I've read several posts on creating a timer that runs in the background. Is it possible to create a scheduled timer that will continue to run once the app has been suspended/terminated?
Apple's own timer achieves this, but it's not clear how. I am guessing they send a local notification for the timer expiry, and maybe they undertake a date object comparison if the app is brought to the foreground while still in the countdown period. Is this a correct assumption? Any pointers would be helpful.
In short, what you're looking to do is not possible - since the amount of time your app is allowed to run in the background is limited to ~3 minutes. Look at this answer for more details.
You could achieve your goal through the use of a push notification, but that would require a server and won't guarantee it is received at the perfect time.
You might also want to look at this question
It also appears based on this answer that you cannot set a timer in the standard clock app either.
TLDR - You can't create a timer app.
Related
I'm trying to add an in-background alarm clock feature to an app I'm developing.
I have read up on the UILocalNotification object and its use, and am aware that it is limited to 30 seconds of audio.
I was thinking of scheduling multiple notifications (say, 5 of them) spaced 30 seconds apart to mimic continuous play, but the problem with this approach is that if the user hits Close, I won't be able to cancel any of the subsequent notifications.
As far as I know, it is impossible to remove or hide the Close button without hiding the notification entirely (i.e., setting the alertBody property to Nil).
So, I thought I might use the repeatInterval property to cause the notification to pop up every 30 seconds, but it seems that I can only set the interval to one minute or one second, and nothing in between.
The feature is meant to allow the user to choose between music and beeps for alarm audio; it seems I may have found a way to do the beeps - setting the repeatInterval to one second, create a second's worth of beeps (which would need to be timed to cleanly repeat) and use that as the notification sound.
However, for the music, this approach limits me to playing 30 seconds of audio, followed by a 30-second gap, followed by 30 seconds of audio, and so on.
I know that there is no straightforward solution here, from my reading of other posts and resources; no third-party app has access to the same functionality as the built-in alarm clock. I am hoping that someone has found a workaround or thinks of something really clever.
UPDATE: I have found that the repeatInterval doesn't help me in this case, as I can't cancel the repetitions without launching the app.
For the time being I have decided not to use a notification as an alarm per se, but have changed the feature to be a reminder (more along the lines of what the notification is intended for).
If I come up with a way to implement user-friendly, reliable alarm functionality to an app, I will update this post.
I am afraid you cannot accomplish this..reason being as you stated the 'Close' button. You won't be getting any call back in the app if Close button is tapped. Further even if you present notifications every 30 seconds, then there will be multiple notifications on the screen which user has to view or close. So the user experience will be crappy. I would recommended making it clear to the users that they can not set alarm with a custom sound more than 30 seconds.
I'm working on an alarm/reminder application and want to show a custom alarm view when specified time is reached.
From what I understand, there are various (real and hypothetic) ways of doing it:
UILocalNotification. It would be perfect, but alert customization features are insufficient, e.g. I can't show a custom alert view, I can't play a sound for more than 30sec etc.
Keep application in the background and use NSTimer or other means to schedule execution after some time. Most likely won't work as the app may be killed any time.
Start my app at specified time to receive the notification. As far as I know it's not allowed at all.
After spending several days searching for a solution, I would give up and stick with UILocalNotification, but I DO know an app that shows custom alert view at specific time AND is available in AppStore. The app is named "Alarmed" and from what it looks like (last app view shown on alarm time before an actual alert; alarm still triggers even after the device is restarted) they found a way to start their app at specific time and still pass Apple's review.
Any ideas how this can be done?
Thanks.
It's not possible to show notifications other than what UILocalNotification offers you, unless the app is running in the foreground. (I just tried to install "Alarmed" and it uses a regular UILocalNotification like you'd expect).
Is it possible to have an App (running iOS4 on hardware supporting multi-tasking) which starts on iPhone startup and then regularly checks for online updates (every 15 minutes) and then refresh the badge, so the user can see how many unread items there are with-out having a push-server?
I was hoping this would be possible with iOS4 Programming Guide seems to suggest it is only possible to to this regarding Locations tracking, VoIP and playing background audio. There is also the possibility to do local-push notifications, but I don't see to find how to trigger a specific function that way.
Thanks in advance for any help!
edit:
Just having read a bit more, if the application is in the background/inactive state, and I son want to update the badge-number without displaying a message, is there an action triggered like didReceiveLocalNotification? There must be a way to schedule something on a regular basis (like email checking) without having to implement a full server-push-nitification system!
Is it possible to have an App ... which starts on iPhone startup and then regularly checks for online updates (every 15 minutes) and then refresh the badge
As you already figured out, the answer is no.
Let me rephrase to make it clearer:
How can I have an "alarm" go off 20 minutes after my app has gone in the background?
Old question:
How can you have the simplest tast happen after 5-10-60 minutes on iOS? Essentially, have an NSTimer fire after a predefined interval.
I do "begin task", sleep( for some time ); and then "end task". However my app usually gets killed if I sleep for more than 5 minutes. I've seen posts around that mention that apps can stay alive in the background for a few hours, how exactly can that be achieved?
When your app goes to the background, the system will try to recollect as many as resources as you can give it to him like Images, nibs, etc. You have a notification for this. (– applicationDidEnterBackground:, etc)
After that, it will "sort" all the background living apps according the resources usage order. The app that uses more resources comes first.
Then when a new app comes to the foreground if the systems thinks it needs more resources than it currently has it will start killing background apps. using the above sorted list.
This means that the less resources you use in the background, the longer your app will live. BUT, there is no guarantee it will live long. (Everything depends on user usage). There is also no notification when it gets killed!, so you cannot assume your app will live for 60 min.
You probably want to read this Apple doc on how to do something in the background (with some time restrictions, off-course) and probably also UIApplicationDelegate class reference.
Hope it helps ;)
Just use a local notification
Was reading through the iOS4 documentation for multitasking, and couldn't figure it out.
I basically need to update the badge count on my app's icon after midnight each day as long as the app is running in suspended mode (with multitasking).
I know this has to be possible, just can't figure out the best way to do it.
Thanks.
iOS "multitasking" is very specific. There's an important distinction between states here:
Suspended: Your app resides in memory, but does not receive any execution time. This is really only useful for fast app switching.
Background: In a few particular cases, you can request that the OS to run your app in the background. (Playing audio, location, finishing a long task, voip.)
So, the short answer to your question is, "you can't."
Here are a couple useful links on iOS multitasking, such as it is.
Understand an Application's States and Transitions
Executing Code in the Background
You could use a UILocalNotification to set the badge (without an alert) but you can't increment the badge because you're app does not have the opportunity to execute any code when the notification fires.
You can schedule up to 64 notifications in advance, one at midnight for the next 64 days, each one setting a new badge number. It would make a lot more sense to schedule a repeating notification but since your app can't execute code it can't increment the badge number that doesn't work.