iOS 添加runloop观察者

可以查看当前线程的runloop状态

- (void)addObserver
{
    /*
     kCFRunLoopEntry = (1UL << 0),1
     kCFRunLoopBeforeTimers = (1UL << 1),2
     kCFRunLoopBeforeSources = (1UL << 2), 4
     kCFRunLoopBeforeWaiting = (1UL << 5), 32
     kCFRunLoopAfterWaiting = (1UL << 6), 64
     kCFRunLoopExit = (1UL << 7),128
     kCFRunLoopAllActivities = 0x0FFFFFFFU
     */
    CFRunLoopObserverRef observer = CFRunLoopObserverCreateWithHandler(CFAllocatorGetDefault(), kCFRunLoopAllActivities, YES, 0, ^(CFRunLoopObserverRef observer, CFRunLoopActivity activity) {
        switch (activity) {
            case 1:
            {
                NSLog(@"进入runloop");
            }
                break;
            case 2:
            {
                NSLog(@"timers");
            }
                break;
            case 4:
            {
                NSLog(@"sources");
            }
                break;
            case 32:
            {
                NSLog(@"即将进入休眠");
            }
                break;
            case 64:
            {
                NSLog(@"唤醒");
            }
                break;
            case 128:
            {
                NSLog(@"退出");
            }
                break;
            default:
                break;
        }
    });
    CFRunLoopAddObserver(CFRunLoopGetCurrent(), observer, kCFRunLoopCommonModes);//将观察者添加到common模式下，这样当default模式和UITrackingRunLoopMode两种模式下都有回调。
    self.obsever  = observer;
    CFRelease(observer);
}