• iOS Run loop使用实例


    http://blog.csdn.net/libaineu2004/article/details/45364737

    一、Runloop简介:

    Run loops 是线程相关的的基础框架的一部分。一个 run loop 就是一个事件处理 的循环,用来不停的调度工作以及处理输入事件。

    使用 run loop的目的是让你的线程在有工作的时候忙于工作,而没工作的时候处于休眠状态。

    Runloop还可以在loop在循环中的同时响应其他输入源,比如界面控件的按钮,手势等。

     

    Run loop 接收输入事件来自两种不同的来源:

    输入源(input source)和定时源 (timer source)。

    输入源传递异步事件,通常消息来自于其他线程或程序。输入源的种类:基于端口的输入源和自定义输入源。

    定时源则传递同步事件,发生在特定时间或者重复的时间间隔。

     

    Run loop 模式是所有要监视的输入源和定时源以及要通知的 run loop 注册观察 者的集合。

    可以将 Run loop 观察者和以下事件关联:

    Run loop 入口

    Run loop 何时处理一个定时器

    Run loop 何时处理一个输入源

    Run loop 何时进入睡眠状态

    Run loop 何时被唤醒,但在唤醒之前要处理的事件

    Run loop 终止

     

    每次运行 Run loop,你线程的 Run loop 对会自动处理之前未处理的消息,并通知相关的观察者。具体的顺序如下:

    1. 通知观察者 Run loop 已经启动。

    2. 通知观察者任何即将要开始的定时器。

    3. 通知观察者任何即将启动的非基于端口的源。

    4. 启动任何准备好的非基于端口的源。

    5. 如果基于端口的源准备好并处于等待状态,立即启动;并进入步骤 9。

    6. 通知观察者线程进入休眠。

    7. 将线程置于休眠直到任一下面的事件发生:

       某一事件到达基于端口的源;

       定时器启动;

       Run loop 设置的时间已经超时;

       Run loop 被显式唤醒。

    8. 通知观察者线程将被唤醒。

    9. 处理未处理的事件

       如果用户定义的定时器启动,处理定时器事件并重启 Run loop。进入步骤 2。

       如果输入源启动,传递相应的消息。

       如果 Run loop 被显式唤醒而且时间还没超时,重启 Run loop,进入步骤 2。

    10. 通知观察者 Run loop 结束。

     

    Run loop 在你要和线程有更多的交互时才需要,比如以下情况:

    使用端口或自定义输入源来和其他线程通信;

    使用线程的定时器;

    Cocoa 中使用任何performSelector...的方法;

    使线程周期性工作。

     

    二、举例说明Runloop的优点。

    一般情况下,当我们使用NSRunLoop的时候,代码如下所示:

    do {

        [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopModebeforeDate:[NSDate distantFuture]];

    } while (!done);

    在上面的代码中,参数done为NO的时候,当前runloop会一直接收处理其他输入源,处理输入源之后会再回到runloop中等待其他的输入源;除非done为NO,否则当前流程一直再runloop中。

    如下面的代码片段所示,有三个按钮,分别对应如下三个action消息,buttonNormalThreadTestPressed,buttonRunloopPressed,buttonTestPressed。

    buttonNormalThreadTestPressed:启动一个线程,在while循环中等待线程执行完再接着往下运行。

    buttonRunloopPressed:启动一个线程,使用runloop,等待线程执行完再接着往下运行。

    buttonTestPressed:仅仅打印两条日志,用来测试UI是否能立即响应的。

    在本测试中,待程序运行后,做如下操作对比:

    1、点击buttonNormalThreadTestPressed,然后立刻点击buttonTestPressed,查看日志输出。

    2、待1完成后,点击buttonRunloopPressed,然后立刻点击buttonTestPressed,查看日志输出,跟1的日志做对比,即可以发现步骤2即使线程没有完成,在runloop等待过程中,界面仍然能够响应。

     

    BOOL threadProcess1Finished =NO;

    -(void)threadProce1{

        NSLog(@"Enter threadProce1.");

       

        for (int i=0; i<5;i++) {

            NSLog(@"InthreadProce1 count = %d.", i);

            sleep(1);

        }   

        threadProcess1Finished =YES;    

        NSLog(@"Exit threadProce1.");

    }

     

    BOOL threadProcess2Finished =NO;

    -(void)threadProce2{

        NSLog(@"Enter threadProce2.");

       

        for (int i=0; i<5;i++) {

            NSLog(@"InthreadProce2 count = %d.", i);

            sleep(1);

        }

       

        threadProcess2Finished =YES;   

        NSLog(@"Exit threadProce2.");

    }

     

    - (IBAction)buttonNormalThreadTestPressed:(UIButton *)sender {

        NSLog(@"EnterbuttonNormalThreadTestPressed");

       

        threadProcess1Finished =NO;

        NSLog(@"Start a new thread.");

        [NSThreaddetachNewThreadSelector: @selector(threadProce1)

                                 toTarget: self

                               withObject: nil];

       

        // 通常等待线程处理完后再继续操作的代码如下面的形式。

        // 在等待线程threadProce1结束之前,调用buttonTestPressed,界面没有响应,直到threadProce1运行完,才打印buttonTestPressed里面的日志。

        while (!threadProcess1Finished) {

            [NSThreadsleepForTimeInterval: 0.5];

        }

       

        NSLog(@"ExitbuttonNormalThreadTestPressed");   

    }

     

    - (IBAction)buttonRunloopPressed:(id)sender {

        NSLog(@"Enter buttonRunloopPressed");

        threadProcess2Finished =NO;

        NSLog(@"Start a new thread.");

        [NSThreaddetachNewThreadSelector: @selector(threadProce2)

                                 toTarget: self

                               withObject: nil];

       

        // 使用runloop,情况就不一样了。

        // 在等待线程threadProce2结束之前,调用buttonTestPressed,界面立马响应,并打印buttonTestPressed里面的日志。

        // 这就是runloop的神奇所在

        while (!threadProcess2Finished) {

            NSLog(@"Begin runloop");

            [[NSRunLoopcurrentRunLoop] runMode:NSDefaultRunLoopMode

                                     beforeDate: [NSDate distantFuture]];

            NSLog(@"End runloop.");

        }

        NSLog(@"Exit buttonRunloopPressed");

    }

     

    - (IBAction)buttonTestPressed:(id)sender{

        NSLog(@"Enter buttonTestPressed");

        NSLog(@"Exit buttonTestPressed");

    }

     

    日志信息如下:

    2013-04-07 14:25:22.829 Runloop[657:11303] EnterbuttonNormalThreadTestPressed

    2013-04-07 14:25:22.830 Runloop[657:11303] Start a new thread.

    2013-04-07 14:25:22.831 Runloop[657:1250f] Enter threadProce1.

    2013-04-07 14:25:22.832 Runloop[657:1250f] In threadProce1 count = 0.

    2013-04-07 14:25:23.833 Runloop[657:1250f] In threadProce1 count = 1.

    2013-04-07 14:25:24.834 Runloop[657:1250f] In threadProce1 count = 2.

    2013-04-07 14:25:25.835 Runloop[657:1250f] In threadProce1 count = 3.

    2013-04-07 14:25:26.837 Runloop[657:1250f] In threadProce1 count = 4.

    2013-04-07 14:25:27.839 Runloop[657:1250f] Exit threadProce1.

    2013-04-07 14:25:27.840 Runloop[657:11303]ExitbuttonNormalThreadTestPressed

    2013-04-07 14:25:27.841 Runloop[657:11303]Enter buttonTestPressed

    2013-04-07 14:25:27.842 Runloop[657:11303] Exit buttonTestPressed

    2013-04-07 14:25:27.843 Runloop[657:11303] Enter buttonTestPressed

    2013-04-07 14:25:27.844 Runloop[657:11303] Exit buttonTestPressed

     

    2013-04-07 14:43:41.790 Runloop[657:11303] Enter buttonRunloopPressed

    2013-04-07 14:43:41.790 Runloop[657:11303] Start a new thread.

    2013-04-07 14:43:41.791 Runloop[657:11303] Begin runloop

    2013-04-07 14:43:41.791 Runloop[657:14f0b] Enter threadProce2.

    2013-04-07 14:43:41.792 Runloop[657:14f0b] In threadProce2 count = 0.

    2013-04-07 14:43:42.542 Runloop[657:11303] End runloop.

    2013-04-07 14:43:42.543 Runloop[657:11303] Begin runloop

    2013-04-07 14:43:42.694 Runloop[657:11303]Enter buttonTestPressed

    2013-04-07 14:43:42.694 Runloop[657:11303]Exit buttonTestPressed

    2013-04-07 14:43:42.695 Runloop[657:11303] End runloop.

    2013-04-07 14:43:42.696 Runloop[657:11303] Begin runloop

    2013-04-07 14:43:42.793 Runloop[657:14f0b] In threadProce2 count = 1.

    2013-04-07 14:43:43.326 Runloop[657:11303] End runloop.

    2013-04-07 14:43:43.327 Runloop[657:11303] Begin runloop

    2013-04-07 14:43:43.438 Runloop[657:11303]Enter buttonTestPressed

    2013-04-07 14:43:43.438 Runloop[657:11303]Exit buttonTestPressed

    2013-04-07 14:43:43.439 Runloop[657:11303] End runloop.

    2013-04-07 14:43:43.440 Runloop[657:11303] Begin runloop

    2013-04-07 14:43:43.795 Runloop[657:14f0b] In threadProce2 count = 2.

    2013-04-07 14:43:44.797 Runloop[657:14f0b] In threadProce2 count = 3.

    2013-04-07 14:43:45.798 Runloop[657:14f0b] In threadProce2 count = 4.

    2013-04-07 14:43:46.800 Runloop[657:14f0b] Exit threadProce2.

     

    三、Runloop简单实例:

    - (void)viewDidLoad

    {

        [super viewDidLoad];

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

       

        [NSThread detachNewThreadSelector: @selector(newThreadProcess)

                                 toTarget: self

                               withObject: nil];

    }

     

    - (void)newThreadProcess

    {

        @autoreleasepool {

            //获得当前thread的Runloop

            NSRunLoop* myRunLoop = [NSRunLoop currentRunLoop];

         

            //设置Run loop observer的运行环境 

            CFRunLoopObserverContext context = {0,self,NULL,NULL,NULL};

           

            //创建Run loop observer对象 

            //第一个参数用于分配observer对象的内存 

            //第二个参数用以设置observer所要关注的事件,详见回调函数myRunLoopObserver中注释 

            //第三个参数用于标识该observer是在第一次进入runloop时执行还是每次进入run loop处理时均执行 

            //第四个参数用于设置该observer的优先级 

            //第五个参数用于设置该observer的回调函数 

            //第六个参数用于设置该observer的运行环境 

            CFRunLoopObserverRef observer =CFRunLoopObserverCreate(kCFAllocatorDefault,kCFRunLoopAllActivities, YES, 0, &myRunLoopObserver, &context);

            if(observer)

            {

                //将Cocoa的NSRunLoop类型转换成CoreFoundation的CFRunLoopRef类型 

                CFRunLoopRef cfRunLoop = [myRunLoop getCFRunLoop];

               

                //将新建的observer加入到当前thread的runloop 

                CFRunLoopAddObserver(cfRunLoop, observer, kCFRunLoopDefaultMode);

            }

           

            //

            [NSTimer scheduledTimerWithTimeInterval: 1

                                            target: self

                                           selector:@selector(timerProcess)

                                          userInfo: nil

                                           repeats: YES];

            NSInteger loopCount = 2;

            do{

                //启动当前thread的loop直到所指定的时间到达,在loop运行时,runloop会处理所有来自与该run loop联系的inputsource的数据 

                //对于本例与当前run loop联系的inputsource只有一个Timer类型的source。 

                //该Timer每隔1秒发送触发事件给runloop,run loop检测到该事件时会调用相应的处理方法。 

               

                //由于在run loop添加了observer且设置observer对所有的runloop行为都感兴趣。  

                //当调用runUnitDate方法时,observer检测到runloop启动并进入循环,observer会调用其回调函数,第二个参数所传递的行为是kCFRunLoopEntry。 

                //observer检测到runloop的其它行为并调用回调函数的操作与上面的描述相类似。 

                [myRunLoop runUntilDate:[NSDate dateWithTimeIntervalSinceNow:5.0]];

                //当run loop的运行时间到达时,会退出当前的runloop。observer同样会检测到runloop的退出行为并调用其回调函数,第二个参数所传递的行为是kCFRunLoopExit。

                loopCount--;

            }while (loopCount);

        }

    }

     

    void myRunLoopObserver(CFRunLoopObserverRef observer,CFRunLoopActivityactivity,void *info)

    {

        switch (activity) { 

                //The entrance of the run loop, beforeentering the event processing loop.  

                //This activity occurs once for each callto CFRunLoopRun and CFRunLoopRunInMode 

            case kCFRunLoopEntry: 

                NSLog(@"run loop entry"); 

                break; 

                //Inside the event processing loop beforeany timers are processed 

            case kCFRunLoopBeforeTimers: 

                NSLog(@"run loop before timers"); 

                break;

                //Inside the event processing loop beforeany sources are processed 

            case kCFRunLoopBeforeSources: 

                NSLog(@"run loop before sources"); 

                break; 

                //Inside the event processing loop beforethe run loop sleeps, waiting for a source or timer to fire.  

                //This activity does not occur ifCFRunLoopRunInMode is called with a timeout of 0 seconds.  

                //It also does not occur in a particulariteration of the event processing loop if a version 0 source fires 

            case kCFRunLoopBeforeWaiting: 

                NSLog(@"run loop before waiting"); 

                break; 

                //Inside the event processing loop afterthe run loop wakes up, but before processing the event that woke it up.  

                //This activity occurs only if the run loopdid in fact go to sleep during the current loop 

            case kCFRunLoopAfterWaiting: 

                NSLog(@"run loop after waiting"); 

                break; 

                //The exit of the run loop, after exitingthe event processing loop.  

                //This activity occurs once for each callto CFRunLoopRun and CFRunLoopRunInMode 

            case kCFRunLoopExit: 

                NSLog(@"run loop exit"); 

                break; 

                /*

                 A combination of all the precedingstages

                 case kCFRunLoopAllActivities:

                 break;

                 */ 

            default: 

                break; 

        } 

    }

     

    - (void)timerProcess{

        for (int i=0; i<5; i++) {       

            NSLog(@"In timerProcess count = %d.", i);

            sleep(1);

        }

    }

     

    调试打印信息如下:

    2012-12-18 09:51:14.174 Texta[645:14807] run loop entry

    2012-12-18 09:51:14.175 Texta[645:14807] run loop before timers

    2012-12-18 09:51:14.176 Texta[645:14807] run loop before sources

    2012-12-18 09:51:14.177 Texta[645:14807] run loop before waiting

    2012-12-18 09:51:15.174 Texta[645:14807] run loop after waiting

    2012-12-18 09:51:15.176 Texta[645:14807] In timerProcess count = 0.

    2012-12-18 09:51:16.178 Texta[645:14807] In timerProcess count = 1.

    2012-12-18 09:51:17.181 Texta[645:14807] In timerProcess count = 2.

    2012-12-18 09:51:18.183 Texta[645:14807] In timerProcess count = 3.

    2012-12-18 09:51:19.185 Texta[645:14807] In timerProcess count = 4.

    2012-12-18 09:51:20.187 Texta[645:14807] run loop exit

    2012-12-18 09:51:20.189 Texta[645:14807] run loop entry

    2012-12-18 09:51:20.190 Texta[645:14807] run loop before timers

    2012-12-18 09:51:20.191 Texta[645:14807] run loop before sources

    2012-12-18 09:51:20.191 Texta[645:14807] run loop before waiting

    2012-12-18 09:51:21.174 Texta[645:14807] run loop after waiting

    2012-12-18 09:51:21.176 Texta[645:14807] In timerProcess count = 0.

    2012-12-18 09:51:22.178 Texta[645:14807] In timerProcess count = 1.

    2012-12-18 09:51:23.181 Texta[645:14807] In timerProcess count = 2.

    2012-12-18 09:51:24.183 Texta[645:14807] In timerProcess count = 3.

    2012-12-18 09:51:25.185 Texta[645:14807] In timerProcess count = 4.

    2012-12-18 09:51:26.187 Texta[645:14807] run loop exit

     

    四、Runloop可以阻塞线程,等待其他线程执行后再执行。

    比如:

    BOOL StopFlag =NO;

    - (void)viewDidLoad

    {

        [super viewDidLoad];

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

       

        StopFlag =NO;

        NSLog(@"Start a new thread.");

        [NSThread detachNewThreadSelector: @selector(newThreadProc)

                                 toTarget:self

                               withObject: nil];

        while (!StopFlag) {

            NSLog(@"Beginrunloop");

            [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode

                                     beforeDate: [NSDate distantFuture]];

            NSLog(@"Endrunloop.");

        }

       

        NSLog(@"OK");

    }

     

    -(void)newThreadProc{

        NSLog(@"Enter newThreadProc.");

       

        for (int i=0; i<10; i++) {

            NSLog(@"InnewThreadProc count = %d.", i);

            sleep(1);

        }

       

        StopFlag =YES;

       

        NSLog(@"Exit newThreadProc.");

    }

    }

    调试打印信息如下:

    2012-12-18 08:50:34.220 Runloop[374:11303] Start a new thread.

    2012-12-18 08:50:34.222 Runloop[374:11303] Begin runloop

    2012-12-18 08:50:34.222 Runloop[374:14b03] Enter newThreadProc.

    2012-12-18 08:50:34.223 Runloop[374:14b03] In newThreadProc count = 0.

    2012-12-18 08:50:35.225 Runloop[374:14b03] In newThreadProc count = 1.

    2012-12-18 08:50:36.228 Runloop[374:14b03] In newThreadProc count = 2.

    2012-12-18 08:50:37.230 Runloop[374:14b03] In newThreadProc count = 3.

    2012-12-18 08:50:38.233 Runloop[374:14b03] In newThreadProc count = 4.

    2012-12-18 08:50:39.235 Runloop[374:14b03] In newThreadProc count = 5.

    2012-12-18 08:50:40.237 Runloop[374:14b03] In newThreadProc count = 6.

    2012-12-18 08:50:41.240 Runloop[374:14b03] In newThreadProc count = 7.

    2012-12-18 08:50:42.242 Runloop[374:14b03] In newThreadProc count = 8.

    2012-12-18 08:50:43.245 Runloop[374:14b03] In newThreadProc count = 9.

    2012-12-18 08:50:44.247 Runloop[374:14b03] Exit newThreadProc.

    2012-12-1808:51:00.000 Runloop[374:11303] End runloop.//时间间隔了好久

    2012-12-18 08:51:00.001 Runloop[374:11303] OK

    从调试打印信息可以看到,while循环后执行的语句会在很长时间后才被执行。因为,改变变量StopFlag的值,runloop对象根本不知道,runloop在这个时候未被唤醒。有其他事件在某个时点唤醒了主线程,这才结束了while循环,但延缓的时长总是不定的。。

     

    将代码稍微修改一下:

    [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode

                                     beforeDate: [NSDate dateWithTimeIntervalSinceNow: 1]];

    缩短runloop的休眠时间,看起来解决了上面出现的问题。

    但这样会导致runloop被经常性的唤醒,违背了runloop的设计初衷。runloop的目的就死让你的线程在有工作的时候忙于工作,而没工作的时候处于休眠状态。

     

    最后,看下下面正确的写法:

    BOOL StopFlag =NO;

    - (void)viewDidLoad

    {

        [super viewDidLoad];

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

       

        StopFlag =NO;

        NSLog(@"Start a new thread.");

        [NSThread detachNewThreadSelector: @selector(newThreadProc)

                                 toTarget: self

                               withObject: nil];

        while (!StopFlag) {

            NSLog(@"Beginrunloop");

            [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode

                                     beforeDate: [NSDatedistantFuture]];

            NSLog(@"Endrunloop.");

        }

       

        NSLog(@"OK");

    }

     

    -(void)newThreadProc{   

        NSLog(@"Enter newThreadProc.");

       

        for (int i=0; i<10; i++) {

            NSLog(@"InnewThreadProc count = %d.", i);

            sleep(1);

        }

        [self performSelectorOnMainThread: @selector(setEnd)

                              withObject: nil

                            waitUntilDone: NO];

       

        NSLog(@"Exit newThreadProc.");

    }

    -(void)setEnd{

        StopFlag = YES;

    }

     

    调试打印信息如下:

    2012-12-18 09:05:17.161 Runloop[410:11303] Start a new thread.

    2012-12-18 09:05:17.163 Runloop[410:14a03] Enter newThreadProc.

    2012-12-18 09:05:17.164 Runloop[410:14a03] In newThreadProc count = 0.

    2012-12-18 09:05:17.165 Runloop[410:11303] Begin runloop

    2012-12-18 09:05:18.166 Runloop[410:14a03] In newThreadProc count = 1.

    2012-12-18 09:05:19.168 Runloop[410:14a03] In newThreadProc count = 2.

    2012-12-18 09:05:20.171 Runloop[410:14a03] In newThreadProc count = 3.

    2012-12-18 09:05:21.173 Runloop[410:14a03] In newThreadProc count = 4.

    2012-12-18 09:05:22.175 Runloop[410:14a03] In newThreadProc count = 5.

    2012-12-18 09:05:23.178 Runloop[410:14a03] In newThreadProc count = 6.

    2012-12-18 09:05:24.180 Runloop[410:14a03] In newThreadProc count = 7.

    2012-12-18 09:05:25.182 Runloop[410:14a03] In newThreadProc count = 8.

    2012-12-18 09:05:26.185 Runloop[410:14a03] In newThreadProc count = 9.

    2012-12-1809:05:27.188 Runloop[410:14a03] Exit newThreadProc.

    2012-12-1809:05:27.188 Runloop[410:11303] End runloop.//不再有延时

    2012-12-18 09:05:27.189 Runloop[410:11303] OK

    把直接设置变量,改为向主线程发送消息,唤醒runloop,延时问题解决。

  • 相关阅读:
    excel VBA构造正则函数(双参数)
    excel VBA构造函数就是这么简单
    excel VBA中正则模块vbscript.regexp的用法
    excel VBA构造正则函数(单参数)
    USB 设备插拔事件处理
    MySQL 修改 root 密码命令
    函数指针
    串口编程需要注意的地方
    写开机自启动程序应该注意的一点
    C++ 中 delete 和 delete[] 的区别
  • 原文地址:https://www.cnblogs.com/zxykit/p/5663740.html
Copyright © 2020-2023  润新知