I get information from a server in my app with a secondsToEnd value and I start a counter after I've received this information.
My project contains a scrollview, so to get around locking my timer due to scrolling around I add the timer to the NSRunLoop in the following way:
[[NSRunLoop currentRunLoop] addTimer:timer
forMode:NSRunLoopCommonModes];
I made a NSTimer property called, how original, timer and this is the whole snippet of my startTimer function:
- (void)startTimer
{
if (_timer || [_timer isValid]) [_timer invalidate], _timer = nil, [_timer release];
NSTimer * timer = [[NSTimer alloc] initWithFireDate:[NSDate date]
interval:1.0
target:self
selector:#selector(timer:)
userInfo:nil
repeats:YES];
[[NSRunLoop currentRunLoop] addTimer:timer
forMode:NSRunLoopCommonModes];
[self setTimer:timer];
[timer release];
}
The reason for the check to invalidate in the start method is because after the secondsToEnd value hits 0, I receive a new one and I call startTimer again.
And in my dealloc method I have this:
if (_timer || [_timer isValid]) [_timer invalidate], _timer = nil, [_timer release];
But it doesn't get invalidated? What am I doing wrong?
What order do these comma separated statements execute in? What happens if _timer is nil when you call invalidate or when you call release?
if (_timer || [_timer isValid]) [_timer invalidate], _timer = nil, [_timer release];
Try this instead, there is no need to check whether _timer is already nil. If it was nil then the method call does nothing.
if ([_timer isValid]) {
[_timer invalidate];
}
[_timer release];
In the dealloc method there is no need to set _timer = nil, its storage is gone after this method ends.
You should first call [timer release] and then timer = nil. Same in dealloc method. The dealloc method might no get called immediately if outer objects are in autrelease pools. In these cases it is called when the system decides to drop your object finally. So it may take some time (if you set a breakpoint).
BTW I would suggest to avoid comma syntax and use blocks within curly braces instead. It's far more easier to read.
Related
I'm trying to to stop an NSTimer with the following code:
- (void)viewDidLoad
{
[super viewDidLoad];
timer3 = [NSTimer timerWithTimeInterval:5.0 target:self selector:#selector(start) userInfo:nil repeats:YES];
[[NSRunLoop mainRunLoop] addTimer:timer3 forMode:NSDefaultRunLoopMode];
}
-(void)invalidate
{
[timer3 invalidate];
timer3 = nil;
}
and I call -(void)invalidate from another class like this:
-(void)timer
{
ClassOfMyTimer *class = [[ClassOfMyTimer alloc] init];
[class invalidate];
}
but the timer doesn't stop. Does anyone know what I'm doing wrong?
You need to call your invalidate method on the same instance of your class that created the timer. In your timer method you create a new instance of your class which could have its own timer and invalidate that.
I'm kind of confused by what you're trying to do here, but I'd guess that you're not maintaining a reference to timer3.
Have you created a property in the .h file for the timer:
#property (strong) NSTimer *timer3;
And then added a synthesize statement in the .m file:
#synthesize timer3;
Then, in viewDidLoad:, you can maintain a reference to the timer you're creating via:
self.timer3 = [[[NSTimer timerWithTimeInterval:5.0 target:self selector:#selector(start) userInfo:nil repeats:YES];
[[NSRunLoop mainRunLoop] addTimer:self.timer3 forMode:NSDefaultRunLoopMode];
And, to invalidate the timer later:
[self.timer3 invalidate]
self.timer3 = nil
On preview, Sven also has a valid solution to an issue that might be impacting you..
The following method causes a crash. The UI is like a button, which handles the start / stop functionality of the NSTimer. If the timer runs, a UILabel is updated. Using the viewDidLoad Method makes my timer work, stopping it works too, but starting it again crashes the app.
Removing the alloc in the viewDidLoad method and trying to use the start button causes a crash instantly. Even the NSLog(#"Start now");is not called.
Code:
- (void)tick {
NSLog(#"tick");
float value = [moneyLabel.text floatValue];
moneyLabel.text = [NSString stringWithFormat:#"%f", value + 1.0];
}
- (IBAction)startStopButtonClicked:(UIButton *)sender {
if ([sender.titleLabel.text isEqualToString:#"Start"]) {
NSLog(#"Start now");
if (timer) {
NSLog(#"Timer valid");
[timer fire];
} else {
NSLog(#"Timer is nil");
timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:#selector(tick) userInfo:nil repeats:YES];
[timer fire];
}
NSLog(#"bla");
[sender setTitle:#"Stop" forState:UIControlStateNormal];
} else {
[timer invalidate];
timer = nil;
NSLog(#"Stopped.");
NSLog(#"Timer isValid: %#", timer);
[sender setTitle:#"Start" forState:UIControlStateNormal];
}
}
I don't see the need to call [NSTimer fire] at all; it should be enough to allow the timer to decide when to fire.
Firstly ensure that timer is nil (it should be if it's an instance variable of the object), although explicitly setting it to nil in - (id)init won't hurt.
Next I would use the state of the timer itself to determine whether start/stop has been pressed, not the text in the button:
- (IBAction)startStopButtonClicked:(UIButton *)sender
{
if (timer != nil)
{
NSLog(#"Stopping timer");
[timer invalidate];
timer = nil;
}
else
{
NSLog(#"Starting timer");
timer = [NSTimer scheduledTimerWithTimeInterval:1
target:self
selector:#selector(tick)
userInfo:nil
repeats:YES];
}
[sender setTitle:(timer != nil ? #"Stop" : #"Start")
forState:UIControlStateNormal];
}
The code you have posted works as desired - just tested it in a new project, so the problem could be somewhere else. I tested it only by declaring the ivar NSTimer *timer; without any initialization in viewDidLoad: or the designated initializers...
I have an NSTimer declared in my .h and in the viewDidLoad of the /m I have the code:
timer = [NSTimer scheduledTimerWithTimeInterval:kComplexTimer target:self selector:#selector (main) userInfo:nil repeats:YES];
I also have [timer release]; in my dealloc.
However when I exit the view and return to it, the timer has not in fact released, it has doubles in speed! How do I solve this & what am I doing wrong???
Thanks
you don't need to release it as you have not retained it - as a rule.
all you need to do is just call [timer invalidate]; which will stop your timer.
Nice Answer , but good to check whether the time is nil or not to avoid unwanted exception..
if( timer ! = nil )
{
[timer invalidate];
timer = nil;
}
Thank you...
[timer invalidate];
timer = nil;
The second line is important if you want to reset the NSTimer
You must not call release on a object that it not be created by "new", "alloc", "retain", "copy".
In this case, you had created a Timer by scheduledTimerWithTimeInterval method, So you must not call release method but call [timer invalidate] to stop the timer.
I'm trying to invalidate a timer when my app goes into background. The timer gets invoked when you hit a button that starts the timer and is in the TimerController.m file. Here is how it gets invoked.
mytimer = [NSTimer timerWithTimeInterval:1 target:self selector:#selector(updateTime) userInfo:nil repeats:YES];//Timer with interval of one second
[[NSRunLoop mainRunLoop] addTimer:mytimer forMode:NSDefaultRunLoopMode];
Now, I'd like to invalidate mytimer when the app goes into background, so I tried putting
[mytimer invalidate];
into the - (void)applicationDidEnterBackground:(UIApplication *)application method the apps delegate. But this won't work since it's undeclared in the delegate. I thought by including TimerController.h into the delegate, this would work, but it won't.
So, I clearly don't know what I'm doing here. Can you help? How do it get it so that mytimer is invalidated when the app goes into background?
There’s also a UIApplicationDidEnterBackgroundNotification notification posted when the application goes into background. You can subscribe for this notification in your controller and handle the transition there:
[[NSNotificationCenter defaultCenter]
addObserver:self
selector:#selector(goBackground)
name:UIApplicationDidEnterBackgroundNotification
object:nil];
// and later:
- (void) goBackground {
[timer invalidate], timer = nil;
}
if (timer) {
[timer invalidate];
timer = nil;
}
in applicationReEnteredForeground notification method will also work
I am aware of the many questions regarding this topic, as I myself have asked one previously however, my issue now seems to be more related to the threading part. I have the following 2 methods.
-(void) restartTimer {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc]init];
self.timer = [NSTimer scheduledTimerWithTimeInterval:1.
target:self
selector:#selector(dim)
userInfo:nil
repeats:YES];
time = 31;
NSLog(#"calling restart timer");
[self performSelectorOnMainThread:#selector(timerImageUpdate) withObject:nil waitUntilDone:NO];
[[NSRunLoop currentRunLoop] addTimer:self.timer forMode:NSDefaultRunLoopMode];
[[NSRunLoop currentRunLoop] run];
[pool drain];
}
-(void) resumeTimer {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc]init];
self.timer = [NSTimer scheduledTimerWithTimeInterval:1.
target:self
selector:#selector(dim)
userInfo:nil
repeats:YES];
NSLog(#"calling resume timer");
[[NSRunLoop currentRunLoop] addTimer:self.timer forMode:NSDefaultRunLoopMode];
[[NSRunLoop currentRunLoop] run];
[pool drain];
}
The restartTimer function is called when the game begins. This works fine and the timer fires the dim selector nicely. The problem occurs when the user clicks my skip button in quick succession. [skip] updates an MKMapView and in the delegate method mapdidfinishloading the follwing is called :
[NSThread detachNewThreadSelector:#selector(restartTimer) toTarget:self withObject:nil];
When this happens it seems several timers are created and thus my dim function is called far too often giving the appearance of the single timer running really fast? What is the best way to start and restart the timer using a secondary thread? Note this problem only seems to happen if the skip button is pressed repeatedly and quickly, while it works fine if just pressed now and again?
Anyone have any ideas? Many thanks
Jules
You can use a bool to know if you have a timer running or not. When you start the timer you set it to true, when you stop the timer you set it to false. When resume timer function is called you check this variable and if it's true you do not start a new timer.
Another solution would be to limit user interaction with the button. If the button is pressed you make it inactive for a time.