直接上代碼：一看你就懂了。

#import "ViewController.h"


@interface ViewController ()
/** 注釋 */
//@property (nonatomic, strong) pthread_t thread;
@end

@implementation ViewController

#pragma mark ----------------------
#pragma mark Events
-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
//    [self observer];
//    [NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:@selector(task) userInfo:nil repeats:YES];
    
    [NSThread detachNewThreadSelector:@selector(task) toTarget:self withObject:nil];
}

- (IBAction)sourceBtnClick:(id)sender
{
    NSLog(@"%s",__func__);
}

#pragma mark ----------------------
#pragma mark
-(void)task
{
    NSLog(@"%s",__func__);
    
//    [NSRunLoop currentRunLoop] runUntilDate:[];
}

-(void)observer
{
    //1.創(chuàng)建監(jiān)聽者
    /*
     第一個參數(shù):怎么分配存儲空間
     第二個參數(shù):要監(jiān)聽的狀態(tài) kCFRunLoopAllActivities 所有的狀態(tài)
     第三個參數(shù):時候持續(xù)監(jiān)聽
     第四個參數(shù):優(yōu)先級 總是傳0
     第五個參數(shù):當狀態(tài)改變時候的回調(diào)
     */
    CFRunLoopObserverRef observer = CFRunLoopObserverCreateWithHandler(CFAllocatorGetDefault(), kCFRunLoopAllActivities, YES, 0, ^(CFRunLoopObserverRef observer, CFRunLoopActivity activity) {
        
        /*
         kCFRunLoopEntry = (1UL << 0),        即將進入runloop
         kCFRunLoopBeforeTimers = (1UL << 1), 即將處理timer事件
         kCFRunLoopBeforeSources = (1UL << 2),即將處理source事件
         kCFRunLoopBeforeWaiting = (1UL << 5),即將進入睡眠
         kCFRunLoopAfterWaiting = (1UL << 6), 被喚醒
         kCFRunLoopExit = (1UL << 7),         runloop退出
         kCFRunLoopAllActivities = 0x0FFFFFFFU
         */
        switch (activity) {
            case kCFRunLoopEntry:
                NSLog(@"即將進入runloop");
                break;
            case kCFRunLoopBeforeTimers:
                NSLog(@"即將處理timer事件");
                break;
            case kCFRunLoopBeforeSources:
                NSLog(@"即將處理source事件");
                break;
            case kCFRunLoopBeforeWaiting:
                NSLog(@"即將進入睡眠");
                break;
            case kCFRunLoopAfterWaiting:
                NSLog(@"被喚醒");
                break;
            case kCFRunLoopExit:
                NSLog(@"runloop退出");
                break;
                
            default:
                break;
        }
    });
    
    /*
     第一個參數(shù):要監(jiān)聽哪個runloop
     第二個參數(shù):觀察者
     第三個參數(shù):運行模式
     */
    CFRunLoopAddObserver(CFRunLoopGetCurrent(),observer, kCFRunLoopDefaultMode);
    
    //NSDefaultRunLoopMode == kCFRunLoopDefaultMode
    //NSRunLoopCommonModes == kCFRunLoopCommonModes
}

@end