的iOS 7 NSURLSession下载多个文件在后台
我想下载使用NSUrlSession文件的列表。的iOS 7 NSURLSession下载多个文件在后台
我有一个计算成功下载@property (nonatomic) int downloadsSuccessfulCounter;
的变量。当正在下载的文件,我禁用Download Button
。当计数器等于下载列表大小,我再次启用按钮和计数器设置为0。我的方法做到这一点:
-(void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didFinishDownloadingToURL:(NSURL *)location {
...
[[NSOperationQueue mainQueue] addOperationWithBlock:^ {
downloadsSuccessfulCounter++;
if(downloadsSuccessfulCounter == self.downloadList.count) {
NSLog(@"All downloads finished");
[self.syncButton setEnabled:YES];
downloadsSuccessfulCounter = 0;
}
}];
}
一切工作正常,但是当我再次打开ViewController我收到消息A background URLSession with identifier com.myApp already exists!
。计数器未设置为0,UI元素(UIButtons,UILabels)没有响应。
我想这个问题是因为NSURLSession仍然是开放的,但我真的不知道它是如何工作的。
我试过所有的教程,但其中99%仅用于下载1个文件,不超过1个... 任何想法?
这里是我的代码:
...
@property (nonatomic, strong) NSURLSession *session;
...
- (void)viewDidLoad {
[super viewDidLoad];
appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
self.downloadList = [[NSMutableArray alloc] init];
NSURLSessionConfiguration *sessionConfiguration = [NSURLSessionConfiguration backgroundSessionConfiguration:@"com.myApp"];
sessionConfiguration.HTTPMaximumConnectionsPerHost = 5;
self.session = [NSURLSession sessionWithConfiguration:sessionConfiguration delegate:self delegateQueue:nil];
}
当我按下Download Button
我调用这个方法( 我有一个Downloadable
对象,它包含一个NSURLSessionDownloadTask
):
-(void)startDownload {
for (int i=0; i<[self.downloadList count]; i++) {
Downloadable *d = [self.downloadList objectAtIndex:i];
if (!d.isDownloading) {
if (d.taskIdentifier == -1) {
d.downloadTask = [self.session downloadTaskWithURL:[NSURL URLWithString:d.downloadSource]];
}else {
d.downloadTask = [self.session downloadTaskWithResumeData:fdi.taskResumeData];
}
d.taskIdentifier = d.downloadTask.taskIdentifier;
[d.downloadTask resume];
d.isDownloading = YES;
}
}
}
当应用程序是背景:
-(void)URLSessionDidFinishEventsForBackgroundURLSession:(NSURLSession *)session{
AppDelegate *appDelegate = [UIApplication sharedApplication].delegate;
[self.session getTasksWithCompletionHandler:^(NSArray *dataTasks, NSArray *uploadTasks, NSArray *downloadTasks) {
if ([downloadTasks count] == 0) {
if (appDelegate.backgroundTransferCompletionHandler != nil) {
void(^completionHandler)() = appDelegate.backgroundTransferCompletionHandler;
appDelegate.backgroundTransferCompletionHandler = nil;
[[NSOperationQueue mainQueue] addOperationWithBlock:^{
completionHandler();
UILocalNotification *localNotification = [[UILocalNotification alloc] init];
localNotification.alertBody = @"All files downloaded";
[[UIApplication sharedApplication] presentLocalNotificationNow:localNotification];
}];
}
}
}];
}
所以,正如我在评论中提到的问题是,每个文件都需要一个独特的NSURLSession,每个NSURLSession需要有一个唯一标识符的NSURLSessionConfiguration。
我认为你很接近 - 并且在某些方面可能比我更合适...... 你只需要创建一个结构来将唯一ID传递到独特的配置中,以填充唯一的会话(比如快10倍)。
这里就是我所做的:
/* *检索的文件列表下载 *也使用该列表的大小来实例化项目 *在我的情况,我打开一个字符返回文本文件我要下载的文件的名称 */
- (void) getMediaList {
NSString *list = @"http://myserver/media_list.txt";
NSURLSession *session = [NSURLSession sharedSession]; // <-- BASIC session
[[session dataTaskWithURL:[NSURL URLWithString:list]
completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
NSString *stringFromData = [[NSString alloc] initWithData: data encoding: NSUTF8StringEncoding];
// Populate Arrays
REMOTE_MEDIA_FILE_PATHS = [stringFromData componentsSeparatedByString:@"\n"];
[self instantiateURLSessions:[REMOTE_MEDIA_FILE_PATHS count]];
// Start First File
[self getFile:[REMOTE_MEDIA_FILE_PATHS objectAtIndex:downloadCounter]:downloadCounter]; // this variable is 0 at the start
}]
resume];
}
/* * 此设置配置的阵列和会话到适当大小, *它还提供了一个唯一的ID,以每一个 */
- (void) instantiateURLSessions : (int) size {
NSMutableArray *configurations = [NSMutableArray array];
NSMutableArray *sessions = [NSMutableArray array];
for (int i = 0; i < size; i++) {
NSString *index = [NSString stringWithFormat:@"%i", i];
NSString *UniqueIdentifier = @"MyAppBackgroundSessionIdentifier_";
UniqueIdentifier = [UniqueIdentifier stringByAppendingString:index];
[configurations addObject: [NSURLSessionConfiguration backgroundSessionConfigurationWithIdentifier:UniqueIdentifier]];
[sessions addObject:[NSURLSession sessionWithConfiguration: [configurations objectAtIndex:i] delegate: self delegateQueue: [NSOperationQueue mainQueue]]];
}
NSURL_BACKGROUND_CONFIGURATIONS = [NSArray arrayWithArray:configurations];
NSURL_BACKGROUND_SESSIONS = [NSArray arrayWithArray:sessions];
}
/* *此设置每个文件的下载任务,以关闭阵列 的指数*它还地连接了路径的实际文件 */
- (void) getFile : (NSString*) file :(int) index {
NSString *fullPathToFile = REMOTE_MEDIA_PATH; // Path To Server With Files
fullPathToFile = [fullPathToFile stringByAppendingString:file];
NSURL *url = [NSURL URLWithString:fullPathToFile];
NSURLSessionDownloadTask *downloadTask = [[NSURL_BACKGROUND_SESSIONS objectAtIndex:index ] downloadTaskWithURL: url];
[downloadTask resume];
}
/* *最后,在我的委托方法中,在下载完成后(从临时数据中移出文件之后),检查我是否完成,是否再次使用更新的计数器调用getFiles方法索引 */
-(void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didFinishDownloadingToURL:(NSURL *)location
{
// Get the documents directory URL
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *dataPath = [documentsDirectory stringByAppendingPathComponent:LOCAL_MEDIA_PATH];
NSURL *customDirectory = [NSURL fileURLWithPath:dataPath];
// Get the file name and create a destination URL
NSString *sendingFileName = [downloadTask.originalRequest.URL lastPathComponent];
NSURL *destinationUrl = [customDirectory URLByAppendingPathComponent:sendingFileName];
// Move the file
NSError *error = nil;
NSFileManager *fileManager = [NSFileManager defaultManager];
if ([fileManager moveItemAtURL:location toURL:destinationUrl error: &error]) {
// List
[self listCustomDirectory];
if(downloadCounter < [REMOTE_MEDIA_FILE_PATHS count] -1) {
// Increment Counter
downloadCounter++;
// Start Next File
[self getFile:[REMOTE_MEDIA_FILE_PATHS objectAtIndex:downloadCounter]:downloadCounter];
}
else {
// FINISH YOUR OPERATION/NOTIFY USER/ETC
}
}
else {
NSLog(@"Damn. Error %@", error);
// Do Something Intelligent Here
}
}
我目前也在探索这个......问题是会话标识符 - 它们必须对每个后续任务都是唯一的。根据此文本>本页来自:https://developer.apple.com/library/ios/documentation/Cocoa/Conceptual/URLLoadingSystem/Articles/UsingNSURLSession.html – 2014-10-19 21:24:55
我猜有两个选择我可以看到:1)编译所有内容到一个zip文件,下载单个文件,然后将其解压到客户端(电话)一侧 - 或者2)创建一个NSMutableArray任务,在运行时为每个文件添加一个新的后台会话并带有唯一标识符。 – 2014-10-19 21:26:27
本教程似乎有多个文件的前提:http://code.tutsplus.com/tutorials/working-with-nsurlsession-part-3--mobile-21879 – 2014-10-19 21:33:43