I have a NSTimeInterval which is basically
NSTimeInterval interval = [date1 timeIntervalSinceDate: [NSDate date]];
I want this computation to be always running in the background when I am in a view X, so I can display a timer counting down in a UILabel.. how do I do this? It's like in the groupon iphone app, but it doesn't show it in details of seconds
You could use an NSTimer to get a method called at a set time interval (however this is all performed on the main thread, not on a background thread):
- (void)setupTimer {
//Start a timer to call update updateInterval: every 1 second
self.timer = [NSTimer scheduledTimerWithTimeInterval:1.0
target:self
selector:#selector(updateInterval:)
userInfo:nil
repeats:YES];
}
- (void)updateInterval:(NSTimer *)timer {
NSTimeInterval interval = [date1 timeIntervaleSinceDate:[NSDate date]];
//Do other things like updating the label
}
Related
Im trying to add a timer to my game so that the user knows how long they have spent playing a level. Ive figured out that I can initialize a timer the following way:
bool showTimer = YES;
NSDate startDate;
UILabel timerLabel; // initialized in viewDidLoad
-(void) showElapsedTime: (NSTimer *) timer {
if (showTimer) {
NSTimeInterval timeSinceStart;
if(!startDate) {
startDate = [NSDate date];
}
timeSinceStart = [[NSDate date] timeIntervalSinceDate:startDate];
NSString *intervalString = [NSString stringWithFormat:#"%.0f",timeSinceStart];
timerLabel.text = intervalString;
if(stopTimer) {//base case
[timer invalidate];
}
}
}
- (void) startPolling {
[NSTimer scheduledTimerWithTimeInterval:0.1f target:self selector:#selector(showElapsedTime:) userInfo:nil repeats:YES];
}
I start the startPolling method in the viewDidLoad. When I run the app, I do see the timer and it tracks the time but when I exit the app and re-enter it, the timer doesnt pause. I'm also not sure how to handle going to another view (like the options menu) and then coming back to this view. I understand NSDefaults and NSCoding and I see how I could save the current value on the timer as a Coding object, keeping a seperate key-value pair in a plist for every level but this seems cumbersome.
Is there a better way to keep track of how long the user spends in a level?
Instead of doing the calculation (subtracting the start time from the current time) every time, since all you care about is an elapsed time, just have a variable like NSTimeInterval elapsedTime that you start at 0 and add time to every time that the timer fires. (If you want to track it to 0.1 seconds like in your example, just divide by 10 before displaying it.) This way, you can pause it whenever you want and it will just continue on from where it was before when it starts up again.
I am building a simple fitness/training app for iPhone. The user can pick a type of training session from a table which takes them to a view controller which contains a stopwatch. This view has labels populated from a mutable array.
I can get the stopwatch to work and the initial labels to populate from the array, but cannot work out how to get the labels to change at set time intervals. These intervals won't be regular so might be at 10mins, then 25, then 45 etc. I have been trying to do this via If statements where the timer == 25, for example. I'm sure this is a basic solution but I'm new to programming and can't work it out.
Timer code as follows:
- (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.S"];
[dateFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0.0]];
NSString *timeString=[dateFormatter stringFromDate:timerDate];
timerLabel.text = timeString;
}
Start timer:
- (IBAction)startTimerButton:(id)sender {
if (timer == nil) {
startDate = [NSDate date];
// Create the stop watch timer that fires every 0.1s
timer = [NSTimer scheduledTimerWithTimeInterval:1.0/10
target:self
selector:#selector(updateTimer)
userInfo:nil
repeats:YES];
}
else {
return;
}
}
I'm not too sure what you're after. If you set the time interval to be 10 minutes/25 minutes etc. instead of 1.0/10 then in your time fired code you will know what the time interval for the timer is.
You can always query the time interval using the timeInterval instance method. Perhaps as follows.
- (void)updateTimer:(NSTimer*)timer
{
if ([timer timeInterval] == 10 * 60) // 10 minutes have elapsed
{
// Do something for this timer.
}
else if ([timer timeInterval] == 20 * 60) // 20 minutes have elapsed
{
}
}
Notice that I've added the timer as an argument to your updateTimer function. You would then have to use the #selector(update:) (with the colon at the end!) selector in your scheduledTimerWithTimeInterval method. When your callback selector gets called, it will then have passed to it the timer.
Or if you have a pointer to the timer you created in your 'startTimerButton' you could use that as follows:
- (void)updateTimer:(NSTimer*)timer
{
if (timer == myTenMinuteTimer) // 10 minutes have elapsed
{
// Do something for this timer.
}
else if (timer == myTwentyMinuteTimer) // 20 minutes have elapsed
{
}
}
Notice that in the second cause you're comparing the pointer to two objects and using that, where as in the first your comparing the value of a method for two objects, so the objects don't have to necessarily be a pointer to the same object in order to be evaluated to be true.
Hope this helps!
First, here is some working code for a stopwatch in Xcode. I got two buttons, Startand Stop. Their titles change when the buttons are pressed. Now I want to add a pause functionality. I know that there are many threads about this, but (I don't know why) I was not able to get it working.
So what is the best approach to implement this function in my code?
I already tried to use a pause date and subtract it from my NSTimeIntervalbut got negative values ...
Thanks so far!
So I did this:
//use timer to update the ui only, store start date (NSDate) and time interval elapsed (NSTimeInterval)
//this is called when the timer is not running, nor paused - a sort of 'first run' function
-(void)onTimerStart
{
//zero the time elapsed
time_passed = 0;
//save the starting date
start_date = [NSDate date];
//start a timer that will update the ui in the onTimer function
timer = [NSTimer timerWithTimeInterval:1.0/10.0 target:self selector:#selector(onTimer) userInfo:nil repeats:YES];
}
//called when the timer is running to pause it
-(void)onPause
{
//calculate the time that passed ( += not = )
time_passed += [[NSDate date] timeIntervalSinceDate: start_date];
//stop the timer
[timer invalidate];
//you can get rid of the start date now (using ARC ........)
}
//restarting the timer that was paused
-(void)onUnpause
{
//get new start date
start_date = [NSDate date];
//start the timer to update ui again
timer = [NSTimer timerWithTimeInterval:1.0/10.0 target:self selector:#selector(onTimer) userInfo:nil repeats:YES];
}
//use this function if you are stopping - not pausing! - the timer.
-(void)onReset
{
//stop timer
[timer invalidate];
//calculate the final time that passed
//THE NEXT LINE IS PROBABLY WRONG AND HAS TO BE time_passed = 0; THEN IT WORKS
time_passed += [[NSDate date] timeIntervalSinceDate: start_date];
//get rid of the start date now
}
//use this function to update UI - this is what gets called by the timer
-(void)onTimer
{
//when timer ticks use ([[NSDate date] timeIntervalSinceDate: start_date] + time_passed)
//to get the amount of time passed for display
}
#pragma mark - View lifecycle
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
[self onTimerStart];
}
WORKING CODE:
#pragma mark - Timer
- (void)timer
{
NSDate *currentDate = [NSDate date];
NSTimeInterval timeInterval = [currentDate timeIntervalSinceDate:startDate];
NSDate *timerDate = [NSDate dateWithTimeIntervalSince1970:timeInterval];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"mm:ss.S"];
[dateFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0.0]];
NSString *timeString=[dateFormatter stringFromDate:timerDate];
timerLabel.text = timeString;
}
#pragma mark - Stopwatch
- (IBAction)onStartPressed:(UIButton *)sender
{
if ([sender.titleLabel.text isEqualToString:#"Start"] && (![timer isValid]) && ([timerLabel.text isEqualToString:#"00:00.0"]))
{
startDate = [NSDate date];
timer = [NSTimer scheduledTimerWithTimeInterval:1.0/10.0
target:self
selector:#selector(timer)
userInfo:nil
repeats:YES];
}
}
- (IBAction)onStopPressed:(UIButton *)sender
{
if ((![timer isValid]) && ([sender.titleLabel.text isEqualToString:#"Reset"]))
{
[timer invalidate];
timer = nil;
timerLabel.text = #"00:00.0";
[sender setTitle:#"Stop" forState:UIControlStateNormal];
}
if (([timer isValid]) && ([sender.titleLabel.text isEqualToString:#"Stop"]))
{
[timer invalidate];
timer = nil;
[sender setTitle:#"Reset" forState:UIControlStateNormal];
}
}
There is no pause/resume functionality built into NSTimer, so you have to implement something along the lines of:
//THIS IS PSEUDOCODE
//use timer to update the ui only, store start date (NSDate) and time interval elapsed (NSTimeInterval)
//this is called when the timer is not running, nor paused - a sort of 'first run' function
- onTimerStart:
{
//zero the time elapsed
time_passed = 0;
//save the starting date
start_date = [NSDate date];
//start a timer that will update the ui in the onTimer function
[timer start]
}
//called when the timer is running to pause it
- onPause
{
//calculate the time that passed ( += not = )
time_passed += [[NSDate date] timeIntervalSinceDate: start_date];
//stop the timer
[timer invalidate];
//you can get rid of the start date now
}
//restarting the timer that was paused
- onUnpause
{
//get new start date
start_date = [NSDate];
//start the timer to update ui again
[timer start];
}
//use this function if you are stopping - not pausing! - the timer.
- onReset
{
//stop timer
[timer invalidate];
//calculate the final time that passed
time_passed += [[NSDate date] timeIntervalSinceDate: start_date];
//get rid of the start date now
}
//use this function to update UI - this is what gets called by the timer
- onTimer
{
//when timer ticks use ([[NSDate date] timeIntervalSinceDate: start_date] + time_passed)
//to get the amount of time passed for display
}
I want to link the time on the iphone such as midnight to change the text of a UILabel to something else anyone help out?
Ive looked through the NSTimer and found nothing that works any help?
Try this:
NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:#selector(update:) userInfo:nil repeats:YES];
And...
- (void) update:(NSTimer *) timer {
myLabel.text = [NSDateFormatter localizedStringFromDate:[NSDate date] dateStyle: NSDateFormatterLongStyle timeStyle: NSDateFormatterLongStyle];
}
There are two other ways: use -[performSelector:withObject:aterDelay:] (and NSObject has a class method to cancel such, or better,
your appDelegate can implement:
-(void)applicationSignificantTimeChange:(UIApplication *)app;
which will get called at midnight, carrier time update, and daylight savings time change
I am using this code:
timer = [NSTimer scheduledTimerWithTimeInterval:2
target:self
selector:#selector(update)
userInfo:nil
repeats:YES];
...
-(void)update {
NSDate *date = [NSDate date];
NSString *Currentdate = [date descriptionWithCalendarFormat:#"%b %d, %Y %I:%M:%S %p"
timeZone:nil
locale:nil];
lbl.text = Currentdate;
}
It works fine but I want to change timer interval from 2 seconds to 1 second at run time. How can I do this?
Thanks in advance.
You can't change a timer interval after it's been created.
// You have to invalidate it...be careful,
// this releases it and will crash if done to an already invalidated timer
if (self.timer != nil) {
[self.timer invalidate];
self.timer = nil;
//... then declare a new one with the different interval.
timer = [NSTimer scheduledTimerWithTimeInterval:newInterval
target:self
selector:#selector(update)
userInfo:nil
repeats:YES];
}
Just invalidate the old timer and create new. I don’t think NSTimer supports changing the time interval, it would be an extra cruft both in the interface and the implementation.