我的NSTimer的选择器无法运行.为什么? [英] The selector of my NSTimer does not run. Why?

问题描述

我的代码是:

-(void) timerRun{...}

-(void) createTimer
{
   NSTimer *timer;
   timer = [NSTimer timerWithTimeInterval:1.0 
                                   target:self 
                                 selector:@selector(timerRun) 
                                 userInfo:nil 
                                  repeats:YES];
}

viewDidLoad
{
   [NSThread detachNewThreadSelector:@selector(createTimmer) 
                            toTarget:self withObject:nil];
   ...

}

当我调试时，方法createTimer运行正常，但是方法timerRun没有运行?

When I debug, the method createTimer runs ok, but the method does timerRun not run?

推荐答案

仅创建计时器并不会启动计时器.您需要创建它并计划它.

Just creating a timer doesn't start it running. You need to both create it and schedule it.

如果要在后台线程上运行，实际上您要做的工作要比实际要做的多. NSTimer附加到NSRunloop，这是事件循环的可可形式.每个NSThread本质上都有一个运行循环，但是您必须告诉它明确运行.

You're actually going to have to do slightly more work than that if you want it to run on a background thread. NSTimers attach to NSRunloops, which are the Cocoa form of an event loop. Each NSThread inherently has a a run loop but you have to tell it to run explicitly.

带有计时器的运行循环可以无限期地运行，但是您可能不希望这样做，因为它将不会为您管理自动释放池.

A run loop with a timer attached can run itself indefinitely but you probably don't want it to because it won't be managing autorelease pools for you.

因此，总而言之，您可能想要(i)创建计时器； (ii)将其附加到该线程的运行循环中； (iii)进入一个创建自动释放池的循环，运行一下运行循环，然后耗尽自动释放池.

So, in summary, you probably want to (i) create the timer; (ii) attach it to that thread's run loop; (iii) enter a loop that creates an autorelease pool, runs the run loop for a bit and then drains the autorelease pool.

代码可能类似于:

// create timer
timer = [NSTimer timerWithTimeInterval:1.0 
                                target:self 
                              selector:@selector(timerRun) 
                              userInfo:nil 
                               repeats:YES];

// attach the timer to this thread's run loop
[[NSRunLoop currentRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];

// pump the run loop until someone tells us to stop
while(!someQuitCondition)
{
    // create a autorelease pool
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

    // allow the run loop to run for, arbitrarily, 2 seconds
    [[NSRunLoop currentRunLoop] runUntilDate:[NSDate dateWithTimeIntervalSinceNow:2.0]];

    // drain the pool
    [pool drain];
}

// clean up after the timer
[timer invalidate];

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