iOS开发——网络连接判断

       iOS开发必然会涉及网络操作，作为优化用户体验的第一步，在请求网络前，往往首先需要判断客户端是否连接网络，并给用户提示。然后用户才会去进行打开网络或连接WiFi等操作。下面我将会使用苹果提供的Reachability文件去进行网络连接的判断。代码已经上传：
https://github.com/chenyufeng1991/JudgeNetworkConnect   。共有两个案例，下面分别来实现：

【静态判断网络连接】

使用该方法会在你需要判断网络连接的地方执行一次判断，是连接还是未连接的。这里说的静态是该判断只会执行一次，并不会根据当前用户的操作动态判断。首先需要导入Reachability.h ,Reachability.m文件。核心代码实现如下：

#import "ViewController.h"
#import "Reachability.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
[super viewDidLoad];

//在需要的地方执行该判断；
[self testConnection];

}

-(void)testConnection{
NSString *result;
if ([self checkNetworkConnection]) {
result = @"连接网络成功！";
}else {
result = @"连接网络失败！";
}

//这里大家可以使用AlertController来弹出提示框；
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"提示" message:result
delegate:self
cancelButtonTitle:@"确定" otherButtonTitles:nil];
[alert show];

}

-(BOOL)checkNetworkConnection
{
struct sockaddr_in zeroAddress;
bzero(&zeroAddress, sizeof(zeroAddress));
zeroAddress.sin_len = sizeof(zeroAddress);
zeroAddress.sin_family = AF_INET;

SCNetworkReachabilityRef defaultRouteReachability = SCNetworkReachabilityCreateWithAddress(NULL, (struct sockaddr *)&zeroAddress);
SCNetworkReachabilityFlags flags;

BOOL didRetrieveFlags = SCNetworkReachabilityGetFlags(defaultRouteReachability, &flags);
CFRelease(defaultRouteReachability);

if (!didRetrieveFlags) {
printf("Error. Count not recover network reachability flags\n");
return NO;
}

BOOL isReachable = flags & kSCNetworkFlagsReachable;
BOOL needsConnection = flags & kSCNetworkFlagsConnectionRequired;
return (isReachable && !needsConnection) ? YES : NO;
}

@end

【动态判断网络连接】

比如用户打开了WiFi，程序就会监测到已经打开WiFi。比如用户关闭了网络，程序就会监测到关闭了网络。是根据当前客户端的网络状态实时监测的。该代码是苹果提供的Reachability的Demo，源程序有点复杂，我做了一些简化，方便使用。首先需要导入Reachability.h ,Reachability.m文件。核心代码实现如下：

#import "APLViewController.h"
#import "Reachability.h"

@interface APLViewController ()

@property (nonatomic) Reachability *hostReachability;

@end

@implementation APLViewController

- (void)viewDidLoad
{
[super viewDidLoad];

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

NSString *remoteHostName = @"http://www.baidu.com";

self.hostReachability = [Reachability reachabilityWithHostName:remoteHostName];
[self.hostReachability startNotifier];
[self updateInterfaceWithReachability:self.hostReachability];

}

- (void) reachabilityChanged:(NSNotification *)note
{
Reachability* curReach = [note object];
[self updateInterfaceWithReachability:curReach];
}

- (void)updateInterfaceWithReachability:(Reachability *)reachability
{
if (reachability == self.hostReachability)
{
[self configureTextField: reachability];

}
}

- (void)configureTextField:(Reachability *)reachability
{
//NetworkStatus定义的枚举，
NetworkStatus netStatus = [reachability currentReachabilityStatus];
BOOL connectionRequired = [reachability connectionRequired];

switch (netStatus){
case NotReachable:
{

NSLog(@"网络不可用");

connectionRequired = NO;
break;
}

case ReachableViaWWAN: {
NSLog(@"连接WWAN");
break;
}
case ReachableViaWiFi: {

NSLog(@"当前连接了WiFi");
break;
}
}

if (connectionRequired){
//没有连接网络的操作；
}
}

@end

      我们不仅要顺手会用这些代码，如果有时间，可以好好研究该功能的实现机制，会大有益处。

github主页：https://github.com/chenyufeng1991 
。欢迎大家访问！