I wish to create a countdown timer in my app in such a way that I can give a certain duration (like 15 minutes or 15:00) and it starts on an action.
I also need for that countdown timer to take elapsed time duration and total time duration information from an external web service and start the countdown for the remaining time.
This is actually for a quiz application where the user will be presented with a series of questions and the timer will be placed on the question screen (for the whole quiz and not for only one question). The user can set the duration for the quiz and the countdown timer will begin as soon as the user start taking the quiz. There is also a pause functionality where user can pause the test and the information of time elapsed and total time duration will be registered in a web-service. The user can resume the quiz anytime with the countdown timer starting right from the time it was paused (taking this information from the web-service, that is).
Thanks in advance.
PS: To be honest, I had no idea on how to go about it. There was too much of confusion on what format will the time be stored over in the web-service and a lot of other stuff like if the program will go forward after the NSTimer is running in a loop etc. So you know what I mean. Yes, NSTimer does solve the problem as Alex told and provided with a sample code as well.
Look at the docs for NSTimer.
Generally, you would create an NSTimer which calls a method every second, like so:
NSTimer *theTimer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:#selector(tick) userInfo:nil repeats:YES];
Then in tick, you would decrement a variable holding the time remaining, and update a label on the display.
Also, if you want some working sample code, check out my little countdown app on GitHub.
Try these codes, I have already implemented it in my App. Best for resend OTP type functionalities.
int secondsLeft;
int hours, minutes, seconds;
secondsLeft = 60;
[self countdownTimer];
-(void)countdownTimer {
// secondsLeft = hours = minutes = seconds = 0;
timer = [NSTimer scheduledTimerWithTimeInterval:1.0f target:self selector:#selector(updateCounter:) userInfo:nil repeats:YES];
}
- (void)updateCounter:(NSTimer *)theTimer {
if(secondsLeft > 0 ) {
secondsLeft -- ;
hours = secondsLeft / 3600;
minutes = (secondsLeft % 3600) / 60;
seconds = (secondsLeft %3600) % 60;
labelSeconds.text = [NSString stringWithFormat:#"%02d seconds left.",seconds];
} else {
[timer invalidate];
return;
}
}
Related
I have CountDown timer like below:
- (void)updateCounterLabel:(NSTimer *)theTimer {
if(secondsLeft > 0 ){
secondsLeft -- ;
hours = secondsLeft / 3600;
minutes = (secondsLeft % 3600) / 60;
seconds = (secondsLeft %3600) % 60;
countDownLabel.text = [NSString stringWithFormat:#"%02d:%02d:%02d", hours, minutes, seconds];
}
else{
secondsLeft = timeInterval;
}
-(void)countdownTimer {
if([timer isValid]){
[timer invalidate];
timer = nil;
}
timer = [NSTimer scheduledTimerWithTimeInterval:1.0f target:self selector:#selector(updateCounterLabel:) userInfo:nil repeats:YES];
}
----My problem is that every time recall this timer it increments like this : secondLeft-3 , secondLeft -5 ,secondLeft - 7..................
Each time my view loads, i create a new timer, but the old ones still exist.in my timer's action method, i am decrementing an index variable that keeps track of the seconds, and each timer runs that method every time it fires. So, if i have three timers, the index will decrements by three each time.
For example:
First Load: 60, 59, 58...
Second Load: 60, 58, 56...
Third Load: 60, 57, 54...
Question : How can i restart or recreate a timer without above problem? somebody help me out pls.
The
timer = [NSTimer scheduledTimerWithTimeInterval:...];
call retains the target (the view controller) while the timer is running,
so that the view controller
is never deallocated and the timer continues to run even if the view controller
is popped off the navigation stack or dismissed.
Therefore, if the view is loaded again, you have two instances of the view controller and
therefore two timers, which both decrement the same global variable secondsLeft.
This hopefully explains why the value is decremented by two each second.
As a solution, you can create the timer in viewWillAppear, and invalidate it
in viewWillDisappear.
I have a timer that have to count up to 8 hours (28800 second)
after that it should be released
im wondering how to keep the timer running at the background and/or when application is closed?
this is the NSTimer :
stopWatchTimer = [NSTimer scheduledTimerWithTimeInterval:1.0
target:self
selector:#selector(updateTimer)
userInfo:nil
repeats:YES];
and this is my condition :
counter++;
if (counter >= 28800) {
[stopWatchTimer invalidate];
counter =0;
timeLabel.text = #"Time Out";
}
You can't - once your app is closed then it's not running anymore so the timer won't be running either.
Take a look at local notifications?
When application goes in background, In –(void)applicationDidEnterBackground: application delegate method add current counter value and current time in nsuserdefault.
Now when application becomes active before that –(void)applicationWillEnterForeground: will called so in that method get total seconds application was in background ie (current time of application) - (time when application went background which is stored in nsuserdefault) calculate in seconds
so add this also in –(void)applicationWillEnterForeground :
if((seconds calculated) > (28800 - (current counter value stored in nsuserdefault)))
{
// stop timer as it has gone beyond eight hours
}
else
{
// continue task
}
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'm trying to implement a button that starts a timer after a random period of time (between 0-10s). While the timer is running it should update a label every 0.005s to show how much time has elapsed. The problem i'm having is 2-fold:
I'm not sure how to get the label to update with the elapsed time every 0.005s.
I'm having trouble getting the app to wait the random amount of time before starting timer. At present I'm using sleep(x) however it seems to cause the app to ignore all the other code in the if statement and causes the button image to freeze up (i.e. it looks like its still clicked).
Here is the code I have so far...
- (IBAction)buttonPressed:(id)sender
{
if ([buttonLabel.text isEqualToString:#"START"])
{
buttonLabel.text = #" "; // Clear the label
int startTime = arc4random() % 10; // Find the random period of time to wait
sleep(startTime); // Wait that period of time
startTime = CACurrentMediaTime(); // Set the start time
buttonLabel.text = #"STOP"; // Update the label
}
else
{
buttonLabel.text = #" ";
double stopTime = CACurrentMediaTime(); // Get the stop time
double timeTaken = stopTime - startTime; // Work out the period of time elapsed
}
}
If anyone has any suggestions on..
A) How to get the label to update with the elapsed time.
or
B) How to fix the 'delay' period from freezing up the app
... it would be really helpful as I'm pretty much stumped at this point. Thanks in advance.
You should use an NSTimer to do this. Try the code:
- (void)text1; {
buttonLabel.text = #" ";
}
- (void)text2; {
buttonLabel.text = #"STOP";
}
- (IBAction)buttonPressed:(id)sender; {
if ([buttonLabel.text isEqualToString:#"START"]) {
int startTime = arc4random() % 10; // Find the random period of time to wait
[NSTimer scheduledTimerWithTimeInterval:(float)startTime target:self selector:#selector(text2:) userInfo:nil repeats:NO];
}
else{
// I put 1.0f by default, but you could use something more complicated if you want.
[NSTimer scheduledTimerWithTimeInterval:1.0f target:self selector:#selector(text1:) userInfo:nil repeats:NO];
}
}
I'm not exactly sure how you want to update label based on the time, but if you post more code, or give an example, I'll post the code on how to do that, but it would just be using an NSTimer as well. Hope that Helps!
The answer to A could be:
Once the random amount of time has passed, (#MSgambel has a good suggestion), then execute:
timer = [NSTimer scheduledTimerWithTimeInterval:kGranularity target:self selector:#selector(periodicallyUpdateLabel) userInfo:nil repeats:YES];
(The above line could go into #MSgambel's -text2 method.)
That will call the -periodicallyUpdateLabel method once every kGranularity seconds, repeatedly. In that method, you could do things like update your label, check for user actions, or end the game if the time is up or some other condition has been met.
And here is the -periodicallyUpdateLabel method:
- (void)periodicallyUpdateView {
counter++;
timeValueLabel.text = [NSString stringWithFormat:#"%02d", counter];
}
You'll have to format the text differently to get what you want. Also, translate from the counter value to time using kGranularity. However, and this is what I found, there is only so many cpu cycles in iOS devices. Trying to go down to microsecond level made the interface sluggish and the time displayed started to drift from the actual time. In other words, you may have to limit your updates of the label to once every one hundredth of a second or tenths. Experiment.
HI , i have made simple application with 5 view controllers with some functionality .. what i want to do now is add a time at the main screen . and it should b running till i quit from application .. i will move to other view controllers also but that timer would b running .. how i will have this functionality ??
Check out the "Timers" section here: http://www.iphoneexamples.com/
Also, refer to Apple's NSTimer Documentation
The most practical way to do this is to fake it - that is, just store the start timestamp, and don't bother to continuously maintain any kind of timePassed variable. This is both easier to code, and actually more reliable since it's stable.
Store an NSDate for the instant the timer was started, and whenever you want to display or update the timer, use NSDate's timeIntervalSinceNow method, which returns the number of seconds passed as an NSTimeInterval, which is basically a typedef for a double. Note: this function returns a negative number when called on a timestamp in the past, which will be the case here.
If part of your display is showing this time, you can update it every second (or even more often) with an NSTimer object that periodically called one of your methods which updates the display.
Sample code:
// In the initialization code:
self.timer = [NSTimer scheduledTimerWithTimeInterval:0.1 target:self
selector:#selector(secondPassed:) userInfo:nil repeats:YES];
// Later:
// (This code assumes #minutes < 60.)
- (void) secondPassed: (NSTimer:) timer {
NSTimeInterval secondsPassed = -1 * [self.timerStart timeIntervalSinceNow];
int minutes = (int)(secondsPassed / 60);
int seconds = (int)(seconds - minutes * 60);
NSString* timerString = [NSString stringWithFormat:#"%02d:%02d",
minutes, seconds];
[self updateTimerDisplay:timerString];
}