转载自http://hi.baidu.com/popln/blog/item/e6ed14884b2fa4a60f2444d1.html
在当前的run循环中通过异步查询UIDevice当前的标志和网络状态,对网络连接状态进行监视。当连接状态变化时,观察者(observer)会以回调函数的形式接收到通知,从而做出相应的处理。
#import <SystemConfiguration/SystemConfiguration.h> #include <netdb.h> #import <dlfcn.h> #import "UIDevice-Reachability.h" @implementation UIDevice (Reachability) SCNetworkConnectionFlags connectionFlags; SCNetworkReachabilityRef reachability; #pragma mark Checking Connections + (void) pingReachabilityInternal { if (!reachability) { BOOL ignoresAdHocWiFi = NO; struct sockaddr_in ipAddress; bzero(&ipAddress, sizeof(ipAddress)); ipAddress.sin_len = sizeof(ipAddress); ipAddress.sin_family = AF_INET; ipAddress.sin_addr.s_addr = htonl(ignoresAdHocWiFi ? INADDR_ANY : IN_LINKLOCALNETNUM); reachability = SCNetworkReachabilityCreateWithAddress(kCFAllocatorDefault, (struct sockaddr *)&ipAddress); CFRetain(reachability); } // Recover reachability flags BOOL didRetrieveFlags = SCNetworkReachabilityGetFlags(reachability, &connectionFlags); if (!didRetrieveFlags)
printf("Error. Could not recover network reachability flags\n"); } #pragma mark Monitoring reachability static void ReachabilityCallback(SCNetworkReachabilityRef target, SCNetworkConnectionFlags flags, void* info) { NSAutoreleasePool *pool = [NSAutoreleasePool new]; [(id)info performSelector:@selector(reachabilityChanged)]; [pool release]; }
// 开启网络连接监视 + (BOOL) scheduleReachabilityWatcher: (id) watcher { if (![watcher conformsToProtocol:@protocol(ReachabilityWatcher)]) { NSLog(@"Watcher must conform to ReachabilityWatcher protocol. Cannot continue."); return NO; } [self pingReachabilityInternal]; SCNetworkReachabilityContext context = {0, watcher, NULL, NULL, NULL}; if(SCNetworkReachabilitySetCallback(reachability, ReachabilityCallback, &context)) { if(!SCNetworkReachabilityScheduleWithRunLoop(reachability, CFRunLoopGetCurrent(), kCFRunLoopCommonModes)) { NSLog(@"Error: Could not schedule reachability"); SCNetworkReachabilitySetCallback(reachability, NULL, NULL); return NO; } } else { NSLog(@"Error: Could not set reachability callback"); return NO; } return YES; } + (void) unscheduleReachabilityWatcher { SCNetworkReachabilitySetCallback(reachability, NULL, NULL); if (SCNetworkReachabilityUnscheduleFromRunLoop(reachability, CFRunLoopGetCurrent(), kCFRunLoopCommonModes)) NSLog(@"Unscheduled reachability"); else NSLog(@"Error: Could not unschedule reachability"); CFRelease(reachability); reachability = nil; } @end