在后台线程的NSTimer回调(NSTimer callback on background thr

我有一个NSTimer定义如下：

timer = [NSTimer scheduledTimerWithTimeInterval:30
                                         target:self
                                       selector:@selector(fooBar)
                                       userInfo:nil
                                        repeats:YES];
[[NSRunLoop mainRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];

我想它来调用回调函数fooBar在这种情况下使用后台线程。但是，当我检查if ([NSThread mainThread])我一直都想与它的主线程上。是否有任何其他方式除了从回调函数调度线程？

Answer 1:

您所添加的定时器主线程。您回电也将在主线程。要安排在后台线程定时器，我认为你需要使用的NSOperation子类，从操作的主要方法内安排计时器[NSRunLoop currentRunLoop。

#import <Foundation/Foundation.h>

@interface BackgroundTimer : NSOperation
{
    BOOL _done;
}
@end



#import "BackgroundTimer.h"

@implementation BackgroundTimer

-(void) main
{
    if ([self isCancelled])
    {
        return;
    }

    NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:30
                                             target:self
                                           selector:@selector(fooBar)
                                           userInfo:nil
                                            repeats:YES];

    [[NSRunLoop currentRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];

    //keep the runloop going as long as needed
    while (!_done && [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode
                                              beforeDate:[NSDate distantFuture]]);

}

@end

Answer 2:

如果你想在后台线程运行一个计时器，最有效的方式做到这一点是有一个调度器：

@property (nonatomic, strong) dispatch_source_t timer;

然后你可以配置该定时器每隔两秒钟火：

- (void)startTimer {
    dispatch_queue_t queue = dispatch_queue_create("com.domain.app.timer", 0);
    self.timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
    dispatch_source_set_timer(self.timer, dispatch_walltime(NULL, 0), 2.0 * NSEC_PER_SEC, 0.1 * NSEC_PER_SEC);
    dispatch_source_set_event_handler(self.timer, ^{
        // call whatever you want here
    });
    dispatch_resume(self.timer);
}

- (void)stopTimer {
    dispatch_cancel(self.timer);
    self.timer = nil;
}

文章来源: NSTimer callback on background thread