问题
I have an NSTimer that I init with this code:
testTimer = [[NSTimer alloc] initWithFireDate:[new objectAtIndex:0] interval:0.0 target:self selector:@selector(works:) userInfo:nil repeats:NO];
[new objectAtIndex:0] is an NSDate in the past.
When I start up the app, the timer is getting created, with a fireDate of immediately (since the date is in the past), however it never calls my works method. (-(void)works:(id)sender
)
Anybody know why this is happening?
回答1:
You will have to add it to the current run loop if you use initWith.. method to create the timer object.
NSRunLoop * theRunLoop = [NSRunLoop currentRunLoop];
[theRunLoop addTimer:testTimer forMode:NSDefaultRunLoopMode];
Or if you would like it set up for you, use the scheduled... methods to create your timer.
回答2:
I just recently had an issue with NSTimer. In my case I didn't realize that the method scheduledTimerWithTimeInterval is not multi thread safe. Once I moved the timer to the main thread it started working.
回答3:
I think I had the same problem as Dobler, but my solution was different.
The problem was that the timer was being created and scheduled in a GCD thread in a block within a
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{})
call (actually nested deep, so it wasn't obvious that this was the case).
Using NSTimer's scheduledTimerWithTimeInterval:... placed the timer into an invalid run loop.
The fix was to change to
timer = [NSTimer timerWithTimeInterval:1.0f target:self selector:@selector(...) userInfo:nil repeats:YES];
[[NSRunLoop mainRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];
来源：https://stackoverflow.com/questions/6752234/nstimer-not-firing