| Version | Status |
|---|---|
| master |   |
| dev |   |
This plugin can be used for creating background services on Android and iOS.
Creating a real background service on a mobile app is real challenge for new mobile developpers. I struggled many times trying to do it the right way. I think I've come up with a solution that works. Running a background service isn't that hard ok. But what if I want that my service execute a bunch of code periodically ? I mean, strictly periodically. I don't want to wait for the user to unlock the screen or whatever.
On iOS, the solution is quite easy, a loop should do the trick, until the system decide that your service should die. In order to prevent that, you must listen the user location. Of course, if you don't need it in your application, it will be impossible to publish your app on the store. Yeah, my solution isn't magic, sorry.
On Android then, that one was hard, especially with the latest Android releases. I must use an Android Service of course, then use a wakelock for my service and finally use a Handler for scheduling periodic calls precisely.
Anyway, it appears to work, and I use this plugin at work for my developments. So feel free to use it and improve it!
First, your MainActivity.cs must inherit from Plugin.BackgroundService.ActivityWithBackgroundService.
You can override the default behavior of asking for battery optimizations by overriding property ActivityWithBackgroundService.AskForBatteryOptimizations.
e.g:
protected override bool AskForBatteryOptimizations
{
get
{
#if DEBUG
return false;
#else
return true;
#endif
}
}In this case, the application won't ask for battery optimization if running in debug.
Why I need this?
Because by default, all applications are 'optimized' by Android. It means that you will be suspended when the system decide to. In order to prevent that behavior, the user must disable the optimization of the application. If set to true, this boolean leads to showing a popup to the user before redirecting him to the settings for disabling the optimization.
Then, given your default OnCreate method in your MainActivity.cs:
protected override void OnCreate(Bundle bundle)
{
TabLayoutResource = Resource.Layout.Tabbar;
ToolbarResource = Resource.Layout.Toolbar;
base.OnCreate(bundle);
Xamarin.Forms.Forms.Init(this, bundle);
var app = new App(new AndroidInitializer());
LoadApplication(app);
}Add the following line after LoadApplication(app):
var builder = new AndroidBackgroundServiceHostBuilder();
builder
.WithAndroidServiceName("YOUR_SERVICE_NAME")
.WithNotification(
$"{Application.PackageName}.YOUR_SERVICE_NAME",
$"{Application.PackageName}.YOUR_SERVICE_NAME",
NotificationImportance.Low,
NotificationVisibility.Public,
Resource.Drawable.ic_media_play_light, // replace with your own icon. This is mandatory, otherwise the notification is not displayed correctly
"SERVICE NOTIFICATION TITLE",
"SERVICE NOTIFICATION CONTENT")
.WithAppContext(this)
.WithIntentLaunchType<MainActivity>()
.WithPeriodicBackgroundService(new APeriodicService, TimeSpan.FromSeconds(X))
.WithBackgroundService(new ARegularService());
NativeBackgroundServiceHost.Init(builder);Ok, that's it for Android. Now, you have a persistent background service. You can kill your app, it will remains in background.
First, your AppDelegate must inherit from AppDelegateWithBackgroundService.
In FinishedLaunching method, add the following line BEFORE base.FinishedLaunching(app, options) call:
var builder = new iOSBackgroundServiceHostBuilder();
builder
.WithPeriodicBackgroundService(new APeriodicService(), TimeSpan.FromSeconds(X))
.WithBackgroundService(new ARegularService());
NativeBackgroundServiceHost.Init(builder);In order to keep the app running, your app must be declared as supporting background tasks.
Annnnd you're done. Unlike Android, the background service can run only if you are listening geolocation for example, and while you're listening to it. If you kill the app, the background service will be stopped too.
Please note that all your IService classes MUST NOT use any form of dependency injection, or at least, not the same as your application. The background service and your application do not have the same life cycle and you may have some mixed up references between your background service and your app if you use the same IoC.
I found a solution for Prism. Take a look at BackgroundServiceBase.cs and AliveService.cs for a hint.
In order to start the background service:
CrossBackgroundService.Current.StartService();For stopping it:
CrossBackgroundService.Current.StopService();Subscribe to background service state:
var subscription = CrossBackgroundService.Current
.WhenBackgroundServiceStateChange
.Subscribe(isRunning => Console.WriteLine(isRunning));
// DO NOT FORGET TO DISPOSE YOUR SUBSCRIPTIONS
subscription.Dispose();Getting background service state:
CrossBackgroundService.Current.IsRunningUpdating the text content of the service notification (Only on Android):
CrossBackgroundService.Current.UpdateNotificationMessage("my new text");IServicehas a new property to implement:string Name { get; }. This property is mainly used on Android for thread naming and logging.IPeriodicService.PeriodicActionAsync()supports cancellation nowIBackgroundServiceexpose a new reactive property to observe background running state:IObservable<bool> BackgroundServiceStateChange { get; }
You used to have this:
Add the following line after LoadApplication(app):
NativeBackgroundServiceHost.Init(
"YOUR_SERVICE_NAME",
$"{Application.PackageName}.YOUR_SERVICE_NAME",
"Your display service name",
Resource.Drawable.ic_media_play_light, // replace with your own icon. This is mandatory, otherwise the notification is not displayed correctly
"SERVICE NOTIFICATION TITLE",
"SERVICE NOTIFICATION CONTENT",
() => new BackgroundServiceHost(list =>
{
list.Add(AServiceYouWantToKeepBackground); // Should inherit from IService or IPeriodicService
}, TimeSpan.FromSeconds(5)), // For periodic services, you can set the interval between calls
typeof(MainActivity));Now replace with:
var builder = new AndroidBackgroundServiceHostBuilder();
builder
.WithAndroidServiceName("YOUR_SERVICE_NAME")
.WithNotification(
$"{Application.PackageName}.YOUR_SERVICE_NAME",
$"{Application.PackageName}.YOUR_SERVICE_NAME",
NotificationImportance.Low,
Resource.Drawable.ic_media_play_light, // replace with your own icon. This is mandatory, otherwise the notification is not displayed correctly
"SERVICE NOTIFICATION TITLE",
"SERVICE NOTIFICATION CONTENT")
.WithAppContext(this)
.WithIntentLaunchType<MainActivity>()
.WithPeriodicBackgroundService(new APeriodicService, TimeSpan.FromSeconds(X))
.WithBackgroundService(new ARegularService());
NativeBackgroundServiceHost.Init(builder);You used to have this:
NativeBackgroundServiceHost.Init(() => new BackgroundServiceHost(list =>
{
list.Add(AServiceYouWantToKeepBackground); // Should inherit from IService or IPeriodicService
... etc
},
TimeSpan.FromSeconds(5)) // For periodic services, you can set the interval between calls
);Now you have to do this:
var builder = new iOSBackgroundServiceHostBuilder();
builder
.WithPeriodicBackgroundService(new APeriodicService(), TimeSpan.FromSeconds(X))
.WithBackgroundService(new ARegularService());
NativeBackgroundServiceHost.Init(builder);