新建 NSThread CFRunLoop

   NSThread * pthread  = [[NSThread alloc] initWithBlock:^{
            NSLog(@"begin----");
            
            // 创建上下文（要初始化一下结构体）
            CFRunLoopSourceContext context = {0};
            
            // 创建source
            CFRunLoopSourceRef source = CFRunLoopSourceCreate(kCFAllocatorDefault, 0, &context);
            
            // 往Runloop中添加source
            CFRunLoopAddSource(CFRunLoopGetCurrent(), source, kCFRunLoopDefaultMode);
            
            // 销毁source
            CFRelease(source);
            
            // 启动
            CFRunLoopRunInMode(kCFRunLoopDefaultMode, 1.0e10, false);
            
//            while (weakSelf && !weakSelf.isStopped) {
//                // 第3个参数：returnAfterSourceHandled，设置为true，代表执行完source后就会退出当前loop
//                CFRunLoopRunInMode(kCFRunLoopDefaultMode, 1.0e10, true);
//            }
            
        }];


 CFRunLoopStop(CFRunLoopGetCurrent());

runLoop 的工作流程

typedef struct __CFRunLoop * CFRunLoopRef;

struct __CFRunLoop {
    pthread_t _pthread;
    CFMutableSetRef _commonModes;
    CFMutableSetRef _commonModeItems;
    CFRunLoopModeRef _currentMode;
    CFMutableSetRef _modes;
};
typedef struct __CFRunLoopMode *CFRunLoopModeRef;

struct __CFRunLoopMode {
    CFStringRef _name;
    CFMutableSetRef _sources0;
    CFMutableSetRef _sources1;
    CFMutableArrayRef _observers;
    CFMutableArrayRef _timers;
};

/* Run Loop Observer Activities */
typedef CF_OPTIONS(CFOptionFlags, CFRunLoopActivity) {
    kCFRunLoopEntry = (1UL << 0), // 即将进入Loop
    kCFRunLoopBeforeTimers = (1UL << 1), // 即将处理Timer
    kCFRunLoopBeforeSources = (1UL << 2), // 即将处理Source
    kCFRunLoopBeforeWaiting = (1UL << 5), // 即将进入休眠
    kCFRunLoopAfterWaiting = (1UL << 6), // 即将从休眠中唤醒
    kCFRunLoopExit = (1UL << 7), //即将退出Loop
    kCFRunLoopAllActivities = 0x0FFFFFFFU
};

添加监听

void observerRunLoopActivity(CFRunLoopObserverRef observer, CFRunLoopActivity activity, void *info)
{
   CFRunLoopMode mode =   CFRunLoopCopyCurrentMode(CFRunLoopGetCurrent());
    NSLog(@"mode == %@", mode);
    switch (activity) {
        case kCFRunLoopEntry: {
            NSLog(@"kCFRunLoopEntry");
        }

        break;
        case kCFRunLoopBeforeTimers: {
            NSLog(@"kCFRunLoopBeforeTimers");
        }

        break;
        case kCFRunLoopBeforeSources: {
            NSLog(@"kCFRunLoopBeforeSources");
        }

        break;
        case kCFRunLoopBeforeWaiting: {
            NSLog(@"kCFRunLoopBeforeWaiting");
        }

        break;
        case kCFRunLoopAfterWaiting: {
            NSLog(@"kCFRunLoopAfterWaiting");
        }

        break;
        case kCFRunLoopExit: {
            NSLog(@"kCFRunLoopExit");
        }

        break;

        default:
            break;
    }
    CFRelease(mode);
}

- (void)createObserver1 {
    // 创建observer
    CFRunLoopObserverRef observer = CFRunLoopObserverCreate(kCFAllocatorDefault, kCFRunLoopAllActivities, YES, 0, observerRunLoopActivity, NULL);
    // 添加observer 到runloop中
    CFRunLoopAddObserver(CFRunLoopGetMain(), observer, kCFRunLoopCommonModes);
    // 释放observer
    CFRelease(observer);
}

- (void)createObserver2 {
    CFRunLoopObserverRef observer =  CFRunLoopObserverCreateWithHandler(kCFAllocatorDefault, kCFRunLoopAllActivities, YES, 0, ^(CFRunLoopObserverRef observer, CFRunLoopActivity activity) {
        switch (activity) {
            case kCFRunLoopEntry: {
                NSLog(@"kCFRunLoopEntry");
            }

            break;
            case kCFRunLoopBeforeTimers: {
                NSLog(@"kCFRunLoopBeforeTimers");
            }

            break;
            case kCFRunLoopBeforeSources: {
                NSLog(@"kCFRunLoopBeforeSources");
            }

            break;
            case kCFRunLoopBeforeWaiting: {
                NSLog(@"kCFRunLoopBeforeWaiting");
            }

            break;
            case kCFRunLoopAfterWaiting: {
                NSLog(@"kCFRunLoopAfterWaiting");
            }

            break;
            case kCFRunLoopExit: {
                NSLog(@"kCFRunLoopExit");
            }

            break;

            default:
                break;
        }
    });
    CFRunLoopAddObserver(CFRunLoopGetMain(), observer, kCFRunLoopCommonModes);
    CFRelease(observer);
}