Playing around with Timers, and trying to make them behave right when app is sent to background, killed etc.
Judging by the generated comments in xcode, you should disable/invalidate timers on resignActive/enterBackground events.
However, i havent done that yet, but checked what happens to my timer when i click the home button and then re-enter the app.
I basically have a method in my view that the timer triggers every second:
NSLog(#"workedTimTimerTick workedTime; %#", timeString);
And when i exit the app, the output stops, when i re-enter the app, the output starts again...
Since i'm not doing anything code-wise to the timer on those lifecycle events, how come it stops getting called?
Input appreciated!
Your app is suspended when it enters background mode (Application States and Transitions).
Your timer won't fire when the app is in background and the time spent in background isn't taken into account for the timer delay.
Related
I have implemented a Timer as detailed in the article below, so that the timer will keep running when i change tabs.
How to implement persistent stopwatch in Flutter?
I have an issue where the Timer "loses" or pauses time, only when not plugged into my computer. When i plug it into my computer, no issues, the emulator runs fine too. I test the flutter timer against a timer on my computer or phone, and after 5mins, they match. But when my phone (Galaxy S9) isn't plugged in, after 5mins of real time, the flutter timer might only be up to 2mins, when i go back into the app the timer is running but the timer wont be what it should be. It doesn't crash or reset, its counting when i get back into the app. I'm finding it hard to debug as when I plug the phone into my computer it seems to work fine! Any ideas?
I had issues with this as well. Things working correctly when running on the Simulator is fools gold. The Timer won't run in the background like you want it to unless you do specific work to keep it running. Here is the official page from Flutter on doing work in the background: https://flutter.dev/docs/development/packages-and-plugins/background-processes
I'll suggest implementing didChangeAppLifecycleState method of the WidgetsBindingObserver and detect when the app goes to the background and when it's back in the foreground. At the point where the app goes into the background, you save the current time e.g (onPauseTime) (you can use SharedPreferences here) and the Duration left on the timer (timerDurationLeft).
When the app is back in the foreground you check if the timer was running before the app entered the background state, if it was, you then check the current time e.g (onResumeTime) and calculate the time difference in seconds (onResumeTime - onPauseTime), using the time difference and the timerDurationLeft you can calculate how much time the timer has left to run and you start/resume the timer from that point or end/set the timer to 0:00 if time has already passed.
P:S Using a background service would be the way to go if you intend to perform some actions in the middle, like set notifications at some point where the timer is almost complete.
I have a quiz application in which the duration of each question is 20 sec. It works fine, but in case, if a user gets a call while playing, I want to pause the application & set it in background.
Does anyone have any idea?
It depends on the implementation of your app but, broadly, your application should stop any running timers, pause the game, pause any sound playback, etc. in the applicationWillResignActive: method.
When the call is finished, your app is invoked again and the applicationDidBecomeActive: method is called. You should resume timers, sound playback, etc. from that method. If it's a game, you should not resume it automatically; keep it paused and wait for the user to resume it manually to comply with Apple's UX guidelines.
When a call comes in, your application is suspended.
And you'll know this is happening because your "UIApplicationDelegate" will get a message of "applicationWillResignActive:". When it comes back, you can start up where you left off or you can bring up a new question or whatever you want to do, it's up to how you decide to implement your quiz app.
When user gets a phone call in iphone application automatically goes into applicationDidEnterBackground state.for example if you are working on radio app then radio automatically get off when user get any call after call ended application comes into below method(appDelegate.m)
(void)applicationWillResignActive:(UIApplication *)application
{
// Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
// Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
}
When press the lock button in app,system will call :
-(void) applicationWillResignActive:(UIApplication *)application and
-(void) applicationDidEnterBackground:(UIApplication *)application
So how can I do to make my app only resignActive but not enter background,and I can run my timer when screen locked(Timer can't execute in background mode).
One method is set the property "Application does not run in background" in .plist to YES,it worked, but my app can never enter background again,however I want it will enter background when press the home button.
Update: I want to play some music in my app at a certain time,just like a music alarm,and I still want it works fine when the screen locked,because keep the screen on may waste a lot of battery,and I don't need to do any thing when user press the home button and exit my app.
Open your Info.plist file and add Application does not run in background. Set value to YES.
Application must have special privileges to do any processing in background such as Audio service/Voip service/Location service.
"I can run my timer when screen locked(Timer can't execute in background mode)"
you cannot run a timer in background which will keep running without using any tentrum and doing so...apple will not accept your application on appstore - that's the worst side if you are targeting appstore...
You can not prevent your app from entering the background. This is decided by the operating system (iOS) and is out of control from applications. However, from reading your updated question, I don't think this is what you need to do.
You can execute background tasks with [UIApplication beginBackgroundTaskWithExpirationHandler;] (see reference). If you want to have something happening after a certain interval, check out [UIApplication scheduleLocalNotification:].
Some services such as VOIP, Audio and CoreLocation are allowed to run in background. Using these for other than their intended purposes (for example, playing silent audio) may risk your app being rejected.
Note that there is nothing you can do to prevent your application from entering the background. It is just that some tasks are allowed to execute in the background. Because of this, you cannot do GUI operations and NSTimers will probably not fire (at least I know some cases where they don't).
It would help knowing what you want to run in the background in order to suggest a solution.
Unless you are playing audio BEFORE the move to background you cannot start audio playback when the app is moved to the background or the screen is locked (which has some weird specifics) suffice to say, its as if you were in the background without actually receiving the applicationDidEnterBackground notification.
The best you can do is schedule a local notification, but in this case your music is limited to 30 seconds and must be part of your application bundle.
I have an alarm clock app which works on a timer. When the alarm is meant to go off and the screen is switched off, it should start playing audio from AVAudioPlayer, but it doesn't. Then when i turn the screen back on, i can see that the rest of the code fired as expected (a stop button is now on the screen). How do i get the AVAudioPlayer to play when the screen is turned off?
Is there any way for me to detect that the screen is turned off?
#zoul is correct that using the default audio session category will result in sound form your app being disabled when the user locks the screen. See the Audio Session Programming Guide for direction on which audio session category you should choose.
However, even once your audio session category is set correctly, you'll have another issue to tackle. When the screen is switched off, your application gets suspended per Apple's documentation here: Executing Code in the Background. This means that when the user locks their phone or switches to a different app, your app will stop running and stay in a freeze-dried (task-suspended) state until the user activates your app again. At that point, your app resumes execution as if nothing happened. That's why it appears that your app has continued to function when you unlock the screen.
For alarm behavior, you'll probably want to schedule the delivery of a local notification. A local notification will ensure that the system provides your alert to the user at the time you request, and allows the user to activate your app. See Scheduling the Delivery of Local Notifications for details on how to accomplish this.
Maybe you have the wrong audio category? See the documentation for AVAudioSession, especially the audio category settings.
I am developing an iphone app which uses background audio (on an infinite loop) to continue playing after the app has entered the background.
My problem is I want to implement a "sleep timer" which stops playback after a specified period of time.
Is this possible? I have spent an hour looking for a method to do this with no avail.
EDIT: My current thought is to use a lower level API, the Audio Queue Services, and manually re-fill the queue with another instance of the loop during the AudioQueueOutputCallback. If the timer has expired I do not fill the loop. I'm assuming this should work since the documentation says audio callbacks are still fired when an app is playing multitasking background audio. Can anyone think of a better way or a reason why this wouldn't work?
While you queue sound data on the background your app remains fully functional and running as if it was in the foreground (well almost), so yes, you should just write a timer that stops the playback at a given time and it will be fired as expected.
Now to the second question: once you stop queueing things up, your app will be "frozen" until the user manually brings it to the foreground... So what you should do is start queueing audio data from the second file before the first one is done playing, and if you DO need to pause or stop, maybe a solution is to play 0 bytes (silence)?
I'm not actually sure this would be allowed in the App Store. An app is not allowed to execute at all in the background, with the exception of VoIP apps and push notifications.