I am using NSTimer that updates 2 different values secondsLeft and totalSecondsLeft. I don't have to change secondsLeft but I have to add more seconds to totalSecondsLeft when an action is performed.
Whenever I assign a value to totalSecondsLeft the timer still updating and printing the previous value. I saw different solutions and tried invalidating the timer and start it again after updating the totalSecondsLeft value but not working.
So I ended up creating 2 different instances of the timer with same variables but printing different values i.e, secondsLeft is same in both cases but totalSecondsLeft is different in both cases.
I tried many solutions and added timer instance to GCD main_queue using functions and invalidating the timer from the same queue still not getting working solution.
Here is my code:
[self settime];
-(void)settime
{
dispatch_async(dispatch_get_main_queue(), ^
{
timer=[NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:#selector(Countdown) userInfo:nil repeats:YES];
});
}
-(void) Countdown
{
secondsLeft=secondsLeft-1;
totalSecondsLeft=totalSecondsLeft-1;
NSLog(#"secondsLeft : %i and totalSecondsLeft : %i",secondsLeft,totalSecondsLeft);
}
-(void)otherMethod
{
dispatch_async(dispatch_get_main_queue(), ^
{
timer=nil;
[timer invalidate];
});
[self settime];
}
Help me to figure out. Thanks in advance
Related
The Problem
I am building an app where I am getting real-time data and updating a MKMapView. I get a batch of data every 10 seconds and between data sets from the webs service I am removing older data points while also adding the new ones.
Instead of updating them all at once I want spread out the animation of the new points I get from the data service over that 10 seconds so I create the 'real-time' feel and avoid as many stops and starts as I can.
Everything seems to be working great except the that the NSTimer is always finishing early... way early. It should loop through the new data over 10 seconds but it will typically finish looping through the new data set 4 to 5 seconds earlier then it should.
I have read through a lot of the Apple documentation and StackOverflow questions (below are two good ones for those that may be looking) :)
https://stackoverflow.com/a/18584973
https://developer.apple.com/library/ios/technotes/tn2169/_index.html#//apple_ref/doc/uid/DTS40013172-CH1-TNTAG8000
But it seems like most of the recommendations are made for gaming apps using CADisplayLink (but I am not building a gaming app) or that if you need to use a high performance timer that it should not be used continuously.
My timer does not need to be exact but if I could even get it within .5 seconds that would be great without having to add the overhead of some of the other options I have seen.
As always any thoughts / code / or directions you could point me would be greatly appreciated.
The Code
Once I collect the new data into arrays I create the time interval and start the timer with the code below
addCount = -1;
timerDelay = 10.0/[timerAdditions count];
delayTimer =[NSTimer scheduledTimerWithTimeInterval:timerDelay target:self selector:#selector(delayMethod) userInfo:nil repeats:YES];
That then fires this method that animates through adding and removing the my map annotations.
-(void) delayMethod {
addCount = addCount +1;
if (addCount >= [timerAdditions count]) {
[timerRemovals removeAllObjects];
[timerAdditions removeAllObjects];
addCount = -1;
[delayTimer invalidate];
delayTimer = nil;
} else {
[myMap addAnnotation:[timerAdditions objectAtIndex:addCount]];
[myMap removeAnnotation:[timerRemovals objectAtIndex:addCount]animated:YES];
}
}
UPDATE
I tried updating my timer through GCD. And what is odd is that the timing loop works every other dataset. Still do not have it working every tie but for some reason it seems to be tied to resetting the dispatch time or the timer interval.
-(void) delayMethod {
dispatch_time_t delay = dispatch_time(DISPATCH_TIME_NOW, NSEC_PER_SEC * timerDelay); // How long
dispatch_after(delay, dispatch_get_main_queue(), ^(void){
addCount = addCount +1;
if (addCount >= [timerAdditions count]) {
[timerRemovals removeAllObjects];
[timerAdditions removeAllObjects];
addCount = -1;
//[delayTimer invalidate];
//delayTimer = nil;
} else {
NSLog(#"Delay fired count %i -- additoins %lu",addCount,(unsigned long)[timerAdditions count]);
[myMap addAnnotation:[timerAdditions objectAtIndex:addCount]];
[myMap removeAnnotation:[timerRemovals objectAtIndex:addCount]animated:YES];
[self delayMethod];
}
});
}
I am using timer as like this to do stuff with timer instance for more accurate result.
- (void)createTimer {
// start timer
if(gameTimer == nil)
gameTimer = [NSTimer timerWithTimeInterval:1.00 target:self selector:#selector(timerFired:) userInfo:nil repeats:YES] ;
[[NSRunLoop currentRunLoop] addTimer:gameTimer forMode:NSDefaultRunLoopMode];
timeCount = 725; // instance variable or you can set it as your need
}
- (void)timerFired:(NSTimer *)timer {
// update label
if(timeCount == 0){
[self timerExpired];
} else {
timeCount--;
if(timeCount == 0) {
// display correct dialog with button
[timer invalidate];
[self timerExpired];
}
}
//do your stuff here for particular time.
}
- (void) timerExpired {
// display an alert or something when the timer expires.
NSLog(#"Your time is over");
[gameTimer invalidate];
gameTimer = nil;
//do your stuff for completion of time.
}
in this take time interval you want. and also Increment decrement stuff as you require. And do stuff with timer fired and completed. In your situation if you don not want to expire timer than its ok. never invalidate timer instance and use only timer fired event to do stuff.
I went down a slightly different path thanks to another SO question I have referenced below. Basically by combining the two timers into one, setting that one timer to the fastest time interval I would need and managing the methods I need to at the changing intervals within the method called by the timer I have solved the problem I was seeing.
https://stackoverflow.com/a/25087473/2939977
timeAdder = (10.0/[timerAdditions count]);
timeCountAnimate = timeAdder;
[NSTimer scheduledTimerWithTimeInterval:0.11 target:self selector:#selector(timerFired) userInfo:nil repeats:YES];
- (void)timerFired {
timeCount += 0.111;
if (timeCount > 10.0) {
// call a method to start a new fetch
timeCount = 0.0;
timeCountAnimate =0.0;
[self timerTest];
}
if (timeCount > timeCountAnimate) {
timeCountAnimate += timeAdder;
[self delayMethod];
}
I need to do a possibly long series of calls that must occur on the main thread (because otherwise UIKit will balk). By "long" I mean 10,000 operations lasting .1 second each on an iPad 3.
Obviously, It's probably not the best idea to just loop through all of them at once.
I don't know how to execute all these on the main thread while leaving enough breathing room to keep UIKit responsive and the watchdog asleep (ie. not get terminated for hogging the run loop).
Does anybody have an idea? I will be targeting iOS 5.
Specifically what I'm trying to do is cache UITextPositions, because a UITextView is apparently taking a non-cached, iterative approach at getting UITextPositions, which means it is very, very slow at doing positionFromPosition:textview.beginningOfDocument offset:600011, but much faster at getting positionFromPosition:aPositionAt600000 offset:11. In fact, in my test case, the former takes over 100 seconds (on the main thread!), while the latter is virtually instantaneous.
Why do you want to do it on the main thread? The typical answer is to do these operations on a background thread, and send UI updates back to the main thread. For example, you could use Grand Central Dispatch:
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
// do my time consuming task and everytime it wants to update the UI,
// it should dispatch that back to the main queue, e.g.
for (NSInteger i = 0; i < 10000; i++)
{
// do my background work
// now update the UI
dispatch_async(dispatch_get_main_queue(), ^{
// update the UI accordingly
});
}
});
Update:
It sounds like you have to do this in the foreground, so perhaps using a NSTimer might be better. I'm not a big NSTimer guy, but it might look something like the following.
First, make sure you have a class instance variable for it:
NSTimer *_timer;
Next, you can initialize it with:
- (void)startTimer
{
_timer = [NSTimer timerWithTimeInterval:0.0 target:self selector:#selector(timerCallback:) userInfo:nil repeats:YES];
NSRunLoop *runloop = [NSRunLoop currentRunLoop];
[runloop addTimer:_timer forMode:NSDefaultRunLoopMode];
}
This will then invoke the timerCallback, perhaps processing a single UITextPosition on each invocation:
- (void)timerCallback:(NSTimer*)theTimer
{
BOOL moreTextPositionsToCalculate = ...;
if (moreTextPositionsToCalculate)
{
// calculate the next UITextPosition
}
else
{
[self stopTimer];
}
}
and when you're done, you could stop your timer like so:
- (void)stopTimer
{
[_timer invalidate];
_timer = nil;
}
I have scheduled a timer using [NSTimer scheduledTimerWithTimeInterval:target:selector:userInfo:] and want to invalidate it at some point when it fires.
- (id)init
{
[NSTimer scheduledTimerWithInterval:1 target:self selector:#selector(fired:) userInfo:nil repeats:YES];
}
- (void)fired:(NSTimer *)timer
{
if (someCondition) {
[timer invalidate];
}
}
Is this allowed? The documentation states
You must send this message from the thread on which the timer was installed. If you send this message from another thread, the input source associated with the timer may not be removed from its run loop, which could prevent the thread from exiting properly.
If this is not a proper way to accomplish this task: What is the proper way?
Calling [timer invalidate] from within the fire method is just fine, that code will be executed in the same thread as the one used when you created the timer.
The Apple Doc you quoted only warns you that if you create a separate thread and invalidate the timer from it, then, and only then, should expect unpredictable behaviour.
Ex.
// Create the background queue
dispatch_queue_t queue = dispatch_queue_create("do not do this", NULL);
// Start work in new thread
dispatch_async(queue, ^ {
// !! do not do this !!
if (someCondition) {
[yourTimer invalidate];
}
// or this
[self fire:yourTimer];
});
// won’t actually go away until queue is empty
dispatch_release(queue);
It is fine to invalidate it from the fired method, as the fired method is on the same thread the timer was scheduled on:
scheduledTimerWithTimeInterval:target:selector:userInfo:repeats:
Creates and returns a new NSTimer object and schedules it on the current run loop in the default mode.
I want to run certain background tasks.
Scenario: I would like a button to activate a thread or timer, and then have the thread/timer to start repeating every second returning a NSRunInformationalAlertPanel to the user with data.
This is what I have for my timer:
-(void)workerThread:(NSTimer*) theTimer {
if(intNumberOfTicks > 0)
{
NSRunInformationalAlertPanel(#"The Serial", [NSString stringWithFormat:#"%d", intNumberOfTicks], #"OK", nil, nil);
//[txtTimeMinutes setStringValue:[NSString stringWithFormat:#"%d", intNumberOfTicks]];
intNumberOfTicks--;
}
else {
[timer invalidate];
}
}
And for starting the method...
intNumberOfTicks = 5;
timer = [[NSTimer scheduledTimerWithTimeInterval:1 target: self selector:#selector(workerThread:) userInfo:self repeats:true] retain];
// Or for threading...
///[NSThread detachNewThreadSelector:#selector(workerThread) toTarget:self withObject:nil];
Can anyone help me implement what I need, maybe providing the most basic examples for a NSThread or NSTimer. I have looked at the Apple Dev Refrences but no luck.
Using NSTimer will execute the selector in the same thread as the one which instantiated and invoked it.
If your task must be carried out in a background thread try calling performSelectorInBackground:withObject:
https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/nsobject_Class/Reference/Reference.html#//apple_ref/occ/instm/NSObject/performSelectorInBackground:withObject:
From that background thread you can use a scheduled timer the way that you described above.
I've been searching for and attempting to program for myself, an answer to this question.
I've got a secondary thread running inside my mainView controller which is then running a timer which counts down to 0.
Whilst this timer is running the secondary thread which initiated the timer should be paused/blocked whatever.
When the timer reaches 0 the secondary thread should continue.
I've Experimented with both NSCondition and NSConditionLock with no avail, so id ideally like solutions that solve my problem with code, or point me to a guide on how to solve this. Not ones that simply state "Use X".
- (void)bettingInit {
bettingThread = [[NSThread alloc] initWithTarget:self selector:#selector(betting) object:nil];
[bettingThread start];
}
- (void)betting {
NSLog(#"betting Started");
for (int x = 0; x < [dealerNormalise count]; x++){
NSNumber *currSeat = [dealerNormalise objectAtIndex:x];
int currSeatint = [currSeat intValue];
NSString *currPlayerAction = [self getSeatInfo:currSeatint objectName:#"PlayerAction"];
if (currPlayerAction != #"FOLD"){
if (currPlayerAction == #"NULL"){
[inactivitySeconds removeAllObjects];
NSNumber *inactivitySecondsNumber = [NSNumber numberWithInt:10];
runLoop = [NSRunLoop currentRunLoop];
betLooper = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:#selector(betLoop) userInfo:nil repeats:YES];
[runLoop addTimer:[betLooper retain] forMode:NSDefaultRunLoopMode];
[runLoop run];
// This Thread needs to pause here, and wait for some input from the other thread, then continue on through the for loop
NSLog(#"Test");
}
}
}
}
- (void)threadKiller {
[betLooper invalidate];
//The input telling the thread to continue can alternatively come from here
return;
}
- (void)betLoop {
NSLog(#"BetLoop Started");
NSNumber *currentSeconds = [inactivitySeconds objectAtIndex:0];
int currentSecondsint = [currentSeconds intValue];
int newSecondsint = currentSecondsint - 1;
NSNumber *newSeconds = [NSNumber numberWithInt:newSecondsint];
[inactivitySeconds replaceObjectAtIndex:0 withObject:newSeconds];
inacTimer.text = [NSString stringWithFormat:#"Time: %d",newSecondsint];
if (newSecondsint == 0){
[self performSelector:#selector(threadKiller) onThread:bettingThread withObject:nil waitUntilDone:NO];
// The input going to the thread to continue should ideally come from here, or within the threadKiller void above
}
}
You can't run a timer on a thread and sleep the thread at the same time. You may want to reconsider whether you need a thread at all.
There's a few things that need to be pointed out here. First, when you schedule your timer:
betLooper = [NSTimer scheduledTimerWithTimeInterval:1
target:self
selector:#selector(betLoop:)
userInfo:nil
repeats:YES];
it's added to and retained by the current run loop by that method, so you don't need to do that manually. Just [myRunLoop run]. Your timer's selector argument is also invalid -- a timer's "target method" needs to look like this:
- (void)timerFireMethod:(NSTimer *)tim;
This also means that you don't need to retain the timer if all you want to do is invalidate it, since you will have a reference to it from inside that method.
Second, it's not clear what you mean by "this thread needs to sleep to wait for input". When you schedule that timer, the method (betLoop) is called on the same thread. If you were to sleep the thread, the timer would stop too.
You seem to be a little mixed up regarding methods/threads. The method betting is running on your thread. It is not itself a thread, and it's possible to call other methods from betting that will also be on that thread. If you want a method to wait until another method has completed, you simply call the second method inside the first:
- (void)doSomethingThenWaitForAnotherMethodBeforeDoingOtherStuff {
// Do stuff...
[self methodWhichINeedToWaitFor];
// Continue...
}
I think you just want to let betting return; the run loop will keep the thread running, and as I said, the other methods you call from methods on the thread are also on the thread. Then, when you've done the countdown, call another method to do whatever work needs to be done (you can also invalidate the timer inside betLoop:), and finalize the thread:
- (void)takeCareOfBusiness {
// Do the things you were going to do in `betting`
// Make sure the run loop stops; invalidating the timer doesn't guarantee this
CFRunLoopStop(CFRunLoopGetCurrent());
return; // Thread ends now because it's not doing anything.
}
Finally, since the timer's method is on the same thread, you don't need to use performSelector:onThread:...; just call the method normally.
You should take a look at the Threading Programming Guide.
Also, don't forget to release the bettingThread object that you created.
NSThread has a class method + (void)sleepForTimeInterval:(NSTimeInterval)ti. Have a look at this :).
NSThread Class Reference