In my beginBackgroundTaskWithExpirationHandler code block in '-applicationDidEnterBackground' method, I have nstimer implemented as follows:
UIBackgroundTaskIdentifier taskId = [application beginBackgroundTaskWithExpirationHandler:^{
timer = [NSTimer scheduledTimerWithTimeInterval:0.0 target:self selector:#selector(print:) userInfo:nil repeats:NO];
}];
And Eventhough its repeats:NO, 'print'method as the selector is called twice, which i can see through NSLog.
This timer hasn't be called from any where else than in applicationDidEnterBackground.
I assure you that there is nothing wrong with:
timer = [NSTimer scheduledTimerWithTimeInterval:0.0 target:self selector:#selector(print:) userInfo:nil repeats:NO];
Your 'print' method wil NOT be called twice. Your problem is with something else.
And another thing, a timer with a 0.0 time interval is rather pointless wouldn't you agree?
Related
I want to my Webservice invoke once every 6 Hours.I am newer in iOS. Please help any help would be apperciated.I am stuck.
You can user NSTimer and schedule it for 6 hours
NSTimer *timer = nil;
timer = [NSTimer scheduledTimerWithTimeInterval:6*60*60 //6 hour
target:self
selector:#selector(performAction)
userInfo:nil
repeats:YES];
you can call using NSTimer. this is automatically called which time you set.
e.g.
NSTimer *timer= [NSTimer scheduledTimerWithTimeInterval:10.0(your time) target:self selector:#selector(someMethod) userInfo:nil repeats:YES];
-(void)someMethod
{
////API called here...
}
In ViewDidLoad
NSTimer *timer = [NSTimer timerWithTimeInterval:360.0 target:self selector:#selector(hideandview) userInfo:nil repeats:YES];
-(void)hideandview
{
////API called here...
}
You should save the last time in prefence (NSUserDefaults) when you make a call.
Whenever the app starts. Start timer and check current time with last saved time and get the difference.
I am getting this exception in the console:
Error:
2015-06-25 23:12:01.841 Copyfeed for Mac[9512:584232]
-[_NSViewLayoutAux invalidate]: unrecognized selector sent to instance 0x6000001657c0
when checking if my timers are valid/and when invalidating them.
if ([_staticTimer isValid]) {
[_staticTimer invalidate];
_selectionTimer =
[NSTimer scheduledTimerWithTimeInterval:2 target:self
selector:#selector(hideHUD) userInfo:nil repeats:NO];
}
if ([_selectionTimer isValid]) {
[_selectionTimer invalidate];
_selectionTimer =
[NSTimer scheduledTimerWithTimeInterval:2 target:self
selector:#selector(hideHUD) userInfo:nil repeats:NO];
}
This is my new code:
if (_selectionTimer != nil) {
[_selectionTimer invalidate];
_selectionTimer = nil;
_selectionTimer = [NSTimer scheduledTimerWithTimeInterval:2 target:self selector:#selector(hideHUD) userInfo:nil repeats:NO];
}
if (_staticTimer != nil) {
[_staticTimer invalidate];
_staticTimer = nil;
_selectionTimer = [NSTimer scheduledTimerWithTimeInterval:2 target:self selector:#selector(hideHUD) userInfo:nil repeats:NO];
}
#property (strong )NSTimer *staticTimer;
#property (strong )NSTimer *selectionTimer;
Now getting this error when I debug with zombie objects on.
2015-06-26 00:39:45.523 Copyfeed for Mac[11191:824502] ***
-[CFRunLoopTimer release]: message sent to deallocated instance 0x608000175e40
There are a couple of potential issues here.
if (_staticTimer != nil) {
[_staticTimer invalidate];
_staticTimer = nil;
_selectionTimer = [NSTimer scheduledTimerWithTimeInterval:2 target:self selector:#selector(hideHUD) userInfo:nil repeats:NO];
}
What you are doing here is overriding the selectionTimer even though it might still contain a timer that is still scheduled in the run loop. So if you reset the property here, you should also make sure to call [_selectionTimer invalidate] before doing so.
Depending on what you are doing when the timer is firing, this could explain the crash on CFRunLoopTimer.
A general advice that turned out to be very helpful for me when working with NSTimer: I would recommend declaring all the properties that hold a scheduled timer as weak as they are retained by the run loop anyway. This way, you don't need to explicitly set them to nil after invalidating them but instead you can simply call invalidate every time you want to get rid of it and it will also automatically become nil once it has fired by the run loop, releasing all the data it might hold on to.
Note that this would still require you to call invalidate in case you want to cancel a timer or before replacing one, but you no longer need to set it to nil after doing so.
After you invalidate it, you should set an NSTimer object to nil.
invalidate method also does a release.
If you didn't do that, calling a method on it like isValid could cause your crash.
if (_selectionTimer != nil) {
[_selectionTimer invalidate];
_selectionTimer = nil;
// do something
}
Check here
if (_staticTimer != nil) {
[_staticTimer invalidate];
_staticTimer = nil;
//_selectionTimer = [NSTimer scheduledTimerWithTimeInterval:2 target:self selector:#selector(hideHUD) userInfo:nil repeats:NO];
_staticTimer = [NSTimer scheduledTimerWithTimeInterval:2 target:self selector:#selector(hideHUD) userInfo:nil repeats:NO];
}
From the documentation:
Because the run loop maintains the timer, from the perspective of
memory management there's typically no need to keep a reference to a
timer after you’ve scheduled it. Since the timer is passed as an
argument when you specify its method as a selector, you can invalidate
a repeating timer when appropriate within that method. In many
situations, however, you also want the option of invalidating the
timer—perhaps even before it starts. In this case, you do need to keep
a reference to the timer, so that you can send it an invalidate
message whenever appropriate. If you create an unscheduled timer (see
“Unscheduled Timers”), then you must maintain a strong reference to
the timer (in a reference-counted environment, you retain it) so that
it is not deallocated before you use it.
So you should make the timer weak instead of strong
Is this code a problem?
self.UpdateTimer = [NSTimer scheduledTimerWithTimeInterval:60. target:self selector:#selector(update:) userInfo:nil repeats:YES];
I notice that this is in a method that is called often. However there is only one place where the timer is invalidated and set to nil ... the dealloc of that class.
Does setting a new timer multiple times automatically invalidate the old timer?
No, setting the timer to a new object does not invalidate the previous timer. You will end up with multiple timers running if you call that line of code multiple times, but only invalidate the currently referenced timer in one place elsewhere.
When you create the timer, you should probably check if one is already set and invalidate it before creating a new one.
if( self.UpdateTimer )
{
[self.UpdateTimer invalidate];
self.UpdateTimer = nil;
}
self.UpdateTimer = [NSTimer scheduledTimerWithTimeInterval:60. target:self selector:#selector(update:) userInfo:nil repeats:YES];
OR, simply leave the original one running, if you don't need to reset the timer interval.
if( !self.UpdateTimer )
{
self.UpdateTimer = [NSTimer scheduledTimerWithTimeInterval:60. target:self selector:#selector(update:) userInfo:nil repeats:YES];
}
I am trying to execute a certain block of code every x amount of time, but it seems that all I am doing is executing it during that time. Here's a block of my code.
while (TRUE) {
NSTimer *countDown = [NSTimer
scheduledTimerWithTimeInterval:(x)
target:self
selector:#selector(timerHandle)
userInfo:nil
repeats:YES];
}
Any ideas as to how to do it?
As written, this is an infinite loop, creating an NSTimer every loop iteration.
Try it without the while loop. This should cause [self timerHandle] to be invoked on interval x by a single background thread/timer. The Apple guide to NSTimer usage (including as others point out, how to properly stop your timed task) is here.
Try this: (It will call executeMethod on every 5 sec)
if (![NSThread isMainThread]) {
dispatch_async(dispatch_get_main_queue(), ^{
[NSTimer scheduledTimerWithTimeInterval:5.0
target:self
selector:#selector(executeMethod)
userInfo:nil
repeats:YES];
});
}
else{
[NSTimer scheduledTimerWithTimeInterval:5.0
target:self
selector:#selector(executeMethod)
userInfo:nil
repeats:YES];
}
Write the code you want to be executed in executeMethod method. Hope this helps.. :)
I have the following method
-(void) showDie: (int) num;{
// do something
}
I want to call that method in time intervals of .5 secs. So far I have the following
SEL runShowDie;
[runShowDie performSelector:#selector(showDie:) withObject:rand];
[NSTimer scheduledTimerWithTimeInterval:.5 target:self selector:runShowDie userInfo:nil repeats:NO];
What am I doing wrong?
You put repeats:No in this line make it YES
[NSTimer scheduledTimerWithTimeInterval:.5 target:self selector:#selector(showDie:) userInfo:[NSString stringWithFormat:#"%d",rand] repeats:YES];
Try with
[self performSelector:#selector(showDie:) withObject: rand afterDelay:0.5f];
And remove NSTimer