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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。
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原文地址：http://www.cnblogs.com/hanguoqing/p/4466161.html
