網(wǎng)絡(luò)監(jiān)聽用到的類為Reachability.h，這個Xcode項目里面是不自帶的，需要從github上面下載，在使用的時候記著導(dǎo)入SystemConfiguration.framework。

首先是在AppDelegate.m中設(shè)置網(wǎng)絡(luò)監(jiān)聽

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(reachabilityChanged:) name:kReachabilityChangedNotification object:nil];

初始化：

_reachability = [Reachability reachabilityForInternetConnection];
[_reachability startNotifier];
[self updateInterfaceWithReachability:_reachability];

實現(xiàn)兩個方法：

- (void) reachabilityChanged: (NSNotification* )note;//網(wǎng)絡(luò)連接改變
- (void) updateInterfaceWithReachability: (Reachability*) curReach;//處理連接改變后的情況

下面是方法的具體實現(xiàn)，可根據(jù)情況自行改變：

// 連接改變
- (void) reachabilityChanged: (NSNotification* )note {
    Reachability* curReach = [note object];
    NSParameterAssert([curReach isKindOfClass: [Reachability class]]);
    [self updateInterfaceWithReachability: curReach];
}
 
//處理連接改變后的情況
- (void) updateInterfaceWithReachability: (Reachability*) curReach {
    //對連接改變做出響應(yīng)的處理動作。
    NetworkStatus status = [curReach currentReachabilityStatus];
     
    if (status == NotReachable) {
        _isReachable = NO;
        //沒有連接到網(wǎng)絡(luò)就彈出提實況
        UIAlertView *netAlert = [[UIAlertView alloc] initWithTitle:@"蜂窩移動數(shù)據(jù)已關(guān)閉" message:@"啟用蜂窩移動數(shù)據(jù)或無線局域網(wǎng)來訪問數(shù)據(jù)" delegate:nil cancelButtonTitle:@"確定" otherButtonTitles:nil];
        [netAlert show];
    } else {
        _isReachable = YES;
    }
}