知道系统何时在额外菜单中进入睡眠状态？

我为 Mac 开发了一个 Menu Extra（menulet），但我想知道使用 Menu Extra 的机器是否已进入睡眠状态。我实现了一个贪睡功能，但由于它是基于时间的方法，因此相当不可靠。任何提示或建议将不胜感激！

Thanks!

您可能想查看NSWorkspaceWillSleepNotification in NS工作区 http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/ApplicationKit/Classes/NSWorkspace_Class/Reference/Reference.html.
诀窍是，您需要在 NSWorkspace 的 notificationCenter 上注册通知，而不是默认的通知。请参阅技术问答 QA1340 http://developer.apple.com/library/mac/#qa/qa1340/_index.html.

示例代码：

- (void) receiveSleepNote: (NSNotification*) note
{
    NSLog(@"receiveSleepNote: %@", [note name]);
}

- (void) fileNotifications
{
    // These notifications are filed on NSWorkspace's notification center, not the default 
    // notification center. You will not receive sleep/wake notifications if you file 
    // with the default notification center.
    [[[NSWorkspace sharedWorkspace] notificationCenter] addObserver:self 
            selector:@selector(receiveSleepNote:) 
            name: NSWorkspaceWillSleepNotification object:nil];
}