試圖獲取網絡錯誤警報以顯示在iPhone應用程序上？

Question

好的，我試圖讓這個應用程序顯示網絡錯誤警報代碼。我添加了SystemConfiguration.framework框架和Apple的「Reachability」示例代碼。

這裏是viewcontroller.h文件：

#import <UIKit/UIKit.h> 

@class Reachability; 

@interface Test_Internet_ConnectionViewController : UIViewController { 

    Reachability* internetReachable; 
    Reachability* hostReachable; 
} 

@property BOOL internetActive; 
@property BOOL hostActive; 

- (void) checkNetworkStatus:(NSNotification *)notice; 

@end 

這裏是viewcontroller.m文件：

#import "Test_Internet_ConnectionViewController.h" 
#import "Reachability.h"; 

@implementation Test_Internet_ConnectionViewController 

@synthesize internetActive; 
@synthesize hostActive; 

/* 
// The designated initializer. Override to perform setup that is required before the view is loaded. 
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil { 
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]; 
    if (self) { 
     // Custom initialization 
    } 
    return self; 
} 
*/ 

/* 
// Implement loadView to create a view hierarchy programmatically, without using a nib. 
- (void)loadView { 
} 
*/ 


// Implement viewDidLoad to do additional setup after loading the view, typically from a nib. 
- (void)viewDidLoad { 
    [super viewDidLoad]; 

     // check for internet connection 
     [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(checkNetworkStatus:) name:kReachabilityChangedNotification object:nil]; 

     internetReachable = [[Reachability reachabilityForInternetConnection] retain]; 
     [internetReachable startNotifier]; 

     // check if a pathway to a random host exists 
     hostReachable = [[Reachability reachabilityWithHostName: @"www.apple.com"] retain]; 
     [hostReachable startNotifier]; 

     // now patiently wait for the notification 
    } 

/* 
// Override to allow orientations other than the default portrait orientation. 
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation { 
    // Return YES for supported orientations 
    return (interfaceOrientation == UIInterfaceOrientationPortrait); 
} 
*/ 

- (void)didReceiveMemoryWarning { 
    // Releases the view if it doesn't have a superview. 
    [super didReceiveMemoryWarning]; 

    // Release any cached data, images, etc that aren't in use. 
} 

- (void)viewDidUnload { 
    // Release any retained subviews of the main view. 
    // e.g. self.myOutlet = nil; 
} 

- (void) checkNetworkStatus:(NSNotification *)notice 
{ 
    // called after network status changes 

    NetworkStatus internetStatus = [internetReachable currentReachabilityStatus]; 
    switch (internetStatus) 

    { 
     case NotReachable: 
     { 
      NSLog(@"The internet is down."); 
      self.internetActive = NO; 

      break; 

     } 
     case ReachableViaWiFi: 
     { 
      NSLog(@"The internet is working via WIFI."); 
      self.internetActive = YES; 

      break; 

     } 
     case ReachableViaWWAN: 
     { 
      NSLog(@"The internet is working via WWAN."); 
      self.internetActive = YES; 

      break; 

     } 
    } 

    NetworkStatus hostStatus = [hostReachable currentReachabilityStatus]; 
    switch (hostStatus) 

      { 
      case NotReachable: 
     { 
      NSLog(@"A gateway to the host server is down."); 
      self.hostActive = NO; 

      break; 

      } 
      case ReachableViaWiFi: 
      { 
      NSLog(@"A gateway to the host server is working via WIFI."); 
      self.hostActive = YES; 

      break; 

    } 
    case ReachableViaWWAN: 
    { 
     NSLog(@"A gateway to the host server is working via WWAN."); 
     self.hostActive = YES; 

     break; 

    } 
} 
} 

- (void)dealloc { 
[super dealloc]; 

    [[NSNotificationCenter defaultCenter] removeObserver:self]; 

} 

@end 

的應用程序運行沒有任何錯誤或警告不錯，但它不顯示沒有互聯網連接時的警報。有沒有人有任何想法，爲什麼這是？

Answer 1

您實際上並沒有在任何地方顯示警報。要做到這一點，你會做類似下面的東西：

UIAlertView *errorView = [[UIAlertView alloc] initWithTitle:@"Internet Unavailable" message:@"MESSAGE ABOUT INTERNET UNAVAILABLE HERE." delegate:nil cancelButtonTitle:@"Dismiss" otherButtonTitles:nil]; 
[errorView show]; 
[errorView release]; 

另外，需要注意的是viewDidLoad中可以被稱爲初始化後視圖控制器上的任意次數是很重要的。最好是在指定的初始化器中聲明任何通知觀察者。