Question

我是一个快速学习者。我正在开发一个项目，我正在使用嵌套在dispatch_after函数内的NSTimer GCD命令。代码的其他部分执行多次迭代，其中一个是invalidate计时器。我成功地使计时器无效。但即使在使计时器无效之后，dispatch_ after块也会执行一次。该响应已经成为我项目中的一个错误。所以我想知道是否有任何方法或方法来阻止或终止dispatch_after方法处于等待状态，类似于Invalidate方法停止NSTimer。对不起，如果我很傻。

timer2=NSTimer.scheduledTimerWithTimeInterval(Double(t.a+t.b), target: self, selector: "updateSequential:", userInfo: nil, repeats: false)
//This is the call for NSTimer.
var f = 0
func updateSequential(timer2:NSTimer)
{
    var x = self.f                                           //Setting the Initial value for sequential order
    self.noDispLabel.text = String(x+1)
    print("\(x)")
    var content=self.imageArray[x]

    self.imageDisp.image=nil
    self.titleDispLabel.text=nil
    self.progressBar.setProgress(5.0, animated: true)

    var delay =  5.0 * Double(NSEC_PER_SEC)
    var time = dispatch_time(DISPATCH_TIME_NOW, Int64(delay))
    dispatch_after(time, dispatch_get_main_queue())
        {
            if(self.timer2 != nil)
            {
                self.imageDisp.image=UIImage(named:content.imageName)
                self.titleDispLabel.text=content.imageTitle
                self.progressBar.setProgress(0.0, animated: false)
            }
    }

    if( self.f < 4)                                     //Increment based on the condition
    {
        self.f++
    }
    else
    {
        self.f = 0
    }
    if(self.q==0)   // q is a global key variable referenced to invalidate the timer.
    {

        self.timer2=NSTimer.scheduledTimerWithTimeInterval(8.0, target: self, selector: "updateSequential:", userInfo: nil, repeats: false)

    }
    else
    {

        [timer2.invalidate]
        self.timer2 = nil
    }
}

此处dispatch_after块必须与NSTimer invalidate一起失效。

Answer 1

你可以这样做......

    dispatch_time_t time = dispatch_time(DISPATCH_TIME_NOW, 5 * NSEC_PER_SEC);
    XYZBlockResponse *response = [[XYZBlockResponse alloc] init];

    dispatch_after(time, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
        if (!response.cancelBlock)
            NSLog(@"XYXBlock executed");
        else
            NSLog(@"XYXBlock did not execute");
    });
    response.cancelBlock = YES; // Set YES or NO.

XYZBlockResponse类很简单......

@interface XYZBlockResponse : NSObject
@property (assign) BOOL cancelBlock;
@end

如何阻止GCD调度_after block返回结果。可能很傻

1 个答案: