Develop Reference

How to run a Jobscheduler or a Service every minute wihout stopping?

I'm doing an Android app that requires sending its location frequently, every 1 minute or 2 minutes at the most. For this, I use a JobSchedulerService. I've already managed to make it run more than once every 15 minutes on devices with Android N version by replacing the .setPeriodic() with a .setMinimumLatency(). The fact is that at the beginning it is executed periodically in the established time, but after a while it runs every 7 or 9 minutes approximately.
I have already included the application in the battery saving white list, but didn't work. Is there any way to execute it or a similar service every minute with no restrictions? Doesn't matter how much battery the app spends.
EDIT:
This is what I've tried:
ReceiverService:
public class ReceiverService extends WakefulBroadcastReceiver {
#Override
public void onReceive(Context ctx, Intent intent) {
if (intent.getAction().equals(Intent.ACTION_BOOT_COMPLETED)) {
if (!isMyServiceRunning(ServiceBackground.class, ctx))
startWakefulService(ctx, new Intent(ctx, ServiceBackground.class));
new ServiceAlarmManager(ctx).register();
}
}
private boolean isMyServiceRunning(Class<?> serviceClass,Context context) {
ActivityManager manager = (ActivityManager)context. getSystemService(Context.ACTIVITY_SERVICE);
for (ActivityManager.RunningServiceInfo service : manager.getRunningServices(Integer.MAX_VALUE)) {
if (serviceClass.getName().equals(service.service.getClassName())) {
Log.i("Service already","running");
return true;
}
}
Log.i("Service not","running");
return false;
}
}
The ServiceAlarmManager is exactly the same as #madking said.

You can put your code that sends location in a Service and implement an AlarmManager that periodically checks if your Service is running and restarts it if the Service has been killed by OS. You'll have to implement the AlarmManager using a WakefulBroadcastReceiver.
ReceiverService.java
public class ReceiverService extends WakefulBroadcastReceiver {
#Override
public void onReceive(Context ctx, Intent intent) {
if (!YourService.isRunning()) {
startWakefulService(ctx, new Intent(ctx, YourService.class));
}
new ServiceAlarmManager(ctx).register();
}
}
ServiceAlarmManager.java
public class ServiceAlarmManager {
private Context ctx;
private static final int TIME_INTERVAL = 300 * 1000;
public ServiceAlarmManager(Context context) {
ctx = context;
}
public void register() {
Intent serviceRestarter = new Intent();
serviceRestarter.setAction("someString");
PendingIntent pendingIntentServiceRestarter = PendingIntent.getBroadcast(ctx, 0, serviceRestarter, 0);
AlarmManager alarmManager = (AlarmManager) ctx.getSystemService(ctx.ALARM_SERVICE);
Date now = new Date();
alarmManager.setExactAndAllowWhileIdle(AlarmManager.RTC_WAKEUP, now.getTime() + TIME_INTERVAL, pendingIntentServiceRestarter);
}
}
Also register your BroadcastReceiver in your Manifest.xml file
<receiver android:name=".ReceiverService">
<intent-filter>
<action android:name="someString" />
</intent-filter>
</receiver>
The register() method does two things.
1- Issues a broadcast which is caught by WakefulBroadcastReceiver and restarts the Service if required
2- Sets the next alarm to be invoked to check if the Service has been killed.
This way the service keeps running even if the OS kills it and you'll be able to send location updates periodically.
Note: Though this practice is not recommended as your application will use more battery but you don't seem to care about it as I did not either as some business requirements don't leave us a choice.

I tried this and it works: in the onCreate() of your activity you schedule an Alarm for every minute (setAlarm). Everytime the alarm is triggered, WakefulBroadcastReceiver is called, and that's where we launch our service(s):
private static long INTERVAL_ALARM = 1 * 60 * 1000;
public static void setAlarm(Context context) {
long current_time = Calendar.getInstance().getTimeInMillis();
Intent myAlarm = new Intent(context.getApplicationContext(), AlarmReceiver.class);
PendingIntent recurringAlarm = PendingIntent.getBroadcast(context.getApplicationContext(), 0, myAlarm, PendingIntent.FLAG_CANCEL_CURRENT);
AlarmManager alarms = (AlarmManager) context.getApplicationContext().getSystemService(Context.ALARM_SERVICE);
alarms.setRepeating(AlarmManager.RTC_WAKEUP, current_time, INTERVAL_ALARM, recurringAlarm);
}
And in the receiver:
public class AlarmReceiver extends WakefulBroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent) {
Intent myService = new Intent(context, MyService.class);
context.startService(myService);
}
}
In your service, you should stopSeflf() in the end of your treatment.
Don't forget to register your BroadcastReceiver in your Manifest.xml file
NB: WakefulBroadcastReceiver is deprecated in API level 26.1.0. JobSchedulerService does the work

Cannot keep android service alive after app is closed

I am trying to spawn a service that stays alive all the time, even if the user closes the application. According to these threads
Keep location service alive when the app is closed
Android Service Stops When App Is Closed
Android: keep Service running when app is killed
this can be accomplished with IntentServices or Service.START_STICKY
Yet, I tried both types of services without success. In other words, my services get killed when the app is closed by the user. Can someone point out if this is can be done and how? Here is what I have tried without success:
With IntentService:
public class MyIntentService extends IntentService {
private final int mPollingTimeMS = 500;
private int mInitializationPollingCount = 0;
private Thread mPollThread;
public MyIntentService() {
super("MyIntentService");
}
#Override
protected void onHandleIntent(Intent intent) {
mPollThread = new Thread() {
public void run() {
while (true) {
try {
Log.e(Constants.Engine.LOGGER_TAG_DEV,
"SDK Service Running: " +
mInitializationPollingCount * mPollingTimeMS +
"ms have elapsed");
mInitializationPollingCount++;
sleep(mPollingTimeMS);
} catch (Exception e) {
StackTraceElement trace = new Exception().getStackTrace()[0];
Logger.e(Constants.Engine.LOGGER_TAG_APP, "[Exception:" + e.toString() + "]" +
trace.getClassName() + "->" + trace.getMethodName() + ":" + trace.getLineNumber());
}
}
}
};
mPollThread.start();
}
}
and with Services:
public class MyService extends Service {
public MyService() {
}
private final int mPollingTimeMS = 500;
private int mInitializationPollingCount = 0;
private Thread mPollThread;
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
mPollThread = new Thread() {
public void run() {
while (true) {
try {
Log.e(Constants.Engine.LOGGER_TAG_DEV,
"SDK Service Running: " +
mInitializationPollingCount * mPollingTimeMS +
"ms have elapsed");
mInitializationPollingCount++;
sleep(mPollingTimeMS);
} catch (Exception e) {
StackTraceElement trace = new Exception().getStackTrace()[0];
Logger.e(Constants.Engine.LOGGER_TAG_APP, "[Exception:" + e.toString() + "]" +
trace.getClassName() + "->" + trace.getMethodName() + ":" + trace.getLineNumber());
}
}
}
};
mPollThread.start();
return Service.START_STICKY;
}
#Override
public IBinder onBind(Intent intent) {
// I tried to return null here, but this
// service gets killed no matter what.
return null;
}
}
and here is the manifest:
<service
android:name=".mycompany.MyService"
android:enabled="true"
android:exported="true"
android:process=":process1">
</service>
<service
android:name=".mycompany.MyIntentService"
android:process=":process2"
android:exported="false">
</service>
I shall added that I am closing the test app not with a close button, but using the Android OS app manager. See picture below
Lastly, the driver activity (not much there)
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Intent intent1 = new Intent(getBaseContext(), MyService.class);
startService(intent1);
Intent intent2 = new Intent(getBaseContext(), MyIntentService.class);
startService(intent2);
}
}
I also try to add a notification and make it a foreground service but still the same thing. The moment I close the app, everything gets killed. This is what I added:
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
showNotification();
...etc..
private void showNotification() {
Intent notificationIntent = new Intent(this, MainActivity.class);
notificationIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
PendingIntent pendingIntent = PendingIntent.getActivity(this, 0,
notificationIntent, 0);
int iconId = R.mipmap.ic_launcher;
int uniqueCode = new Random().nextInt(Integer.MAX_VALUE);
Notification notification = new NotificationCompat.Builder(this)
.setSmallIcon(iconId)
.setContentText("Context Text")
.setContentIntent(pendingIntent).build();
startForeground(uniqueCode, notification);
}

Here is an example of foreground service that I use and that works, it remains active when the app is closed. Of course, it also must be started, and for that task the app must be running at a first glance, or a receiver of a boot event must be set, but this is another story.
public class MyService extends Service {
static final int NOTIFICATION_ID = 543;
public static boolean isServiceRunning = false;
#Override
public void onCreate() {
super.onCreate();
startServiceWithNotification();
}
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
if (intent != null && intent.getAction().equals(C.ACTION_START_SERVICE)) {
startServiceWithNotification();
}
else stopMyService();
return START_STICKY;
}
// In case the service is deleted or crashes some how
#Override
public void onDestroy() {
isServiceRunning = false;
super.onDestroy();
}
#Override
public IBinder onBind(Intent intent) {
// Used only in case of bound services.
return null;
}
void startServiceWithNotification() {
if (isServiceRunning) return;
isServiceRunning = true;
Intent notificationIntent = new Intent(getApplicationContext(), MyActivity.class);
notificationIntent.setAction(C.ACTION_MAIN); // A string containing the action name
notificationIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
PendingIntent contentPendingIntent = PendingIntent.getActivity(this, 0, notificationIntent, 0);
Bitmap icon = BitmapFactory.decodeResource(getResources(), R.drawable.my_icon);
Notification notification = new NotificationCompat.Builder(this)
.setContentTitle(getResources().getString(R.string.app_name))
.setTicker(getResources().getString(R.string.app_name))
.setContentText(getResources().getString(R.string.my_string))
.setSmallIcon(R.drawable.my_icon)
.setLargeIcon(Bitmap.createScaledBitmap(icon, 128, 128, false))
.setContentIntent(contentPendingIntent)
.setOngoing(true)
// .setDeleteIntent(contentPendingIntent) // if needed
.build();
notification.flags = notification.flags | Notification.FLAG_NO_CLEAR; // NO_CLEAR makes the notification stay when the user performs a "delete all" command
startForeground(NOTIFICATION_ID, notification);
}
void stopMyService() {
stopForeground(true);
stopSelf();
isServiceRunning = false;
}
}
Then I run it with
Intent startIntent = new Intent(getApplicationContext(), MyService.class);
startIntent.setAction(C.ACTION_START_SERVICE);
startService(startIntent);
Please note the two constants used as Actions, these are Strings that must start with the package name.

IntentService
Using IntentService is probably not the best approach. By default IntentService stops itself after onHandleIntent(Intent) returns and there's no work left to do (i.e. the request queue is empty). This is explained in the official docs of IntentService:
When all requests have been handled, the IntentService stops itself, so you should not call stopSelf().
In your case, onHandleIntent(Intent) creates a thread but returns right away, which makes it stop by itself.
Service + startForeground()
Using a regular Service in foreground mode should work as long as you keep that service running on a separate process. For that, you need:
Make the onStartCommand() return START_STICKY.
Call the method to show the notification right in onCreate().
Run the service in a separate process (using android:process=":something").
Based on the post, it seems that you've tried some of these steps in isolation but never tried all of them at the same time.

If none of the answers above are working, maybe it is a manufacturer specific issue. Some MI phones, for instance, kill the foreground service when the user kill the app via task manager.
I recommend you to test the app on a virtual device, so you can check if it is or isn't this kind of issue.
Hope it helps!

You can simply call your service in your onStop() method inside your activity.
Even when user stops the app the service will still be running.

Try the answers for this similar question: Bad notification for startForeground in Android app

Run upload process in background even when phone is asleep

So I have developed an android application that determines the user's location every 5 seconds using the fused location (LocationClient), and send this data to my server. This whole process repeats itself every 5 seconds when the app is running. I am uploading the data in background using AsyncTask class.
The Problem:
Data uploading stops when user closes the app or when the phone is put to sleep.
What I want:
I want the app to continuously send location data to my server even when the user closes the app or when the phone is asleep. This process should run on a seperate thread as I don't want this process to make my UI thread unresponsive.
What I found till now:
I have heard of services, intentservices and alarmmanager but I don't know which one to use. I also heard of wakelocks to force the CPU not to sleep. Remember I don't want to keep the screen ON all the time as this will drain the battery.
How can I make my app send data to server all the time ?

Here you can create one Service and call this service with AlarmManager at every 5/10 seconds as per your need...
In your MainActivity
public static AlarmManager alarm;
public static PendingIntent pintent;
// write this code on button click
Calendar cal = Calendar.getInstance();
cal.add(Calendar.SECOND, 10);
Intent intent = new Intent(this, MyService.class);
pintent = PendingIntent.getService(this, 0, intent, 0);
alarm = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
alarm.setRepeating(AlarmManager.RTC_WAKEUP, cal.getTimeInMillis(), 5000, pintent);
// button click functionality over
// write this code outside onCreate()
protected ServiceConnection mConnection = new ServiceConnection() {
#Override
public void onServiceConnected(ComponentName name, IBinder service) {
// TODO Auto-generated method stub
}
#Override
public void onServiceDisconnected(ComponentName name) {
// TODO Auto-generated method stub
}
};
MyService
public class MyService extends Service {
public static int counter = 0;
public MyService() {
}
#Override
public IBinder onBind(Intent intent) {
return new Binder() ;
}
#Override
public void onCreate() {
Toast.makeText(this, "First Service was Created", Toast.LENGTH_SHORT).show();
}
#Override
public void onStart(Intent intent, int startId) {
counter++;
Toast.makeText(this, " First Service Started" + " " + counter, Toast.LENGTH_SHORT).show();
}
#Override
public void onDestroy() {
Toast.makeText(this, "Service Destroyed", Toast.LENGTH_SHORT).show();
}
public void onTaskRemoved (Intent rootIntent){
MainActivity.alarm.cancel(MainActivity.pintent);
this.stopSelf();
}
Add this to
manifest
<application
....
<activity
.....
</activity>
<service
android:name=".MyService"
android:enabled="true"
android:exported="true" >
</service>
</application>

you can create a service lunched by your application. It will work in the background , and keep working until the user close it from the task-manager (if you don't call onDestroy in your code).

The process of the service is killed after the application is removed from the application tray

I am starting a service (or re-starting the running service) when an activity is launched, using :
Intent intent = new Intent(this, MyService.class);
startService(intent);
Later on based on certain actions, the same activity binds to the service using
bindService(new Intent(this, MyService.class), mConnection, Context.BIND_AUTO_CREATE);
And when the activity is destroyed, I call
unbindService(mConnection);
Earlier, the service used to restart when I killed the same activity/application from the application tray and showed the "message 1 process 1 service running" under running apps.
Now, the service does not restart on killing the same activity/application.
And I get the message "0 process 1 service running", which means the service is actually not running.
The service does not restart on application being closed. My application consists of one activity. Also the service is successfully started when launched after a system boot.
Why does the process of the service gets killed when I start it using startService() ??
edit
The service used to re-start earlier after i closed the app from the application tray. But now suddenly with the SAME code, it doesn't. It happens with other apps too when i close them. eg.

Here is a workaround I came across and works well for re-starting a service if its process is killed on closing the application. In your service, add the following code.
I came across this workaround in this thread.
#Override
public void onTaskRemoved(Intent rootIntent){
Intent restartServiceIntent = new Intent(getApplicationContext(), this.getClass());
restartServiceIntent.setPackage(getPackageName());
PendingIntent restartServicePendingIntent = PendingIntent.getService(getApplicationContext(), 1, restartServiceIntent, PendingIntent.FLAG_ONE_SHOT);
AlarmManager alarmService = (AlarmManager) getApplicationContext().getSystemService(Context.ALARM_SERVICE);
alarmService.set(
AlarmManager.ELAPSED_REALTIME,
SystemClock.elapsedRealtime() + 1000,
restartServicePendingIntent);
super.onTaskRemoved(rootIntent);
}
Seems to be a bug that the process of the application is killed. There is no point for a service to run if its process is killed.

Please be aware of that: onDestroy is not always called. You should not put code that way.
When activity forced closed or closed by system abnormally, onDestroy is not getting called.

Unfortunately, this is a complicated problem due to the way Android works. There are a number of strategies that each work around different parts of the problem. For best results, combine multiple strategies together.
Note that some of these strategies may no longer be necessary in more recent Android versions.
1. Start an activity
What to do
Taken from Foreground service killed when receiving broadcast after acitivty swiped away in task list:
In the foreground service:
#Override
public void onTaskRemoved( Intent rootIntent ) {
Intent intent = new Intent( this, DummyActivity.class );
intent.addFlags( Intent.FLAG_ACTIVITY_NEW_TASK );
startActivity( intent );
}
In the manifest:
<activity
android:name=".DummyActivity"
android:theme="#android:style/Theme.NoDisplay"
android:enabled="true"
android:allowTaskReparenting="true"
android:noHistory="true"
android:excludeFromRecents="true"
android:alwaysRetainTaskState="false"
android:stateNotNeeded="true"
android:clearTaskOnLaunch="true"
android:finishOnTaskLaunch="true"
/>
(If your service is in a different process then set this activity's process to the same one.)
In DummyActivity.java:
public class DummyActivity extends Activity {
#Override
public void onCreate( Bundle icicle ) {
super.onCreate( icicle );
finish();
}
}
Side effects
Causes the recents activity to close. Normally, swiping away an app doesn't close the recents activity.
Disadvantages
This only takes effect when the dummy activity starts, which may take half a second or more, so this still leaves the service open to being killed for a bit.
Explanation
When you remove/swipe your app away, a flag called waitingToKill is set. While this flag is set, Android may kill the process at any point in the future, such as when you receive a broadcast. Starting an activity clears this flag.
2. Spam a BroadcastReceiver with foreground broadcasts
What to do
Merge this into your service code:
if (Build.VERSION.SDK_INT >= 16) {
Intent intent = new Intent(this, DummyReceiver.class);
intent.addFlags(Intent.FLAG_RECEIVER_FOREGROUND);
//This seems to be timing-related; the more times we do this,
//the less likely the process gets killed
for (int i = 0; i < 50; ++i)
sendBroadcast(intent);
}
Create a dummy broadcast receiver:
public class DummyReceiver extends BroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent) {}
}
Add the receiver to your manifest:
<receiver android:name=".DummyReceiver" />
Side effects
May cause a slight (~250ms) delay/hang when the task is removed from the recents screen.
Disadvantages
This only keeps the process alive while it is receiving the broadcasts. the waitingToKill flag is still set, so the process may still be killed afterwards, such as when a broadcast is received.
Explanation
If your process isn't running in foreground priority, Android will try to kill it immediately. Receiving foreground broadcasts temporarily prevents this, resulting in the waitingToKill flag being set instead.
3. Don't bind to services
Binding to a service seems to increase the likelihood of the service's process being killed immediately when a task is removed.

I know this question is old but I recently encountered this problem and suddenly my service get stopped on closing app. Earlier it was working fine. This problem wasted my lot of time. To others who have similar problem make sure that YOUR BACKGROUND DATA RESTRICTION IS OFF.
This was the problem I had and it actually makes sense as when background data is Restricted background process won't run.

onDestroy is not always called. The Main problem in your case is ur unable to start the service when app closed,that time android OS(In Some OS) will kill the service, If you are not able to restart the service then call a alarm manger to start the reciver like this,
Manifest is,
<service
android:name=".BackgroundService"
android:description="#string/app_name"
android:enabled="true"
android:label="Notification" />
<receiver android:name="AlarmReceiver">
<intent-filter>
<action android:name="REFRESH_THIS" />
</intent-filter>
</receiver>
IN Main Activty start alarm manger in this way,
String alarm = Context.ALARM_SERVICE;
AlarmManager am = (AlarmManager) getSystemService(alarm);
Intent intent = new Intent("REFRESH_THIS");
PendingIntent pi = PendingIntent.getBroadcast(this, 123456789, intent, 0);
int type = AlarmManager.RTC_WAKEUP;
long interval = 1000 * 50;
am.setInexactRepeating(type, System.currentTimeMillis(), interval, pi);
this will call reciver and reciver is,
public class AlarmReceiver extends BroadcastReceiver {
Context context;
#Override
public void onReceive(Context context, Intent intent) {
this.context = context;
System.out.println("Alarma Reciver Called");
if (isMyServiceRunning(this.context, BackgroundService.class)) {
System.out.println("alredy running no need to start again");
} else {
Intent background = new Intent(context, BackgroundService.class);
context.startService(background);
}
}
public static boolean isMyServiceRunning(Context context, Class<?> serviceClass) {
ActivityManager activityManager = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
List<ActivityManager.RunningServiceInfo> services = activityManager.getRunningServices(Integer.MAX_VALUE);
if (services != null) {
for (int i = 0; i < services.size(); i++) {
if ((serviceClass.getName()).equals(services.get(i).service.getClassName()) && services.get(i).pid != 0) {
return true;
}
}
}
return false;
}
}
And this Alaram reciver calls once when android app is opened and when app is closed.SO the service is like this,
public class BackgroundService extends Service {
private String LOG_TAG = null;
#Override
public void onCreate() {
super.onCreate();
LOG_TAG = "app_name";
Log.i(LOG_TAG, "service created");
}
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
Log.i(LOG_TAG, "In onStartCommand");
//ur actual code
return START_STICKY;
}
#Override
public IBinder onBind(Intent intent) {
// Wont be called as service is not bound
Log.i(LOG_TAG, "In onBind");
return null;
}
#TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH)
#Override
public void onTaskRemoved(Intent rootIntent) {
super.onTaskRemoved(rootIntent);
Log.i(LOG_TAG, "In onTaskRemoved");
}
#Override
public void onDestroy() {
super.onDestroy();
Log.i(LOG_TAG, "In onDestroyed");
}
}

when there is no binding to a service or well established foreground then android system recognize the service as unused overloading service that should be shut down. Here is the best way to maintain your service even if the app is closed: AlarmManager or Service

How can we prevent a Service from being killed by OS?

I am using Service in my application and it needs to run until my application is uninstalled, but the problem is it gets killed by OS.
How can we prevent it from being killed by OS? Or if it gets killed can we restart that service again through programmatically?

You may run the service in the foreground using startForeground().
A foreground service is a service that's considered to be something
the user is actively aware of and thus not a candidate for the system
to kill when low on memory.
But bear in mind that a foreground service must provide a notification for the status bar (read here), and that the notification cannot be dismissed unless the service is either stopped or removed from the foreground.
Note: This still does not absolutely guarantee that the service won't be killed under extremely low memory conditions. It only makes it less likely to be killed.

I've been puzzled by the same issue to yours recently.but now,I've found a good solution.
First of all,you should know that, even your service was killed by OS, the onCreate method of your service would be invoked by OS in a short while.So you can do someting with the onCreate method like this:
#Override
public void onCreate() {
Log.d(LOGTAG, "NotificationService.onCreate()...");
//start this service from another class
ServiceManager.startService();
}
#Override
public void onStart(Intent intent, int startId) {
Log.d(LOGTAG, "onStart()...");
//some code of your service starting,such as establish a connection,create a TimerTask or something else
}
the content of "ServiceManager.startService()" is:
public static void startService() {
Log.i(LOGTAG, "ServiceManager.startSerivce()...");
Intent intent = new Intent(NotificationService.class.getName());
context.startService(intent);
}
However, this solution is just available for the situation of your service being killed by GC.Sometimes our service might be killed by user with Programme Manager.In this situation,your prosses will be killed,and your service will never been re-instantiated.So your service can not be restarted.
But the good news is,when the PM kill your service,it will call your onDestroy method.So we can do something with that method.
#Override
public void onDestroy() {
Intent in = new Intent();
in.setAction("YouWillNeverKillMe");
sendBroadcast(in);
Log.d(LOGTAG, "onDestroy()...");
}
The string of "YouWillNeverKillMe" is a custom action.
The most important thing of this method is,don't add any code before send the broadcast.As system will not wait for completion of onDestroy(),you must send out the broadcast as soon as posible.
Then regist a receiver in manifast.xml:
<receiver android:name=".app.ServiceDestroyReceiver" >
<intent-filter>
<action android:name="YouWillNeverKillMe" >
</action>
</intent-filter>
</receiver>
Finally,create a BroadcastReceiver,and start your service in the onReceive method:
#Override
public void onReceive(Context context, Intent intent) {
Log.d(LOGTAG, "ServeiceDestroy onReceive...");
Log.d(LOGTAG, "action:" + intent.getAction());
Log.d(LOGTAG, "ServeiceDestroy auto start service...");
ServiceManager.startService();
}
Hope this will be helpful to you,and excuse my poor written english.

Override method onStartCommand() in your service class and simply return START_STICKY (as suggested by "Its not blank"). That's all you need. If the process that runs your service gets killed (by a low memory condition for example), the Android system will restart it automatically (usually with some delay, like 5 seconds).
Don't use onStart() anymore as suggested in another answer, it's deprecated.

use
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
//**Your code **
// We want this service to continue running until it is explicitly
// stopped, so return sticky.
return START_STICKY;
}
ref Documentation lifecycle of Service.
Edit added method.

As far i know, onDestroy() will be called only when the service is explicitly stopped(Force Stop). But this method won't get called in case the service gets killed by OS/swiping the Recent Apps list. In those cases another event handler named onTaskRemoved(Intent) gets called. This is due to a defect in Android 4.3-4.4 as per the link here. Try using the below code:-
public void onTaskRemoved(Intent intent){
super.onTaskRemoved(intent);
Intent intent=new Intent(this,this.getClass());
startService(intent);
}

I found another solution of the problem which gurantees that your service will be always alive. In my case, this scheme resloves also the problem with FileObserver, which stops work after some period of time.
Use an activity (StartServicesActivity) to start the service (FileObserverService) as Foreground service.
Use BroadcastReceiver class (in example CommonReceiver) to restart your service in some special situations and in case it was killed.
I used this code in my app "Email Pictures Automatically"
https://play.google.com/store/apps/details?id=com.alexpap.EmailPicturesFree
Here is CommonReceiver class.
public class CommonReceiver extends BroadcastReceiver {
public void onReceive(Context paramContext, Intent paramIntent)
{
paramContext.startService(new Intent(paramContext, FileObserverService.class));
}
}
Here is its definition in AndroidManifest.xml just before application closing tag.
<receiver android:name="com.alexpap.services.CommonReceiver">
<intent-filter>
<action android:name="android.intent.action.BOOT_COMPLETED"/>
</intent-filter>
<intent-filter>
<action android:name="android.net.conn.CONNECTIVITY_CHANGE"/>
</intent-filter>
<intent-filter>
<action android:name="android.intent.action.USER_PRESENT"/>
</intent-filter>
</receiver>
Start service in StartServicesActivity activity.
Intent iFileObserver = new Intent(StartServicesActivity.this, FileObserverService.class);
StartServicesActivity.this.startService(iFileObserver);
Here is onStartCommand() method of the service.
public int onStartCommand(Intent intent, int flags, int startId) {
int res = super.onStartCommand(intent, flags, startId);
/*** Put your code here ***/
startServiceForeground(intent, flags, startId);
return Service.START_STICKY;
}
public int startServiceForeground(Intent intent, int flags, int startId) {
Intent notificationIntent = new Intent(this, StartServicesActivity.class);
notificationIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, notificationIntent, 0);
Notification notification = new NotificationCompat.Builder(this)
.setContentTitle("File Observer Service")
.setContentIntent(pendingIntent)
.setOngoing(true)
.build();
startForeground(300, notification);
return START_STICKY;
}
I tested this code using Task Killer app, and each time the service was killed, it was restarted again almost immediately (performs onStartCommand()). It is restarted also each time you turn on the phone and after rebooting.
I use this code in my application, which emails every picture you take with your phone to predefinde list of emails. The sending email and list of receiving emails are set in another activity and are stored in Shared Preferences. I took about 100 pictures in several hours and all they were sent properly to receiving emails.

#Override
public void onDestroy() {
super.onDestroy();
startService(new Intent(this, YourService.class));
}
write above code in your service and your service will never stop even user want to destroy it or they want to kill it it will never kill untill your app not get uninstall from your device

You can try to start your service repeatedly, for example every 5 sec.
This way, when your service is running, it will perform onStartCommand() every 5 sec. I tested this scheme and it is very reliable, but unfortunately it increases slightly phone overhead.
Here is the code in your activity where you start the service.
Intent iFileObserver = new Intent(StartServicesActivity.this, FileObserverService.class);
PendingIntent pendingIntentFileObserver = PendingIntent.getService(StartServicesActivity.this, 0, iFileObserver, 0);
AlarmManager alarmManager = (AlarmManager)getSystemService(ALARM_SERVICE);
Date now = new Date();
//start every 5 seconds
alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, now.getTime(), 5*1000, pendingIntentFileObserver);
And here is onStartCommand() of the service.
//class variable
public static boolean isStarted = false;
public int onStartCommand(Intent intent, int flags, int startId) {
int res = super.onStartCommand(intent, flags, startId);
//check if your service is already started
if (isStarted){ //yes - do nothing
return Service.START_STICKY;
} else { //no
isStarted = true;
}
/**** the rest of your code ***/
return Service.START_STICKY;
}

First create service in another process, and write broadcaster which runs in recursion in time intervals
protected CountDownTimer rebootService = new CountDownTimer(9000, 9000) {
#Override
public void onTick(long millisUntilFinished) {
}
#Override
public void onFinish() {
sendBroadcast(reboot);
this.start();
Log.d(TAG, "rebootService sending PREVENT AUTOREBOT broadcast");
}
};
After that register broadcast receiver in main process also with timer recursion that is launched after first broadcast from service arrived
protected static class ServiceAutoRebooter extends BroadcastReceiver {
private static ServiceAutoRebooter instance = null;
private RebootTimer rebootTimer = null;
private static ServiceAutoRebooter getInstance() {
if (instance == null) {
instance = new ServiceAutoRebooter();
}
return instance;
}
public class RebootTimer extends CountDownTimer {
private Context _context;
private Intent _service;
public RebootTimer(long millisInFuture, long countDownInterval) {
super(millisInFuture, countDownInterval);
}
#Override
public void onTick(long millisUntilFinished) {
}
#Override
public void onFinish() {
_context.startService(_service);
this.cancel();
Log.d(TAG, "Service AutoRebooted");
}
}
#Override
public void onReceive(Context context, Intent intent) {
if (rebootTimer == null) {
Log.d(TAG, "rebootTimer == null");
rebootTimer = new RebootTimer(10000, 10000);
rebootTimer._context = context;
Intent service = new Intent(context, SomeService.class);
rebootTimer._service = service;
rebootTimer.start();
} else {
rebootTimer.cancel();
rebootTimer.start();
Log.d(TAG, "rebootTimer is restarted");
}
}
}
Service will be auto-rebooted if time at RebootTimer (main process) expires, which means that "PREVENT AUTOREBOT" broadcast from service hasn't arrived

i found a solution .... late answer but i wanted to answer...
we can send a broadcast in the ondestroy of the service and create a receiver that receives the broadcast and starts the service again.... when it is destroyed by any reasons...

pls try following:
final Messenger mMessenger = new Messenger(new IncomingHandler());
class IncomingHandler extends Handler {
#Override
public void handleMessage(Message msg) {
switch (msg.what) {
default:
super.handleMessage(msg);
}
}
}
#Override
public void onCreate() {
super.onCreate();
makeServiceForeground();
}
#Override
public IBinder onBind(Intent arg0) {
return mMessenger.getBinder();
}
private void makeServiceForeground() {
IActivityManager am = ActivityManagerNative.getDefault();
try {
am.setProcessForeground(onBind(null), android.os.Process.myPid(), true);
} catch (RemoteException e) {
Log.e("", "cant set to foreground" + e.toString());
}
}
also need add in manifest.xml
<uses-permission android:name="android.permission.SET_PROCESS_LIMIT"/>