Apple 设备可在用户不感知的情况下进行wifi的切换，如果我们在App 内部需要感知设备wifi切换的变化，可以在 Darwin Notify Center 中注册监听 kNotifySCNetworkChange 通知，如下:
static void onNotifyCallback(CFNotificationCenterRef center,
void *observer,
CFStringRef name,
const void *object,
CFDictionaryRef userInfo) {
if (CFStringCompare(name, CFSTR(kNotifySCNetworkChange), kCFCompareCaseInsensitive) == kCFCompareEqualTo) {
//TODO when wifi changed
}
}
+ (void)startMonitorWifiChange {
CFNotificationCenterAddObserver(CFNotificationCenterGetDarwinNotifyCenter(),
NULL,
&onNotifyCallback,
CFSTR(kNotifySCNetworkChange),
NULL,
CFNotificationSuspensionBehaviorDeliverImmediately);
}
+ (void)stopMonitorWifiChange {
CFNotificationCenterRemoveObserver(CFNotificationCenterGetDarwinNotifyCenter(),
NULL,
CFSTR(kNotifySCNetworkChange),
NULL);
}需要:
#import "/usr/include/notify_keys.h"
上述代码中 kNotifySCNetworkChange 在该头文件中定义，跳至该头文件还可看到:
/* * File System notifications * These advise clients of various filesystem events. */ #define kNotifyVFSMount "com.apple.system.kernel.mount" #define kNotifyVFSUnmount "com.apple.system.kernel.unmount" #define kNotifyVFSUpdate "com.apple.system.kernel.mountupdate" #define kNotifyVFSLowDiskSpace "com.apple.system.lowdiskspace" #define kNotifyVFSLowDiskSpaceRootFS "com.apple.system.lowdiskspace.system" #define kNotifyVFSLowDiskSpaceOtherFS "com.apple.system.lowdiskspace.user" /* * System Configuration notifications * These advise clients of changes in the system configuration * managed by the system configuration server (configd). * Note that a much richer set of notifications are available to * clients using the SCDynamicStore API. */ #define kNotifySCHostNameChange "com.apple.system.hostname" #define kNotifySCNetworkChange "com.apple.system.config.network_change" /* * Time Zone change notification * Sent by notifyd when the system's timezone changes. */ #define kNotifyTimeZoneChange "com.apple.system.timezone" /* * System clock change notification * Sent when a process modifies the system clock using the settimeofday system call. */ #define kNotifyClockSet "com.apple.system.clock_set"
由此可猜测在 Darwin Notify Center 中还可监听系统时区改变，系统时间改变，系统 hostname 改变的通知，未验证。
在 CFNotificationCenter Reference 中有关于 CFNotificationCenterGetDarwinNotifyCenter 的描述如下:
This notification center is used to cover the Core OS notification mechanism (see /usr/include/notify.h). An application has only one Darwin notification center, so this function returns the same value each time it is called.
The Darwin Notify Center has no notion of per-user sessions, all notifications are system-wide. As with distributed notifications, the main thread’s run loop must be running in one of the common modes (usually kCFRunLoopDefaultMode) for Darwin-style notifications to be delivered.
由此可见， Darwin Notify Center 是系统级别，每次使用接口 CFNotificationCenterGetDarwinNotifyCenter 返回的都是同一个 Darwin Notify Center 实例。
关于 Darwin Notify Center 的更多信息可以参考: