We might have a long-running task that we need to execute when the device starts. This may be needed to set up some service or configuration for other services.
When we want to perform a task when the device starts up, we can start a service when we receive the ActionBootComplete intent action:
- As subscribing to the boot events is a privileged action, we have to request special permission to do so:
[assembly: UsesPermission( Manifest.Permission.ReceiveBootCompleted)]
- Before we can start our task, we need a
Serviceinstance that will perform the actual task:[Service] public class XamarinService : IntentService { protected override void OnHandleIntent(Intent intent) { // some startup task } } - Once we have the service and permission, we need to listen for the boot events using a
BroadcastReceiverinstance:[BroadcastReceiver] [IntentFilter(new []{ Intent.ActionBootCompleted })] public class ServiceStarter : BroadcastReceiver { public override void OnReceive( Context context, Intent intent) { var serviceIntent = new Intent( context, typeof(XamarinService)); context.StartService(serviceIntent); } } - Finally, to prevent the user from having to reboot the device just to start using the app, we manually check whether the service has run when the app is launched:
var intent = new Intent(this, typeof(XamarinService)); StartService(intent);
If we want to perform any task as soon as the device starts up, for example to start a service or to execute a configuration or security task, we need to register a broadcast receiver with the Android OS.
Before we can register for the boot notification, we need to request permission to do so. This is done by requesting the ReceiveBootCompleted permission. Another important aspect to realize is that the app has to be launched manually by the user at least once before the receiver is allowed to receive the intent. Also, if the user force stops the app from the device settings, they will have to relaunch the app before the receiver is registered.
In order to listen for the ActionBootCompleted intent, we need to create a BroadcastReceiver instance that filters the ActionBootCompleted action. As soon as the device has finished booting, it will broadcast the intent and we will be able to perform a task.
As a BroadcastReceiver instance usually executes the OnReceive() method on the UI thread, we need to execute the task on a new thread. However, we cannot use asynchronous tasks in a broadcast receiver, because as soon as the OnReceive() method is returned, the receiver is terminated, and if there are any threads, they will be leaked. Thus, we should use a service with a broadcast receiver.
As the intent is broadcasted when the device is booted, we need to ensure that even if the user does not reboot the device, we still perform the tasks when the user launches the app. For example, if we want to start a service when the device is booted, we have to ensure that if the app is launched without rebooting, we start the service manually.