ios - dispatch_after 循环/重复

Question

我正在尝试创建一个这样的循环:

while (TRUE){
  dispatch_after(...{
    <some action>
  });
}

在 viewDidLoad 之后。这个想法是反复重复 dispatch_after 。 dispatch_after 在执行操作之前等待两秒钟。

这不起作用 - 屏幕只是空白？它是卡在循环中还是...？

Answer 1

是的，您可以使用 gcd 做到这一点。不过，您还需要两个额外的 C 函数。

static void dispatch_async_repeated_internal(dispatch_time_t firstPopTime, double intervalInSeconds, dispatch_queue_t queue, void(^work)(BOOL *stop)) {    
    __block BOOL shouldStop = NO;
    dispatch_time_t nextPopTime = dispatch_time(firstPopTime, (int64_t)(intervalInSeconds * NSEC_PER_SEC));
    dispatch_after(nextPopTime, queue, ^{
        work(&shouldStop);
        if(!shouldStop) {
            dispatch_async_repeated_internal(nextPopTime, intervalInSeconds, queue, work);
        }
    });
}

void dispatch_async_repeated(double intervalInSeconds, dispatch_queue_t queue, void(^work)(BOOL *stop)) {
    dispatch_time_t firstPopTime = dispatch_time(DISPATCH_TIME_NOW, intervalInSeconds * NSEC_PER_SEC);
    dispatch_async_repeated_internal(firstPopTime, intervalInSeconds, queue, work);
}

已测试!按预期工作。

https://gist.github.com/4676773