源码分析之AFNetworking ②AFNetworkReachabilityManager

Posted 2021-08-10 梦想家-mxj

AFNetworkReachabilityManager对象用于监听设备当前连接网络的状态。
AFNetworkReachabilityManager提供了4种创建方法：

• (instancetype)sharedManager; //创建单例

• (instancetype)manager;//创建实例对象

• (instancetype)managerForDomain:(NSString *)domain;//根据地址名创建实例对象

• (instancetype)managerForAddress:(const void *)address;//根据sockaddr创建实例对象

• (instancetype)sharedManager {
  static AFNetworkReachabilityManager *_sharedManager = nil;
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
  _sharedManager = [self manager];
  });

  return _sharedManager;
  }
  shareManager调用manager方法创建一个AFNetworkReachabilityManager对象

通过枚举值查看网络状态
typedef NS_ENUM(NSInteger, AFNetworkReachabilityStatus) {
AFNetworkReachabilityStatusUnknown = -1,
AFNetworkReachabilityStatusNotReachable = 0,//未连接
AFNetworkReachabilityStatusReachableViaWWAN = 1,//蜂窝
AFNetworkReachabilityStatusReachableViaWiFi = 2,//wifi
};
网络监听
AFNetworkReachabilityManager通过startMonitoring和stopMonitoring方法来开始和停止监听当前设备连接的网络状态

• (void)startMonitoring {
  [self stopMonitoring];

  if (!self.networkReachability) {
  return;
  }

  __weak __typeof(self)weakSelf = self;
  AFNetworkReachabilityStatusCallback callback = ^(AFNetworkReachabilityStatus status) {
  __strong __typeof(weakSelf)strongSelf = weakSelf;

    strongSelf.networkReachabilityStatus = status;
    if (strongSelf.networkReachabilityStatusBlock) {
        strongSelf.networkReachabilityStatusBlock(status);
    }
    
    return strongSelf;
  

  };

  SCNetworkReachabilityContext context = {0, (__bridge void *)callback, AFNetworkReachabilityRetainCallback, AFNetworkReachabilityReleaseCallback, NULL};
  SCNetworkReachabilitySetCallback(self.networkReachability, AFNetworkReachabilityCallback, &context);
  SCNetworkReachabilityScheduleWithRunLoop(self.networkReachability, CFRunLoopGetMain(), kCFRunLoopCommonModes);

  dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0),^{
  SCNetworkReachabilityFlags flags;
  if (SCNetworkReachabilityGetFlags(self.networkReachability, &flags)) {
  AFPostReachabilityStatusChange(flags, callback);
  }
  });
  }
  startMonitoring方法中首先调用stopMonitoring方法，即先停止之前的监听，然后调用SCNetworkReachabilitySetCallback方法设置networkReachability的回调函数、AFNetworkReachabilityCallback和上下文context对象
  另外AFPostReachabilityStatusChange的实现
  static void AFPostReachabilityStatusChange(SCNetworkReachabilityFlags flags, AFNetworkReachabilityStatusCallback block) {
  AFNetworkReachabilityStatus status = AFNetworkReachabilityStatusForFlags(flags);//根据flags获取当前网络连接状态status
  dispatch_async(dispatch_get_main_queue(), ^{
  AFNetworkReachabilityManager *manager = nil;
  if (block) {
  manager = block(status);
  }
  NSNotificationCenter *notificationCenter = [NSNotificationCenter defaultCenter];
  NSDictionary *userInfo = @{ AFNetworkingReachabilityNotificationStatusItem: @(status) };
  [notificationCenter postNotificationName:AFNetworkingReachabilityDidChangeNotification object:manager userInfo:userInfo];
  });
  }
  此方法首先根据系统回调的AFNetworkReachabilityStatusForFlags方法以及falgs参数，获取网络连接状态，然后进入block，将status抛出外界，同时抛一个通知将status抛给外界，当网络状态发生改变，会同事用这两种方式传递给外界。
  AFNetworkReachabilityStatusForFlags方法是核心方法，负责根据flag的状态值，转化为相应的枚举值AFNetworkReachabilityStatus。

• (void)stopMonitoring {
  if (!self.networkReachability) {
  return;
  }
  SCNetworkReachabilityUnscheduleFromRunLoop(self.networkReachability, CFRunLoopGetMain(), kCFRunLoopCommonModes);
  }
  该方法通过监听的方法让networkReachability对象从runloop中注销。

//监听网络状态的demo

[[AFNetworkReachabilityManager sharedManager] startMonitoring];
    [[AFNetworkReachabilityManager sharedManager] setReachabilityStatusChangeBlock:^(AFNetworkReachabilityStatus status) {
        switch (status) {
            case AFNetworkReachabilityStatusUnknown:
                NSLog(@"未知");
                break;
            case AFNetworkReachabilityStatusNotReachable:
                NSLog(@"未连接");
                break;
            case AFNetworkReachabilityStatusReachableViaWWAN:
                NSLog(@"移动");
                break;
            case AFNetworkReachabilityStatusReachableViaWiFi:
                NSLog(@"WiFi");
                break;
            default:
                break;
        }
    }];