iOS的 - 時加載外部數據

在我的應用程序委託我有這樣的：iOS的 - 時加載外部數據

Reachability* reach = [Reachability reachabilityWithHostname:@"www.google.com"]; 

[[NSNotificationCenter defaultCenter] addObserver:self 
             selector:@selector(reachabilityChanged:) 
              name:kReachabilityChangedNotification 
              object:nil]; 

[reach startNotifier]; 

HomeViewController_iPhone *homeViewController = [[HomeViewController_iPhone alloc] initWithNibName:@"HomeViewController_iPhone" bundle:nil]; 
homeViewController.managedObjectContext = self.managedObjectContext; 
UINavigationController *homeNavController = [[UINavigationController alloc] initWithRootViewController: homeViewController]; 
homeNavController.navigationBar.barStyle = UIBarStyleBlackTranslucent; 

self.tabBarController.viewControllers = [NSArray arrayWithObjects:homeNavController, nil]; 

... 

-(void)reachabilityChanged:(NSNotification*)note 
{ 
Reachability * reach = [note object]; 

if([reach isReachable]) 
{ 
    NSLog(@"Notification Says Reachable"); 
    self.isConnected = YES; 
} 
else 
{ 
    NSLog(@"Notification Says UN-Reachable"); 
    self.isConnected = NO; 
} 
}

的問題是，在我的HomeViewController（viewDidLoad中）我這樣做：

AppDelegate *appDelegate = (AppDelegate*)[[UIApplication sharedApplication] delegate]; 

if (appDelegate.isConnected) 
{ 
    dispatch_async(kBgQueue, ^{ 
     NSData* data = [NSData dataWithContentsOfURL: kFeedURL]; 
     [self performSelectorOnMainThread:@selector(fetchedData:) 
           withObject:data waitUntilDone:YES]; 
    }); 
}

但appDelegate.isConnected即使當我有連接時也總是NO。我認爲這個檢查是在Reachability類建立了連接之前進行的。但是，我在哪裏打電話來獲取數據？我已經嘗試過viewDidLoad和viewWillAppear，但isConnected在這兩點上仍然沒有。

來源

2012-08-09 soleil

此外，取作品，如果我不，如果（appDelegate.isConnected）語句中使用，但我需要做的檢查，因爲如果用戶不具備dispatch_async通話將崩潰的應用程序的連接。 – soleil 2012-08-09 23:15:39

也許這個答案將有所幫助 - > http://stackoverflow.com/questions/5195012/how-to-use-reachability-class-to-detect-valid-internet-connection?rq=1 – dnstevenson 2012-08-10 00:28:57

通過在應用程序委託中執行此操作解決，在創建視圖控制器之前，如dnstevenson所建議的答案。

Reachability *reachability = [Reachability reachabilityForInternetConnection];  
NetworkStatus internetStatus = [reachability currentReachabilityStatus]; 
if (internetStatus != NotReachable) { 
    //my web-dependent code 
} 
else { 
    //there-is-no-connection warning 
}

來源

2012-08-11 04:11:58 soleil

iOS的 - 時加載外部數據

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