
}
func executeConnection(received:(NSURL!,NSError!)->Void, progress:(Double)->Void){
var request : NSURLRequest = NSURLRequest(URL: self.url,
cachePolicy: .ReloadIgnoringLocalCacheData,
timeoutInterval: 60.0)
//I attempt to async-ly download the file here
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), { () -> Void in
var connectionManager : NSURLConnection? = NSURLConnection(request:request,
delegate: self,
startImmediately: false)
connectionManager?.scheduleInRunLoop(NSRunLoop.mainRunLoop(),
forMode: NSRunLoopCommonModes)
connectionManager?.start()
})
self.dataBlock = received
self.progressBlock = progress
}
//nonsense
}