You have to start a service in your Application class to run it always.
If you do that, your service will be always running. Even though user terminates your app from task manager or force stop your app, it will start running again.
Create a service:
public class YourService extends Service {
@Nullable
@Override
public IBinder onBind(Intent intent) {
return null;
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
// do your jobs here
return super.onStartCommand(intent, flags, startId);
}
}
Create an Application class and start your service:
public class App extends Application {
@Override
public void onCreate() {
super.onCreate();
startService(new Intent(this, YourService.class));
}
}
Add "name" attribute into the "application" tag of your AndroidManifest.xml
android:name=".App"
Also, don't forget to add your service in the "application" tag of your AndroidManifest.xml
<service android:name=".YourService"/>
And also this permission request in the "manifest" tag (if API level 28 or higher):
<uses-permission android:name="android.permission.FOREGROUND_SERVICE"/>
UPDATE
After Android Oreo, Google introduced some background limitations. Therefore, this solution above won't work probably. When a user kills your app from task manager, Android System will kill your service as well. If you want to run a service which is always alive in the background. You have to run a foreground service with showing an ongoing notification. So, edit your service like below.
public class YourService extends Service {
private static final int NOTIF_ID = 1;
private static final String NOTIF_CHANNEL_ID = "Channel_Id";
@Nullable
@Override
public IBinder onBind(Intent intent) {
return null;
}
@Override
public int onStartCommand(Intent intent, int flags, int startId){
// do your jobs here
startForeground();
return super.onStartCommand(intent, flags, startId);
}
private void startForeground() {
Intent notificationIntent = new Intent(this, MainActivity.class);
PendingIntent pendingIntent = PendingIntent.getActivity(this, 0,
notificationIntent, 0);
startForeground(NOTIF_ID, new NotificationCompat.Builder(this,
NOTIF_CHANNEL_ID) // don't forget create a notification channel first
.setOngoing(true)
.setSmallIcon(R.drawable.ic_notification)
.setContentTitle(getString(R.string.app_name))
.setContentText("Service is running background")
.setContentIntent(pendingIntent)
.build());
}
}
EDIT: RESTRICTED OEMS
Unfortunately, some OEMs (Xiaomi, OnePlus, Samsung, Huawei etc.) restrict background operations due to provide longer battery life. There is no proper solution for these OEMs. Users need to allow some special permissions that are specific for OEMs or they need to add your app into whitelisted app list by device settings. You can find more detail information from https://dontkillmyapp.com/.
If background operations are an obligation for you, you need to explain it to your users why your feature is not working and how they can enable your feature by allowing those permissions. I suggest you to use AutoStarter library (https://github.com/judemanutd/AutoStarter) in order to redirect your users regarding permissions page easily from your app.
By the way, if you need to run some periodic work instead of having continuous background job. You better take a look WorkManager (https://developer.android.com/topic/libraries/architecture/workmanager)
