iOS学习笔记12—Runloop 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]Exit buttonNormalThreadTestPressed 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 { [superviewDidLoad]; // Doany additional setup after loading the view, typically from a nib.
[NSThreaddetachNewThreadSelector: @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); }
// [NSTimerscheduledTimerWithTimeInterval: 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,CFRunLoopActivity activity,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 { [superviewDidLoad]; // Doany additional setup after loading the view, typically from a nib.
StopFlag =NO; NSLog(@"Start a new thread."); [NSThreaddetachNewThreadSelector: @selector(newThreadProc) toTarget:self withObject: nil]; while (!StopFlag) { NSLog(@"Beginrunloop"); [[NSRunLoopcurrentRunLoop] 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. 2012-12-18 08:51:00.000 Runloop[374:11303] End runloop. 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: [[NSRunLoopcurrentRunLoop] runMode:NSDefaultRunLoopMode beforeDate: [NSDatedateWithTimeIntervalSinceNow: 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 { [superviewDidLoad]; // Doany additional setup after loading the view, typically from a nib.
StopFlag =NO; NSLog(@"Start a new thread."); [NSThreaddetachNewThreadSelector: @selector(newThreadProc) toTarget: self withObject: nil]; while (!StopFlag) { NSLog(@"Beginrunloop"); [[NSRunLoopcurrentRunLoop] 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); } [selfperformSelectorOnMainThread: @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. 2012-12-18 09:05:27.188 Runloop[410:14a03] Exit newThreadProc. 2012-12-18 09:05:27.188 Runloop[410:11303] End runloop. 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。
|
|
来自: 最初九月雪 > 《NSRunLoop》