I have an android app and a server application written in Java. I basically want the app to connect to the server every few seconds to get the newest information, and if neccessary display a push notification, like a Messenger App. I'm new to this, and I've tried multiple ways, but nothing of what I tried seems to work.
I've used a Service which connects to the server every X seconds and gets the newest information from it. The service restarts when It gets destroyed, so it even runs in the background when the app is terminated, but after a while it just stops working and doesn't restart with the error message Not allowed to start service Intent {snip}: app is in background. I have no idea if this approach is even a good idea, and I've tried some other things too, but I don't get anywhere, so any advice on how an application like this should be done would be really helpful!
This is my Service class:
public int counter=0;
public ConnectionService(Context applicationContext) {
super();
}
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
super.onStartCommand(intent, flags, startId);
startTimer();
return START_STICKY;
}
#Override
public void onDestroy() {
super.onDestroy();
Intent broadcastIntent = new Intent(this, BootBroadcastReceiver.class);
sendBroadcast(broadcastIntent);
stoptimertask();
}
private Timer timer;
private TimerTask timerTask;
public void startTimer() {
timer = new Timer();
initializeTimerTask();
timer.schedule(timerTask, 1000, 1000); //
}
public void initializeTimerTask() {
timerTask = new TimerTask() {
public void run() {
counter++;
ConnectionManager.oneWayCall(new DebugPacket("Debug Packet: " + counter));
}
};
}
I don't neccessarily need help with this exact code, if apps like these should be done in a completely different way, please point me into the right direction.
now you can not run services in background forever . system will terminate it after sometime even if you use foreground service.
instead of fetching data every x seconds i would recommend ask your backend guy to send data in fcm notification if data is not large.
if you can wait for 15 minutes for fetching new data you can use workmanager.
there is one ugly way of keeping services alive for longer time i will suggest not to use it .
you can start service every x seconds when you receive notification your app is considered in foreground when you receive notification in this window you can start service. catch is you have to send notifications every x seconds.
Related
I was reading about services in Android and especially i came down to this
While an app is in the foreground, it can create and run both
foreground and background services freely. When an app goes into the
background, it has a window of several minutes in which it is still
allowed to create and use services. At the end of that window, the app
is considered to be idle. At this time, the system stops the app's
background services, just as if the app had called the services'
Service.stopSelf() methods.
In the code below, when the app goes to background after one minute or so the services gets destroy but the thread still executes.
So what is the point of killing a service? The process/thread is still being execute.
Why killing a service in the first place? What if i want to execute a download process and NOT wanted to be a foreground process?
public class HelloService extends Service {
private Looper mServiceLooper;
private ServiceHandler mServiceHandler;
// Handler that receives messages from the thread
private final class ServiceHandler extends Handler {
public ServiceHandler(Looper looper) {
super(looper);
}
#Override
public void handleMessage(Message msg) {
// Normally we would do some work here, like download a file.
// For our sample, we just sleep for 5 seconds.
Log.d("sssssssss",msg.toString()+"sssssssssss");
while(true){
Log.d("sssssssss","sssssssssss");
}
// Stop the service using the startId, so that we don't stop
// the service in the middle of handling another job
//stopSelf(msg.arg1);
}
}
#Override
public void onCreate() {
// Start up the thread running the service. Note that we create a
// separate thread because the service normally runs in the process's
// main thread, which we don't want to block. We also make it
// background priority so CPU-intensive work doesn't disrupt our UI.
HandlerThread thread = new HandlerThread("ServiceStartArguments",
Process.THREAD_PRIORITY_BACKGROUND);
thread.start();
// Get the HandlerThread's Looper and use it for our Handler
mServiceLooper = thread.getLooper();
mServiceHandler = new ServiceHandler(mServiceLooper);
}
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
Toast.makeText(this, "service starting", Toast.LENGTH_SHORT).show();
// For each start request, send a message to start a job and deliver the
// start ID so we know which request we're stopping when we finish the job
Message msg = mServiceHandler.obtainMessage();
msg.arg1 = startId;
mServiceHandler.sendMessage(msg);
// If we get killed, after returning from here, restart
return START_STICKY;
}
#Override
public void onDestroy() {
Toast.makeText(this, "service done", Toast.LENGTH_SHORT).show();
}
#Nullable
#Override
public IBinder onBind(Intent intent) {
return null;
}
}
System is letting You perform a clean finish of the Service by triggering its destroy method. Your thread won't run forever, I think 30 min is hard limit before app process is killed.
This is new policy since android O to preserve battery life and improve performance. A lot of developers performed heavy operations in background (sockets open non-stop, periodic sensor readings etc.) and without foreground notification users were unaware of why their devices were sluggish and had poor battery uptime.
Read more on Background Execution Limits doc.
I'm targeting sdk version 27 with a minimum version of 19 and trying to get a service that runs continuously in the background. I tried different service start options but it still got killed with the app. I tried using a BroadcastReceiver to start the service when it got killed but that gave me an error saying that the app was in the background and couldn't start a service so I tried using the JobScheduler and that gave me the same error. How is this supposed to be done? For example, if I were making a pedometer app, how could I keep that running in the background?
In oreo release Android defined limits to background services.
To improve the user experience, Android 8.0 (API level 26) imposes
limitations on what apps can do while running in the background.
Still if app need to run its service always, then we can create foreground service.
Background Service Limitations: While an app is idle, there are limits
to its use of background services. This does not apply to foreground
services, which are more noticeable to the user.
So create a foreground service. In which you will put a notification for user while your service is running. See this answer (There are many others)
Now what if you don't want a notification for your service. A solution is for that.
You can create some periodic task that will start your service, service will do its work and stops itself. By this your app will not be considered battery draining.
You can create periodic task with Alarm Manager, Job Scheduler, Evernote-Jobs or Work Manager.
Instead of telling pros & cons of each one. I just tell you best. Work manager is best solution for periodic tasks. Which was introduced with Android Architecture Component.
Unlike Job-Scheduler(only >21 API) it will work for all versions.
Also it starts work after a Doze-Standby mode.
Make a Android Boot Receiver for scheduling service after device boot.
I created forever running service with Work-Manager, that is working perfectly.
Since Android 8.0 many background service limitations have been introduced.
Two solutions:
if you need to get total control of task and execution timing, you have to choose Foreground Service.
Pros: your app will be considered to be alive, then is more unlikely that the os will kill it to free resources.
Cons: your user will always see the Foreground Notification.
if you need to schedule periodically task, then Work Manager (introduced in Google I/O 18) is the best solution. This component choose the best possible scheduler (Jobscheduler, JobDispatcher, AlarmManager..). Keep in mind that work manager APIs are useful only for the tasks that require guaranteed execution and they are deferrable.
Ref: Android Dev Documentation
The only solution I would suggest is using Firebase Cloud Messages.
Or foreground services.
Using BroadcastReciever we can run backgrouund service continuously, but if it will get killed , destroy automatically re-instance the old service instance
When service stops forcefully it will call onDestroy() method, in this case use one receiver and send one broadcast when ever service destroy and restart service again. in thee following method com.android.app is custom action of reciever class which extends BroadcastReciever
public void onDestroy() {
try {
myTimer.cancel();
timerTask.cancel();
} catch (Exception e) {
e.printStackTrace();
}
Intent intent = new Intent("com.android.app");
intent.putExtra("valueone", "tostoreagain");
sendBroadcast(intent);
}
and in onReceive Method
#Override
public void onReceive(Context context, Intent intent) {
Log.i("Service Stoped", "call service again");
context.startService(new Intent(context, ServiceCheckWork.class));
}
In case device is restarted then we have onBootCompleted action for receiver to catch
When you are targeting SdkVersion "O"
In MainActivity.java define getPendingIntent()
private PendingIntent getPendingIntent() {
Intent intent = new Intent(this, YourBroadcastReceiver.class);
intent.setAction(YourBroadcastReceiver.ACTION_PROCESS_UPDATES);
return PendingIntent.getBroadcast(this, 0, intent,
PendingIntent.FLAG_UPDATE_CURRENT);
}
here we use PendingIntent with BroadcastReceiver and This BroadcastReceiver has already been defined in AndroidManifest.xml.
Now in YourBroadcastReceiver.java class which contains an onReceive() method:
Override
public void onReceive(Context context, Intent intent) {
if (intent != null) {
final String action = intent.getAction();
if (ACTION_PROCESS_UPDATES.equals(action)) {
NotificationResult result = NotificationResult.extractResult(intent);
if (result != null) {
List<Notification> notifications = result.getNotification();
NotificationResultHelper notificationResultHelper = new
NotificationResultHelper(
context, notifications);
// Save the notification data to SharedPreferences.
notificationResultHelper.saveResults();
// Show notification with the notification data.
notificationResultHelper.showNotification();
Log.i(TAG,
NotificationResultHelper.getSavedNotificationResult(context));
}
}
}
}
as you say:
I tried using a BroadcastReceiver to start the service when it got
killed but that gave me an error saying that the app was in the
background and couldn't start a service
in Oreo when you are in background and you want to start a service that service must be a foreground service use this code:
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
context.startForegroundService(intent);
} else {
context.startService(intent);
}
if you use this code in Oreo you have a few seconds in onStartCommand to start foreground otherwise your service considered as not responding and may be force close by user (in Android 8 or above)
There is no need to use BroadcastReceiver to start service after it is closed it is enough to just return START_STICKY or START_REDELIVER_INTENT from onStartCommand of your service to restart service after it is closed
A working hack for this is to simply start a foreground service which is only visible for the fraction of a second and starts your background service. In the background service you'd then periodically start the foreground service.
Before I give an example you should really ask yourself if this is the way to go for you, there might be other solutions to given problems (like using JobIntentService etc.); and keep in mind that this is a hack, it might be patched some time around and I'd generally not use it (I tested it with screen off and battery saving enabled though and it stayed alive the whole time - but this might prevent your device from dozing.. again, this is a dirty hack!)
Example:
public class TemporaryForegroundService extends Service {
public static final int NOTIFICATION_ID = 666;
private static Notification notification;
#Override
public void onCreate() {
super.onCreate();
if(notification == null)
notification = new NotificationCompat.Builder(this, NotificationChannels.importantChannel(this)).
setSmallIcon(R.mipmap.ic_launcher).setContentTitle("The unseen blade").setContentText("If you see me, congrats to you.").build();
startForeground(NOTIFICATION_ID, notification);
startService(new Intent(this, PermanentBackgroundService.class));
stopForeground(true);
stopSelf();
}
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
return START_NOT_STICKY;
}
#Nullable
#Override
public IBinder onBind(Intent intent) {
return null;
}
}
public class PermanentBackgroundService extends Service {
private Runnable keepAliveRunnable = new Runnable() {
#Override
public void run() {
keepServiceAlive();
if(handler != null) handler.postDelayed(this, 15*1000);
}
};
private Handler handler;
public void onCreate(){
handler = new Handler();
handler.postDelayed(keepAliveRunnable, 30* 1000);
}
public void onDestroy() {
super.onDestroy();
keepServiceAlive();
}
private void keepServiceAlive() {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
startForegroundService(new Intent(PermanentBackgroundService.this, TemporaryForegroundService .class));
} else {
startService(new Intent(PermanentBackgroundService.this, TemporaryForegroundService .class));
}
}
}
In my app I need to update an object if the user didn't refresh it for 30 days. I tried several things to approach this, but none of them worked
1. Using System.currentTimeMillies()
My first try was to just store the time when the object was updated and compare it to the current time. Everything worked fine, but the problem was, that the user could change the os time and then the time check would be useless...
2. Using AlarmManager
Here I had the same problem as above
3. Implementing a Service that contains a timer
Here I implemented a Service with a Timer that just counts up to 30 days. This seemed to be the best solution, but the Service stops when I close the app.
the onCreate and onStartCommand of my Service look like this (I just changed 30 days to 2 minutes for testing and it contains multiple timers for multiple objects):
#Override
public void onCreate() {
Log.i(TAG, "[onCreate]");
super.onCreate();
registerReceiver(new StopServiceReceiver(), new IntentFilter(STOP_SERVICE_REQUEST));
context = this;
//retrieveTimers();
}
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
if (intent == null) {
Log.i(TAG, "[onStartCommand] intent = null");
return super.onStartCommand(intent, flags, startId);
}
//prevent starting 2 timers for the same id
String id = intent.getStringExtra(KEY_CARD_ID);
if (timerHashMap.containsKey(id)) {
Log.i(TAG, "[onStartCommand] timer already exists");
return super.onStartCommand(intent, flags, startId);
}
//create and start timer
Log.i(TAG, "[onStartCommand] schedule timer");
Timer timer = new Timer();
timer.schedule(new CounterTask(id), MAX_MILLIES_WITHOUT_UPDATE);
timerHashMap.put(id, timer);
// storeTimers();
return super.onStartCommand(intent, flags, startId);
}
I also tried to store the timer map in the shared preferences but later on I realized that thsi was kind of stupid because the timers should continue and serializing a timer to store it was also not possible (and as I said kind of stupid ;-))
Thanks for your help!
You can use JobScheduler (or some variations of it).
There are Minimum Latency and Periodic options to schedule the Job to run after 30 days.
Refer this article for more info: Scheduling jobs like a pro with JobScheduler
There is JobIntentService in the latest Support Library and Firebase JobDispatcher for backward compatibility.
What is the recommended approach for checking for new data regardless if the app is in the foreground or background? I am wondering which Android API people are typically using to do this. There seems to be a few ways to achieve my goal, and I want to make sure I'm on the right path.
I have something put together which uses AlarmManager.SetInexactRepeating() to call an IntentService which does the sync and inserts/updates data in the database. This works while the app is in the foreground and background, but if I force stop the app then I keep seeing "Unfortunately, has stopped working" messages when the AlarmManager alarm would've triggered. In this case, I only care about checking for new data only when the app is running in the foreground or background.
My first thought is to detect when the app is force closed, and stop the alarm, but that does not seem possible. So I am asking here, is my approach wrong? If so, which approach is used to perform some periodic task regardless if the phone is in the foreground or background? The problem with the AlarmManager solution I am using is the alarms continue to fire even when the app is closed.
If your idea is to check if your API has new data and perform a background sync to your local database or other data storage, I think you would like to take a look at this:
Creating a Sync Adapter
Running a Sync Adapter
The Sync adapter is the recommended way of achieving this in Android. The pros of using it are multiple:
Optimisations out of the box - the OS bundles calls, uses the most appropriate windows to run the sync adapter at a minimal bandwidth and battery cost
The lifecycle of your background sync component is managed internally by the OS
Observers can be notified when data has been changed so the UI can be updated easily
Multiple ways of running the sync - at intervals, automatically with the OS message to keep TCP/IP connections open or on demand
However, implementing this requires some things, that can cause a bit of a pain at first:
It is mandatory that the adapter works with a ContentProvider
Sync Adapters use Account for authentication. If this is not needed, a Stub has to be provided
For backgrounding on Android usually you use even a Service that can run alone and independently from the App or a Bounded service that takes and returns data from the App. A complete reference on backgrounding can be found here
Using a Service is the right way to go. Have your app start the Service and it will continue running while the app is in the foreground or the background. Then, if you want to kill the Service when your app closes, you could just call stopService(yourServiceIntent); from the onDestroy() override in your app's activity. That should effectively shut down the service when the app closes.
So some sample code of how this works (taken from the Services docs)...
The Service (just Logs a message every 1 second for 60 seconds):
public class MyService extends Service {
private Looper mServiceLooper;
private ServiceHandler mServiceHandler;
// Handler that receives messages from the thread
private final class ServiceHandler extends Handler {
public ServiceHandler(Looper looper) {
super(looper);
}
#Override
public void handleMessage(Message msg) {
long endTime = System.currentTimeMillis() + 60*1000;
while (System.currentTimeMillis() < endTime) {
synchronized (this) {
try {
wait(1000);
Log.d("SERVICE", "The service is still running.");
} catch (Exception e) {
e.printStackTrace();
}
}
}
stopSelf(msg.arg1);
}
}
#Override
public void onCreate() {
HandlerThread thread = new HandlerThread("ServiceStartArguments", Process.THREAD_PRIORITY_BACKGROUND);
thread.start();
mServiceLooper = thread.getLooper();
mServiceHandler = new ServiceHandler(mServiceLooper);
}
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
Message msg = mServiceHandler.obtainMessage();
msg.arg1 = startId;
mServiceHandler.sendMessage(msg);
return START_NOT_STICKY;
}
#Override
public IBinder onBind(Intent intent) {
return null;
}
#Override
public void onDestroy() {
}
}
And in your activity you would do something like:
public class MainActivity extends AppCompatActivity {
Intent serviceIntent;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
serviceIntent = new Intent(this, MyService.class);
startService(serviceIntent);
}
#Override
protected void onDestroy() {
stopService(serviceIntent);
super.onDestroy();
}
The title may seem duplicate but the question not about how to make the request, im sending a HTTP Get request from my android application to a web server after a specified interval using a service, the problem is it is stopped after i perform any other action on the device like play a video. The service looks like
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
final Context ctx=this;
Timer timer = new Timer();
timer.scheduleAtFixedRate(new TimerTask() {
#Override
public void run() {
//perform GET here
}, 0, 5000);
return Service.START_STICKY;
}
any idea why such behaviour im experiencing even though im returning the Service.START_STICKY
Regards.
As mentioned in comment you can take the approach of PendingIntents and BroadcastReceiver in which you can leave a pending intent at specified time and register a receiver and in onreceive you can perform you operation whether to start service or hit a werbservice.
Please go through http://code.tutsplus.com/tutorials/android-fundamentals-scheduling-recurring-tasks--mobile-5788
also http://www.sitepoint.com/scheduling-background-tasks-android/ for better understanding
Try running your service in the 'foreground'. This way it is less likely to get killed.
Check out: http://developer.android.com/guide/components/services.html#Foreground