1 - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{
 2 //开启网络状况的监听
 3 //来订阅实时的网络状态变化通知。导入Reachability.h头文件，然后注册一个对象来订阅网络状态变化的信息，网络状态变化的信息名称为kReachabilityChanged-Notification
 4
 5 [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(reachabilityChanged:) name:kReachabilityChangedNotification object:nil];
 6 //通过检查某个主机能否访问来判断当前网络是否可用：
 7 self.hostReach = [Reachability reachabilityWithHostName:@"www.baidu.com"] ;
 8
 9 //开始监听，会启动一个run loop
10 [self.hostReach startNotifier];
11
12 }
13
14 -(void)reachabilityChanged:(NSNotification *)note{
15 Reachability *currReach = [note object];
16
17 NSParameterAssert([currReach isKindOfClass:[Reachability class]]);
18
19 //对连接改变做出响应处理动作
20
21 NetworkStatus status = [currReach currentReachabilityStatus];
22
23 //如果没有连接到网络就弹出提醒实况
24
25 self.isReachable = YES;
26
27 if(status == NotReachable){
28
29 UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"网络连接异常" message:nil delegate:nil cancelButtonTitle:@"确定" otherButtonTitles:nil];
30 [alert show];
31 [alert release];
32 self.isReachable = NO;
33 return;
34
35 }
36
37 if (status==kReachableViaWiFi||status==kReachableViaWWAN) {
38
39 UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"网络连接信息" message:@"网络连接正常" delegate:nil cancelButtonTitle:@"确定" otherButtonTitles:nil];
40
41 //        [alert show];
42
43 [alert release];
44 self.isReachable = YES;
45
46 }
47 }
48
49 然后在每个页面的viewWillAppear:加上：
50
51 -(void)viewWillAppear:(BOOL)animated{
52 [super viewWillAppear:YES];
53 AppDelegate *appDlg = (AppDelegate *)[[UIApplication sharedApplication] delegate];
54 if(appDlg.isReachable){
55 NSLog(@"网络已连接");//执行网络正常时的代码
56 }
57 else{
58 NSLog(@"网络连接异常");//执行网络异常时的代码
59 UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"网络连接异常" message:nil delegate:nil cancelButtonTitle:@"确定" otherButtonTitles:nil];
60 [alert show];
61 [alert release];
62 }
63 }

 1 -(void)afn{
 2     //1.创建网络状态监测管理者
 3     AFNetworkReachabilityManager *manger = [AFNetworkReachabilityManager sharedManager];
 4  //开启监听，记得开启，不然不走block
 5     [manger startMonitoring];
 6     //2.监听改变
 7     [manger setReachabilityStatusChangeBlock:^(AFNetworkReachabilityStatus status) {
 8         /*
 9          AFNetworkReachabilityStatusUnknown          = -1,
10          AFNetworkReachabilityStatusNotReachable     = 0,
11          AFNetworkReachabilityStatusReachableViaWWAN = 1,
12          AFNetworkReachabilityStatusReachableViaWiFi = 2,
13          */
14         switch (status) {
15             case AFNetworkReachabilityStatusUnknown:
16                 NSLog(@"未知");
17                 break;
18             case AFNetworkReachabilityStatusNotReachable:
19                 NSLog(@"没有网络");
20                 break;
21             case AFNetworkReachabilityStatusReachableViaWWAN:
22                 NSLog(@"3G|4G");
23                 break;
24             case AFNetworkReachabilityStatusReachableViaWiFi:
25                 NSLog(@"WiFi");
26                 break;
27             default:
28                 break;
29         }
30     }];
31 }