1.在github下载Reachability框架
https://github.com/tonymillion/Reachability
2.导入系统框架 SystemConfiguration.framework

Snip20160929_8.png

4.在appDelegate.m 实现

#import "AppDelegate.h"

#import "Reachability.h"

@interface AppDelegate ()

@property(nonatomic,strong)Reachability*hostReah;

/// 记录网络改变之前的网络状态@property(nonatomic,assign)NetworkStatus status;```

@end

@implementation AppDelegate

-(BOOL)application:(UIApplication*)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

//开启网络状况的监听
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(reachabilityChanged:)name:kReachabilityChangedNotification object:nil];

Reachability *reach = [Reachability reachabilityWithHostName:@"www.apple.com"];
[reach startNotifier];


//开始监听，会启动一个runloop

[self.hostReach startNotifier];


return YES;

}
/// 通知 调用的方法
-(void)reachabilityChanged:(NSNotification *)notification

   Reachability *reach = [notification object];
    if([reach isKindOfClass:[Reachability class]]){
        NetworkStatus status = [reach currentReachabilityStatus];
        //如果网络状态发生改变
        if (status != self.status) {
            //记录当前网络状态
            self.status = status;
            UIAlertView * alert = [[UIAlertView alloc]initWithTitle:nil message:[self isInternetWith:status] delegate:nil cancelButtonTitle:@"ok" otherButtonTitles:nil];
            [alert show];
        }
        }
}
///返回根据status返回当前网络状态

-(NSString*)isInternetWith:(NetworkStatus)status
```{
    switch (status) {
        case NotReachable:
            return @"没网";
            break;
        case ReachableViaWiFi:
            return @"WIFI上网";
            break;
        case ReachableViaWWAN:
            return @"移动上网";
            break;
            
        default:
            break;
    }
}```