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 :)
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]
}
...
}
I created a timer, and was wondering if it is at all possible to make the timer go slower when it reaches a certain second: 1..2..3..4..4.1..4.2.
For example, the timer is increasing by 1 second, then at 4 seconds, the time slows down showing milliseconds.
if(i = 4) {
}
It depends on what you want.
Of course, you can't slow down the time, but you can simulate it.
For example, you check how much time has already passed. If it is 1, 2, 3 seconds, you NSLog 1, 2, 3. Then when 4 seconds has passed, you start logging milliseconds.
E.g.
if (i < 4) {
NSLog(#"%d", i);
} else {
NSLog(#"4.%d", i - 4);
}
Sure, logging can be substituted with whatever you need.
P.S. The answer is in Objective-C, but that changes nothing.
You can use a solution like this:
Declare a float to register your time and a NSTimer to perform the action.
#property NSTimer *timer;
#property float time;
Call startTimer to start the actions.
- (void) startTimer {
self.timer = [NSTimer scheduledTimerWithTimeInterval:1
target:self
selector:#selector(secondsAction)
userInfo:nil
repeats:YES];
}
- (void) secondsAction {
self.time += 1;
NSLog(#"%d", (int)self.time);
if(self.time == 4) {
[self.timer invalidate];
self.timer = [NSTimer scheduledTimerWithTimeInterval:0.1
target:self
selector:#selector(milisecondsAction)
userInfo:nil
repeats:YES];
}
}
- (void) milisecondsAction {
self.time += 0.1;
NSLog(#"%.1f", self.time);
}
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.
I make one 30:00 min countdown timer, now when I load next page and back on first page my timer is on but label which show time it's stopped.
Any idea for that when I come on first page and my timer is on and start at same point, in short I need run my timer in background.
This is the code which I use in same view controller where the timer is, but it's not working.
- (void)viewWillDisappear:(BOOL)animated
{
[Timecount invalidate];
}
-(void)viewDidAppear:(BOOL)animated
{
// [self countdownTimer];
}
-(void)viewWillAppear:(BOOL)animated
{
[self countdownTimer];
}
-(void)countdownTimer
{
secondsLeft = hours = minutes = seconds = 0;
if([Timecount isValid])
{
}
Timecount = [NSTimer scheduledTimerWithTimeInterval:1.0f target:self selector:#selector(updateCounter:) userInfo:nil repeats:YES];
}
I have a void function which just have NSLog(#"Call me"); in its body.
I call it in my view in every ten seconds by using
NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:10 target:self selector:#selector(yourMethod) userInfo:nil repeats:YES];
But I want it to stop it after 5 iterations. However it goes to infinity. How can I do that?
1) Keep a global variable, that increments from 0 to 5.
int i = 0;
2) Incement this variable inside your timer function..
-(void) yourFunction:(NSTimer*)timer{
//do your action
i++;
if(i == 5){
[timer invalidate];
}
}
3) When creating timer
NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:10
target:self
selector:#selector(yourMethod:) // <== see the ':', indicates your function takes an argument
userInfo:nil
repeats:YES];
You should take one counter, increment it every time when your method get called, count for 5 and then invalidate your timer using below code.
[timer invalidate];
To destroy the timer from the current loop, you should call [timer invalidate];
To determine five occurrences, you need to maintain a variable and increment its count each time. If it is equal to 5, call invalidate method.
First of all you need to declare an int and declare your NSTimer *timer, so we can stop it:
#interface AppDelegate : UIViewController {
int myInt;
NSTimer *timer;
}
To start the NSTimer you'll need to change just a bit of the code:
timer = [NSTimer scheduledTimerWithTimeInterval:10 target:self selector:#selector(yourMethod) userInfo:nil repeats:YES];
Inside your void function you can make the verification to check if the code's running after 5 iterations:
- (void)myVoid{
NSLog(#"Call Me");
if (myInt == 5) {
[timer invalidate];
timer = nil;
}
myInt++;
}