Reachability实时监控网络变化

Reachability是一种实时观察网络发生变化控件，如当你的手机处于WiFi情况下，他就会检测环境，当处于GPS的情况下改变环境，当处于无网络的情况下又是一种环境。下面我们看下关于Reachability的用法、

1.用到Reachability的情况下，首先引入SystemConfiguration；

Reachability.h:

#import <Foundation/Foundation.h>
#import <SystemConfiguration/SystemConfiguration.h>
#import <netinet/in.h>

typedef enum : NSInteger {
    NotReachable = 0,
    ReachableViaWiFi,
    ReachableViaWWAN
} NetworkStatus;

extern NSString *kReachabilityChangedNotification;

@interface Reachability : NSObject

+ (instancetype)reachabilityWithHostName:(NSString *)hostName;

+ (instancetype)reachabilityWithAddress:(const struct sockaddr_in *)hostAddress;

+ (instancetype)reachabilityForInternetConnection;

+ (instancetype)reachabilityForLocalWiFi;

- (BOOL)startNotifier;
- (void)stopNotifier;

- (NetworkStatus)currentReachabilityStatus;

Reachability.m:

#import <arpa/inet.h>
#import <ifaddrs.h>
#import <netdb.h>
#import <sys/socket.h>

#import <CoreFoundation/CoreFoundation.h>

#import "Reachability.h"

NSString *kReachabilityChangedNotification = @"kNetworkReachabilityChangedNotification";

#pragma mark - Supporting functions

#define kShouldPrintReachabilityFlags 1

static void PrintReachabilityFlags(SCNetworkReachabilityFlags flags, const char* comment)
{
#if kShouldPrintReachabilityFlags

NSLog(@"Reachability Flag Status: %c%c %c%c%c%c%c%c%c %s\n",
          (flags & kSCNetworkReachabilityFlagsIsWWAN)                ? 'W' : '-',
          (flags & kSCNetworkReachabilityFlagsReachable)            ? 'R' : '-',

(flags & kSCNetworkReachabilityFlagsTransientConnection)  ? 't' : '-',
          (flags & kSCNetworkReachabilityFlagsConnectionRequired)   ? 'c' : '-',
          (flags & kSCNetworkReachabilityFlagsConnectionOnTraffic)  ? 'C' : '-',
          (flags & kSCNetworkReachabilityFlagsInterventionRequired) ? 'i' : '-',
          (flags & kSCNetworkReachabilityFlagsConnectionOnDemand)   ? 'D' : '-',
          (flags & kSCNetworkReachabilityFlagsIsLocalAddress)       ? 'l' : '-',
          (flags & kSCNetworkReachabilityFlagsIsDirect)             ? 'd' : '-',
          comment
          );
#endif
}

static void ReachabilityCallback(SCNetworkReachabilityRef target, SCNetworkReachabilityFlags flags, void* info)
{
#pragma unused (target, flags)
    NSCAssert(info != NULL, @"info was NULL in ReachabilityCallback");
    NSCAssert([(__bridge NSObject*) info isKindOfClass: [Reachability class]], @"info was wrong class in ReachabilityCallback");

Reachability* noteObject = (__bridge Reachability *)info;
    // Post a notification to notify the client that the network reachability changed.
    [[NSNotificationCenter defaultCenter] postNotificationName: kReachabilityChangedNotification object: noteObject];
}

#pragma mark - Reachability implementation

@implementation Reachability
{
    BOOL _alwaysReturnLocalWiFiStatus; //default is NO
    SCNetworkReachabilityRef _reachabilityRef;
}

+ (instancetype)reachabilityWithHostName:(NSString *)hostName
{
    Reachability* returnValue = NULL;
    SCNetworkReachabilityRef reachability = SCNetworkReachabilityCreateWithName(NULL, [hostName UTF8String]);
    if (reachability != NULL)
    {
        returnValue= [[self alloc] init];
        if (returnValue != NULL)
        {
            returnValue->_reachabilityRef = reachability;
            returnValue->_alwaysReturnLocalWiFiStatus = NO;
        }
    }
    return returnValue;
}

+ (instancetype)reachabilityWithAddress:(const struct sockaddr_in *)hostAddress
{
    SCNetworkReachabilityRef reachability = SCNetworkReachabilityCreateWithAddress(kCFAllocatorDefault, (const struct sockaddr *)hostAddress);

Reachability* returnValue = NULL;

if (reachability != NULL)
    {
        returnValue = [[self alloc] init];
        if (returnValue != NULL)
        {
            returnValue->_reachabilityRef = reachability;
            returnValue->_alwaysReturnLocalWiFiStatus = NO;
        }
    }
    return returnValue;
}

+ (instancetype)reachabilityForInternetConnection
{
    struct sockaddr_in zeroAddress;
    bzero(&zeroAddress, sizeof(zeroAddress));
    zeroAddress.sin_len = sizeof(zeroAddress);
    zeroAddress.sin_family = AF_INET;
    
    return [self reachabilityWithAddress:&zeroAddress];
}

+ (instancetype)reachabilityForLocalWiFi
{
    struct sockaddr_in localWifiAddress;
    bzero(&localWifiAddress, sizeof(localWifiAddress));
    localWifiAddress.sin_len = sizeof(localWifiAddress);
    localWifiAddress.sin_family = AF_INET;

// IN_LINKLOCALNETNUM is defined in <netinet/in.h> as 169.254.0.0.
    localWifiAddress.sin_addr.s_addr = htonl(IN_LINKLOCALNETNUM);

Reachability* returnValue = [self reachabilityWithAddress: &localWifiAddress];
    if (returnValue != NULL)
    {
        returnValue->_alwaysReturnLocalWiFiStatus = YES;
    }
    
    return returnValue;
}

#pragma mark - Start and stop notifier

- (BOOL)startNotifier
{
    BOOL returnValue = NO;
    SCNetworkReachabilityContext context = {0, (__bridge void *)(self), NULL, NULL, NULL};

if (SCNetworkReachabilitySetCallback(_reachabilityRef, ReachabilityCallback, &context))
    {
        if (SCNetworkReachabilityScheduleWithRunLoop(_reachabilityRef, CFRunLoopGetCurrent(), kCFRunLoopDefaultMode))
        {
            returnValue = YES;
        }
    }
    
    return returnValue;
}

- (void)stopNotifier
{
    if (_reachabilityRef != NULL)
    {
        SCNetworkReachabilityUnscheduleFromRunLoop(_reachabilityRef, CFRunLoopGetCurrent(), kCFRunLoopDefaultMode);
    }
}

- (void)dealloc
{
    [self stopNotifier];
    if (_reachabilityRef != NULL)
    {
        CFRelease(_reachabilityRef);
    }
}

#pragma mark - Network Flag Handling

- (NetworkStatus)localWiFiStatusForFlags:(SCNetworkReachabilityFlags)flags
{
    PrintReachabilityFlags(flags, "localWiFiStatusForFlags");
    NetworkStatus returnValue = NotReachable;

if ((flags & kSCNetworkReachabilityFlagsReachable) && (flags & kSCNetworkReachabilityFlagsIsDirect))
    {
        returnValue = ReachableViaWiFi;
    }
    
    return returnValue;
}

- (NetworkStatus)networkStatusForFlags:(SCNetworkReachabilityFlags)flags
{
    PrintReachabilityFlags(flags, "networkStatusForFlags");
    if ((flags & kSCNetworkReachabilityFlagsReachable) == 0)
    {
        // The target host is not reachable.
        
    
        return NotReachable;
    }

NetworkStatus returnValue = NotReachable;

if ((flags & kSCNetworkReachabilityFlagsConnectionRequired) == 0)
    {
        /*
         If the target host is reachable and no connection is required then we'll assume (for now) that you're on Wi-Fi...
         */
        returnValue = ReachableViaWiFi;
    }

if ((((flags & kSCNetworkReachabilityFlagsConnectionOnDemand ) != 0) ||
        (flags & kSCNetworkReachabilityFlagsConnectionOnTraffic) != 0))
    {
        /*
         ... and the connection is on-demand (or on-traffic) if the calling application is using the CFSocketStream or higher APIs...
         */

if ((flags & kSCNetworkReachabilityFlagsInterventionRequired) == 0)
        {
            /*
             ... and no [user] intervention is needed...
             */
           
            returnValue = ReachableViaWiFi;
        }
    }

if ((flags & kSCNetworkReachabilityFlagsIsWWAN) == kSCNetworkReachabilityFlagsIsWWAN)
    {
        /*
         ... but WWAN connections are OK if the calling application is using the CFNetwork APIs.
         */
        
        returnValue = ReachableViaWWAN;
    }
    
    return returnValue;
}

- (BOOL)connectionRequired
{
    NSAssert(_reachabilityRef != NULL, @"connectionRequired called with NULL reachabilityRef");
    SCNetworkReachabilityFlags flags;

if (SCNetworkReachabilityGetFlags(_reachabilityRef, &flags))
    {
        return (flags & kSCNetworkReachabilityFlagsConnectionRequired);
    }

return NO;
}

- (NetworkStatus)currentReachabilityStatus
{
    NSAssert(_reachabilityRef != NULL, @"currentNetworkStatus called with NULL SCNetworkReachabilityRef");
    NetworkStatus returnValue = NotReachable;
    SCNetworkReachabilityFlags flags;
    
    if (SCNetworkReachabilityGetFlags(_reachabilityRef, &flags))
    {
   
        
        if (_alwaysReturnLocalWiFiStatus)
        {
            returnValue = [self localWiFiStatusForFlags:flags];
            
         
            
        }
        else
        {
            returnValue = [self networkStatusForFlags:flags];
            
            
        }
    }
    
    return returnValue;
}

@end

以上只是第三方组件，加之一些个人对其封装的一些方法，下面我门就要具体道每个Controller上了，来检测网络环境发生的变化

Controller.h

#import <UIKit/UIKit.h>
#import "Reachability.h"

@interface ReachViewController : UIViewController
- (void) reachabilityChanged:(NSNotification *)note;
- (void)updateInterfaceWithReachability:(Reachability *)reachability;
- (void)configureTextField:(UITextField *)textField imageView:(UIImageView *)imageView reachability:(Reachability *)reachability;

@end

Controller.m

#import "ReachViewController.h"
#import "MBProgressHUD.h"
#import "HUD.h"
@interface ReachViewController ()
@property (nonatomic) Reachability *hostReachability;
@property (nonatomic) Reachability *internetReachability;
@property (nonatomic) Reachability *wifiReachability;

@end

@implementation ReachViewController

- (void)viewDidLoad {
    [super viewDidLoad];

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(reachabilityChanged:) name:kReachabilityChangedNotification object:nil];
    NSString *remoteHostName = @"www.apple.com";
    NSString *remoteHostLabelFormatString = NSLocalizedString(@"Remote Host: %@", @"Remote host label format string");

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

}

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

- (void)updateInterfaceWithReachability:(Reachability *)reachability
{
    
    NetworkStatus netStatus = [reachability currentReachabilityStatus];

switch (netStatus) {
        case ReachableViaWWAN:
        {
            [HUD promptWithString:@"正在使用流量,建议用WiFi" onView:self.view];

}
            break;
        case ReachableViaWiFi:
        {
            [HUD promptWithString:@"WiFi已连接" onView:self.view];
        
        }
            break;
        default:
            break;
    }
    
    
    
    
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}
当你网络环境发生变化的时候你就可以实时观察到。代码没有任何bug，新建demo，复制粘贴就可以看下效果，如果你的开发环境出现错误就是版本问题了。