Develop Reference

How to show Android Notification within a timeframe

I want to show a notification every 15 minutes only between 8:00 and 16:00. Here is the code:
Calendar calendar = Calendar.getInstance();
Calendar calendarStartOfTheDay = Calendar.getInstance();
Calendar calendarEndOfTheDay = Calendar.getInstance();
calendarStartOfTheDay.set(Calendar.HOUR_OF_DAY, 8);
calendarStartOfTheDay.set(Calendar.MINUTE, 0);
calendarStartOfTheDay.set(Calendar.SECOND, 0);
calendarEndOfTheDay.set(Calendar.HOUR_OF_DAY, 16);
calendarEndOfTheDay.set(Calendar.MINUTE, 0);
calendarEndOfTheDay.set(Calendar.SECOND, 0);
AlarmManager alarmManager = (AlarmManager) context.getSystemService(ALARM_SERVICE);
if (alarmManager != null && calendar.getTimeInMillis() > calendarStartOfTheDay.getTimeInMillis() && calendar.getTimeInMillis() < calendarEndOfTheDay.getTimeInMillis()) {
alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis() + 15 * 60 * 1000, AlarmManager.INTERVAL_FIFTEEN_MINUTES, pendingIntent);
}
Is there a solution except checking the current time before notificationManager.notify()
If this is the only solution, wouldn't it drain your battery too much during the night?

This can be done by job scheduler in android. As alarm manager is outdated and
no longer used. Job scheduler also provide you with the flexibility of scheduling the task to run under specific conditions,
such as:
Device is charging
Device is connected to an unmetered network
Device is idle
Start before a certain deadline
Start within a predefined time window, e.g., within the next hour
Start after a minimal delay, e.g., wait a minimum of 10 minutes
you can follow this link to implement this
https://medium.com/google-developers/scheduling-jobs-like-a-pro-with-jobscheduler-286ef8510129

Alarm goes off too early in android

I want to set alarm for a specific time, I tried the code below. The problem is, most of the time alarm goes off within 10 seconds. I tried getting value of time in a toast and that seems to be perfectly fine.
Calendar cur_cal = new GregorianCalendar();
cur_cal.setTimeInMillis(System.currentTimeMillis());//set the current time and date for this calendar
Calendar cal = new GregorianCalendar();
cal.add(Calendar.DAY_OF_YEAR, cur_cal.get(Calendar.DAY_OF_YEAR));
cal.set(Calendar.HOUR_OF_DAY, 1);
cal.set(Calendar.MINUTE, 54);
cal.set(Calendar.SECOND, 0);
cal.set(Calendar.MILLISECOND, 0);
cal.set(Calendar.DATE, cur_cal.get(Calendar.DATE));
cal.set(Calendar.MONTH, cur_cal.get(Calendar.MONTH));
long futureInMillis = SystemClock.elapsedRealtime() + delay;
long time = cal.getTimeInMillis()-(System.currentTimeMillis());
AlarmManager alarmManager = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
alarmManager.setRepeating(AlarmManager.ELAPSED_REALTIME_WAKEUP, time, (1000*60*60*24) , pendingIntent);
Toast.makeText(context, "alarm set for" + time, Toast.LENGTH_SHORT).show();
I also tried,
alarmManager.set(AlarmManager.ELAPSED_REALTIME_WAKEUP, time, pendingIntent);
also,
alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, cal.getTimeInMillis(), 24*60*60*1000, pendingIntent);
and,
alarmManager.set(AlarmManager.RTC_WAKEUP, cal.getTimeInMillis(), pendingIntent);

As I understand your question("I want to set alarm for a specific time"), you want the alarm to sound at--lets say 10 AM tomorrow. However, your code seems to be in contradiction to this statement, because you are calculating a time difference:
long time = cal.getTimeInMillis()-(System.currentTimeMillis());
You may also be experiencing an issue the AlarmManager has by with the setRepeating() method. The Android documentation says:
Note: as of API 19, all repeating alarms are inexact. If your
application needs precise delivery times then it must use one-time
exact alarms, rescheduling each time as described above. Legacy
applications whose targetSdkVersion is earlier than API 19 will
continue to have all of their alarms, including repeating alarms,
treated as exact.
So, if you do want to set an alarm for a specific time (and not a time difference) just try this:
long time = cal.getTimeInMillis();
You might also consider changing to the setExact() method and creating code to repeat as needed (there are examples on the Internet).
Link to Android documentation:
https://developer.android.com/reference/android/app/AlarmManager.html#setRepeating(int,%20long,%20long,%20android.app.PendingIntent)

How to avoid the alarm triggering when the alarm time is past?

I have scheduled an alarm to trigger on every day 10 AM.
I am setting this alarm at 12 AM Monday.
If the alarm time is past then the alarm will be triggered immediately.
but for my requirement I don't want to trigger immediately. Is fine for me to trigger on next day 10 AM.
Below is my current code to set Alarm:
Calendar activeModeTime = Calendar.getInstance();
// activeModeTime.setTimeZone(TimeZone.getTimeZone(Constants.TIME_ZONE));
activeModeTime.set(Calendar.HOUR_OF_DAY,
mSharedPrefManager.getActiveStartHourPref());
activeModeTime.set(Calendar.MINUTE,
Constants.DEFAULT_ACTIVE_START_MINUTE);
activeModeTime.set(Calendar.SECOND,
Constants.ALL_START_END_DEFAULT_SECOND);
mAlarmManager.setRepeating(AlarmManager.RTC_WAKEUP,
activeModeTime.getTimeInMillis(), AlarmManager.INTERVAL_DAY,
getActiveModeAlarmPendingIntent());
how do I achieve this.

Check if the time that you've set is in the past and if it is then add 24 hrs to your trigger time.
if(activeModeTime < System.currentTimeMillis()){
activeModeTime += AlarmManager.INTERVAL_DAY;
}

write interval instead of REPEATING_INTERVAL.
For above example of 10 AM you need to write AlarmManager.INTERVAL_DAY instead of REPEATING_INTERVAL in below code.
if(Calendar.getInstance().getTimeInMillis()>=calendar.getTimeInMillis()){
timeInMillis = calendar.getTimeInMillis() + REPEATING_INTERVAL;
}else {
timeInMillis = calendar.getTimeInMillis();
}
alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, timeInMillis,REPEATING_INTERVAL, pendingIntent);

Alarmmanager - Fire alarm on top of every minute

I am trying to fire an Alarm on top of every minute. But as for some reason it doesn't want to work. It is for an Widget Clock which should update every minute. For battery reasons i've made an reciever for screen off and on. So my Alarm only fires when the screen is on. The minutes should be syncron with my System clock.
public static void startClockTickAlarm() {
AlarmManager alarmManager = (AlarmManager)_context.getSystemService(Context.ALARM_SERVICE);
Calendar calendar = Calendar.getInstance();
calendar.setTimeInMillis(System.currentTimeMillis());
calendar.add(Calendar.SECOND, 1);
calendar.add(Calendar.HOUR, 1);
alarmManager.setRepeating(AlarmManager.RTC, utcMillisNextMin(), 60000, createClockTickIntent(_context));
}
public static final long utcMillisNextMin() {
Time t = new Time();
t.setToNow();
t.second = 0;
t.minute++;
System.out.println("Next Alarm: " + t.hour + ":" + t.minute + ":" + t.second);
return t.normalize(true);
}
My System.out gives me exactly what it should. For example i enable my widget at 11:30:15 the returning result is 11:31:00 - This means my alarm should firstly fire at 11:31. According to my System Clock, the alarm is 5-15 seconds too late. The seconds which the alarm fires too late are not always the same (between 5 and 15 seconds).
Thanks in advance.

Like #mighter said, API >= 19 if you must use exact timing, use the setExact() API.
if(android.os.Build.VERSION.SDK_INT < 19) {
alarmManager.setRepeating(AlarmManager.RTC, utcMillisNextMin(), 60000, createClockTickIntent(_context));
} else {
alarmManager.setExact(...);
}

There's following statement in docs:
Note: as of API 19, all repeating alarms are inexact. If your
application needs precise delivery times then it must use one-time
exact alarms, rescheduling each time as described above. Legacy
applications whose targetSdkVersion is earlier than API 19 will
continue to have all of their alarms, including repeating alarms,
treated as exact.
If you're running on Android 4.4.4 then this might be the reason.

Android AlarmManager - RTC_WAKEUP vs ELAPSED_REALTIME_WAKEUP

Can someone explain to me the difference between AlarmManager.RTC_WAKEUP and AlarmManager.ELAPSED_REALTIME_WAKEUP? I have read the documentation but still don't really understand the implication of using one over the other.
Example code:
alarmManager.set(AlarmManager.ELAPSED_REALTIME_WAKEUP,
scheduledAlarmTime,
pendingIntent);
alarmManager.set(AlarmManager.RTC_WAKEUP,
scheduledAlarmTime,
pendingIntent);
How different will the two lines of code execute? When will those two lines of code execute relative to each other?
I appreciate your help.

AlarmManager.ELAPSED_REALTIME_WAKEUP type is used to trigger the alarm since boot time:
alarmManager.set(AlarmManager.ELAPSED_REALTIME_WAKEUP, 600000, pendingIntent);
will actually make the alarm go off 10 min after the device boots.
There is a timer that starts running when the device boots up to measure the uptime of the device and this is the type that triggers your alarm according to the uptime of the device.
Whereas, AlarmManager.RTC_WAKEUP will trigger the alarm according to the time of the clock. For example if you do:
long thirtySecondsFromNow = System.currentTimeMillis() + 30 * 1000;
alarmManager.set(AlarmManager.RTC_WAKEUP, thirtySecondsFromNow , pendingIntent);
this, on the other hand, will trigger the alarm 30 seconds from now.
AlarmManager.ELAPSED_REALTIME_WAKEUP type is rarely used compared to AlarmManager.RTC_WAKEUP.

Despite the currently accepted and up-voted answer, AlarmManager.ELAPSED_REALTIME* types along with SystemClock.elapsedRealtime() has always been more reliable than the RTC clocks for alarms and timing.
Using ELAPSED_REALTIME_WAKEUP with AlarmManager will rely on a monotonic clock starting from boot time "and continues to tick even when the CPU is in power saving modes, so is the recommend basis for general purpose interval timing". So,
alarmManager.set(AlarmManager.ELAPSED_REALTIME_WAKEUP, SystemClock.elapsedRealtime()
+ 60*1000, pendingIntent);
will make your PendingIntent fire in 1 min (60*1000 milliseconds).
Whereas, AlarmManager.RTC_WAKEUP is for the the standard "wall" time in milliseconds since the epoch. So,
alarmManager.set(AlarmManager.RTC_WAKEUP, System.currentTimeMillis()
+ 60*10000, pendingIntent);
may also trigger the alarm 60 seconds from now, but not reliably, because as noted in the SystemClock documentation:
The wall clock can be set by the user or the phone network (see
setCurrentTimeMillis(long)), so the time may jump backwards or
forwards unpredictably. This clock should only be used when
correspondence with real-world dates and times is important, such as
in a calendar or alarm clock application. Interval or elapsed time
measurements should use a different clock. If you are using
System.currentTimeMillis(), consider listening to the
ACTION_TIME_TICK, ACTION_TIME_CHANGED and ACTION_TIMEZONE_CHANGED
Intent broadcasts to find out when the time changes.
Also, the question only referenced only the *_WAKEUP alarms but see also the AlarmManager documentation on that to make sure you understand what the wakeup vs non-wakeup alarms provide.

Just a note. You can get the uptime millis calling:
long uptimeMillis = SystemClock.elapsedRealtime();
So if you want to fire the alarm 30 seconds from now, and you want to use the uptime clock instead of the normal clock, you can do:
long thirtySecondsFromNow = SystemClock.elapsedRealtime() + 30 * 1000;
alarmManager.set(AlarmManager.ELAPSED_REALTIME_WAKEUP, thirtySecondsFromNow, pendingIntent);
Whenever you want to check for some elapsed time instead of a specific date/time, it's best to use the uptime. That's because the current time set by the user in the device can change if the user changes it using the settings.

I programmed this problem in my own project this way. in below code i am using
AlarmManager.ELAPSED_REALTIME_WAKEUP
to set alarm at a specific time.
the variable 'intentName' is used in the intentFilter to receiver this alarm. because i am firing many alarms of this type. when i cancel all alarms. i use the method cancel. given at bottom.
//to hold alarms and cancel when needed
public static ArrayList<String> alarmIntens = new ArrayList<String>();
//
public static String setAlarm(int hour, int minutes, long repeatInterval,
final Context c) {
/*
* to use elapsed realTime monotonic clock, and fire alarm at a specific time
* we need to know the span between current time and the time of alarm.
* then we can add this span to 'elapsedRealTime' to fire the alarm at that time
* this way we can get alarms even when device is in sleep mood
*/
Time nowTime = new Time();
nowTime.setToNow();
Time startTime = new Time(nowTime);
startTime.hour = hour;
startTime.minute = minutes;
//get the span from current time to alarm time 'startTime'
long spanToStart = TimeUtils.spanInMillis(nowTime, startTime);
//
intentName = "AlarmBroadcast_" + nowTime.toString();
Intent intent = new Intent(intentName);
alarmIntens.add(intentName);
PendingIntent pi = PendingIntent.getBroadcast(c, alarms++, intent,
PendingIntent.FLAG_UPDATE_CURRENT);
//
AlarmManager am = (AlarmManager) c
.getSystemService(Context.ALARM_SERVICE);
//adding span to elapsedRealTime
long elapsedRealTime = SystemClock.elapsedRealtime();
Time t1 = new Time();
t1.set(elapsedRealTime);
t1.second=0;//cut inexact timings, seconds etc
elapsedRealTime = t1.toMillis(true);
if (!(repeatInterval == -1))
am.setRepeating(AlarmManager.ELAPSED_REALTIME_WAKEUP,
elapsedRealTime + spanToStart, repeatInterval, pi);
else
am.set(AlarmManager.ELAPSED_REALTIME_WAKEUP, elapsedRealTime
+ spanToStart, pi);
where span function is this:
public static long spanInMillis(Time startTime, Time endTime) {
long diff = endTime.toMillis(true) - startTime.toMillis(true);
if (diff >= 0)
return diff;
else
return AlarmManager.INTERVAL_DAY - Math.abs(diff);
}
alarm cancel function is this.
public static void cancel(Context c) {
AlarmManager am = (AlarmManager) c
.getSystemService(Context.ALARM_SERVICE);
// cancel all alarms
for (Iterator<String> iterator = alarmIntens.iterator(); iterator
.hasNext();) {
String intentName = (String) iterator.next();
// cancel
Intent intent = new Intent(intentName);
PendingIntent pi = PendingIntent.getBroadcast(c, 0, intent,
PendingIntent.FLAG_UPDATE_CURRENT);
am.cancel(pi);
//
iterator.remove();
}
}

Some important notes when choosing which alarm to use:(for whom who already read the upvoted votes)
The RTC_WAKEUP death valley - time change:
If the user has manually change time to the past the alarm won't go off, and future will cause the alarm to go off immediately if it past the RTC timestamp. Do not use this alarm to do any client side verification / important jobs because it have a chance to fail.
The WAKEUP meaning (Marshmallow and above)
In general - not much. Will not wakeup the device when idle or while in doze, for that alarmManager.setExactAndAllowWhileIdle or alarmManager.setAndAllowWhileIdle (Doze & Idle)