I am working on a alarm application. I faced a problem from last 2 weeks. My problem is: My application is running in background.First time I install the application and set the alarm & close the app. If the alarm time is more than 3 minutes from current time then its not ringing means after 3 min alarm is not ringing in background process. If application is on then alarm is working.
This is my code:
self->bgTask = 0;
NSAssert(self->bgTask == UIBackgroundTaskInvalid, nil);
bgTask = [application beginBackgroundTaskWithExpirationHandler: ^
{
NSLog(#"beginBackgroundTaskWithExpirat");
dispatch_async(dispatch_get_main_queue(), ^
{
NSLog(#"dispatch_async");
[application endBackgroundTask:self->bgTask];
self->bgTask = UIBackgroundTaskInvalid;
});
}];
dispatch_async(dispatch_get_main_queue(), ^
{
NSLog(#"dispatch_get_main_queue");
//Start BG Timer
[self Start_Update_Timer];
self->bgTask = UIBackgroundTaskInvalid;
});
// This is my timer for background running ..
-(void) Start_Update_Timer
{
//If timer is already running, stop the timer
if(self.callTimer)
{
[self.callTimer invalidate];
self.callTimer=nil;
}
//call the timer for every one sec
self.callTimer =[NSTimer scheduledTimerWithTimeInterval:60 target:self selector:#selector(update_Alarm_List) userInfo:nil repeats:YES];
[[NSRunLoop mainRunLoop] addTimer:self.callTimer forMode:NSRunLoopCommonModes];
}
Because applications are not supposed to work like this. If you want your app to continuously play sound on the background, then it should be registered as an app that does it specially. Like a music player. If your app only delivers alarms, then you have to use a local notification to "trigger" the sound from your app. The notification can be played with a 30 secs sound and replay again at certain intervals. Your app wont play after 3 minutes because your "background" execution time has expired. That is the time that apple lets your app run in the background to do whatever you have to do after the user has closed your application.
This is for the case in where you want to keep playing sound on the background. Note that if the playback stops your app will stop.
https://developer.apple.com/library/ios/qa/qa1668/_index.html#//apple_ref/doc/uid/DTS40010209
If you want to use notifications with sound (30 secs max) see here:
https://developer.apple.com/library/ios/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/Chapters/IPhoneOSClientImp.html
Related
I have a timer running when the device enters the background as I want to keep a check on a small amount of data in my service. I am using the following code in the applicationDidEnterBackground method in app delegate
UIApplication *app = [UIApplication sharedApplication];
//create new uiBackgroundTask
__block UIBackgroundTaskIdentifier bgTask = [app beginBackgroundTaskWithExpirationHandler:^{
[app endBackgroundTask:bgTask];
bgTask = UIBackgroundTaskInvalid;
}];
//and create new timer with async call:
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
//run function methodRunAfterBackground
NSString *server = [variableStore sharedGlobalData].server;
NSLog(#"%#",server);
if([server isEqual:#"_DEV"]){
arrivalsTimer = [NSTimer scheduledTimerWithTimeInterval:30 target:self selector:#selector(getArrivals) userInfo:nil repeats:YES];
}
else {
arrivalsTimer = [NSTimer scheduledTimerWithTimeInterval:300 target:self selector:#selector(getArrivals) userInfo:nil repeats:YES];
}
[[NSRunLoop currentRunLoop] addTimer:arrivalsTimer forMode:NSDefaultRunLoopMode];
[[NSRunLoop currentRunLoop] run];
});
This works absolutely fine, until the device auto-locks and then the timer stops ticking. Any suggestions on how to stop this from happening? The default live time is 5 minutes so the majority of devices will be locked long before this even ticks once.
Thanks
A couple of observations:
As Mr. H points out, beginBackgroundTaskWithExpirationHandler only gives you 30 seconds (previously 3 minutes) in contemporary iOS versions. So an attempt to fire a timer in five minutes won't work.
You can use [[UIApplication sharedApplication] backgroundTimeRemaining] to inquire as to how much time you have left.
When the device locks, the background tasks continue. You should not see the app terminating. If the user manually terminates the app through the "double tap the home button and swipe up on task switcher screen", that will kill the background tasks, but not simply locking the device.
A few comments on timers:
The code is adding timer to background queue. That's generally not necessary. Just because the app is in a background state, you can still continue to use the main run loop for timers and the like.
So, just call scheduledTimerWithTimeInterval from the main thread and you're done. There's no point in using up a GCD worker thread with a run loop unless absolutely necessary (and even then, I might create my own thread and add a run loop to that).
By the way, if it's absolutely necessary to schedule timer on some background dispatch queue, it's probably easier to use dispatch timer instead. It eliminates the run loop requirement entirely.
BTW, it's not appropriate to use scheduledTimerWithTimeInterval with addTimer. You call scheduledTimerWithTimeInterval to create a timer and add it to the current run loop. You use timerWithTimeInterval and then call addTimer if you want to add it to another run loop.
- (NSTimer *) timer
{
(!_timer)
{
_timer = [NSTimer timerWithTimeInterval:86400 target:self selector:#selector(timeset:) userInfo:nil repeats:YES];
}
return _timer;
}
You can't schedule execution for a specific time in the background on iOS. You can schedule a UILocalNotification - but your app will only be launched if the user taps on the notification.
Your best bet is to use background fetch mode. You app will be woken at intervals and given an opportunity to fetch new data. You can check to see if the time is at or after 7 and decide whether to refresh the data.
Hey I am developing an app in which i have to make API call every 30 sec, so i created NSTimer for it.
But when my app goes into background timer stops firing after 3-4 minutes. So it works only 3-4 minutes in background,but not after that. How can i modify my code so that timer would not stop.
Here is some of my code.
- (IBAction)didTapStart:(id)sender {
NSLog(#"hey i m in the timer ..%#",[NSDate date]);
[objTimer invalidate];
objTimer=nil;
UIBackgroundTaskIdentifier bgTask = UIBackgroundTaskInvalid;
UIApplication *app = [UIApplication sharedApplication];
bgTask = [app beginBackgroundTaskWithExpirationHandler:^{
[app endBackgroundTask:bgTask];
}];
objTimer = [NSTimer scheduledTimerWithTimeInterval:30.0 target:self
selector:#selector(methodFromTimer) userInfo:nil repeats:YES];
[[NSRunLoop currentRunLoop] addTimer:objTimer forMode:UITrackingRunLoopMode];
}
-(void)methodFromTimer{
[LOG debug:#"ViewController.m ::methodFromTimer " Message:[NSString stringWithFormat:#"hey i m from timer ....%#",[NSDate date] ]];
NSLog(#"hey i m from timer ....%#",[NSDate date]);
}
I even changed the code with the following:
[[NSRunLoop mainRunLoop] addTimer:objTimer forMode:NSRunLoopCommonModes];
This didn't work either.
Don't create UIBackgroundTaskIdentifier task as local and make it global as below:
Step -1
Step -2
Step -3
Step -4
As local one loose scope and global one won't ,and I created a demo and ran it for sometime with 1 sec repeating timer ,and worked smooth.
Still if u face issue pls let me know.
I ran again demo and here are logs of it running.
So its working fine and more than 3 minutes. Also that 3 minute logic is right but as uibackgroundtask is initiated so it shouldn't let it kill this task of timer.
Edited Part:-
bgTask = [app beginBackgroundTaskWithExpirationHandler:^{
[app endBackgroundTask:bgTask]; //Remove this line and it will run as long as timer is running and when app is killed then automatically all vairbles and scopes of it are dumped.
}];
Check it and let me know if it works out or not.
Hey I run ur code and I reached the expirationHandler but after released debug point ,the timer was running smooth.
No, don't do background tasks with NSTimer. It will not work as you might expect. You should be making use of background fetch APIs provided by Apple only. You can set the duration at which you want it to be called in that API. Though usually it is not recommended setting duration of the call you would like to make. Take a look at this apple background programming documentation
Also, to get you started quickly, you can follow this Appcoda tutorial
This worked for me, so I'm adding it to StackOverflow for any future answer seekers.
Add the following utility method to be called before you start your timer. When we call AppDelegate.RestartBackgroundTimer() it will ensure that your app will remain active - even if it's in the background or if the screen is locked. However, this will only ensure that for 3 minutes (as you mentioned):
class AppDelegate: UIResponder, UIApplicationDelegate {
static var backgroundTaskIdentifier: UIBackgroundTaskIdentifier? = nil;
static func RestartBackgroundTimer() {
if (AppDelegate.backgroundTaskIdentifier != nil) {
print("RestartBackgroundTimer: Ended existing background task");
UIApplication.sharedApplication().endBackgroundTask(AppDelegate.backgroundTaskIdentifier!);
AppDelegate.backgroundTaskIdentifier = nil;
}
print("RestartBackgroundTimer: Started new background task");
AppDelegate.backgroundTaskIdentifier = UIApplication.sharedApplication().beginBackgroundTaskWithExpirationHandler({
UIApplication.sharedApplication().endBackgroundTask(AppDelegate.backgroundTaskIdentifier!);
AppDelegate.backgroundTaskIdentifier = nil;
})
}
}
Also, when starting your app, ensure the following runs. It will ensure that audio is played even if the app is in the background (and while you're at it, also ensure that your Info.plist contains "Required background modes" and that "App plays audio or streams audio/video using AirPlay" a.k.a. "audio" is in its collection):
import AVFoundation;
// setup audio to not stop in background or when silent
do {
try AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayback);
try AVAudioSession.sharedInstance().setActive(true);
} catch { }
Now, in the class that needs the timer to run more than 3 minutes (if in the background), you need to play a sound when only 30 seconds remains of background time. This will reset the background time remaining to 3 minutes (just create a "Silent.mp3" with e.g. AudaCity and drag & drop it to your XCode project).
To wrap it all up, do something like this:
import AVFoundation
class MyViewController : UIViewController {
var timer : NSTimer!;
override func viewDidLoad() {
// ensure we get background time & start timer
AppDelegate.RestartBackgroundTimer();
self.timer = NSTimer.scheduledTimerWithTimeInterval(0.25, target: self, selector: #selector(MyViewController.timerInterval), userInfo: nil, repeats: true);
}
func timerInterval() {
var bgTimeRemaining = UIApplication.sharedApplication().backgroundTimeRemaining;
print("Timer... " + NSDateComponentsFormatter().stringFromTimeInterval(bgTimeRemaining)!);
if NSInteger(bgTimeRemaining) < 30 {
// 30 seconds of background time remaining, play silent sound!
do {
var audioPlayer = try AVAudioPlayer(contentsOfURL: NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource("Silent", ofType: "mp3")!));
audioPlayer.prepareToPlay();
audioPlayer.play();
} catch { }
}
}
}
It is normal behavior.
After iOS7, you got exactly 3 minutes of background time. Before that there was 10 minutes if i remember correctly. To extend that, your app needs to use some special services like location, audio or bluetooth which will keep it "alive" in the background.
Also, even if you use one of these services the "Background app refresh" setting must be enabled on your device for the app.
See this answer for details or the background execution part of the documentatio.
I am trying to get this to work correctly but it always seems to end early at 174 seconds (2.9 mins). I been following every tutorial possible online on how to use beginBackgroundTaskWithExpirationHandler and I don't see anything wrong with my code. I need this to end at 8.5 mins. The endBackgroundTask method doesn't even gets call before the expiration handler gets called. Is anything wrong with this?
- (void)applicationDidEnterBackground:(UIApplication *)application {
if([[UIDevice currentDevice] respondsToSelector:#selector(isMultitaskingSupported)])
{
NSLog(#"Multitasking Supported");
backgroundTask = [application beginBackgroundTaskWithExpirationHandler:^ {
NSLog(#"Terminated");
//Clean up code. Tell the system that we are done.
[application endBackgroundTask: backgroundTask];
backgroundTask = UIBackgroundTaskInvalid;
}];
timer = [NSTimer scheduledTimerWithTimeInterval:1
target:self
selector:#selector(count:)
userInfo:nil
repeats:YES];
}
else
{
NSLog(#"Multitasking Not Supported");
}
}
-(void)turnOffDesktops:(NSTimer *)time {
//do smth
if(count < (60*8.5)){
NSLog(#"%d",count);
count++;
}else{
[application endBackgroundTask: backgroundTask];
backgroundTask = UIBackgroundTaskInvalid;
[timer invalidate];
timer = nil;
count = 0;
}
}
There has never been a commitment from Apple on how long you would be allowed to perform your background tasks. Historically (until iOS7), apps were given usually 10 minutes to run in the background. This is no longer the case! Watch the WWDC 2013 video on backgrounding. With the addition of the new download & upload API in NSURLSession (ability to schedule download and upload tasks on an external dedicated daemon), Apple has reduced the allowed background time significantly. They've done this because this API has always been meant for download and upload, not arbitrary tasks in the background.
You can determine the amount of time left in background by querying - [UIApplication backgroundTimeRemaining]. You can use this to schedule your code to start at the latest possible.
I'm currently writing an application which depends on location tracking and sending data about the position to the server. The problem, however, is that it has to run 24/7 and currently I'm experiencing random crashes which occur every 2-3 days. What I have done to make the application run constantly in the background is I put a NSTimer in a beginBackgroundTaskWithExpirationHandler method right iside the applicationDidEnterBackground method. The timer executes each minute and stops/starts the location service.
Here is a sample crash log
The code basically looks like this:
UIApplication *app = [UIApplication sharedApplication];
__block UIBackgroundTaskIdentifier bgTaskId = 0;
bgTaskId = [app beginBackgroundTaskWithExpirationHandler:^{
NSTimer *t = [NSTimer scheduledTimerWithTimeInterval: 1 * 60.0 target: self selector: #selector(onTick) userInfo: nil repeats: YES];
[t fire];
if (bgTaskId != UIBackgroundTaskInvalid){
[app endBackgroundTask: bgTaskId];
bgTaskId = UIBackgroundTaskInvalid;
}
}];
I am using GCDAsyncSockets for connection purposes, each call having a timeout of approximately 30 seconds.
I'm really out of ideas, what might be the reason the crashes occur?
Your timer is probably firing off AFTER the task is invalidated (after [UIApplication sharedApplication].backgroundTimeRemaining gets to 0.
The thing is that you can't make the application run constantly in the background. If you want to execute code every once in a while, your only option is going to be using the background location API, setting that your app is using the location background mode in its plist.
You would be getting the CLLocationManagerDelegate callbacks, and you have some time to do some work when those methods are called.
See the Apple documentation regarding background modes: http://developer.apple.com/library/ios/#DOCUMENTATION/iPhone/Conceptual/iPhoneOSProgrammingGuide/ManagingYourApplicationsFlow/ManagingYourApplicationsFlow.html
And the location-awarness manual: http://developer.apple.com/library/ios/#DOCUMENTATION/UserExperience/Conceptual/LocationAwarenessPG/Introduction/Introduction.html#//apple_ref/doc/uid/TP40009497