我使用urlsession从服务器下载了一些文件,每次下载后都会触发委托“didFinishDownloadingTo”。但是我希望在所有下载完成后触发一些内容。
是我必须使用的委托“didCompleteWithError”?
如何知道是否已下载所有文件?
func downloadPdf() {
for k in self.resultAddressServer {
let fileURL = URL(string: k)
let sessionConfig = URLSessionConfiguration.default
let operationQueue = OperationQueue()
let urlSession = URLSession(configuration: sessionConfig, delegate: self, delegateQueue: operationQueue)
let request = URLRequest(url:fileURL!)
let downloadTask = urlSession.downloadTask(with: request)
downloadTask.resume()
}
}
func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL) {
do {
let manager = FileManager.default
let destinationURL = try manager.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: true)
.appendingPathComponent(downloadTask.originalRequest!.url!.lastPathComponent)
try? manager.removeItem(at: destinationURL)
try manager.moveItem(at: location, to: destinationURL)
print(destinationURL)
} catch {
print(error)
}
func urlSession(_ session: URLSession, task: URLSessionTask, didCompleteWithError error: Error?) {
if error != nil {
DispatchQueue.main.async() {
self.statusLabel.text = "Download failed"
}
} else {
DispatchQueue.main.async() {
self.statusLabel.text = "Download finished"
}
}
根据其他帖子的建议,我添加了一个数组,我在其中添加了downloadTask标识号,然后在委托中,我在任务完成时删除了该标识符#。最后要知道是否所有下载都已完成,我只检查array.count是否等于0。
func downloadPdf() {
for k in self.resultAddressServer {
let fileURL = URL(string: k)
let sessionConfig = URLSessionConfiguration.background(withIdentifier: "com.Test")
let urlSession = URLSession(configuration: sessionConfig, delegate: self, delegateQueue: OperationQueue())
let request = URLRequest(url:fileURL!)
let downloadTask = urlSession.downloadTask(with: request)
self.tasksArray.append(downloadTask.taskIdentifier)
print(downloadTask.taskIdentifier)
downloadTask.resume()
}
func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL) {
do {
let manager = FileManager.default
let destinationURL = try manager.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: true)
.appendingPathComponent(downloadTask.originalRequest!.url!.lastPathComponent)
try? manager.removeItem(at: destinationURL)
try manager.moveItem(at: location, to: destinationURL)
print(destinationURL)
} catch {
print(error)
}
if let index = self.tasksArray.index(of: downloadTask.taskIdentifier) {
self.tasksArray.remove(at: index)
print(self.tasksArray.count)
}
DispatchQueue.main.async() {
if self.tasksArray.count == 0 {
//Do whatever you want, all downloads are completed
//the DispatchQueue is for what I use this for...maybe not needed in you case
}
}
}