ios背景更新和下载

ios背景更新和下载

by 吴雪莹

- ( BOOL )application:( UIApplication *)application didFinishLaunchingWithOptions:( NSDictionary *)launchOptions {
    [application setMinimumBackgroundFetchInterval : UIApplicationBackgroundFetchIntervalMinimum ];
    NSLog ( @"Launched in background %d" , UIApplicationStateBackground == application. applicationState );
    return YES ;
}
// 1. 利用 Background Fetch
- ( void )application:( UIApplication *)application performFetchWithCompletionHandler:( void (^)( UIBackgroundFetchResult ))completionHandler {
    NSURLSessionConfiguration *sessionConfiguration = [ NSURLSessionConfiguration defaultSessionConfiguration ];
    NSURLSession *session = [ NSURLSession sessionWithConfiguration :sessionConfiguration];
    NSURL *url = [[ NSURL alloc ] initWithString : @"http://127.0.0.1/data.json" ];
    NSURLSessionDataTask *task = [session  dataTaskWithURL :url
                                         completionHandler :^( NSData *data, NSURLResponse *response, NSError *error) {
                                             if (error) {
                                                 completionHandler( UIBackgroundFetchResultFailed );
                                                 return ;
                                             }
                                             completionHandler( UIBackgroundFetchResultNewData );
                                         }];
    [task resume ];
}
// 2. 利用 Remote Notification
/*
  推送的内容
 {
 "aps" : {
 "content-available" : 1
 },
 "content-id" : 42
 }
 */
- ( void )application:( UIApplication *)application
didReceiveRemoteNotification:( NSDictionary *)userInfo
fetchCompletionHandler:( void (^)( UIBackgroundFetchResult ))completionHandler
{
    NSLog ( @"Received remote notification with userInfo %@" , userInfo);
   
    NSNumber *contentID = userInfo[ @"content-id" ];
    NSString *downloadURLString = [ NSString stringWithFormat : @"http://yourserver.com/downloads/%d.mp3" , [contentID intValue ]];
    NSURL * downloadURL = [ NSURL URLWithString :downloadURLString];
   
    NSURLRequest *request = [ NSURLRequest requestWithURL :downloadURL];
    NSURLSessionDownloadTask *task = [[ self backgroundURLSession ] downloadTaskWithRequest :request];
    task. taskDescription = [ NSString stringWithFormat : @"Podcast Episode %d" , [contentID intValue ]];
    [task resume ];
    completionHandler( UIBackgroundFetchResultNewData );
}

- ( NSURLSession *)backgroundURLSession
{
    static NSURLSession *session = nil ;
    static dispatch_once_t onceToken;
    dispatch_once (&onceToken, ^{
        NSString *identifier = @"io.objc.backgroundTransferExample" ;
        NSURLSessionConfiguration * sessionConfig = [ NSURLSessionConfiguration backgroundSessionConfiguration :identifier];
        session = [ NSURLSession sessionWithConfiguration :sessionConfig
                                                delegate : self
                                           delegateQueue :[ NSOperationQueue mainQueue ]];
    });
    return session;

}

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