NSTimer的精确度

1、iOS中一般UI上面常用两种定时器 NSTimer和CADisplayLink，那么它们分别的精确度是如何呢？

　　CADisplayLink 是用于帧刷新定时器，也就是和界面的刷新率保持一致，理想情况下FPS为60，并尽力保持60

　　NSTimer是否可以比CADisplayLink更加精确呢，最精确能下面的间隔是多少呢？NSTimer和CADisplayLink都作为一种事件加入到NSRunloop的事件源中，

　　NSRunloop不断循环，判断是否应该触发这一类事件，如下面所示，NSRunloop包涵下面这些不同的事件：

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), // 刚从休眠中唤醒

    kCFRunLoopExit          = (1UL << 7), // 即将退出Loop

};

　　可以看出，如果想让CADisplayLink正常工作，NSRunloop至少每秒循环60次，也就是至多17ms，那么NSRunloop每秒最多循环多少次呢？

2、NSRunloop每秒循环多少次

　　通过注册一个观察者到主线程中，观察每一种事件执行的log，来看看NSRunloop的执行情况

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

    // Override point for customization after application launch.

    CFRunLoopObserverRef observer = CFRunLoopObserverCreateWithHandler(NULL, (kCFRunLoopAllActivities), YES, 0, ^(CFRunLoopObserverRef observer, CFRunLoopActivity activity)

    {

        static unsigned long count = 0;

        if(activity & kCFRunLoopEntry)

        {

            NSLog(@"activity %lu: %@", ++count, @"kCFRunLoopEntry");

        }

        else if(activity & kCFRunLoopBeforeTimers)

        {

            NSLog(@"activity %lu: %@", ++count, @"kCFRunLoopBeforeTimers");

        }

        else if(activity & kCFRunLoopBeforeSources)

        {

            NSLog(@"activity %lu: %@", ++count, @"kCFRunLoopBeforeSources");

        }

        else if(activity & kCFRunLoopBeforeWaiting)

        {

            NSLog(@"activity %lu: %@", ++count, @"kCFRunLoopBeforeWaiting");

        }

        else if(activity & kCFRunLoopAfterWaiting)

        {

            NSLog(@"activity %lu: %@", ++count, @"kCFRunLoopAfterWaiting");

        }

        else if(activity & kCFRunLoopExit)

        {

            NSLog(@"activity %lu: %@", ++count, @"kCFRunLoopExit");

        }

    });

    CFRunLoopAddObserver(CFRunLoopGetMain(), observer, kCFRunLoopCommonModes);

    return YES;

}

　　这里打印出每一类的事件，同时需要加上两类定时器到主线程中

- (void)viewDidLoad {

    [super viewDidLoad];

    // Do any additional setup after loading the view, typically from a nib.

   NSTimer *timer = [NSTimer timerWithTimeInterval:0.001 repeats:YES block:^(NSTimer * _Nonnull timer) {

       static int timerCount = 0;

       //do nothing

       NSLog(@"timer do nothing, timerCount = %d", timerCount++);

   }];

   [[NSRunLoop currentRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];

    CADisplayLink *link = [CADisplayLink displayLinkWithTarget:self selector:@selector(update:)];

    [link addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];

}

- (void)update:(id)sender

{

    static int linkCount = 0;

    NSLog(@"link do nothing, linkCount = %d", linkCount++);

}

　　可以观察出每一类事件执行的情况，测试是在iphone5s， ios10.2的系统上

输出：

NSRunloop：

2017-03-18 13:01:54.145100 NSTimerTest[1121:267663] activity 20: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.148893 NSTimerTest[1121:267663] activity 24: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.150659 NSTimerTest[1121:267663] activity 28: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.153758 NSTimerTest[1121:267663] activity 32: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.155796 NSTimerTest[1121:267663] activity 36: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.158515 NSTimerTest[1121:267663] activity 40: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.160481 NSTimerTest[1121:267663] activity 44: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.162514 NSTimerTest[1121:267663] activity 48: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.165265 NSTimerTest[1121:267663] activity 52: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.169531 NSTimerTest[1121:267663] activity 56: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.229129 NSTimerTest[1121:267663] activity 74: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.232630 NSTimerTest[1121:267663] activity 78: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.233628 NSTimerTest[1121:267663] activity 82: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.235007 NSTimerTest[1121:267663] activity 86: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.236381 NSTimerTest[1121:267663] activity 90: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.237788 NSTimerTest[1121:267663] activity 94: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.238881 NSTimerTest[1121:267663] activity 98: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.239719 NSTimerTest[1121:267663] activity 102: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.240767 NSTimerTest[1121:267663] activity 106: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.241759 NSTimerTest[1121:267663] activity 110: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.242658 NSTimerTest[1121:267663] activity 114: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.243716 NSTimerTest[1121:267663] activity 118: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.244833 NSTimerTest[1121:267663] activity 122: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.245719 NSTimerTest[1121:267663] activity 126: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.247445 NSTimerTest[1121:267663] activity 130: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.248342 NSTimerTest[1121:267663] activity 134: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.250020 NSTimerTest[1121:267663] activity 138: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.251359 NSTimerTest[1121:267663] activity 142: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.252876 NSTimerTest[1121:267663] activity 146: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.254850 NSTimerTest[1121:267663] activity 150: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.256126 NSTimerTest[1121:267663] activity 154: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.257336 NSTimerTest[1121:267663] activity 158: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.258301 NSTimerTest[1121:267663] activity 162: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.259885 NSTimerTest[1121:267663] activity 166: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.261638 NSTimerTest[1121:267663] activity 170: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.262796 NSTimerTest[1121:267663] activity 174: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.264645 NSTimerTest[1121:267663] activity 178: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.265702 NSTimerTest[1121:267663] activity 182: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.266818 NSTimerTest[1121:267663] activity 186: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.268355 NSTimerTest[1121:267663] activity 190: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.269167 NSTimerTest[1121:267663] activity 194: kCFRunLoopBeforeWaiting

2017-03-18 13:01:54.269909 NSTimerTest[1121:267663] activity 198: kCFRunLoopBeforeWaiting

　　NSTimer

2017-03-18 13:01:54.127460 NSTimerTest[1121:267663] timer do nothing, timerCount = 0

2017-03-18 13:01:54.135893 NSTimerTest[1121:267663] timer do nothing, timerCount = 1

2017-03-18 13:01:54.140639 NSTimerTest[1121:267663] timer do nothing, timerCount = 2

2017-03-18 13:01:54.142266 NSTimerTest[1121:267663] timer do nothing, timerCount = 3

2017-03-18 13:01:54.143658 NSTimerTest[1121:267663] timer do nothing, timerCount = 4

2017-03-18 13:01:54.147695 NSTimerTest[1121:267663] timer do nothing, timerCount = 5

2017-03-18 13:01:54.151489 NSTimerTest[1121:267663] timer do nothing, timerCount = 6

2017-03-18 13:01:54.154552 NSTimerTest[1121:267663] timer do nothing, timerCount = 7

2017-03-18 13:01:54.156480 NSTimerTest[1121:267663] timer do nothing, timerCount = 8

2017-03-18 13:01:54.159303 NSTimerTest[1121:267663] timer do nothing, timerCount = 9

2017-03-18 13:01:54.161246 NSTimerTest[1121:267663] timer do nothing, timerCount = 10

2017-03-18 13:01:54.163655 NSTimerTest[1121:267663] timer do nothing, timerCount = 11

2017-03-18 13:01:54.170411 NSTimerTest[1121:267663] timer do nothing, timerCount = 12

2017-03-18 13:01:54.226209 NSTimerTest[1121:267663] timer do nothing, timerCount = 13

2017-03-18 13:01:54.228032 NSTimerTest[1121:267663] timer do nothing, timerCount = 14

2017-03-18 13:01:54.231912 NSTimerTest[1121:267663] timer do nothing, timerCount = 15

2017-03-18 13:01:54.234140 NSTimerTest[1121:267663] timer do nothing, timerCount = 16

2017-03-18 13:01:54.235779 NSTimerTest[1121:267663] timer do nothing, timerCount = 17

2017-03-18 13:01:54.236939 NSTimerTest[1121:267663] timer do nothing, timerCount = 18

2017-03-18 13:01:54.238231 NSTimerTest[1121:267663] timer do nothing, timerCount = 19

2017-03-18 13:01:54.239210 NSTimerTest[1121:267663] timer do nothing, timerCount = 20

2017-03-18 13:01:54.240251 NSTimerTest[1121:267663] timer do nothing, timerCount = 21

2017-03-18 13:01:54.241185 NSTimerTest[1121:267663] timer do nothing, timerCount = 22

2017-03-18 13:01:54.242131 NSTimerTest[1121:267663] timer do nothing, timerCount = 23

2017-03-18 13:01:54.243136 NSTimerTest[1121:267663] timer do nothing, timerCount = 24

2017-03-18 13:01:54.244139 NSTimerTest[1121:267663] timer do nothing, timerCount = 25

2017-03-18 13:01:54.245170 NSTimerTest[1121:267663] timer do nothing, timerCount = 26

2017-03-18 13:01:54.246129 NSTimerTest[1121:267663] timer do nothing, timerCount = 27

2017-03-18 13:01:54.248936 NSTimerTest[1121:267663] timer do nothing, timerCount = 28

2017-03-18 13:01:54.250729 NSTimerTest[1121:267663] timer do nothing, timerCount = 29

2017-03-18 13:01:54.252273 NSTimerTest[1121:267663] timer do nothing, timerCount = 30

2017-03-18 13:01:54.253343 NSTimerTest[1121:267663] timer do nothing, timerCount = 31

2017-03-18 13:01:54.255634 NSTimerTest[1121:267663] timer do nothing, timerCount = 32

2017-03-18 13:01:54.256494 NSTimerTest[1121:267663] timer do nothing, timerCount = 33

2017-03-18 13:01:54.257829 NSTimerTest[1121:267663] timer do nothing, timerCount = 34

2017-03-18 13:01:54.259261 NSTimerTest[1121:267663] timer do nothing, timerCount = 35

2017-03-18 13:01:54.260290 NSTimerTest[1121:267663] timer do nothing, timerCount = 36

2017-03-18 13:01:54.262144 NSTimerTest[1121:267663] timer do nothing, timerCount = 37

2017-03-18 13:01:54.263531 NSTimerTest[1121:267663] timer do nothing, timerCount = 38

2017-03-18 13:01:54.266225 NSTimerTest[1121:267663] timer do nothing, timerCount = 39

2017-03-18 13:01:54.267656 NSTimerTest[1121:267663] timer do nothing, timerCount = 40

2017-03-18 13:01:54.268629 NSTimerTest[1121:267663] timer do nothing, timerCount = 41

2017-03-18 13:01:54.269641 NSTimerTest[1121:267663] timer do nothing, timerCount = 42

2017-03-18 13:01:54.271133 NSTimerTest[1121:267663] timer do nothing, timerCount = 43

2017-03-18 13:01:54.272366 NSTimerTest[1121:267663] timer do nothing, timerCount = 44

2017-03-18 13:01:54.273213 NSTimerTest[1121:267663] timer do nothing, timerCount = 45

2017-03-18 13:01:54.274115 NSTimerTest[1121:267663] timer do nothing, timerCount = 46

2017-03-18 13:01:54.275425 NSTimerTest[1121:267663] timer do nothing, timerCount = 47

2017-03-18 13:01:54.276400 NSTimerTest[1121:267663] timer do nothing, timerCount = 48

2017-03-18 13:01:54.278951 NSTimerTest[1121:267663] timer do nothing, timerCount = 49

2017-03-18 13:01:54.281740 NSTimerTest[1121:267663] timer do nothing, timerCount = 50

2017-03-18 13:01:54.283120 NSTimerTest[1121:267663] timer do nothing, timerCount = 51

2017-03-18 13:01:54.284362 NSTimerTest[1121:267663] timer do nothing, timerCount = 52

　　CADisplayLink

2017-03-18 13:01:54.138378 NSTimerTest[1121:267663] link do nothing, linkCount = 0

2017-03-18 13:01:54.149657 NSTimerTest[1121:267663] link do nothing, linkCount = 1

2017-03-18 13:01:54.166121 NSTimerTest[1121:267663] link do nothing, linkCount = 2

2017-03-18 13:01:54.225401 NSTimerTest[1121:267663] link do nothing, linkCount = 3

2017-03-18 13:01:54.233023 NSTimerTest[1121:267663] link do nothing, linkCount = 4

2017-03-18 13:01:54.247794 NSTimerTest[1121:267663] link do nothing, linkCount = 5

2017-03-18 13:01:54.265119 NSTimerTest[1121:267663] link do nothing, linkCount = 6

2017-03-18 13:01:54.280689 NSTimerTest[1121:267663] link do nothing, linkCount = 7

2017-03-18 13:01:54.298406 NSTimerTest[1121:267663] link do nothing, linkCount = 8

2017-03-18 13:01:54.315036 NSTimerTest[1121:267663] link do nothing, linkCount = 9

2017-03-18 13:01:54.331416 NSTimerTest[1121:267663] link do nothing, linkCount = 10

2017-03-18 13:01:54.346888 NSTimerTest[1121:267663] link do nothing, linkCount = 11

2017-03-18 13:01:54.363696 NSTimerTest[1121:267663] link do nothing, linkCount = 12

2017-03-18 13:01:54.380435 NSTimerTest[1121:267663] link do nothing, linkCount = 13

2017-03-18 13:01:54.398125 NSTimerTest[1121:267663] link do nothing, linkCount = 14

2017-03-18 13:01:54.414091 NSTimerTest[1121:267663] link do nothing, linkCount = 15

2017-03-18 13:01:54.430187 NSTimerTest[1121:267663] link do nothing, linkCount = 16

2017-03-18 13:01:54.447019 NSTimerTest[1121:267663] link do nothing, linkCount = 17

2017-03-18 13:01:54.463854 NSTimerTest[1121:267663] link do nothing, linkCount = 18

2017-03-18 13:01:54.480343 NSTimerTest[1121:267663] link do nothing, linkCount = 19

2017-03-18 13:01:54.513566 NSTimerTest[1121:267663] link do nothing, linkCount = 21

2017-03-18 13:01:54.530110 NSTimerTest[1121:267663] link do nothing, linkCount = 22

2017-03-18 13:01:54.547502 NSTimerTest[1121:267663] link do nothing, linkCount = 23

2017-03-18 13:01:54.565346 NSTimerTest[1121:267663] link do nothing, linkCount = 24

2017-03-18 13:01:54.580107 NSTimerTest[1121:267663] link do nothing, linkCount = 25

2017-03-18 13:01:54.598014 NSTimerTest[1121:267663] link do nothing, linkCount = 26

2017-03-18 13:01:54.629988 NSTimerTest[1121:267663] link do nothing, linkCount = 28

2017-03-18 13:01:54.646657 NSTimerTest[1121:267663] link do nothing, linkCount = 29

2017-03-18 13:01:54.663800 NSTimerTest[1121:267663] link do nothing, linkCount = 30

2017-03-18 13:01:54.680001 NSTimerTest[1121:267663] link do nothing, linkCount = 31

2017-03-18 13:01:54.697108 NSTimerTest[1121:267663] link do nothing, linkCount = 32

2017-03-18 13:01:54.713726 NSTimerTest[1121:267663] link do nothing, linkCount = 33

2017-03-18 13:01:54.729956 NSTimerTest[1121:267663] link do nothing, linkCount = 34

2017-03-18 13:01:54.746658 NSTimerTest[1121:267663] link do nothing, linkCount = 35

2017-03-18 13:01:54.763778 NSTimerTest[1121:267663] link do nothing, linkCount = 36

2017-03-18 13:01:54.779953 NSTimerTest[1121:267663] link do nothing, linkCount = 37

2017-03-18 13:01:54.796732 NSTimerTest[1121:267663] link do nothing, linkCount = 38

2017-03-18 13:01:54.813729 NSTimerTest[1121:267663] link do nothing, linkCount = 39

2017-03-18 13:01:54.829980 NSTimerTest[1121:267663] link do nothing, linkCount = 40

2017-03-18 13:01:54.846751 NSTimerTest[1121:267663] link do nothing, linkCount = 41

2017-03-18 13:01:54.863757 NSTimerTest[1121:267663] link do nothing, linkCount = 42

2017-03-18 13:01:54.879957 NSTimerTest[1121:267663] link do nothing, linkCount = 43

2017-03-18 13:01:54.896619 NSTimerTest[1121:267663] link do nothing, linkCount = 44

2017-03-18 13:01:54.913648 NSTimerTest[1121:267663] link do nothing, linkCount = 45

2017-03-18 13:01:54.930006 NSTimerTest[1121:267663] link do nothing, linkCount = 46

2017-03-18 13:01:54.946953 NSTimerTest[1121:267663] link do nothing, linkCount = 47

2017-03-18 13:01:54.963751 NSTimerTest[1121:267663] link do nothing, linkCount = 48

2017-03-18 13:01:54.980065 NSTimerTest[1121:267663] link do nothing, linkCount = 49

3、总结

　　可以看出来，CADisplayLink“尽量”保证17ms执行一次，主要看NSRunloop中有没有执行其它事件时被阻塞

　　NSTimer的触发周期最小可以和NSRunloop的循环保持一致，也就是由NSRunloop的执行周期决定，大概2～3ms

　　因此这也是NSTimer也是不精确的原因

代码：https://github.com/liqiushui/NSRunloop

NSTimer的精确度的更多相关文章

CADisplayLink以及和NSTimer的区别
什么是CADisplayLink CADisplayLink是一个能让我们以和屏幕刷新率相同的频率将内容画到屏幕上的定时器.我们在应用中创建一个新的 CADisplayLink 对象,把它添加到一个r ...
iOS - OC NSTimer 定时器
前言 @interface NSTimer : NSObject 作用在指定的时间执行指定的任务. 每隔一段时间执行指定的任务. 1.定时器的创建当定时器创建完(不用 scheduled 的,添加 ...
iOS开发中深入理解CADisplayLink和NSTimer
一.什么是CADisplayLink 简单地说,它就是一个定时器,每隔几毫秒刷新一次屏幕. CADisplayLink是一个能让我们以和屏幕刷新率相同的频率将内容画到屏幕上的定时器.我们在应用中创建一 ...
iOS开发--计时器-NSTimer与CADisplayLink
如果程序要让某个方法重复执行,可以借助定时器来完成.CADisplayLink是一个能让我们以和屏幕刷新率相同的频率将内容画到屏幕上的定时器,NSTimer的精确度低了点,比如NSTimer的触发时间 ...
深入理解CADisplayLink和NSTimer
一.什么是CADisplayLink 简单地说,它就是一个定时器,每隔几毫秒刷新一次屏幕. CADisplayLink是一个能让我们以和屏幕刷新率相同的频率将内容画到屏幕上的定时器.我们在应用中创建一 ...
iOS---->CADisplayLink、比NSTimer更精确的定时器
什么是CADisplayLink CADisplayLink是一个能让我们以和屏幕刷新率相同的频率将内容画到屏幕上的定时器.我们在应用中创建一个新的 CADisplayLink 对象,把它添加到一个r ...
CADisplayLink & NSTimer
屏幕刷新与UI更新不同步:屏幕刷新由硬件(+GPU)保证,UI更新由软件(CPU保证). 出现卡顿的原因是软件的计算速度跟不上硬件的刷新速度. 一简介 1 所在框架 CADisplayLink和其它 ...
iOS中定时器的使用
1. NSTimer 不是很精确 2.CADisplayLink 屏幕 3.通过GCD来实现定时间器 //定时循环执行事件 //dispatch_source_set_timer 方法值得一提的是最后 ...
Core Animation系列之CADisplayLink
一直以来都想好好学习下CoreAnimation,奈何涉及的东西太多,想要一次性全部搞定时间上不允许,以后会断断续续的补全.最近项目里用到了CADisplayLink,就顺便花点时间看了看. 一.简介 ...

随机推荐

zookeeper 介绍
ZooKeeper 是一个分布式的,开放源码的分布式应用程序协调服务,它包含一个简单的原语集,分布式应用程序可以基于它实现同步服务,配置维护和命名服务等. Zookeeper是hadoop的一个子项目 ...
关于在VI中查看BIN文件二进制值不对的问题
通常,我们在vim中,可以使用命令 %!xxd 来查看文件对应的二进制值.但是最近发生了一个事情,查看到的BIN文件二进制值和直接用hexdump打印出来的不一样. 经过检查定位,发现是因为vimrc ...
我的Java笔记
第一章一计算机程序:一系列有序的指令集合. 二 java语言分为三个领域 javaSE java技术核心(桌面应用程序)qq 百度云 javaEE 企业版(面向internet的应用程序)京东淘 ...
C# 6 与 .NET Core 1.0 高级编程 - 39 章 Windows 服务（上）
译文,个人原创,转载请注明出处(C# 6 与 .NET Core 1.0 高级编程 - 39 章 Windows 服务(上)),不对的地方欢迎指出与交流. 章节出自<Professional C ...
CoreData和FMDB你用哪个？
概括: 我们先说说这两个东西,CoreData 和 FMDB,其实就我自己而言觉得这两个都不错,刚开始是接触FMDB的,CoreData是工作后自己看的.苹果推荐开发者去使用CoreData,但 FM ...
windows下搭建Nexus3私服和基于IDEA15的Maven学习笔记
搭建Nexus私服. 首先去官网下载window下用的zip文件.https://www.sonatype.com/download-oss-sonatype. 解压之后包含下面两个文件进入nexu ...
从头开始搭建一个Spring boot+RabbitMQ环境
*:first-child { margin-top: 0 !important; } body>*:last-child { margin-bottom: 0 !important; } /* ...
Codeforces 719B Anatoly and Cockroaches
B. Anatoly and Cockroaches time limit per test:1 second memory limit per test:256 megabytes input:st ...
简学Python第三章__函数式编程、递归、内置函数
#cnblogs_post_body h2 { background: linear-gradient(to bottom, #18c0ff 0%,#0c7eff 100%); color: #fff ...
&与&& C语言
&是一个位运算符,就是将两个二进制的数逐位相与,就是都是1才是1,只要有一个为0则为0,结果是相与之后的结果.&&是一个逻辑运算符,就是判断两个表达式的真假性,只有两个表达式同 ...

NSTimer的精确度

NSTimer的精确度的更多相关文章

随机推荐

热门专题