How to reset a timer in Objective C?

Question

I create a counter in this app that it starts when I click a button and stops when I click at the same button.

The problem is that when I start again, the label that displays the count does not reset it keeps the counting from where it stopped.

So any one could help me??

- (void)timerTick:(NSTimer *)timer {

_lblCounter.text = @"0:00:00";

double seconds = 0.0;
double minutes = 0.0;
double hours = 0.0;

ticks += 1.0;
seconds = fmod(ticks, 60.0);
minutes = fmod(trunc(ticks / 60.0), 60.0);
hours = trunc(ticks / 3600.0);
_lblCounter.text = [NSString stringWithFormat:@"%2.0f:%02.0f:%02.0f", hours, minutes, seconds];
}


- (IBAction)btnProcessa:(UIButton *)sender {


if ([sender.titleLabel.text isEqualToString:@"Iniciar"]) {

    //Zera contador
    _lblCounter.text = @"0:00:00";

    //Define hora de início
    _startTime = [NSDate date];

    //Exibe hora inicial formatada no Label
    NSString *strHoraInicial = [[self formatter] stringFromDate:_startTime];
    _lblStartTime.text = strHoraInicial;

    //Contador
    timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(timerTick:) userInfo:nil repeats:YES];

    //Modifica botão
    [sender setTitle:@"Encerrar" forState:UIControlStateNormal];
    [sender setTitleColor:[UIColor redColor] forState:UIControlStateNormal];
    NSLog(@"Hora de início: %@", strHoraInicial);

 } else {
    //Para contador
    [timer invalidate];

    //Define a hora do encerramento
    NSDate *currentTime = [NSDate date];

    //Exibe hora final formatada no Label
    NSString *strHoraFinal = [[self formatter] stringFromDate:currentTime];
    _lblEndTime.text = strHoraFinal;

    //Calcula a diferença e exibe no Label
    NSTimeInterval elapsedTime = [currentTime timeIntervalSinceDate:_startTime];
    double cost = elapsedTime / 3600.0 * 5.0;
    NSString *valor = [[NSString alloc] initWithFormat:@"R$ %.2f",cost];
    NSLog(@"%@", valor);
    _lblValorPagar.text = valor;
    float fltQtdPessoa = [_txtQtdPessoa.text floatValue];
    float fltValor = cost / fltQtdPessoa;
    NSString *strValor = [[NSString alloc] initWithFormat:@"R$ %.2f", fltValor];
    _lblValorPessoa.text = strValor;

    //Modifica Botão
    [sender setTitle:@"Iniciar" forState:UIControlStateNormal];
    [sender setTitleColor:[UIColor colorWithRed:0.208 green:0.710 blue:0.271 alpha:1.000] forState:UIControlStateNormal];

}

}

Answer 1

Hey guys I managed to fix the problem by coding like this:

- (void)timerTick:(NSTimer *)timer {

NSDate *strStartTime = timer.userInfo;

NSTimeInterval interval = -[strStartTime timeIntervalSinceNow];
NSLog(@"%.0f", interval);
div_t h = div(interval, 3600);
float hours = h.quot;
div_t m = div(h.rem, 60);
float minutes = m.quot;
float seconds = m.rem;
_lblCounter.text = [[NSString alloc] initWithFormat:@"%2.0f:%02.0f:%02.0f", hours, minutes, seconds];
}



- (IBAction)btnProcessa:(UIButton *)sender {


if ([sender.titleLabel.text isEqualToString:@"Iniciar"]) {

    //Zera contador
    _lblCounter.text = @"0:00:00";

    //Define hora de início
    _startTime = [NSDate date];

    //Exibe hora inicial formatada no Label
    NSString *strHoraInicial = [[self formatter] stringFromDate:_startTime];
    _lblStartTime.text = strHoraInicial;

    //Contador
    contador = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(timerTick:) userInfo:[NSDate date] repeats:YES];

    //Modifica botão
    [sender setTitle:@"Encerrar" forState:UIControlStateNormal];
    [sender setTitleColor:[UIColor redColor] forState:UIControlStateNormal];
    NSLog(@"Hora de início: %@", strHoraInicial);

} else {
    //Para contador
    [contador invalidate];

    //Define a hora do encerramento
    NSDate *currentTime = [NSDate date];

    //Exibe hora final formatada no Label
    NSString *strHoraFinal = [[self formatter] stringFromDate:currentTime];
    _lblEndTime.text = strHoraFinal;

    //Calcula a diferença e exibe no Label
    NSTimeInterval elapsedTime = [currentTime timeIntervalSinceDate:_startTime];
    double cost = elapsedTime / 3600.0 * 5.0;
    NSString *valor = [[NSString alloc] initWithFormat:@"R$ %.2f",cost];
    NSLog(@"%@", valor);
    _lblValorPagar.text = valor;
    float fltQtdPessoa = [_txtQtdPessoa.text floatValue];
    float fltValor = cost / fltQtdPessoa;
    NSString *strValor = [[NSString alloc] initWithFormat:@"R$ %.2f", fltValor];
    _lblValorPessoa.text = strValor;

    //Modifica Botão
    [sender setTitle:@"Iniciar" forState:UIControlStateNormal];
    [sender setTitleColor:[UIColor colorWithRed:0.208 green:0.710 blue:0.271 alpha:1.000] forState:UIControlStateNormal];

}

}