How do I pause a stopwatch, then have it pick back up from where it started? - objective-c

Question

I am designing a timer that I want to be able to pause and continue from the same place. I tried doing it but the code wouldn't work for me. Here is my code:
.m file:
-(IBAction)buttonPause:(id)sender {
NSString *dateString = timer.text;
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"HH:mm:ss.SS"];
NSDate *dateFromString = [[NSDate alloc] init];
dateFromString = [dateFormatter dateFromString:dateString];
dateFromString = startDate;
}
- (IBAction)buttonStart:(id)sender {
startDate = [NSDate date];
stopWatchTimer = [NSTimer scheduledTimerWithTimeInterval:1.0/100.0
target:self
selector:#selector(updateTimer)
userInfo:nil
repeats:YES];
}
- (void)updateTimer{
NSDate *currentDate = [NSDate date];
NSTimeInterval timeInterval = [currentDate timeIntervalSinceDate:startDate];
NSDate *timerDate = [NSDate dateWithTimeIntervalSince1970:timeInterval];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"HH:mm:ss.SS"];
[dateFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0.0]];
NSString *timeString = [dateFormatter stringFromDate:timerDate];
timer.text = timeString;
}
My problem appears to lie in the buttonPause method. What am I doing wrong or am not doing? Thank you in advanced.

Answer 1

You can use NSTimeInterval instead of timer. I have a functional code to pause and stop the timer.
#interface PerformBenchmarksViewController () {
int currMinute;
int currSecond;
int currHour;
int mins;
NSDate *startDate;
NSTimeInterval secondsAlreadyRun;
}
#end
- (void)viewDidLoad
{
[super viewDidLoad];
running = false;
}
- (IBAction)StartTimer:(id)sender {
if(running == false) {
//start timer
running = true;
startDate = [[NSDate alloc] init];
startTime = [NSDate timeIntervalSinceReferenceDate];
[sender setTitle:#"Pause" forState:UIControlStateNormal];
[self updateTime];
}
else {
//pause timer
secondsAlreadyRun += [[NSDate date] timeIntervalSinceDate:startDate];
startDate = [[NSDate alloc] init];
[sender setTitle:#"Start" forState:UIControlStateNormal];
running = false;
}
}
- (void)updateTime {
if(running == false) return;
//calculate elapsed time
NSTimeInterval currentTime = [NSDate timeIntervalSinceReferenceDate];
NSTimeInterval elapsed = secondsAlreadyRun + currentTime - startTime;
// extract out the minutes, seconds, and hours of seconds from elapsed time:
int hours = (int)(mins / 60.0);
elapsed -= hours * 60;
mins = (int)(elapsed / 60.0);
elapsed -= mins * 60;
int secs = (int) (elapsed);
//update our lable using the format of 00:00:00
timerLabel.text = [NSString stringWithFormat:#"%02u:%02u:%02u", hours, mins, secs];
//call uptadeTime again after 1 second
[self performSelector:#selector(updateTime) withObject:self afterDelay:1];
}
Hope this will help. Thanks