iphone －线程 使用run loop对象 2
如果你在非main thread中运行run loop，你必须至少为该run loop添加一个input sources或timer。如果你运行的run loop没有监控任何的输入源，该run loop将在你运行后立即退出。
Run loop observer
使用detachNewThreadSelector:toTarget:withObject:创建一个thread：
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[NSThread detachNewThreadSelector:@selector(observerRunLoop) toTarget:self withObject:nil];
在新thread的run loop中添加observer：
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- (void)observerRunLoop { //建立自动释放池 NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; //获得当前thread的Run loop 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run loop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Core Foundation的CFRunLoopRef类型 CFRunLoopRef cfRunLoop = [myRunLoop getCFRunLoop]; //将新建的observer加入到当前thread的run loop CFRunLoopAddObserver(cfRunLoop, observer, kCFRunLoopDefaultMode); } //Creates and returns a new NSTimer object and schedules it on the current run loop in the default mode [NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(doFireTimer:) userInfo:nil repeats:YES]; NSInteger loopCount = 10; do { //启动当前thread的loop直到所指定的时间到达，在loop运行时，run loop会处理所有来自与该run loop联系的input source的数据 //对于本例与当前run loop联系的input source只有一个Timer类型的source。 //该Timer每隔0.1秒发送触发事件给run loop，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run loop行为都感兴趣。 //当调用runUnitDate方法时，observer检测到run loop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run loop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:1.0]]; //当run loop的运行时间到达时，会退出当前的run loop。observer同样会检测到run loop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); //释放自动释放池 [pool release]; } 设置observer的回调函数：view plain void myRunLoopObserver(CFRunLoopObserverRef observer, CFRunLoopActivity activity, void *info) { switch (activity) { //The entrance of the run loop, before entering the event processing loop. //This activity occurs once for each call to CFRunLoopRun and CFRunLoopRunInMode case kCFRunLoopEntry: NSLog(@"run loop entry"); break; //Inside the event processing loop before any timers are processed case kCFRunLoopBeforeTimers: NSLog(@"run loop before timers"); break; //Inside the event processing loop before any sources are processed case kCFRunLoopBeforeSources: NSLog(@"run loop before sources"); break; //Inside the event processing loop before the run loop sleeps, waiting for a source or timer to fire. //This activity does not occur if CFRunLoopRunInMode is called with a timeout of 0 seconds. //It also does not occur in a particular iteration of the event processing loop if a version 0 source fires case kCFRunLoopBeforeWaiting: NSLog(@"run loop before waiting"); break; //Inside the event processing loop after the run loop wakes up, but before processing the event that woke it up. //This activity occurs only if the run loop did in fact go to sleep during the current loop case kCFRunLoopAfterWaiting: NSLog(@"run loop after waiting"); break; //The exit of the run loop, after exiting the event processing loop. //This activity occurs once for each call to CFRunLoopRun and CFRunLoopRunInMode case kCFRunLoopExit: NSLog(@"run loop exit"); break; /* A combination of all the preceding stages case kCFRunLoopAllActivities: break; */ default: break; } }