Develop Reference

Android: How to handle a context within an AlarmService

In android (as a beginner) I have created an AlarmService class to act as a service, i.e. to run every fixed interval in the background, to check data and probably to notify the user that something is going on.
The AlarmService class is defined as follows:
public class AlarmService extends Service
{
Alarm alarm = new Alarm(this);
public void onCreate()
{
super.onCreate();
}
#Override
public int onStartCommand(Intent intent, int flags, int startId)
{
alarm.SetAlarm(this);
return START_STICKY;
}
#Override
public void onStart(Intent intent, int startId)
{
alarm.SetAlarm(this);
}
#Override
public IBinder onBind(Intent intent)
{
return null;
}
}
and the actual Alarm is implemented as follows:
public class Alarm extends BroadcastReceiver
{
private Context mContext;
public final static String LOGHEAD = "StoxxAlarm";
public Alarm() {
mContext = null;
}
public Alarm(Context context) {
mContext = context;
}
#Override
public void onReceive(Context context, Intent intent)
{
SharedPreferences sharedPref = PreferenceManager.getDefaultSharedPreferences(mContext);
int updateInterval = Integer.parseInt(sharedPref.getString("updateInterval", "24")); // ##PROBLEM##
// ... do something here
}
public void SetAlarm(Context context)
{
// get the update cylce from the prefences
SharedPreferences sharedPref = PreferenceManager.getDefaultSharedPreferences(mContext);
int updateInterval = Integer.parseInt(sharedPref.getString("updateInterval", "24"));
AlarmManager am = (AlarmManager)context.getSystemService(Context.ALARM_SERVICE);
Intent intent = new Intent(context, Alarm.class);
PendingIntent pi = PendingIntent.getBroadcast(context, 0, intent, 0);
am.setRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(), 1000 * 60 * 60 * updateInterval, pi); // Millisec * Second * Minute
}
public void CancelAlarm(Context context)
{
Intent intent = new Intent(context, Alarm.class);
PendingIntent sender = PendingIntent.getBroadcast(context, 0, intent, 0);
AlarmManager alarmManager = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
alarmManager.cancel(sender);
}
}
The problem occurs in the line marked with ##PROBLEM## as the context is null. How can I fix the problem?
The funny thing is, that I fixed something else in the code which did not work. Before that fix (related to something else), this kind of worked. But now, how to make sure the function becomes a proper 'context' (what ever this is, I still do not understand properly what a context is...).

How can I fix the problem?
With respect to this specific concern, mContext will always be null, because Android will not use your one-parameter constructor when it sends you a broadcast. Get rid of mContext, and use the Context that is passed into onReceive().
Beyond that:
I do not know why you are returning START_STICKY
I do not know why you are overriding onStart() and onStartCommand(), given that onStart() was deprecated 6-7 years ago
I do not know why you have SetAlarm() and ClearAlarm() as methods on Alarm, forcing you to create an Alarm and then throw it away, instead of having those methods be implemented on the service, or have them be implemented as static methods somewhere
You are using RTC_WAKEUP, which is fine, but unless the work you plan to do is sub-millisecond in duration, you really need to use the WakefulBroadcastReceiver pattern, so you do not tie up the app's main application thread in onReceive() and also can keep the device awake

instead of mContext, you should use context

Why Background Service stops working when app is closed?

I am trying to create a background service that will be called every ten minutes, perform a task and this should not be killed when the application is closed.
The following is the code snippet:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_location_service);
Intent intent = new Intent(this, AlarmReceiverLifeLog.class);
PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0, intent, PendingIntent.FLAG_CANCEL_CURRENT);
AlarmManager alarms = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
Calendar calendar = Calendar.getInstance();
alarms.setRepeating(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(), 10 * 60 * 1000, pendingIntent);
}
In onCreate, it will call the AlarmReceiverLifeLog class every ten minutes. The following is the code for AlarmReceiverLifeLog class:
public class AlarmReceiverLifeLog extends BroadcastReceiver {
static Context context;
#Override
public void onReceive(Context context, Intent intent) {
Intent ll24Service = new Intent(context, LifeLogService.class);
context.startService(ll24Service);
}
}
public class LifeLogService extends Service {
#Override
public void onCreate() {
super.onCreate();
}
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
return START_STICKY;
}
#Override
public void onDestroy() {
}
#Override
public void onTaskRemoved(Intent rootIntent) {
Intent restartService = new Intent(getApplicationContext(), this.getClass());
restartService.setPackage(getPackageName());
PendingIntent restartServicePI = PendingIntent.getService(getApplicationContext(), 1, restartService, PendingIntent.FLAG_ONE_SHOT);
Calendar calendar = Calendar.getInstance();
AlarmManager alarmService = (AlarmManager) getApplicationContext().getSystemService(Context.ALARM_SERVICE);
alarmService.set(AlarmManager.ELAPSED_REALTIME, calendar.getTimeInMillis() + 100, restartServicePI);
}
#Override
public IBinder onBind(Intent intent) {
return null;
}
}
I am not able to figure out what I have missed. When I close the app the background services is getting killed.
Can anyone suggest anything regarding this?

when the app is closed the service get closed also because they are in a one thread, so the service should be on another thread in order fot it not to be closed, look into that and look into keeping the service alive with alarm manager here an example http://www.vogella.com/articles/AndroidServices/article.html this way your service won't be shown in notification.

Service doesn't start alarm after closing the app

I want to create an alarm application, which will sound the alarm when you set the time. I've got it to work partially. I'm stuck at the alarm not being set after the app is closed via recent tray(Not with force stop). To tackle this, I created a service which will run in the background(even if the app is closed) and will sound the alarm.
My problem right now, is that even after using a service, I'm unable to sound the alarm after the app is closed. However, the service seems to be running after the closure of the app(I've seen in running apps. It says My App has a service running in the background).
NOTE : I've also bound the service with my activity so that I can use its methods.
NOTE 2 : The service sounds the alarm when the application is open, Only fails to do so when the app is closed.
This is my code :
Calling the service from my Activity :
public void startOnClick(View view) {
int aHour = alarmTimePicker.getCurrentHour();
int aMin = alarmTimePicker.getCurrentMinute();
Alarms alarm = new Alarms(aHour, aMin); //I've created an Alarms class Seperately
myService.setAlarm2(alarm); //Setting the alarm via service
Toast.makeText(this, "Alarm SET.", Toast.LENGTH_LONG).show();
}
In MyService : `package com.wars.tap.tapwars;
public class MyService extends Service {
private final IBinder myBinder = new MyBinder();
Alarms alarm = new Alarms();
private PendingIntent pendingIntent;
private AlarmManager alarmManager;
private ServiceCallBacks serviceCallbacks;
public MyService() {
}
#Override
public IBinder onBind(Intent intent) {
return myBinder;
}
public class MyBinder extends Binder {
MyService getService() {
return MyService.this;
}
}
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
return START_STICKY;
}
public void setCallbacks(ServiceCallBacks callbacks) {
serviceCallbacks = callbacks;
}
public void setAlarm2(final Alarms alarm){
Runnable r = new Runnable() {
#Override
public void run() {
try {
Calendar calendar = Calendar.getInstance();
calendar.set(Calendar.HOUR_OF_DAY, alarm.get_hour());
calendar.set(Calendar.MINUTE, alarm.get_min());
AlarmManager AM = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
Intent i = new Intent(MyService.this, AlarmReceiver.class);
i.addFlags(Intent.FLAG_RECEIVER_FOREGROUND);
pendingIntent = PendingIntent.getBroadcast(MyService.this, 934, i, PendingIntent.FLAG_UPDATE_CURRENT);
AM.set(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(), pendingIntent);
} catch (Exception e) {
}
}
};
Thread t = new Thread(r);
t.start();
}
}
`
So, the setAlarm2 is the method I'm using in the service to sound the alarm. It's working when the app is open, but fails to work when the app is being closed. As you can see, this is my first post on StackOverflow and I'm also new to android programming. I've been stuck with this for a long time and would appreciate some help. Thank you.

Your alarm could be working, but the notification center is not aware of allowing your app any privileges to highlight the event that is occurring. Check out this link here for details on Notifications.
EDIT
Check out the code below I extracted from a previous project. I left out the necessary parts:
public class MyClass extends Service {
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
return START_NOT_STICKY;
}
#Override
public void onDestroy() {
super.onDestroy();
}
#Nullable
#Override
public IBinder onBind(Intent intent) {
return null;
}
public void onTaskRemoved(Intent rootIntent) {
// Input your code here prior to exit.
stopSelf();
}
}

Pending intent get service

I am having a problem getting my pendingIntent to fire. I have done some troubleshooting using the logcat etc. and in the end I am almost positive that my problem is actually in my pendingIntent method. The times I have set are correct, and the method is getting called, but nothing happens at the scheduled times.
Here is the method that I use to create the pendingIntent
public void scheduleAlarm(){
Log.d("Alarm scheduler","Alarm is being scheduled");
Intent changeVol = new Intent();
changeVol.setClass(this, VolumeService.class);
PendingIntent sender = PendingIntent.getService(this, 0, changeVol, 0);
AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
alarmManager.set(AlarmManager.RTC_WAKEUP, time, sender);
//Toast.makeText(this, "Volume Adjusted!", Toast.LENGTH_LONG).show();
}
Here is the service class:
public class VolumeService extends Service{
#Override
public void onCreate() {
super.onCreate();
Log.d("Service", "Service has been called.");
Toast.makeText(getApplicationContext(), "Service Called!", Toast.LENGTH_LONG).show();
}
#Override
public IBinder onBind(Intent arg0) {
// TODO Auto-generated method stub
return null;
}
}
The log in the scheduleAlarm() class is working as I planned but then nothing happens, so I assume it is my pendingIntent.
Thanks in advance!

Figured it out! The problem was in the Service class, I changed a few other things around too.
However, I believe the main problem was that in my service class in the onCreate method I was trying to run my code. But this needed to be done in the onStartCommand method
public class VolumeService extends Service{
#Override
public void onCreate() {
super.onCreate();
}
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
Toast.makeText(getApplicationContext(), "Service started", Toast.LENGTH_LONG).show();
return START_NOT_STICKY;
}
#Override
public IBinder onBind(Intent arg0) {
// TODO Auto-generated method stub
return null;
}
}
and a few changes were made in the class starting the service as seen here:
public void scheduleAlarm(){
Log.d("Alarm scheduler","Alarm is being scheduled");
Intent intent = new Intent(AlarmSettings.this, VolumeService.class);
PendingIntent pintent = PendingIntent.getService(AlarmSettings.this, 0, intent, 0);
AlarmManager alarm = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
alarm.set(AlarmManager.RTC_WAKEUP, time, pintent);
}

BroadcastReceiver not triggered by Alarm

I am trying to set up an alarm that will run in the background and trigger (eventually) a save event. At the moment I simply have this code attached to a button. Press the button and the alarm should start leaving Toast messages behind as an indication that it is functioning. At the moment everything runs except the onReceive in the BroadcastReceiver is never triggered.
Here is my code:
The class setting up the alarm:
//FIXME - rename (ie BackgroundSave; more descriptive)
public class AlarmReceiver extends Service{
//FIXME - make sure you kill the service
public void onCreate() {
super.onCreate();
Toast.makeText(getApplication().getApplicationContext(), "Service onCreate called", Toast.LENGTH_SHORT).show();
}
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
Toast.makeText(getApplication().getApplicationContext(), "Service started", Toast.LENGTH_SHORT).show();
setAlarm(AlarmReceiver.this);
// We want this service to continue running until it is explicitly
// stopped, so return sticky.
return START_STICKY;
}
public void setAlarm(Context c) {
AlarmManager alarmManager = (AlarmManager)c.getSystemService(Context.ALARM_SERVICE);
Intent i = new Intent(c, Alarm.class);
PendingIntent pi = PendingIntent.getBroadcast(c, 0, i, 0);
alarmManager.setRepeating(AlarmManager.ELAPSED_REALTIME_WAKEUP, System.currentTimeMillis() + 1000, 1000, pi);
Toast.makeText(c.getApplicationContext(), "setAlarm called", Toast.LENGTH_SHORT).show();
}
public void cancelAlarm(Context context) {
Intent intent = new Intent(context, Alarm.class);
PendingIntent sender = PendingIntent.getBroadcast(context, 0, intent, 0);
AlarmManager alarmManager = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
alarmManager.cancel(sender);
}
#Override
public IBinder onBind(Intent arg0) {
// TODO Auto-generated method stub
return null;
}
}
Here is the BroadcastReceiver:
public class Alarm extends BroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent) {
Toast.makeText(context, "Alarm", Toast.LENGTH_SHORT).show();
}
}
And here is my manifest:
<!-- Alarm -->
<service android:name="com.xxxx.android.tools.AlarmReceiver" android:enabled="true" />
<receiver android:name="com.xxxx.android.tools.Alarm" ></receiver>
The alarm onReceive is never triggered.

You have to use android.os.SystemClock.elapsedRealtime() as your base time when using AlarmManager.ELAPSED_REALTIME_WAKEUP.
That said i think to use the AlarmManager for your saving purpose is not the best approach. The alarm manager is pretty heavyweight. You should consider using a simple Handler to trigger your save action.
Have a look at Handler.postAtTime().