添加SystemConfiguration.framework 到工程中

对应的.h文件

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController
//如果方法前面加+，就相当于类的静态方法，这里要注意一下
- (BOOL) connectedToNetwork;
@end

#import "ViewController.h"
#import <Foundation/Foundation.h>
#import <CommonCrypto/CommonHMAC.h>
#import <SystemConfiguration/SystemConfiguration.h>
#import <netdb.h>
#import <arpa/inet.h>

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    UIButton *btn = [[UIButton alloc]init];
    btn.frame = CGRectMake(20, 20, 40, 40);
    btn.backgroundColor = [UIColor brownColor];
    [self.view addSubview:btn];
    [btn addTarget:self action:@selector(testOut:) forControlEvents:UIControlEventTouchUpInside];
    // Do any additional setup after loading the view, typically from a nib.
}
-(BOOL) connectedToNetwork
{
    // Create zero addy
    struct sockaddr_in zeroAddress;
    bzero(&zeroAddress, sizeof(zeroAddress));
    zeroAddress.sin_len = sizeof(zeroAddress);
    zeroAddress.sin_family = AF_INET;
    
    // Recover reachability flags
    SCNetworkReachabilityRef defaultRouteReachability = SCNetworkReachabilityCreateWithAddress(NULL, (struct sockaddr *)&zeroAddress);
    SCNetworkReachabilityFlags flags;
    
    BOOL didRetrieveFlags = SCNetworkReachabilityGetFlags(defaultRouteReachability, &flags);
    CFRelease(defaultRouteReachability);
    
    if (!didRetrieveFlags)
        {
        printf("Error. Could not recover network reachability flags\n");
        return NO;
        }
    
    BOOL isReachable = ((flags & kSCNetworkFlagsReachable) != 0);
    BOOL needsConnection = ((flags & kSCNetworkFlagsConnectionRequired) != 0);
    return (isReachable && !needsConnection) ? YES : NO;
}


//在调用的时候，在对应的按钮中加入判断：
- (IBAction)testOut:(UIButton *)sender
{
    if(![self connectedToNetwork])
        {
        UIAlertView *alert=[[UIAlertView alloc] initWithTitle:@"温馨提示" message:@"网络连接失败,请查看网络是否连接正常！" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
        [alert show];
        }
    
    NSLog(@"testOut Event");
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

iOS 判断网络状态 简单示例