检查网络是否存在

加入SystemConfiguration.framework控件。

//////////////////////////////////////////////////////////////////////////////////////////////////////

//  CheckNetwork.h

#import

@interface CheckNetwork : NSObject { 
}
(BOOL)i***istenceNetwork;
@end

///////////////////////////

//CheckNetwork.m
#import "CheckNetwork.h"
#import "Reachability.h"
@implementation CheckNetwork
(BOOL)i***istenceNetwork
{
 BOOL i***istenceNetwork;
 Reachability *r = [Reachability reachabilityWithHostName:@""];
    switch ([r currentReachabilityStatus]) {
        case NotReachable:
       i***istenceNetwork=FALSE;       
            break;
        case ReachableViaWWAN:
       i***istenceNetwork=TRUE;        
            break;
        case ReachableViaWiFi:
       i***istenceNetwork=TRUE;                 
            break;
    }
 if (!i***istenceNetwork) {
  UIAlertView *myalert = [[UIAlertView alloc] initWithTitle:@"警告" message:@"无网络存在" delegate:self cancelButtonTitle:@"确认" otherButtonTitles:nil,nil];
  [myalert show];
  [myalert release];
 }
 return i***istenceNetwork;
}
@end

 

///////////////////////////////////////////////////////////////////////////////////////

//Reachability.h
 
#import
#import

typedef enum {
 NotReachable = 0,
 ReachableViaWiFi,
 ReachableViaWWAN
} NetworkStatus;
#define kReachabilityChangedNotification @"kNetworkReachabilityChangedNotification"

@interface Reachability: NSObject
{
 BOOL localWiFiRef;
 SCNetworkReachabilityRef reachabilityRef;
}

//reachabilityWithHostName- Use to check the reachability of a particular host name.
(Reachability*) reachabilityWithHostName: (NSString*) hostName;

//reachabilityWithAddress- Use to check the reachability of a particular IP address.
(Reachability*) reachabilityWithAddress: (const struct sockaddr_in*) hostAddress;

//reachabilityForInternetConnection- checks whether the default route is available. 
//  Should be used by applications that do not connect to a particular host
(Reachability*) reachabilityForInternetConnection;

//reachabilityForLocalWiFi- checks whether a local wifi connection is available.
(Reachability*) reachabilityForLocalWiFi;

//Start listening for reachability notifications on the current run loop
- (BOOL) startNotifier;
- (void) stopNotifier;

- (NetworkStatus) currentReachabilityStatus;
//WWAN may be available, but not active until a connection has been established.
//WiFi may require a connection for VPN on Demand.
- (BOOL) connectionRequired;
@end

//////////////////////////////////////////

// Reachability.m

#import
#import
#import
#import
#import
#import

#import

#import "Reachability.h"

#define kShouldPrintReachabilityFlags 1

static void PrintReachabilityFlags(SCNetworkReachabilityFlags    flags, const char* comment)
{
#if kShouldPrintReachabilityFlags
 
    NSLog(@"Reachability Flag Status: %c%c %c%c%c%c%c%c%c %s\n",
   (flags & kSCNetworkReachabilityFlagsIsWWAN)      ? 'W' : '-',
   (flags & kSCNetworkReachabilityFlagsReachable)            ? 'R' : '-',
   
   (flags & kSCNetworkReachabilityFlagsTransientConnection)  ? 't' : '-',
   (flags & kSCNetworkReachabilityFlagsConnectionRequired)   ? 'c' : '-',
   (flags & kSCNetworkReachabilityFlagsConnectionOnTraffic)  ? 'C' : '-',
   (flags & kSCNetworkReachabilityFlagsInterventionRequired) ? 'i' : '-',
   (flags & kSCNetworkReachabilityFlagsConnectionOnDemand)   ? 'D' : '-',
   (flags & kSCNetworkReachabilityFlagsIsLocalAddress)       ? 'l' : '-',
   (flags & kSCNetworkReachabilityFlagsIsDirect)             ? 'd' : '-',
   comment
   );
#endif
}

@implementation Reachability
static void ReachabilityCallback(SCNetworkReachabilityRef target, SCNetworkReachabilityFlags flags, void* info)
{
 #pragma unused (target, flags)
 NSCAssert(info != NULL, @"info was NULL in ReachabilityCallback");
 NSCAssert([(NSObject*) info isKindOfClass: [Reachability class]], @"info was wrong class in ReachabilityCallback");

 NSAutoreleasePool* myPool = [[NSAutoreleasePool alloc] init];
 
 Reachability* noteObject = (Reachability*) info; 
 [[NSNotificationCenter defaultCenter] postNotificationName: kReachabilityChangedNotification object: noteObject];
 
 [myPool release];
}

- (BOOL) startNotifier
{
 BOOL retVal = NO;
 SCNetworkReachabilityContext context = {0, self, NULL, NULL, NULL};
 if(SCNetworkReachabilitySetCallback(reachabilityRef, ReachabilityCallback, &context))
 {
  if(SCNetworkReachabilityScheduleWithRunLoop(reachabilityRef, CFRunLoopGetCurrent(), kCFRunLoopDefaultMode))
  {
   retVal = YES;
  }
 }
 return retVal;
}

- (void) stopNotifier
{
 if(reachabilityRef!= NULL)
 {
  SCNetworkReachabilityUnscheduleFromRunLoop(reachabilityRef, CFRunLoopGetCurrent(), kCFRunLoopDefaultMode);
 }
}

- (void) dealloc
{
 [self stopNotifier];
 if(reachabilityRef!= NULL)
 {
  CFRelease(reachabilityRef);
 }
 [super dealloc];
}

(Reachability*) reachabilityWithHostName: (NSString*) hostName;
{
 Reachability* retVal = NULL;
 SCNetworkReachabilityRef reachability = SCNetworkReachabilityCreateWithName(NULL, [hostName UTF8String]);
 if(reachability!= NULL)
 {
  retVal= [[[self alloc] init] autorelease];
  if(retVal!= NULL)
  {
   retVal->reachabilityRef = reachability;
   retVal->localWiFiRef = NO;
  }
 }
 return retVal;
}

(Reachability*) reachabilityWithAddress: (const struct sockaddr_in*) hostAddress;
{
 SCNetworkReachabilityRef reachability = SCNetworkReachabilityCreateWithAddress(kCFAllocatorDefault, (const struct sockaddr*)hostAddress);
 Reachability* retVal = NULL;
 if(reachability!= NULL)
 {
  retVal= [[[self alloc] init] autorelease];
  if(retVal!= NULL)
  {
   retVal->reachabilityRef = reachability;
   retVal->localWiFiRef = NO;
  }
 }
 return retVal;
}

(Reachability*) reachabilityForInternetConnection;
{
 struct sockaddr_in zeroAddress;
 bzero(&zeroAddress, sizeof(zeroAddress));
 zeroAddress.sin_len = sizeof(zeroAddress);
 zeroAddress.sin_family = AF_INET;
 return [self reachabilityWithAddress: &zeroAddress];
}

(Reachability*) reachabilityForLocalWiFi;
{
 struct sockaddr_in localWifiAddress;
 bzero(&localWifiAddress, sizeof(localWifiAddress));
 localWifiAddress.sin_len = sizeof(localWifiAddress);
 localWifiAddress.sin_family = AF_INET;
 // IN_LINKLOCALNETNUM is defined in as 169.254.0.0
 localWifiAddress.sin_addr.s_addr = htonl(IN_LINKLOCALNETNUM);
 Reachability* retVal = [self reachabilityWithAddress: &localWifiAddress];
 if(retVal!= NULL)
 {
  retVal->localWiFiRef = YES;
 }
 return retVal;
}

#pragma mark Network Flag Handling

- (NetworkStatus) localWiFiStatusForFlags: (SCNetworkReachabilityFlags) flags
{
 PrintReachabilityFlags(flags, "localWiFiStatusForFlags");

 BOOL retVal = NotReachable;
 if((flags & kSCNetworkReachabilityFlagsReachable) && (flags & kSCNetworkReachabilityFlagsIsDirect))
 {
  retVal = ReachableViaWiFi; 
 }
 return retVal;
}

- (NetworkStatus) networkStatusForFlags: (SCNetworkReachabilityFlags) flags
{
 PrintReachabilityFlags(flags, "networkStatusForFlags");
 if ((flags & kSCNetworkReachabilityFlagsReachable) == 0)
 {
  // if target host is not reachable
  return NotReachable;
 }

 BOOL retVal = NotReachable;
 
 if ((flags & kSCNetworkReachabilityFlagsConnectionRequired) == 0)
 {
  // if target host is reachable and no connection is required
  //  then we'll assume (for now) that your on Wi-Fi
  retVal = ReachableViaWiFi;
 }
 
 
 if ((((flags & kSCNetworkReachabilityFlagsConnectionOnDemand ) != 0) ||
  (flags & kSCNetworkReachabilityFlagsConnectionOnTraffic) != 0))
 {
   // ... and the connection is on-demand (or on-traffic) if the
   //     calling application is using the CFSocketStream or higher APIs

   if ((flags & kSCNetworkReachabilityFlagsInterventionRequired) == 0)
   {
    // ... and no [user] intervention is needed
    retVal = ReachableViaWiFi;
   }
  }
 
 if ((flags & kSCNetworkReachabilityFlagsIsWWAN) == kSCNetworkReachabilityFlagsIsWWAN)
 {
  // ... but WWAN connections are OK if the calling application
  //     is using the CFNetwork (CFSocketStream?) APIs.
  retVal = ReachableViaWWAN;
 }
 return retVal;
}

- (BOOL) connectionRequired;
{
 NSAssert(reachabilityRef != NULL, @"connectionRequired called with NULL reachabilityRef");
 SCNetworkReachabilityFlags flags;
 if (SCNetworkReachabilityGetFlags(reachabilityRef, &flags))
 {
  return (flags & kSCNetworkReachabilityFlagsConnectionRequired);
 }
 return NO;
}

- (NetworkStatus) currentReachabilityStatus
{
 NSAssert(reachabilityRef != NULL, @"currentNetworkStatus called with NULL reachabilityRef");
 NetworkStatus retVal = NotReachable;
 SCNetworkReachabilityFlags flags;
 if (SCNetworkReachabilityGetFlags(reachabilityRef, &flags))
 {
  if(localWiFiRef)
  {
   retVal = [self localWiFiStatusForFlags: flags];
  }
  else
  {
   retVal = [self networkStatusForFlags: flags];
  }
 }
 return retVal;
}
@end