I want to maintain timer with multiple UIViewControllers.
Like, I am creating one timer in ViewController1 for 60 second interval.
after 20 second, application navigates to ViewController2.(so 40 second is remaining to execute timer).
After 20 second stay i come back to ViewController1, at this time timer should execute after 40 second of come back and then after it will execute after 60 second.
So how can I do this?
Thanks in advance.
If you want to use one item across several instances, try it with the singleton design pattern. But like it seems, you never navigate back from your VC1, so all obejects are still there.
On the base of How to Pause/Play NSTimer? you can change some parts to make it fitting your case.
- (void)stopTimer
{
if( timer )
{
[timer invalidate];
[timer release]; // if not ARC
timer = nil;
}
}
- (void)startTimer
{
[self stopTimer];
int interval = 1.;
timer = [[NSTimer scheduledTimerWithTimeInterval:interval
target:self
selector:#selector(countUp)
userInfo:nil repeats:YES] retain]; // retain if not ARC
}
-(void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
[self timerStart];
}
-(void)viewWillDisappear:(BOOL)animated
{
[self stopTimer];
[super viewWillDisappear:animated];
}
-(void)countUp
{
if(timePassed++ >= 60) // defined in header
{
timePassed=0;
[self myCustomEvent];
}
}
Although it may be a solution with better practices, you can set the NSTimer inside your AppDelegate and make the AppDelegate manage segues to push or pop your UIViewControllers
Related
A strange situation:
If I started my Timer again and again without stopping it first, it will count increasingly fast. I guess it is because it starts multiple timers now?
However, when I finally want to stop it, it cannot be stopped...keep going forever.
(Maybe for design consideration, I should disable users from pressing start again, but I'm wondering what is really behind this and why the timer can't be stopped.)
- (IBAction)Start:(id)sender {
countInt = 0;
self.Time.text = [NSString stringWithFormat:#"%i", countInt];
timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:#selector(countTimer) userInfo:nil repeats:YES];
}
- (IBAction)Stop:(id)sender {
[timer invalidate];
}
- (void) countTimer {
countInt += 1;
self.Time.text = [NSString stringWithFormat:#"%i", countInt];
}
#end
The simple solution is to call stop at the beginning of the start method.
Note that in stop you should also set timer = nil;
Assuming there is a property timer
#property NSTimer *timer;
the most reliable way to start and stop the timer only once respectively is to create two methods.
- (void)startTimer
{
if (self.timer == nil) {
self.timer = [NSTimer scheduledTimerWithTimeInterval:1.0
target:self
selector:#selector(countTimer)
userInfo:nil
repeats:YES];
}
}
- (void)stopTimer
{
if (self.timer != nil) {
[self.timer invalidate];
self.timer = nil;
}
}
Both methods perform a check, so the timer can't be restarted while it's running and vice versa.
Now just call the methods in the start/stop IBActions (the names should start with a lowercase letter).
- (IBAction)Start:(id)sender {
countInt = 0;
self.Time.text = [NSString stringWithFormat:#"%i", countInt];
[self startTimer];
}
- (IBAction)Stop:(id)sender {
[self stopTimer];
}
The benefit is pressing Start has no effect when the timer is already running.
When you hit 'start' multiple times you are creating multiple timers. So you are getting multiple timers firing and executing your timer callback. In this timer callback you increment counters. Since there are many timers now, they are all incrementing your counter, hence explaining your rapid increase in the counter.
You can allow the user to tap Start twice, as long you can define what happens when you hit Start while the timer is already going. But you definitely need to invalidate the old timer before creating a new one.
- (IBAction)Start:(id)sender {
...
// Stop previous timer before creating a new timer.
if (timer != nil) {
[timer invalidate]
}
...
}
My timer does not stop even if i am doing "invalidate" and "nil" after reading other links. My code is as below:
#property(nonatomic,strong) NSTimer *mytimer;
- (void)viewDidLoad {
[self performSelectorOnMainThread:#selector(updateProgressBar:) withObject:nil waitUntilDone:NO];
<do some other work>
}
- (void) updateProgressBar :(NSTimer *)timer{
static int count =0;
count++;
NSLog(#"count = %d",count);
if(count<=10)
{
self.DownloadProgressBar.progress= (float)count/10.0f;
}
else{
NSLog(#"invalidating timer");
[self.mytimer invalidate];
self.mytimer = nil;
return;
}
if(count <= 10){
NSLog(#"count = %d **",count);
self.mytimer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:#selector(updateProgressBar:) userInfo:nil repeats:YES];
}
}
1) The timer goes on infinetly even when invalidating timer else condition is hit after count >10 and count keeps on incrementing.
2) i want to do this on a non-main thread . i want to continue in viewdidload() after starting the timer. How to do this ?
I visited other links on SO, all i understood was to call invalidate and nil on timer pointer. I am still facing problems. Could anyone tell me what i am missing here and what i can i do to run the updateProgressBar on background thread and update the progress bar ?
don't need to schedule a timer each time, schedule it once and timer will fire every second for example u can do like below,
- (void)viewDidLoad
{
[super viewDidLoad];
[self performSelectorOnMainThread:#selector(startTimerUpdate) withObject:nil waitUntilDone:NO]; //to start timer on main thread
}
//hear schedule the timer
- (void)startTimerUpdate
{
self.mytimer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:#selector(updateProgressBar:) userInfo:nil repeats:YES];
}
- (void) updateProgressBar :(NSTimer *)timer{
static int count =0;
count++;
NSLog(#"count = %d",count);
if(count<=10)
{
//self.DownloadProgressBar.progress= (float)count/10.0f;
NSLog(#"progress:%f",(float)count/10.0f);
}
else
{
NSLog(#"invalidating timer");
[self.mytimer invalidate];
self.mytimer = nil;
return;
}
if(count <= 10){
NSLog(#"count = %d **",count);
}
}
I think you are scheduling timer multiple time. I think 10 time. just schedule time one time or if require many time then invalidate it that many time as schedule.
Update according to comment : Schedule timer from viewdidload and addobserver means notification on task. when your task will completed invalidate timer. and update your progress in selector method of timer so when you invalidate it it will automatically stop progress bar.
Second thing : you should invalidate timer before moving another viewcontroller also because this objects remains live untill invalidate.
Hope this will hellp :)
So I've got a timer that is not repetitive. Each time it fires, the method that being executed decide if to reschedule it or not according to some inner logic of my app.
This method is available from other parts of the app, so the first thing that I'm doing in the method is to check if the timer is still valid (to know if the initiator was the timer or a different entity) so in case it wasn't initiated by the timer I want to invalidate it:
if (self.pollingTimer.isValid) {
[self.pollingTimer invalidate];
self.pollingTimer = nil;
}
I've noticed that if the method is being called due to the timer being fired - I always receive a true value from the isValid property, even though when looking at the NSTimer documentations under the scheduledTimerWithTimeInterval:(NSTimeInterval)seconds target:(id)target selector:(SEL)aSelector userInfo:(id)userInfo repeats:(BOOL)repeats method:
repeats
If YES, the timer will repeatedly reschedule itself until invalidated. If NO, the timer will be invalidated after it fires.
Discussion
After seconds seconds have elapsed, the timer fires,
sending the message aSelector to target.
I'm having hard time to understand when the timer is being automatically invalidated which bring me to my questions:
Any idea why I always get YES from isValid?
What is the exact definition of the timer fires? Is it just sending the message aSelector to target as stated in the documentation? or is it finishing the execution of the method? (which might explain what I'm experiencing)
Thanks in advance.
A timer is not a real-time mechanism; it fires only when one of the run loop modes to which the timer has been added is running and able to check if the timer’s firing time has passed. Therefore, the timer does not immediately invalidate itself, but at the end of the run loop.
As a simple test, you can see:
- (void)viewDidLoad {
[super viewDidLoad];
_timer = [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:#selector(timerFired) userInfo:nil repeats:NO];
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
if (self.timer.isValid){
NSLog(#"--> TIMER VALID");
} else {
NSLog(#"TIMER INVALID!");
}
});
}
- (void) timerFired {
if (self.timer.isValid){
NSLog(#"--> TIMER VALID");
} else {
NSLog(#"TIMER INVALID!");
}
}
This will log --> TIMER VALID from the timerFired method and when the block from dispatch_after is called, you will see TIMER INVALID!. So, when you schedule a timer with repeats:NO, it is guaranteed to not reschedule itself but it will not invalidate immediately.
So, to answer your question:
repeats
If YES, the timer will repeatedly reschedule itself until
invalidated. If NO, the timer will be invalidated after it fires (but not immediately)
I made a test like this:
self.timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:#selector(xx) userInfo:nil repeats:NO];
- (void)xx
{
if ([self.timer isValid]) {
NSLog(#"isvalid");
}
dispatch_async(dispatch_get_main_queue(), ^{
if ([self.timer isValid]) {
NSLog(#"isvalid");
}else{
NSLog(#"isInvalid");
}
});
static int i = 0;
NSLog(#"%d",i++);
}
and the result is:
isvalid
0
isInvalid
thus, I guess when timer is fired,the function is execute like this:
void __NSFireTimer(){
id yourObj;
[yourObj performSelector:#selector(yourSelector)];
timer.isvalid = NO;
}
what you believe is:
void __NSFireTimer(){
id yourObj;
timer.isvalid = NO;
[yourObj performSelector:#selector(yourSelector)];
}
So, just accept it.You can put your check valid code in dispatch_asyn() ,like the test code.
This is how I used my timers. First initialise it on the top as
#property (strong, nonatomic) NSTimer *refreshTimer;
then this two methods, to create and invalidate the timer. "Its very important to invalidate the current timer if you want to create another timer with same name" otherwise their will be two timers.
- (void)startTimer {
if (_refreshTimer) {
[self invalidateTimer];
}
_refreshTimer = [NSTimer scheduledTimerWithTimeInterval:15.0
target:self
selector:#selector(determineIfPartOfgroup)
userInfo:nil
repeats:YES];
}
- (void)invalidateTimer {
if (_refreshTimer) {
[_refreshTimer invalidate];
_refreshTimer = nil;
}
}
I hope this will help you.
[self performSelectorInBackground:#selector(method) withObject:nil];
-(void)method
{
timer1 = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:#selector(getLastImageName1) userInfo:nil repeats:YES];
runLoop = [NSRunLoop currentRunLoop];
[runLoop addTimer:timer1 forMode:NSRunLoopCommonModes];
[runLoop run];
}
-(void)viewdidunload
{
[timer1 invalidate];
timer1=nil;
}
I start Timer in HomeViewController even I invalidate, it keeps running in OtherViewController. What is wrong with my code?
First of all, when you're overriding life cycle methods, you should include a call to the super version of that method.
Second of all, Objective-C is case sensitive, so even if your app would try to call the life-cycle even, viewDidUnload, your method would simply never be called because that's what you titled your method.
Third of all, viewDidUnload was deprecated in iOS 6.0 and shouldn't be used at all by this point unless you're going way out of your way to support backward compatibility. It will never be called in iOS 6.0 and greater.
If you want the timer to stop when the user navigates away from the current view, you'll want something like this:
- (void)viewDidDisappear:(BOOL)animated {
[super viewDidDisappear:animated];
if (timer1.isValid) {
[timer1 invalidate];
}
timer1 = nil;
}
If you're looking for something else, you'll need to elaborate on what it is you want to accomplish exactly.
If you ARE working on a pre-iOS 6.0 project, for whatever reason, the reason your method isn't being called is at least in part because it is spelled wrong. Again, Objective-C is case sensitive. Your method name should be spelled viewDidUnload.
For future reference, the question shouldn't really be "why isn't my timer invalidating?" You should have start by using breakpoints or NSLog statements to determine whether or not your method, viewdidunload, which tries to invalidate the timer even fires. When you find out it's not being called, do a search to ask "How come viewdidunload isn't called?" Then you'll go fix the capitalization problem and the problem will (probably) remain, so do some more research. And if at the end, you still can't figure it out, as a worst case scenario, the post question should be "how come viewdidunload isn't called?"
timer1 = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:#selector(getLastImageName1:) userInfo:nil repeats:YES];
set colon for function in selector
-(void) getLastImageName1 :(NSTimer*)timer1
{
//Do your all process and invalidate after completion
[timer1 invalidate];
}
or if you want to remove timer after moving to next view controller use how #nhgrif mentioned
- (void)viewDidDisappear:(BOOL)animated
{
[timer1 invalidate];
}
[self performSelector:#selector(method) withObject:nil afterDelay:0.0];
-(void)method
{
timer1 = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:#selector(getLastImageName1) userInfo:nil repeats:YES];
runLoop = [NSRunLoop currentRunLoop];
[runLoop addTimer:timer1 forMode:NSRunLoopCommonModes];
[runLoop run];
}
- (void)viewDidDisappear:(BOOL)animated
{
[super viewDidDisappear:animated];
[timer1 invalidate];
timer1=nil;
}
There is no need to add the timer (again) on the main run loop. Or is it necessary for You to run it also in commonModes? For me it was never necessary.
From the NSTimer Documentation:
scheduledTimerWithTimeInterval:invocation:repeats:
Creates and returns a new NSTimer object and schedules it on the
current run loop in the default mode.
Since the NSRunLoop Documentation points out that you can add timer on several run loop modes, maybe this is the problem.
addTimer:forMode:
Discussion You can add a timer to multiple input modes. While running
in the designated mode, the receiver causes the timer to fire on or
after its scheduled fire date. Upon firing, the timer invokes its
associated handler routine, which is a selector on a designated
object.
Also I don't get why you are invoking the timer creation with performSelector?
I just wrote a minimalistic sample. thats totally working!
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
self.timer = [NSTimer scheduledTimerWithTimeInterval:1.0f target:self selector:#selector(doWork:) userInfo:Nil repeats:YES];
}
- (void)viewDidDisappear:(BOOL)animated{
[self.timer invalidate];
[super viewDidDisappear:animated];
}
- (void) doWork:(id) userInfo
{
NSLog(#"Working again");
}
Hope this helps.
-(void)viewDidUnload is a delegate which fires on memory warning only and is deprecated after iOS 6. It will also never fire on the simulator.
Stop timer in
- (void)viewWillDisappear:(BOOL)animated
or in
- (void)viewDidDisappear:(BOOL)animated
I need to create a routine that save automatically a file content in a constant time period, ie, a backgroung loop that perform the save instructions. I thinked in use a recursive call of performSelector like below:
- (void)viewWillAppear:(BOOL)animated{
[super viewWillAppear:animated];
[self performSelector:#selector(saveMethod) withObject:nil afterDelay:kTimeConstant];
}
- (void)saveMethod{
//The save logic should to be here
[self performSelector:#selector(saveMethod) withObject:nil afterDelay:kTimeConstant];
}
It works, but when I get out of viewController, it still running, and it must to stop.
are there any better way to execute it? Thank you!
This is probably a better implementation:
- (void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
// Start timer and sets it to a property called saveTimer
self.saveTimer = [NSTimer scheduledTimerWithTimeInterval:2.0
target:self
selector:#selector(saveMethod:)
userInfo:nil
repeats:YES];
}
- (void)saveMethod:(NSTimer*)theTimer {
// The save logic should to be here
// No recursion
}
- (void)viewWillDisappear:(BOOL)animated {
[super viewWillDisappear:animated];
// Stop timer
[self.saveTimer invalidate];
}
This is running on the main thread so it is probably not the best implementation but it should work better than what you currently have.
There is a function NSRunLoop cancelPreviousPerformRequestsWithTarget:selector:object: which allows you to cancel the performSelector call. Call this when you unload the view controller
ie.
[NSRunLoop cancelPreviousPerformRequestsWithTarget:self selector:#selector(saveMethod) object:nil];