Develop Reference

Xamarin service - run according to a time schedule

I am developing an app built on this example: https://github.com/xamarin/mobile-samples/tree/master/BackgroundLocationDemo
The example works and the location updates are coming in as expected. However, Android keeps showing an notification that the service is running and draining battery. Now, all my users have a defined working schedule (list of Start to End DateTime per day e.g 8am-1pm, 4pm-8pm), and I want that the service is only running between those working times. This means that I need to start/stop the service whenever the schedule says the user is working or not.
I've asked this question before but wondering if anyone figured out an efficient and solid way to achieve this type of service that is operating from a time schedule?

You can use AlarmManager to execute a task in specific time.
For example, I want my task running at the 10:51 am every day, I can use following code to execute it.
public static void startAlarmBroadcastReceiver(Context context)
{
Intent _intent = new Intent(context, typeof( AlarmBroadcastReceiver));
PendingIntent pendingIntent = PendingIntent.GetBroadcast(context, 0, _intent, 0);
AlarmManager alarmManager = (AlarmManager)context.GetSystemService(Context.AlarmService);
// Remove any previous pending intent.
alarmManager.Cancel(pendingIntent);
Calendar cal = Calendar.Instance;
cal.Set( CalendarField.HourOfDay, 10);
cal.Set(CalendarField.Minute, 51);
cal.Set(CalendarField.Second, 0);
alarmManager.SetRepeating(AlarmType.RtcWakeup, cal.TimeInMillis, AlarmManager.IntervalDay, pendingIntent);
}
Here is code about AlarmBroadcastReceiver.
[BroadcastReceiver(Enabled = true, Exported = false)]
public class AlarmBroadcastReceiver : BroadcastReceiver
{
public override void OnReceive(Context context, Intent intent)
{
Toast.MakeText(context, "Received intent!", ToastLength.Short).Show();
}
}
Do not forget to add following permissions.
<uses-permission android:name="com.android.alarm.permission.SET_ALARM" />
<uses-permission android:name="android.permission.WAKE_LOCK" />
Here is running gif.

BroadcastReceiver on Android P

Since Android 9 is online and I am having a troubles to send a notification with my JobIntentService, which launched using the BroadcastReceiver .
It works great on other devices with Android <= 8.1 and I can get the notification in no time .
Sometimes It works on Android P too, but sometimes the System doesn't fire the registered services with the AlarmManager ! OR I am not able to receive it.
What is going wrong ?
AlarmReceiver.java
public class AlarmReceiver extends BroadcastReceiver {
private static final String TAG = "AlarmReceiver";
#Override
public void onReceive(Context context, Intent intent) {
if ("android.intent.action.BOOT_COMPLETED".equals(intent.getAction())) {
onBoot(context);
}
Log.d("action", "i recieved an action");
try {
Bundle bundle = intent.getExtras();
String message = bundle.getString("Push_Message", "No Content");
int type = bundle.getInt("Push_Type", -1);
Intent newIntent = new Intent(context, AppJobService.class);
newIntent.putExtra("Push_Message", message);
newIntent.putExtra("Push_Type", type);
newIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
AppJobService.enqueueWork(context, AppJobService.class, AppJobService.JOB_ID, newIntent);
} catch (Exception e) {
e.printStackTrace();
}
}
permissions in AndroidManifest.xml
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
<uses-permission android:name="android.permission.WAKE_LOCK" />
Here I've added the Receiver to the AndroidManifest.xml
<receiver
android:name=".notifications.AlarmReceiver"
android:enabled="true">
<intent-filter>
<action android:name="android.intent.action.BOOT_COMPLETED" />
</intent-filter>
</receiver>
And I am registering the Service with the AlarmManager in this way inside a class, that inherits from JobIntentService
AppJobService.java
public void sendTimedNotification(String message, int type, long timeInMillis) {
Intent intent = new Intent(this, AlarmReceiver.class);
intent.putExtra("Push_Message", message);
intent.putExtra("Push_Type", type);
Calendar cal = Calendar.getInstance();
cal.setTimeInMillis(timeInMillis);
PendingIntent sender = PendingIntent.getBroadcast(this, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);
AlarmManager am = (AlarmManager) getSystemService(ALARM_SERVICE);
am.set(AlarmManager.RTC_WAKEUP, timeInMillis, sender);
}

As Per Document:
Alarms do not fire when the device is idle in Doze mode. Any scheduled
alarms will be deferred until the device exits Doze. If you need to
ensure that your work completes even when the device is idle there are
several options available. You can use setAndAllowWhileIdle() or
setExactAndAllowWhileIdle() to guarantee that the alarms will execute.
Another option is to use the new WorkManager API, which is built to
perform background work either once or periodically. For more
information, see Schedule tasks with WorkManager.
Take a look at https://developer.android.com/training/scheduling/alarms

AlarmManager alarm start when system time is changed by user?

i am using AlarmManager class for setting Alarms it is working fine.
But if i set alarm like 9pm and current time is 8pm and i changed the system time to 10pm
then alarm 9pm alarm start automatically. so to solve this issue
i have searched so much but did not found any good answer
Please help
here is my code for alarm setting
final int id = (int) System.currentTimeMillis();
Intent intent = new Intent(this, AlarmReceiver.class);
intent.putExtra("requestCode", id);
PendingIntent pendingIntent = PendingIntent.getBroadcast(this, id, intent, PendingIntent.FLAG_UPDATE_CURRENT);
AlarmManager alarmManager = (AlarmManager)getSystemService(ALARM_SERVICE);
alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(), 2*60*1000, pendingIntent);

One of the options is to store all set alarms in database, then create a BroadcastReceiver which will listen for ACTION_TIME_CHANGE action. When user changes time it will be triggered. Then create a IntentService which will be responsible for resetting alarms. In this service class:
Read db and identify all passed alarms.
Cancel passed alarms
Set alarms for next day
Your code may look like as below:
In your Manifest:
<uses-permission android:name="android.permission.ACTION_TIME_CHANGE"/>
and below activities:
<receiver android:name=".TimeChangedReceiver" android:enabled="true">
<intent-filter>
<action android:name="android.intent.action.TIME_SET" />
</intent-filter>
</receiver>
<service android:name=".RestartAlarmsService"/>
Create class "TimeChangedReceiver" inside of which:
public class TimeChangedReceiver extends BroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent) {
if("android.intent.action.TIME_SET".equals(intent.getAction())) {
Intent i = new Intent(context, RestartAlarmsService.class);
ComponentName service = context.startService(i);
}
}
}
Create "RestartAlarmsService" class inside of which:
public class RestartAlarmsService extends IntentService {
public RestartAlarmsService() {
super("RestartAlarmsService");
}
#Override
protected void onHandleIntent(Intent intent) {
// read db here
// then cancel passed alarms
// reset them to next day
}
}
You can find many tutorials on how to use Databases and implement it in your code. Hope my answer is somehow helpful.

yes it will give you broadcast, as your pending intent object is still attached to that event while you change time that is greater than you alarm firing time.
solution- validate your condition while you receive broadcast from alarm manager

Alarm is killed when OS kills app

My alarm is killed when OS kills the app. I thought that was one of the points of an Alarm, that it would keep running even though OS killed the app? I check the life of the Alarm using the "./adb shell dumpsys alarm" command, and every time OS kills my app, the Alarm is also gone. How I start my Alarm:
public static void startLocationAlarm(Context context){
if(ActivityLifecycleHandler.isApplicationInForeground()) {
return; // If App is in foreground do not start alarm!
}
String alarm = Context.ALARM_SERVICE;
AlarmManager am = ( AlarmManager ) context.getSystemService( alarm );
Intent intent = new Intent(locationBroadcastAction);
PendingIntent pi = PendingIntent.getBroadcast( context.getApplicationContext(), 0, intent, 0 );
int type = AlarmManager.ELAPSED_REALTIME_WAKEUP;
long interval = ONE_MINUTE;
long triggerTime = SystemClock.elapsedRealtime() + interval;
am.setRepeating(type, triggerTime, ONE_MINUTE, pi );
}
To add some more context, I am trying do some location operation in a service (not IntentService) in background. Here is my receiver. Used Wakeful because I did not want the service to be killed before it was done.
public class LocationBroadcastReceiver extends WakefulBroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent ) {
Intent myIntent = new Intent( context, LocationServiceAlarmOwnGoogleClient.class );
//context.startW( myIntent );
LocationBroadcastReceiver.startWakefulService(context, myIntent);
}
}
For some more information: I cancel the alarm in OnStart method of several activities that the user can return to after having it in the background. I do not know if that can cause this weird behaviour? Here is my cancel method:
public static void stopLocationAlarm(Context context){
Intent intent = new Intent(locationBroadcastAction);
PendingIntent sender = PendingIntent.getBroadcast(context.getApplicationContext(), 0, intent, 0);
AlarmManager alarmManager = (AlarmManager) context.getSystemService(context.ALARM_SERVICE);
alarmManager.cancel(sender);
}

You can add service which listens to the phone's turning on callback.
add this permission into the manifest
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
and register reciever
<receiver android:name=".util.notification.local.MyBootCompletedService">
<intent-filter>
<action android:name="android.intent.action.BOOT_COMPLETED" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</receiver>
public class MyBootCompletedService extends BroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent) {
AlarmReceiver.startLocalNotificationService(context);
}
}

The error that caused the Alarm to be canceled had actually nothing to do with the code, but had to do with special battery settings on Huawei devices. If your app is not set as "protected" in "protected apps", the system will cancel your alarm when it kills the app. Adding your app to "protected apps" will solve this problem. Same goes for Xiaomi devices. Have to add them to "Protected apps", then the Alarm will work as intended. Thank you #CommonsWare for leading me to the solution.

How do you start an Activity with AlarmManager in Android?

I've poured through a dozen tutorials and forum answers about this problem, but still haven't been able to get some working code together. I'll try to keep the question straightforward:
How do you use AlarmManager (in the Android API) to start an Activity at a given time? Any solution to this problem will do.
My latest attempt to achieve this is below.
(Imports omitted. I expect MyActivity to start 3 seconds after the program is opened, which it doesn't. There are no error messages to speak of.)
public class AndroidTest2Activity extends Activity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Context context = this;//.getApplicationContext();
AlarmManager manager = (AlarmManager) getSystemService(Context.ALARM_SERVICE); // CORRECT
Intent intent = new Intent(context, myReceiver.class); // CORRECT
PendingIntent pending = PendingIntent.getBroadcast( context, 0, intent, 0 ); // CORRECT
manager.set( AlarmManager.RTC, System.currentTimeMillis() + 3000, pending ); // CORRECT
setContentView(R.layout.main);
}
}
public class myReceiver extends BroadcastReceiver {
public void onReceive(Context context, Intent intent) {
Intent i=new Intent(context, myActivity.class);
i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
context.startActivity(i);
}
}
public class myActivity extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.d("", "Elusive success");
setContentView(R.layout.main);
}
}
Any advice would be appreciated.
Please note: I've got myReceiver in the manifest already

In case someone else stumbles upon this - here's some working code (Tested on 2.3.3 emulator):
public final void setAlarm(int seconds) {
// create the pending intent
Intent intent = new Intent(MainActivity.this, AlarmReceiver.class);
// intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
pendingIntent = PendingIntent.getBroadcast(MainActivity.this, 0,
intent, 0);
// get the alarm manager, and scedule an alarm that calls the receiver
((AlarmManager) getSystemService(ALARM_SERVICE)).set(
AlarmManager.RTC, System.currentTimeMillis() + seconds
* 1000, pendingIntent);
Toast.makeText(MainActivity.this, "Timer set to " + seconds + " seconds.",
Toast.LENGTH_SHORT).show();
}
public static class AlarmReceiver extends BroadcastReceiver {
public void onReceive(Context context, Intent intent) {
Log.d("-", "Receiver3");
}
}
AndroidManifest.xml:
<receiver android:name="com.example.test.MainActivity$AlarmReceiver" >
</receiver>
Issues with BenLambell's code :
EITHER:
Move the receiver to it's own .java file or
make the inner class static - so it can be accessed from outside
Receiver is not declared correctly in the manifest:
if it's an inner class in MainActivity use:
<receiver android:name="package.name.MainActivity$AlarmReceiver" ></receiver>
if it's in a separate file:
<receiver android:name="package.name.AlarmReceiver" ></receiver>
If your intention is to display a dialog in the receiver's onReceive (like me): that's not allowed - only activities can start dialogs. This can be achieved with a dialog activity.
You can directly call an activity with the AlarmManager:
Intent intent = new Intent(MainActivity.this, TriggeredActivity.class);
PendingIntent pendingIntent = PendingIntent.getActivity(MainActivity.this, 0, intent, PendingIntent.FLAG_ONE_SHOT);
((AlarmManager) getSystemService(ALARM_SERVICE)).set(AlarmManager.RTC_WAKEUP, System.currentTimeMillis() + seconds * 1000, pendingIntent);

How do you use AlarmManager (in the Android API) to start an Activity at a given time?
Supply a PendingIntent to the set() call that identifies the activity to start up. Or, do what you're doing, which should work just fine.
This sample project is a bit elaborate, because it's 19 tutorials deep into one of my books, but if you look at classes like EditPreferences, OnBootReceiver, and OnAlarmReceiver, you will see the same basic recipe that you're using above. In this case, I could have just used a getActivity() PendingIntent, but the tutorial after this one gives the user a choice of launching an activity or displaying a Notification, so a BroadcastReceiver makes more sense.
Look for warnings in addition to errors in LogCat. Most likely, your receiver or activity is not in your manifest.
Note that popping up an activity out of the middle of nowhere is generally not a good idea. Quoting myself from the book in question:
Displaying the lunchtime alarm via a full-screen activity certainly works,
and if the user is looking at the screen, it will get their attention. However,
it is also rather disruptive if they happen to be using the phone right that
instant. For example, if they are typing a text message while driving, your
alarm activity popping up out of nowhere might distract them enough to
cause an accident. So, in the interest of public safety, we should give the user an option to
have a more subtle way to remind them to have lunch.

add this in your android mainifest file and it will hopefully work
<activity android:name=".MyReceiver" />
<receiver android:name=".MyReceiver"> </receiver>

In my experience you can achieve this without broadcast receiver, just use PendingIntent.getActivity() instead of getbroadcast()
private void setReminder(){
AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
Calendar startTime = Calendar.getInstance();
startTime.add(Calendar.MINUTE, 1);
Intent intent = new Intent(ReminderActivity.this, ReminderActivity.class);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
PendingIntent pendingIntent = PendingIntent.getActivity(ReminderActivity.this, 1, intent, PendingIntent.FLAG_UPDATE_CURRENT);
alarmManager.set(AlarmManager.RTC, startTime.getTimeInMillis(), pendingIntent);
}
I've tested this code on android O but I'm not sure about other android versions please inform me if this doesn't work on any other android version.

Main Problem : if you close completely you're app and expect to start you're activity after 3 seconds, you wrong. because when you close you're app , you're app cant receive broadcast, for solve this problem use services instead of broadcasts.
Point: when you're service would ran ,you cant start your activity if your app wouldn't in foreground.
Solution: I think when your service started you can again set Alarmmanager to start your activity with PendingIntent for just now.
Remember :
When you create your intent for pass it to pendingIntent add the FLAG_ACTIVITY_NEW_TASK to it.
For this PendingIntent use PendingIntent.getActivity() method and for the first PendingIntent use PendingIntent.getService() method.
I hope this help you.

I had this problem too long ago to know which answer is correct, but thank you to everyone for their responses. I'm self-answering so the question isn't still open.

According to Java convention class name begin with Capital letter.So change your
"myReceiver" to "MyReceiver" and "myActivity" to "MyActivity".
Then add your receiver in the manifest file like the below.
<application
------------
<receiver android:name="MyReceiver"></receiver>
---------------------
</application>

you are not sending any broadcast for the receiver to receiver and further more it lokks like u want a splash screen or something like that for that purpose u can start a new thread wait for some sec then start ur activity in that and for that time period u can do what ever u want on the UI thread ...