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.
Related
I'm working on a very simple iPhone game that involves choosing the right colored button as many times in a row based on a randomized voice prompt. I have it set up so that if the button is one color and gets clicked, it always goes to a hard-coded color every time (e.g. if you click red, it always turns blue). The color change method is set up in an IBOutlet. I have a timer set up in a while loop, and when the timer ends it checks if the player made the right selection. The problem is that the button color change does not occur until after the timer runs out, and this causes a problem with the method used to check the correct answer. Is there a way to make this color change happen instantly? From what I've searched I know it has something to do with storyboard actions not occurring until after code executes, but I haven't found anything with using a timer. Here is a section of the method that calls the timer if the answer is correct:
BOOL rightChoice = true;
int colorNum;
NSDate *startTime;
NSTimeInterval elapsed;
colorNum = [self randomizeNum:middle];
[self setTextLabel:colorNum];
while (rightChoice){
elapsed = 0.0;
startTime = [NSDate date];
while (elapsed < 2.0){
elapsed = [startTime timeIntervalSinceNow] * -1.0;
NSLog(#"elapsed time%f", elapsed);
}
rightChoice = [self correctChoice:middleStatus :colorNum];
colorNum = [self randomizeNum:middle];
}
One of two things stood out
You're using a while loop as a timer, don't do this - the operation is synchronous.
If this is run on the main thread, and you code doesn't return, your UI will update. The mantra goes: 'when you're not returning you're blocking.'
Cocoa has NSTimer which runs asynchronously - it is ideal here.
So let's get to grips with NSTimer (alternatively you can use GCD and save a queue to an ivar, but NSTimer seems the right way to go).
Make an ivar called timer_:
// Top of the .m file or in the .h
#interface ViewController () {
NSTimer *timer_;
}
#end
Make some start and stop functions. How you call these is up to you.
- (void)startTimer {
// If there's an existing timer, let's cancel it
if (timer_)
[timer_ invalidate];
// Start the timer
timer_ = [NSTimer scheduledTimerWithTimeInterval:5.0
target:self
selector:#selector(onTimerFinish:)
userInfo:nil
repeats:NO];
}
- (void)onTimerFinish:(id)sender {
NSLog(#"Timer finished!");
// Clean up the timer
[timer_ invalidate];
timer_ = nil;
}
- (void)stopTimer {
if (!timer_)
return;
// Clean up the timer
[timer_ invalidate];
timer_ = nil;
}
And now
Put your timer test code in the onTimerFinish function.
Make an ivar that stores the current choice. Update this ivar when a choice is made and make the relevant changes to the UI. Call stopTimer if the stop condition is met.
In the onTimerFinished you can conditionally call and startTimer again if you desire.
Hope this helps!
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.
I am using MBProgressHUD to display a progress indicator. The delegate that is called when the indicator is shown is:
- (void)myTask {
while (self.show_progress == NO){
}
}
basically when it goes out of the loop it dismisses the indicator. Now the issue is that I would like do something more in this method. I would like to check for how long has the indicator been spinning for, if it has been more than 5 seconds then I would like to re-load the request. The question is how do I check for this?
This is just to prevent the apps waiting for an infinite amount of time just in case the response never got back or got stuck somewhere.
I'm not familiar with MBProgressHUD , but on general terms you could do the following:
When you first make the request do:
NSDate *startTime = [NSDate date];
Then whenever you want to check how long has it been:
NSTimeInterval timePassed = -[startTime timeIntervalSinceNow];
timePassed will have the value, in seconds, of how long has it been since you made your request. May be you should consider using NSTimer for this: Schedule a timer that will fire 5 seconds after you performed your request, if it triggers cancel the request but if you receive a response before the timer triggers invalidate the timer.
If I understand correctly, your code just waits until the property show_progress becomes NO. I don't know why your code does this, it seems a little inelegant. If you want to keep it this way, at least use a condition lock to prevent the 100% CPU usage:
Prepare the condition lock like this:
NSConditionLock *progressLock = [[NSConditionLock alloc] initWithCondition:0];
In your second thread, once your loading stuff or whatever finishes, change the condition like this:
[progressLock lock];
[progressLock unlockWithCondition:1];
And in your method, do this:
- (void)myTask {
NSDate *timeoutDate = [NSDate dateWithTimeIntervalSinceNow:5];
if ([progressLock lockWhenCondition: 1 beforeDate:timeoutDate) {
// we aquired the lock, processing has finished
[progressLock unlock];
} else {
// we didn't aquire the lock because the 5 seconds have passed
// reload the request or do whatever you want to do
}
}
This method waits 5 seconds, and then times out. It uses no CPU in those 5 seconds, because it waits for a signal at the lockWhenCondition:beforeDate: call.
The way I've gone about similar situations is to set up a timer. The basic concept would be to start the timer when the indicator starts spinning. Then invalidate it when the indicator stops. Else if it goes on for 5 seconds, execute your method.
So in your header, you'll want
NSTimer *myTimer;
then in the implementation, when you start the indicator spinning,
[indicator startAnimating];
if (myTimer != nil) {
[myTimer invalidate];
myTimer = nil;
}
myTimer = [NSTimer scheduledTimerWithTimeInterval:5.0 target:self selector:#selector(reloadRequest) serInfo:nil repeats:NO];
when you stop the indicator from spinning, send [myTimer invalidate]; and myTimer = nil;. If the specified time is reached beforehand, reload the request in your reloadRequest method
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
}
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];
}