学步园

      这个类可以用来检测用户是否连接到internet.  用法非常简单，只有一个方法，返回 YES或NO。

一个简单的例子：

if ([Connection isConnected]) { ... }<br /> else { ... }

这个类的头文件：

//<br /> // Connection.h<br /> //<br /> #import <Foundation/Foundation.h><br /> #import <SystemConfiguration/SystemConfiguration.h><br /> #import <netinet/in.h><br /> #import <arpa/inet.h><br /> #import <netdb.h> </p> <p>@interface Connection : NSObject { </p> <p>} </p> <p>+ (BOOL) isConnected; </p> <p>@end

类的实现文件：

//<br /> // Connection.m<br /> // </p> <p>#import "Connection.h" </p> <p>@implementation Connection </p> <p>+ (BOOL) isConnected {<br /> // Create zero addy<br /> struct sockaddr_in zeroAddress;<br /> bzero(&zeroAddress, sizeof(zeroAddress));<br /> zeroAddress.sin_len = sizeof(zeroAddress);<br /> zeroAddress.sin_family = AF_INET;<br /> // Recover reachability flags<br /> SCNetworkReachabilityRef defaultRouteReachability = SCNetworkReachabilityCreateWithAddress(NULL, (struct sockaddr *)&zeroAddress);<br /> SCNetworkReachabilityFlags flags;<br /> BOOL didRetrieveFlags = SCNetworkReachabilityGetFlags(defaultRouteReachability, &flags);<br /> CFRelease(defaultRouteReachability);<br /> if (!didRetrieveFlags) {<br /> NSLog(@"Error. Could not recover network reachability flags");<br /> return NO;<br /> }<br /> BOOL isReachable = flags & kSCNetworkFlagsReachable;<br /> BOOL needsConnection = flags & kSCNetworkFlagsConnectionRequired;<br /> BOOL nonWiFi = flags & kSCNetworkReachabilityFlagsTransientConnection;<br /> NSURL *testURL = [NSURL URLWithString:@"http://www.google.com/"];<br /> NSURLRequest *testRequest = [NSURLRequest requestWithURL:testURL cachePolicy:NSURLRequestReloadIgnoringLocalCacheData timeoutInterval:20.0];<br /> NSURLConnection *testConnection = [[[NSURLConnection alloc] initWithRequest:testRequest delegate:self] autorelease];<br /> return ((isReachable && !needsConnection) || nonWiFi) ? (testConnection ? YES : NO) : NO;<br /> } </p> <p>@end<br />

最后别忘了添加必要的frameworks: SystemConfiguration and libz.1.1.3.dylib

标题中提到的Reachability也具有检测网络的功能。大家可以参考资料：http://www.raddonline.com/blogs/geek-journal/iphone-sdk-testing-network-reachability/

http://developer.apple.com/iphone/library/samplecode/Reachability/index.html