iOS动态监听网络变化

#import "Reachability.h"

//注册网络状态改变通知
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(reachabilityChanged:) name:kReachabilityChangedNotification object:nil];
hostReach = [[Reachability reachabilityWithHostName:@"www.baidu.com"] retain];//可以以多种形式初始化
[hostReach startNotifier];  //开始监听,会启动一个run loop

-(void)reachabilityChanged:(NSNotification *)note
{
NetworkStatus status = [hostReach currentReachabilityStatus];
if (status == NotReachable){
NSLog(@"网络不可用哦");
isNetworkAvalible = NO;
}else{
NSLog(@"网络可用了哦");
isNetworkAvalible = YES;
[self startMonitor];
}
}