How to create a app where that app services always runs in background even if the app is closed in Xamarin (Android)? - xamarin

Question

I am creating an application in Xamarin using visual studio,where that app services always should be running in background even if the app is closed and that service should send notification in a interval.
If that app is closed by the system(in the condition when it is taking more memory space) then it should restart the services by showing the status as "0 process and 0 service Restarting.." under running services list in Settings.
Can anyone help me how to achieve that having some reference of sample project.
In BackgroundService.cs
[Service]
public class BackgroundService : Service
{
const int SERVICE_RUNNING_NOTIFICATION_ID = 123;
const string NOTIFICATION_CHANNEL_ID = "com.company.app.channel";
public override StartCommandResult OnStartCommand(Intent intent, StartCommandFlags flags, int startId)
{
Log.Debug("service", "Service Started");
// Check if device is running Android 8.0 or higher and call StartForeground() if so
if (Build.VERSION.SdkInt >= BuildVersionCodes.O)
{
var notification = new NotificationCompat.Builder(this, NOTIFICATION_CHANNEL_ID)
.SetContentTitle(Resources.GetString(Resource.String.app_name))
.SetContentText(Resources.GetString(Resource.String.notification_text))
.SetSmallIcon(Resource.Drawable.notification_icon_background)
.SetOngoing(true)
.Build();
var notificationManager =
GetSystemService(NotificationService) as NotificationManager;
var chan = new NotificationChannel(NOTIFICATION_CHANNEL_ID, "On-going Notification", NotificationImportance.Min);
notificationManager.CreateNotificationChannel(chan);
StartForeground(SERVICE_RUNNING_NOTIFICATION_ID, notification);
}
return StartCommandResult.NotSticky;
}
public override IBinder OnBind(Intent intent)
{
return null;
}
public override void OnTaskRemoved(Intent rootIntent)
{
Intent restartServiceIntent = new Intent(this, this.Class);
restartServiceIntent.SetPackage(this.PackageName);
Log.Debug("service", "Service Restarted");
PendingIntent restartServicePendingIntent = PendingIntent.GetService(this, 1, restartServiceIntent, PendingIntentFlags.OneShot);
AlarmManager alarmService = (AlarmManager)this.GetSystemService(Context.AlarmService);
alarmService.Set(
AlarmType.ElapsedRealtime,
SystemClock.ElapsedRealtime() + 1000,
restartServicePendingIntent);
base.OnTaskRemoved(rootIntent);
}
}
Updtaed MainActivity.cs
public class MainActivity : AppCompatActivity
{
String alarm = Android.Content.Context.AlarmService;
const string NOTIFICATION_CHANNEL_ID = "com.companyname.ServiceSample3";
protected override void OnCreate(Bundle savedInstanceState)
{
base.OnCreate(savedInstanceState);
SetContentView(Resource.Layout.abc_activity_chooser_view);
Android.Support.V7.Widget.Toolbar toolbar = FindViewById<Android.Support.V7.Widget.Toolbar>(Resource.Id.toolbar);
SetSupportActionBar(toolbar);
//var alarmIntent = new Intent(this, typeof(AlarmReceiver));
//alarmIntent.PutExtra("title", "Hello");
//alarmIntent.PutExtra("message", "World!");
Intent intent = new Intent(NOTIFICATION_CHANNEL_ID);
intent.SetClass(this, typeof(AlarmReceiver));
var pending = PendingIntent.GetBroadcast(this, 0, intent, PendingIntentFlags.UpdateCurrent);
var alarmManager = GetSystemService(AlarmService).JavaCast<AlarmManager>();
alarmManager.SetRepeating(AlarmType.ElapsedRealtime, DateTime.Now.Millisecond, 5 * 100, pending);
}
}
Thanks in advance.

Answer 1

Please refer the below sample.You can use alarm manager for restarting the service.
Please follow the steps.
Step 1 :
Create BroadcastReceiver
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Android.App;
using Android.Content;
using Android.OS;
using Android.Runtime;
using Android.Views;
using Android.Widget;
namespace AlarmManagerApp
{
[BroadcastReceiver(Enabled = true)]
[IntentFilter(new[] { Android.Content.Intent.ActionBootCompleted })]
class AlarmReceiver : BroadcastReceiver
{
Context context;
public override void OnReceive(Context context, Intent intent)
{
this.context = context;
Toast.MakeText(context,"Recieved",ToastLength.Long).Show();
Intent background = new Intent(context, typeof(BackgroundService));
context.StartService(background);
}
}
}
Step 2: Add AlarmManager in the MainActivity where you want to call the service
namespace AlarmManagerApp
{
[Activity(Label = "#string/app_name", Theme = "#style/AppTheme.NoActionBar", MainLauncher = true)]
public class MainActivity : AppCompatActivity
{
String alarm = Context.AlarmService;
protected override void OnCreate(Bundle savedInstanceState)
{
base.OnCreate(savedInstanceState);
SetContentView(Resource.Layout.activity_main);
Android.Support.V7.Widget.Toolbar toolbar = FindViewById<Android.Support.V7.Widget.Toolbar>(Resource.Id.toolbar);
SetSupportActionBar(toolbar);
var alarmIntent = new Intent(this, typeof(AlarmReceiver));
alarmIntent.PutExtra("title", "Hello");
alarmIntent.PutExtra("message", "World!");
var pending = PendingIntent.GetBroadcast(this, 0, alarmIntent, PendingIntentFlags.UpdateCurrent);
var alarmManager = GetSystemService(AlarmService).JavaCast<AlarmManager>();
alarmManager.SetRepeating(AlarmType.ElapsedRealtime,DateTime.Now.Millisecond, 5 * 100, pending);
}
}
Step 3: Add you Service
namespace AlarmManagerApp
{
[Service]
public class BackgroundService : Service
{
public override void OnCreate()
{
base.OnCreate();
}
public override StartCommandResult OnStartCommand(Intent intent, StartCommandFlags flags, int startId)
{
Log.Debug("service","Service Started");
//init the handler in oncreate
System.Timers.Timer Timer1 = new System.Timers.Timer();
Timer1.Start();
Timer1.Interval = 3000;
int a = 0;
Timer1.Enabled = true;
//Timer1.Elapsed += OnTimedEvent;
Timer1.Elapsed += (object sender, System.Timers.ElapsedEventArgs e) =>
{
Timer1.Stop();
Timer1.Start();
a++;
//Delete time since it will no longer be used.
Timer1.Dispose();
};
Timer1.Start();
return StartCommandResult.Sticky;
}
public override IBinder OnBind(Intent intent)
{
return null;
}
public override void OnTaskRemoved(Intent rootIntent)
{
Intent restartServiceIntent = new Intent(this, this.Class);
restartServiceIntent.SetPackage(this.PackageName);
Log.Debug("service", "Service Restarted");
PendingIntent restartServicePendingIntent = PendingIntent.GetService(this, 1, restartServiceIntent, PendingIntentFlags.OneShot);
AlarmManager alarmService = (AlarmManager)this.GetSystemService(Context.AlarmService);
alarmService.SetRepeating(AlarmType.RtcWakeup, SystemClock.CurrentThreadTimeMillis(), 30 * 1000, restartServicePendingIntent);
NotificationManager notificationManager =
(NotificationManager)GetSystemService(NotificationService);
Notification.Builder builder = new Notification.Builder(this);
Intent notificationIntent = new Intent(this, typeof(MainActivity));
PendingIntent contentIntent = PendingIntent.GetActivity(this, 0, notificationIntent, 0);
//set
builder.SetContentIntent(contentIntent);
builder.SetSmallIcon(Resource.Mipmap.ic_launcher);
builder.SetContentText("Contents");
builder.SetContentTitle("title");
builder.SetAutoCancel(true);
builder.SetDefaults(NotificationDefaults.All);
notificationManager.Notify(1, builder.Build());
base.OnTaskRemoved(rootIntent);
}
}
}
This works also if app is closed and device restarted.