判断联网 phone

-(BOOL) isConnected {  //创建零地址，0.0.0.0的地址表示查询本机的网络连接状态   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;    //获得连接的标志   BOOL didRetrieveFlags = SCNetworkReachabilityGetFlags(defaultRouteReachability, &flags);   CFRelease(defaultRouteReachability);    //如果不能获取连接标志，则不能连接网络，直接返回   if (!didRetrieveFlags)  {   return NO;  }    //根据获得的连接标志进行判断  BOOL isReachable = flags & kSCNetworkFlagsReachable;  BOOL needsConnection = flags & kSCNetworkFlagsConnectionRequired;  return (isReachable && !needsConnection) ? YES : NO;   }   2.发送数据 -(NSData *)sendPostRequest:(NSString *)postString theUrl:(NSString *)urlString{     //NSError *error=[[NSError alloc] autorelease];  NSData *postData = [postString dataUsingEncoding:NSUTF8StringEncoding allowLossyConversion:YES];     NSString *postLength = [NSString stringWithFormat:@"%d", [postData length]];     NSURL *url=[[NSURL alloc]initWithString:urlString];  NSMutableURLRequest  *request=[[NSMutableURLRequest alloc]init];  [request setURL: url];   [request setHTTPMethod:@"POST"];     [request setValue:postLength forHTTPHeaderField:@"Content-Length"];     [request setValue:@"text/xml" forHTTPHeaderField:@"Content-Type"];    // [request setTimeoutInterval:15];  [request setCachePolicy:NSURLRequestReloadIgnoringLocalCacheData];  [request setHTTPBody:postData];       //定义一个计时器    connection = [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:true];  [NSTimer scheduledTimerWithTimeInterval:60.0 target:self selector:@selector(cancelConnection:) userInfo:nil repeats:NO];  [url release];  [request release];  if(connection)  {   receivedData = [[NSMutableData data] retain];  }  else  {   NSLog(@"<<Net_Http.m-->sendPostRequest-->connection-->nil");  } //暂停，等待NSTimer的结束  while(!finished) {   [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];  }     return receivedData; } 3.接受数据 -(NSData *)sendGetRequest:(NSString *)getString theUrl:(NSString *)urlString{     //NSError *error=[[NSError alloc] autorelease];  NSData *getData = [getString dataUsingEncoding:NSUTF8StringEncoding allowLossyConversion:YES];     NSString *getLength = [NSString stringWithFormat:@"%d", [getData length]];     NSURL *url=[[NSURL alloc]initWithString:urlString];  NSMutableURLRequest  *request=[[NSMutableURLRequest alloc]init];  [request setURL: url];   [request setHTTPMethod:@"GET"];     [request setValue:getLength forHTTPHeaderField:@"Content-Length"];     [request setValue:@"text/xml" forHTTPHeaderField:@"Content-Type"];    // [request setTimeoutInterval:15];  [request setCachePolicy:NSURLRequestReloadIgnoringLocalCacheData];  [request setHTTPBody:getData];       //定义一个计时器    connection = [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:true];  [NSTimer scheduledTimerWithTimeInterval:60.0 target:self selector:@selector(cancelConnection:) userInfo:nil repeats:NO];  [url release];  [request release];  if(connection)  {   receivedData = [[NSMutableData data] retain];  }  else  {   NSLog(@"<<Net_Http.m-->sendGetRequest-->connection-->nil");  }  while(!finished) {   [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];  }     return receivedData; } 4.json连接网络的代理函数 - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {  NSLog(@"<<Net_Http.m-->connection-->didReceiveResponse-->get the whole response:%@",response);  [receivedData setLength:0]; } - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {  NSLog(@"<<Net_Http.m-->connection-->didReceiveData-->getting data");  [receivedData appendData:data]; } -(void)connection:(NSURLConnection *)connection_ didFailWithError:(NSError *)error {     if (mianViewLoadFlag==YES)   {   NSLog(@"<<Net_Http.m-->connection-->didFailWithError-->加载完成!");   receivedData=nil;   [self connectionDidFinishLoading:connection_];     }else   {   NSLog(@"<<Net_Http.m-->connection-->didFailWithError-->加载出错!");   [self showErrorAlert:@"网络错误\n请检查您的网络或稍后重试"];   [self connectionDidFinishLoading:connection_];  }    } - (void)connectionDidFinishLoading:(NSURLConnection *)connection {  finished=YES;  mianViewLoadFlag=YES;  NSLog(@"<<Net_Http.m-->connectionDidFinishLoading-->YES");  } 4. -(void)cancelConnection:(NSTimer *)timer{    //取消连接   NSLog(@"<<Net_Http.m-->cancelConnection-->计时器已到时间");  [self connection:connection didFailWithError:error];  [connection cancel];   } -(void)showErrorAlert:(NSString *)message{  myAlert = [[UIAlertView alloc]       initWithTitle:@""       message:message              delegate:self       cancelButtonTitle:nil       otherButtonTitles:@"确定",nil];    [myAlert show];  [myAlert release]; } -(void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex{ // if (alertView == myAlert) {   switch (buttonIndex) {    case 0:      //[[UIApplication sharedApplication] terminateWithSuccess];     break;    case 1:         break;         default:     break;   } // } } -(void)setMainViewLoadFlag:(BOOL)mainFlag{  mianViewLoadFlag=mainFlag; } 5.NET_HTTP.h   BOOL mianViewLoadFlag; @interface Net_Http : NSObject {     NSURLConnection *connection;  NSMutableData *receivedData;  BOOL finished;  UIAlertView *myAlert;  NSError *error; } -(NSData *)sendPostRequest:(NSString *)postString theUrl:(NSString *)urlString; -(NSData *)sendGetRequest:(NSString *)getString  theUrl:(NSString *)urlString; -(void)showErrorAlert:(NSString *)message; -(BOOL) isConnected; -(BOOL)setMainViewLoadFlag;