倒计时开始4至1

Question

当我开始玩测验定时器开始“4 ... 3 ... 2 ... 1 ...”的倒计时。 我想在测验的第一个问题中添加此倒计时。倒计时后显示第一个问题。

任何一个可以帮我请

我想要做这个，但我did'nt得到格式倒计时。

NSTimer *timer_total = [NSTimer scheduledTimerWithTimeInterval:1.0/10.0 target:self selector:@selector(updateTimer) userInfo:nil repeats:YES]; 

- (void)updateTimer 
{ 
    NSDate *currentDate = [NSDate date]; 
    NSTimeInterval timeInterval = [currentDate timeIntervalSinceDate:startDate_total]; 
    NSDate *timerDate = [NSDate dateWithTimeIntervalSince1970:timeInterval]; 
    self.df_total = [[NSDateFormatter alloc] init]; 
    [self.df_total setDateFormat:@"mm:ss"]; 
    [self.df_total setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0.0]]; 
    NSString *timeString=[self.df_total stringFromDate:timerDate]; 
    self.lbl_total_Timer.text = timeString; 
} 

Answer 1

你可以像

int currentTime; 
- (IBAction)start{ 

    currentTime = 5; 
    lbl=[[UILabel alloc]init]; 
    //creates and fires timer every second 
    myTimer = [[NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(showTime) userInfo:nil repeats:YES]retain]; 
} 

-(void)showTime{ 


    if(currentTime==0) 
    { 
     [myTimer invalidate]; 
     myTimer = nil; 
    } 
    else{ 


    currentTime--; 
    lbl.text = [NSString stringWithFormat:@"%.2d", currentTime]; 
    } 
    NSLog(@"my lable == %@",lbl.text); 


} 

- (void)viewWillAppear:(BOOL)animated 
{ 
    [self start]; 
    [super viewWillAppear:YES]; 

}