I have developed two applications and they are both using a background agent. When I turned on Airplane Mode last night, and woke up tomorrow I saw (Settings > Background Tasks) that 1 Background Task was running fine, and the other was not.
The one that was disabled gets data from a Weather API, and the other just generates random tiles (no internet connection).
When I opened the app, and went back to the Background Tasks it enabled itself.
What is going on here? I know that a background task will disable itself when the app is not used for 14(?) days, but this is not the case. And of course I know that the background task won't run when the phone is in Airplane Mode.
So, how can I enable my app to turn itself on again when the Airplane Mode is turned off? Just like my other (offline) app does.
Kind regards,
Niels
It probably means that your background task doesn't handle graciously no-connectivity errors. When your background agent fails two times in a row, it's automatically disabled by the OS.
Just put your network call in a try/catch block to solve the issue.
Related
In our app users can track and submit journeys they have recorded. I need a simple way of creating a task in iOS. I have already created and tested this on Android. It works via:
The user selects the journeys they would like to submit.
Taps sync and a foreground service is created that syncs the journeys to our API.
This service will continue to sync journeys even if the app is put into the background or even closed.
So in short how can i achieve this on iOS 9-13?
I have already tried creating a background-safe tasks using:
nint taskID = UIApplication.SharedApplication.BeginBackgroundTask( () => {});
However, this only gives the task 2 mins to run which isn't enough. I have looked into the NSURlSessions but they require URls, whereas we are using our own API wrapper.
I would simply like a way of creating a task when the user taps 'sync' and this task also being capable to run in the background. I am not too bothered if the task is cancelled when the app is closed, although if possible would like the task to continue.
Thanks.
This service will continue to sync journeys even if the app is put
into the background or even closed.
First, if your app is closed in iOS, I'm sure do can't run any service in background.
Then if your app is put into background, Apple has strict limit to allow apps running in the background. background-tasks has time limits, you can read the document about more information. There is a section about handling-background-task-time-limits which you can have a try.
Also, Apple allows some specific apps to run in background which have to perform tasks in the background. For example, app that needs to play music in background, update location in background and etc. You can see the Application Registration Categories here. If your app meets the requirement there, you can apply for a background running permission from system.
Refer: Backgrounding in Xamarin.iOS
I would advise you to leverage on Shiny to achieve it.
PerformFetch is the closest thing to what you ask for, it will run in the background and update your app when iOS thinks it is needed (it predicts that according to the previous behavior the user will soon open your app and that the new content is available).
The only alternative is to send the push notification when you want the app to be updated.
That's about it, I understand your wish but it is just that - a wish and not something that can be real.
I'm new to the UWP, and I'm facing right now an issue where I want to continue an operation that the app was doing before getting into suspended or terminated state.
I've read about Extended execution and background task, but as far as I have understood for extended execution you have only 30 seconds before it gets terminated or it could be revoked before getting into it.
for Background task I should make another project for it ( Windows Runtime Component) and I have to add an entry in the Declarations in the appxmanifest. It sounds that Background task is the only possible way to achieve it, but how to move an operation (Action, Func, or task or whatever) to background task if the app get into those states and what should happen after resume?!
Any ideas from experienced people?
Windows 10 universal Windows platform (UWP) app lifecycle
Before Windows 8, apps had a simple lifecycle. Win32 and .NET apps are either running or not running. Now, there are three app model in UWP app Running in foreground,Running in background and suspended state. You could know more detail through this official document.
Extended execution
There are cases where an app may need to keep running, rather than be suspended, while it is minimized. If an app needs to keep running, either the OS can keep it running, or it can request to keep running.
For this scenario, you need use ExtendedExecution to realize. ExtendedExecution support to start a long running operation in order to defer the Suspending state. And there are some document and code sample introducing this feature.
Background Task
For Background Task, it provide functionality when your app is suspended or not running. You can also use background tasks for real-time communication apps like VOIP, mail, and IM. However, it will trigger under specific conditions. For more please refer this.
You have mentioned out-process Background Task in your case and another Background Task(in process) could also be used in UWP app. It is simpler to implement than out-of-process background tasks.
I have been testing a C# Companion Device Framework application, which unlocks my laptop fine for the most part. However, it doesn't seem to work after I leave my laptop locked for a while.
I used the code from the CDF GitHub sample to fire a toast notification when the background task for my UWP companion app is triggered.
This shows me that there is never an issue when I attempt an unlock shortly after locking the machine. When I lock my machine, I immediately see the toast notification indicating that the background task was triggered. However, if I lock my laptop and leave it for a few minutes, it doesn't appear that the background task gets triggered again, even though I wake up the screen and press buttons.
I want my CDF app to always be able to unlock my machine. What did I do wrong? Hopefully I don't need it, but is there a workaround like registering a second trigger for the background task to a custom service?
UPDATE: It appears this occurs only if the computer does not go to sleep, which may occur in the case that someone has either set a long time before sleep or has sleep off completely (as I did previously). If the laptop does go to sleep, and has to be woken up with a trackpad click, then the background task seems to fire.
The problem is, Windows UWP stops to fire the event WaitForUserConfirmation after awhile.
At present, we have 2 possible solutions:
user hits the keyboard and the background task catches the event CollectingCredential and invokes the companion device authentication
once the background task is running, it loops until the event CredentialAuthenticated, and it runs the companion device authentication periodically.
I have a UWP app that needs to check for new data (from network) every x seconds. I do this by starting a new async thread. The app can be minimized or even navigated from in Windows Phone, and this suspends the app.
How do I restore the loop when the user goes back to the app again (it appears to be still open, at the same Page)? This can be done either by re-navigating to the Page in question on relaunch or by restoring the loop. What's the easiest way to do so?
Generally when your app is suspended, if you don't cancel your tasks, the OS will do it. Therefore it's recommended that you will send a suitable signal to your tasks along with saving some progress for resuming operation.
However, in UWP there is something like ExtendedExecution - it should allow your app to run in background up to 10 minutes (as far as I know this is the limit for battery powered devices - not 100% sure about this, and it of course may change on various scenarios).
Nevertheless, I think that checking for changes in few seconds interval may be a bad idea. Maybe you can change the design little and use BackgroundTasks which are designed for background processing.
Most of information about app states you will find at MSDN.
I've posted previously about synchronisation issues with my background scheduled task having to access a SQLite DB and IsolatedStorge that the foreground app uses.
To simplify the process I thought about just preventing my background task from running altogther, it isn't imperative that it runs, especially when the foreground app is active.
Is there a way to do this?
I thought about using IsolatedStorage to set a flag when the app launches then remove it when it exits, then have the background task check the setting, protected by mutex.
I think the idea is fine in principle, but I guess there will be times when the flag isn't unset, for example if the battery dies... Which means potentially, after turning the phone on, if the user never uses the app and exits properly, the background task will never run. This might not be too much of an issue.
Is using some kind of flag like this the only way to achieve such functionality?
Thanks
There is an inter process communication mechanism to achieve this functionality.
As both the foreground app and scheduletask run as different processes, IPC could be used for it.
Please refer to Named Events.
In your OnInvoke Method subscribe for a named event which will be fired by your foreground app as soon as it is launched/resumed.
As soon as you get a signal via this event in background agent, just call NotifyComplete and you are done.