iOS后台下载
后台下载是 NSURLSession 带来的一个新特性，区别于以往进入后台只有5分钟完成额外操作
- (void) doUpdate
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
[self beginBackgroundUpdateTask];
NSURLResponse * response = nil;
NSError * error = nil;
NSData * responseData = [NSURLConnection sendSynchronousRequest: request returningResponse: &response error: &error];
// Do something with the result
[self endBackgroundUpdateTask];
});
}
- (void) beginBackgroundUpdateTask
{
//必须的，否则进入后台超时后，APP会被杀掉
self.backgroundUpdateTask = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
[self endBackgroundUpdateTask];
}];
}
- (void) endBackgroundUpdateTask
{
[[UIApplication sharedApplication] endBackgroundTask: self.backgroundUpdateTask];
self.backgroundUpdateTask = UIBackgroundTaskInvalid;
}
iOS7以后允许我们，将下载任务交给系统管理，只要 APP 不是被强制用户杀掉，系统会在下载任务完成后，通过特定的函数通知我们。
//生成一个后台session，当然 APP 在前台时，此session 也和普通 session 一样工作。
let config = NSURLSessionConfiguration.backgroundSessionConfigurationWithIdentifier("downloadSession")
self.session = NSURLSession(configuration: config, delegate: self, delegateQueue: NSOperationQueue.mainQueue())
func application(application: UIApplication, handleEventsForBackgroundURLSession identifier: String, completionHandler: () -> Void) {
print(identifier)
let _ = TaskManager.sharedInstance
ch = completionHandler
}
extension TaskManager: NSURLSessionDownloadDelegate{
func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask,
didFinishDownloadingToURL location: NSURL) {
print("URLSession(sessionNSURLSessiondownloadTaskNSURLSessionDownloadTask didFinishDownloadingToURL locationNSURL")
var fileName = ""
for (index, task) in taskList.enumerate() {
if task.taskIdentifier == downloadTask.taskIdentifier {
taskList[index].finished = true
fileName = task.url.lastPathComponent!
}
}
if let documentURL = NSFileManager.defaultManager().URLsForDirectory(NSSearchPathDirectory.DocumentDirectory, inDomains: NSSearchPathDomainMask.UserDomainMask).first {
let destURL = documentURL.URLByAppendingPathComponent(fileName+"123")
do {
try NSFileManager.defaultManager().moveItemAtURL(location, toURL: destURL)
}
catch {
print(error)
}
saveTaskList()
NSNotificationCenter.defaultCenter().postNotificationName(DownloadTaskNotification.Finish.rawValue, object: downloadTask.taskIdentifier)
}
}
func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask, didResumeAtOffset fileOffset: Int64, expectedTotalBytes: Int64) {
}
func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask, didWriteData bytesWritten: Int64, totalBytesWritten: Int64, totalBytesExpectedToWrite: Int64) {
print("URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask, didWriteData bytesWritten: Int64, totalBytesWritten: Int64, totalBytesExpectedToWrite: Int64)")
let progressInfo = ["taskIdentifier": downloadTask.taskIdentifier,
"totalBytesWritten": NSNumber(longLong: totalBytesWritten),
"totalBytesExpectedToWrite": NSNumber(longLong: totalBytesExpectedToWrite)]
NSNotificationCenter.defaultCenter().postNotificationName(DownloadTaskNotification.Progress.rawValue, object: progressInfo)
}
func URLSessionDidFinishEventsForBackgroundURLSession(session: NSURLSession) {
print("URLSessionDidFinishEventsForBackgroundURLSession")
(UIApplication.sharedApplication().delegate as! AppDelegate).ch?()
(UIApplication.sharedApplication().delegate as! AppDelegate).ch = nil
}
}
上述 API 调用顺序如下:
