秒表-从UIDatePicker设置开始日期

Question

I have a simple stopwatch that will give elapsed time since the start button was pressed in seconds. What I need is for the start time to be set from a date picker.

How can I get the "NSTimeInterval time;" to equal that of my datepicker? or do I need to do something else in order to set the user's time?

@implementation ViewController {

bool start;

// Gets time when the button is pressed.
NSTimeInterval time;

}

• (void)viewDidLoad { [super viewDidLoad];

  self.display.text = @"0:00";

  start = false;

}

-(void)update {

if (start == false) {

    return;

}

NSTimeInterval currentTime = [NSDate timeIntervalSinceReferenceDate];
NSTimeInterval elapsedTime = currentTime - time;

//  minutes.
int minutes = (int)(elapsedTime / 60.0);

// seconds.
int seconds = (int)(elapsedTime = elapsedTime - (minutes * 60));


self.display.text = [NSString stringWithFormat:@"%u:%02u", minutes, seconds];

[self performSelector:@selector(update) withObject:self afterDelay:0.1];

}

Answer 1

You can use:

NSTimeInterval timePicker = [[self.datePicker date] timeIntervalSinceReferenceDate];
NSTimeInterval currentTime = [[NSDate date] timeIntervalSinceReferenceDate];
NSTimeInterval elapsedTime = currentTime - timePicker;
//  minutes.
   int minutes = (int)(elapsedTime / 60.0);

// seconds.
   int seconds = (int)(elapsedTime = elapsedTime - (minutes * 60));

Answer 2

Just save the start NSDate. Later get the current NSDate. Later get the current NSDate and use timeIntervalSinceDate: or timeIntervalSinceNow` to get the elapsed time.

Save the start time:

NSTimeInterval startTime = [NSDate date];

Later:

NSTimeInterval elapsedTime = -[[NSDate date] timeIntervalSinceNow];