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  1. 1. 实时监测手机的联网状态，并作出对应的回调处理，源码学习子AFNetworkReachabilityManager.

实时监测手机的联网状态，并作出对应的回调处理，源码学习子AFNetworkReachabilityManager.

  • 首先定义网络状态的所有可能的状态的枚举
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typedef NS_ENUM(NSInteger, AFNetworkReachabilityStatus) {
//未知
AFNetworkReachabilityStatusUnknown          = -1,

//与App通信的服务器，不可达
AFNetworkReachabilityStatusNotReachable     = 0,

//与App通信的服务器，可达且通过3G，4G ...
AFNetworkReachabilityStatusReachableViaWWAN = 1,

//与App通信的服务器，可达且通过WiFi
AFNetworkReachabilityStatusReachableViaWiFi = 2,
};
  • 定义了网络状态变化后的通知Key
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//状态改变后的通知key
extern NSString * const AFNetworkingReachabilityDidChangeNotification;

//从通知实例中获取到当前状态的key
extern NSString * const AFNetworkingReachabilityNotificationStatusItem;
  • AFNetworkReachabilityManager的向外暴露的属性
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/**
The current network reachability status.
*/
@property (readonly, nonatomic, assign) AFNetworkReachabilityStatus networkReachabilityStatus;

/**
Whether or not the network is currently reachable.
*/
@property (readonly, nonatomic, assign, getter = isReachable) BOOL reachable;

/**
Whether or not the network is currently reachable via WWAN.
*/
@property (readonly, nonatomic, assign, getter = isReachableViaWWAN) BOOL reachableViaWWAN;

/**
Whether or not the network is currently reachable via WiFi.
*/
@property (readonly, nonatomic, assign, getter = isReachableViaWiFi) BOOL reachableViaWiFi;
  • AFNetworkReachabilityManager的只向内暴露的属性
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//保存转换成oc对象后的SCNetworkReachabilityRef结构体实例
@property (readwrite, nonatomic, strong) id networkReachability;

@property (readwrite, nonatomic, assign) AFNetworkReachabilityAssociation networkReachabilityAssociation;

@property (readwrite, nonatomic, assign) AFNetworkReachabilityStatus networkReachabilityStatus;

@property (readwrite, nonatomic, copy) AFNetworkReachabilityStatusBlock networkReachabilityStatusBlock;

  • AFNetworkReachabilityManager实例化的集中方式

  • 1) 使用默认的监测地址

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+ (instancetype)sharedManager {
static AFNetworkReachabilityManager *_sharedManager = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{

//1. 构造默认的地址
struct sockaddr_in address;
bzero(&address, sizeof(address));
address.sin_len = sizeof(address);
address.sin_family = AF_INET;

//2. 调用传入ip地址的方法创建AFNetworkReachabilityManager实例
_sharedManager = [self managerForAddress:&address];
});

return _sharedManager;
}
  • 2) 使用指定的服务器域名作为监测地址（注意:SCNetworkReachabilityCreateWithName）
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+ (instancetype)managerForDomain:(NSString *)domain {

//1. 根据传入的域名字符串，创建SCNetworkReachabilityRef实例（网络连接）
SCNetworkReachabilityRef reachability = SCNetworkReachabilityCreateWithName(kCFAllocatorDefault, [domain UTF8String]);

//2. 创建AFNetworkReachabilityManager实例，并保存上面创建的SCNetworkReachabilityRef实例
AFNetworkReachabilityManager *manager = [[self alloc] initWithReachability:reachability];

//3. 标示来自域名
manager.networkReachabilityAssociation = AFNetworkReachabilityForName;

return manager;
}
  • 3) 直接使用ip地址作为监测地址（注意:SCNetworkReachabilityCreateWithAddress）
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+ (instancetype)managerForAddress:(const void *)address {

//1. 根据传入的ip地址结构体实例，创建SCNetworkReachabilityRef实例（网络连接）
SCNetworkReachabilityRef reachability = SCNetworkReachabilityCreateWithAddress(kCFAllocatorDefault, (const struct sockaddr *)address);

//2. 创建AFNetworkReachabilityManager实例，并保存上面创建的SCNetworkReachabilityRef实例
AFNetworkReachabilityManager *manager = [[self alloc] initWithReachability:reachability];

//3. 标示来自ip地址
manager.networkReachabilityAssociation = AFNetworkReachabilityForAddress;

return manager;
}
  • 创建AFNetworkReachabilityManager时，传入SCNetworkReachabilityRef的初始化方法
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- (instancetype)initWithReachability:(SCNetworkReachabilityRef)reachability {
self = [super init];
if (!self) {
return nil;
}

//1. 将`SCNetworkReachabilityRef结构体实例`转换成oc中的对象
self.networkReachability = CFBridgingRelease(reachability);

//2. 初始网络状态设置为未知
self.networkReachabilityStatus = AFNetworkReachabilityStatusUnknown;

return self;
}
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CFBridgingRelease()这个c函数主要作用:

1. 将【非Objective-C对象】转换为【Objective-C对象】
2. 同时将对象的管理权交给ARC，开发者无需手动管理内存
3. 效果和 __bridge_transfer 是一样的

  • AFNetworkReachabilityManager的init函数与dealloc函数

  • init函数，在ARC环境下被标记为不可用

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- (instancetype)init NS_UNAVAILABLE
{
return nil;
}
  • dealloc函数，在执行时停止网络状态改变的监测
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- (void)dealloc {
[self stopMonitoring];
}
  • NS_UNAVAILABLE这个宏的使用
  • ARC 状态时候 标记一些 函数不能够使用
  • 使用AFNetworkReachabilityManager实例，获取当前网络状态的Api
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- (BOOL)isReachable {
return [self isReachableViaWWAN] || [self isReachableViaWiFi];
}

- (BOOL)isReachableViaWWAN {
return self.networkReachabilityStatus == AFNetworkReachabilityStatusReachableViaWWAN;
}

- (BOOL)isReachableViaWiFi {
return self.networkReachabilityStatus == AFNetworkReachabilityStatusReachableViaWiFi;
}
  • 使用AFNetworkReachabilityManager实例开启网络状态改变监听（注意，AFN默认是没有开启网络状态监听的，需要自己start开启）
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- (void)startMonitoring {

//1. 如果当前有正在监听，先停止当前的监听
[self stopMonitoring];

//2. 如果没有要监听的网络连接，就结束此次start操作
if (!self.networkReachability) {
return;
}

//3. 设置当使用ios c函数库的回调的回调Block
__weak __typeof(self)weakSelf = self;
AFNetworkReachabilityStatusBlock callback = ^(AFNetworkReachabilityStatus status) {
__strong __typeof(weakSelf)strongSelf = weakSelf;

// 保存当前改变后的网络状态
strongSelf.networkReachabilityStatus = status;

// 执行使用AFNetworkReachabilityManager传入的用户回调Block
if (strongSelf.networkReachabilityStatusBlock) {
strongSelf.networkReachabilityStatusBlock(status);
}

};

//4. 取出AFNetworkReachabilityManager实例保存的SCNetworkReachabilityRef实例
id networkReachability = self.networkReachability;

//5. 建立 SCNetworkReachabilityContext 实例，需要使用几个Block
//先将如下这几个Block存入到context，后面再从context中取出来
//回调Block1: 前面创建的AFNetworkReachabilityStatusBlock类型的callback
//回调Block2: AFNetworkReachabilityRetainCallback
//回调Block3: AFNetworkReachabilityReleaseCallback
SCNetworkReachabilityContext context = {0, (__bridge void *)callback, AFNetworkReachabilityRetainCallback, AFNetworkReachabilityReleaseCallback, NULL};

//6. 设置使用ios c函数库，监听到网络连接状态改变后的回调函数
//参数1: 网络连接
//参数2: AFNetworkReachabilityCallback回调函数，这个函数是在使用c函数库，监听到网络状态改变时由iOS sdk触发的回调
//参数3: 指定为上面创建的Context
SCNetworkReachabilitySetCallback((__bridge SCNetworkReachabilityRef)networkReachability, AFNetworkReachabilityCallback, &context);

//7. 执行网络监测的操作
//在`主线程的runloop`上调度
//`runloop mode`为kCFRunLoopCommonModes，也就是任何情况下都要进行调度
SCNetworkReachabilityScheduleWithRunLoop((__bridge SCNetworkReachabilityRef)networkReachability, CFRunLoopGetMain(), kCFRunLoopCommonModes);

//8. 判断当前网络监听是来自 1)domain 2)ip地址
switch (self.networkReachabilityAssociation) {

//如果是domain，就不发通知
case AFNetworkReachabilityForName:
break;

//如果是ip地址，就发送通知
case AFNetworkReachabilityForAddress:
case AFNetworkReachabilityForAddressPair:
default: {
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0),^{

//首先得到网络连接的flags
SCNetworkReachabilityFlags flags;
SCNetworkReachabilityGetFlags((__bridge SCNetworkReachabilityRef)networkReachability, &flags);

//根据flags得到当前网络状态
AFNetworkReachabilityStatus status = AFNetworkReachabilityStatusForFlags(flags);

//然后再回到主队列，发送通知，告知网络状态已经改变
dispatch_async(dispatch_get_main_queue(), ^{
callback(status);

NSNotificationCenter *notificationCenter = [NSNotificationCenter defaultCenter];
[notificationCenter postNotificationName:AFNetworkingReachabilityDidChangeNotification object:nil userInfo:@{ AFNetworkingReachabilityNotificationStatusItem: @(status) }];

});
});
}
break;
}
}
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这个【函数】是在使用ios sdk 的 c函数库监听到网络状态改变时由iOS sdk触发的回调执行的函数

static void AFNetworkReachabilityCallback(SCNetworkReachabilityRef __unused target, SCNetworkReachabilityFlags flags, void *info) {

//1. 根据flags得到网络状态
AFNetworkReachabilityStatus status = AFNetworkReachabilityStatusForFlags(flags);

//2. 取出之前设置的callback，并执行
AFNetworkReachabilityStatusBlock block = (__bridge AFNetworkReachabilityStatusBlock)info;
if (block) {
block(status);
}

//3. 发送网络状态改变的通知
dispatch_async(dispatch_get_main_queue(), ^{
NSNotificationCenter *notificationCenter = [NSNotificationCenter defaultCenter];
NSDictionary *userInfo = @{ AFNetworkingReachabilityNotificationStatusItem: @(status) };
[notificationCenter postNotificationName:AFNetworkingReachabilityDidChangeNotification object:nil userInfo:userInfo];
});

}
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创建SCNetworkReachabilityContext时，指定的retain Block

static const void * AFNetworkReachabilityRetainCallback(const void *info) {
return Block_copy(info);
}
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创建SCNetworkReachabilityContext时，指定的release Block

static void AFNetworkReachabilityReleaseCallback(const void *info) {
if (info) {
Block_release(info);
}
}
  • 停止网络监听
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- (void)stopMonitoring {
if (!self.networkReachability) {
return;
}

//从主线程的runloop unschedule 监听操作
SCNetworkReachabilityUnscheduleFromRunLoop((__bridge SCNetworkReachabilityRef)self.networkReachability, CFRunLoopGetMain(), kCFRunLoopCommonModes);
}

  • 发现AFNetworkReachabilityManager.m有一个关于kvo的函数

  • 源码如下

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+ (NSSet *)keyPathsForValuesAffectingValueForKey:(NSString *)key {

//1. 如果当前被修改的key是: 1) reachable 2) reachableViaWWAN 3) reachableViaWiFi 其中的一种，那么就发出networkReachabilityStatus属性被修改的通知
if ([key isEqualToString:@"reachable"] || [key isEqualToString:@"reachableViaWWAN"] || [key isEqualToString:@"reachableViaWiFi"]) {
return [NSSet setWithObject:@"networkReachabilityStatus"];
}

//2. 返回当前被修改的属性
return [super keyPathsForValuesAffectingValueForKey:key];
}
  • 这个方法的作用
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1. 如果一个@property的变化，依赖于某个对象的一个或者多个@property的变化
2. 一旦这些一个或者多个@property的值发生变化，那么之前的主动依赖的@property也表示发生变化，并发送KVO修改通知
  • 上如源码的作用
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1. networkReachabilityStatus属性变化，依赖于 1) reachable 2) reachableViaWWAN 3) reachableViaWiFi 这三个属性值的变化

2. 一旦后三个其中一个属性值变化，就代表networkReachabilityStatus属性值发生变化
  • 使用这个方法注意:
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属性必须实现 setter方法与gettter方法
  • 将SCNetworkReachabilityFlags解析成网络状态枚举
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static AFNetworkReachabilityStatus AFNetworkReachabilityStatusForFlags(SCNetworkReachabilityFlags flags) {

//1. 
BOOL isReachable = ((flags & kSCNetworkReachabilityFlagsReachable) != 0);
BOOL needsConnection = ((flags & kSCNetworkReachabilityFlagsConnectionRequired) != 0);
BOOL canConnectionAutomatically = (((flags & kSCNetworkReachabilityFlagsConnectionOnDemand ) != 0) || ((flags & kSCNetworkReachabilityFlagsConnectionOnTraffic) != 0));
BOOL canConnectWithoutUserInteraction = (canConnectionAutomatically && (flags & kSCNetworkReachabilityFlagsInterventionRequired) == 0);
BOOL isNetworkReachable = (isReachable && (!needsConnection || canConnectWithoutUserInteraction));

//2. 
AFNetworkReachabilityStatus status = AFNetworkReachabilityStatusUnknown;
if (isNetworkReachable == NO) {
status = AFNetworkReachabilityStatusNotReachable;
}
#if    TARGET_OS_IPHONE
else if ((flags & kSCNetworkReachabilityFlagsIsWWAN) != 0) {
status = AFNetworkReachabilityStatusReachableViaWWAN;
}
#endif
else {
status = AFNetworkReachabilityStatusReachableViaWiFi;
}

return status;
}

  • 主要使用的是iOS sdk提供的SCNetworkReachability.h

  • SCNetworkReachabilityContext结构体

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typedef struct {
CFIndex        version;
void *        info;
const void    *(*retain)(const void *info);
void        (*release)(const void *info);
CFStringRef    (*copyDescription)(const void *info);
} SCNetworkReachabilityContext;
``` 

- SCNetworkReachabilityFlags枚举值

enum {
kSCNetworkReachabilityFlagsTransientConnection = 1<<0,
kSCNetworkReachabilityFlagsReachable = 1<<1,
kSCNetworkReachabilityFlagsConnectionRequired = 1<<2,
kSCNetworkReachabilityFlagsConnectionOnTraffic = 1<<3,
kSCNetworkReachabilityFlagsInterventionRequired = 1<<4,
kSCNetworkReachabilityFlagsConnectionOnDemand = 1<<5, // OSX_AVAILABLE_STARTING(MAC_10_6,__IPHONE_3_0)
kSCNetworkReachabilityFlagsIsLocalAddress = 1<<16,
kSCNetworkReachabilityFlagsIsDirect = 1<<17,

#if TARGET_OS_IPHONE
kSCNetworkReachabilityFlagsIsWWAN = 1<<18,

#endif // TARGET_OS_IPHONE

kSCNetworkReachabilityFlagsConnectionAutomatic = kSCNetworkReachabilityFlagsConnectionOnTraffic
};
typedef uint32_t SCNetworkReachabilityFlags;

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- 获取SCNetworkReachabilityGetFlags的Api

Boolean//返回bool，表示获取是否成功
SCNetworkReachabilityGetFlags (
SCNetworkReachabilityRef target,
SCNetworkReachabilityFlags *flags
) OSX_AVAILABLE_STARTING(MAC_10_3,__IPHONE_2_0);

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- SCNetworkReachabilityCallBack，block声明

typedef void (SCNetworkReachabilityCallBack) (
SCNetworkReachabilityRef target,
SCNetworkReachabilityFlags flags,
void info
);

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- 创建`SCNetworkReachabilityRef`的Api

方式1:

SCNetworkReachabilityRef//返回值类型
SCNetworkReachabilityCreateWithName (
CFAllocatorRef allocator,
const char *nodename
) OSX_AVAILABLE_STARTING(MAC_10_3,__IPHONE_2_0);

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方式2:

SCNetworkReachabilityRef//返回值类型
SCNetworkReachabilityCreateWithAddress (
CFAllocatorRef allocator,
const struct sockaddr *address
) OSX_AVAILABLE_STARTING(MAC_10_3,__IPHONE_2_0);

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方式3:

SCNetworkReachabilityRef//返回值类型
SCNetworkReachabilityCreateWithAddressPair (
CFAllocatorRef allocator,
const struct sockaddr localAddress,
const struct sockaddr remoteAddress
) OSX_AVAILABLE_STARTING(MAC_10_3,__IPHONE_2_0);

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- 设置使用`SCNetworkReachability`监听到状态改变后的回调函数

Boolean//返回一个bool，返回是否设置成功
SCNetworkReachabilitySetCallback (
SCNetworkReachabilityRef target,
SCNetworkReachabilityCallBack callout,
SCNetworkReachabilityContext *context
) OSX_AVAILABLE_STARTING(MAC_10_3,__IPHONE_2_0);

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- 在一个runloop开始调度执行网络状态监听

Boolean//返回一个bool，返回是否开始调度成功
SCNetworkReachabilityScheduleWithRunLoop (
SCNetworkReachabilityRef target,
CFRunLoopRef runLoop,
CFStringRef runLoopMode
) OSX_AVAILABLE_STARTING(MAC_10_3,__IPHONE_2_0);

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- 在一个runloop移除结束执行网络状态监听

Boolean//返回一个bool，返回是否移除调度成功
SCNetworkReachabilityUnscheduleFromRunLoop (
SCNetworkReachabilityRef target,
CFRunLoopRef runLoop,
CFStringRef runLoopMode
) OSX_AVAILABLE_STARTING(MAC_10_3,__IPHONE_2_0);

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- 暂时不知道做什么的...

Boolean
SCNetworkReachabilitySetDispatchQueue (
SCNetworkReachabilityRef target,
dispatch_queue_t queue
) OSX_AVAILABLE_STARTING(MAC_10_6,__IPHONE_4_0);
`

Contents
  1. 1. 实时监测手机的联网状态，并作出对应的回调处理，源码学习子AFNetworkReachabilityManager.