在循环中使用NSTimer

问题描述

我需要显示一个从30到0的计时器，几次。 （30到0，从30开始，等等）然而，当我把它放在一个for循环，而不是等到定时器无效，开始下一个定时器，循环遍历和几个定时器创建。

如何构成一个等待计时器失效的循环？

- （IBAction）startCountdown：（id）sender {

 NSNumber * rounds = [[NSNumber alloc] initWithInt：sliderRounds.value]; 
 for（int i = rounds.intValue; i> 0; i--）{
 [self timer]; 
 
 $ / code $ / $ p 
 
解决方案
您可以使用scheduledTimerWithTimeInterval  
 
 
  [NSTimer scheduledTimerWithTimeInterval：0.5 
 target：self 
 selector：@selector（handleTimer :) 
 userInfo：nil 
 repeats：NO]; 
  
在handleTimer内部创建下一个定时器
I need to show a timer counting down from 30 to 0, several times. (30 to 0, start over at 30, etc) However when I placed it in a for-loop, instead of waiting till the timer invalidates to begin the next timer, the loop iterates through and several timers are created. 
How can I form a loop that waits until the timer has invalidated?
 - (IBAction)startCountdown:(id)sender {
    NSNumber *rounds = [[NSNumber alloc]initWithInt:sliderRounds.value];
    for (int i = rounds.intValue; i > 0; i--) {
        [self timer];
}
 解决方案 
You can use the scheduledTimerWithTimeInterval
[NSTimer scheduledTimerWithTimeInterval: 0.5
             target: self
             selector: @selector(handleTimer:)
             userInfo: nil
             repeats: NO];
And inside the handleTimer you create the next timer
                        
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