So I am tring to schedule alarm at a particular time on current day using AlarmManager.
To do that I am using ZoneDateTime to get current time and then updating it to the hour at which I need to set the alarm. But for some reason time.withHour is giving me 8pm or 8am no matter what hour I am passing to it. Am I doing something wrong here?
var time = ZonedDateTime.now() //getting current time at my timezone
time = time.withHour(22).withMinute(8).withSecond(0)
print(time) //getting 8am/8pm at my timezone
val timeMilis = time.toInstant().toEpochMilli()
Related
I was trying to get the next alarm clock, by the following which returns the next clock timestamp of utc wall time.
val alarmManager = getSystemService(Context.ALARM_SERVICE) as AlarmManager
val next = alarmManager.nextAlarmClock.triggerTime
If the next clock is at 19:00 of tomorrow, the next will result of 18:00 of tomorrow, what is the difference of utc wall time and utc time, I have googled for nothing.
Problem solved when I change a phone, there may be some fault on the first phone, because the result is not consistent when the alarm clock changes.
I have a logic that schedules reminders using AlarmManager. I need to implement the following:
Logic 1: when the user changes time zone, eg he travels from UK (UTC+0) to central Europe (UTC+1), alarms should follow the time zone.
Example, a reminder scheduled at 3PM UTC+0 should fire at 4PM UTC+1
Logic 2: when a time shift occurs, eg time shifts to daylight saving time in spring (from UTC+1 to UTC+2), alarms should keep the original time
Example, a reminder scheduled at 3PM UTC+1 should fire at 3PM UTC+2
How can I achieve this? As of now I have no particular logic in place and all the alarms follow Logic 1. I have found no way to identify when a time shift happens.
Scheduling logic is very simple:
LocalDateTime reminderTime = LocalDateTime.of(...)
ZoneOffset currentOffsetForMyZone = ZoneId.systemDefault().getRules().getOffset(Instant.now());
reminderTime.toInstant(currentOffsetForMyZone).toEpochMilli();
alarmManager.setExact(AlarmManager.RTC_WAKEUP, reminderTime, pendingIntent);
For each alarm store the time of day and the time zone in which it was set. This suffices for firing the alarm at the right time no matter if the user is currently in a different time zone. And Java will take summer time (DST) into account.
Your example times and UTC offsets correspond to standard time in those time zones, so let’s start with an example date in standard time even though it was a couple of days ago now:
LocalTime alarmTime = LocalTime.of(15, 0);
ZoneId alarmTimeZone = ZoneId.of("Europe/London");
// Travel to Paris and see the alarm go off at 4, assuming standard time
ZoneId currentTimeZone = ZoneId.of("Europe/Paris");
Instant actualAlarmTime = LocalDate.of(2021, Month.MARCH, 18)
.atTime(alarmTime)
.atZone(alarmTimeZone)
.toInstant();
ZonedDateTime timeOnLocation = actualAlarmTime.atZone(currentTimeZone);
System.out.format("Scheduled at %s or %d millis, goes off at %s local time%n",
actualAlarmTime, actualAlarmTime.toEpochMilli(), timeOnLocation);
The code prints:
Scheduled at 2021-03-18T15:00:00Z or 1616079600000 millis, goes off at
2021-03-18T16:00+01:00[Europe/Paris] local time
Let’s also try a date in the summer time part of the year. I have changed Paris to London and MARCH to APRIL:
// Stay back home in the UK
ZoneId currentTimeZone = ZoneId.of("Europe/London");
Instant actualAlarmTime = LocalDate.of(2021, Month.APRIL, 18)
.atTime(alarmTime)
.atZone(alarmTimeZone)
.toInstant();
Scheduled at 2021-04-18T14:00:00Z or 1618754400000 millis, goes off at
2021-04-18T15:00+01:00[Europe/London] local time
The basic trick is: don’t use the current offset for the time zone where you set the alarm. Let Java automatically apply the offset for the date and time where the alarm is to go off.
If anyone is interested, the fix was to apply the correct offset for the date and time where the alarm is to go of, as pointed out by Ole. My silly mistake was to apply always the current timezone.
LocalDateTime alarmTime = LocalDateTime.of(...)
ZoneId zone = ZoneId.systemDefault();
ZonedDateTime zoneDateTime = ZonedDateTime.of(alarmTime , zone);
long startAtMillis = zoneDateTime.toInstant().toEpochMilli();
//Fire alarm
notificationAlarm.setExactAndAllowWhileIdle(AlarmManager.RTC_WAKEUP, startAtMillis, pendingIntent);
I tried:
TimeZone.getDefault();
I tried:
Calendar mCalendar = new GregorianCalendar();
TimeZone mTimeZone = mCalendar.getTimeZone();
I tried:
Calendar c = Calendar.getInstance();
mTimeZone = c.getTimeZone();
No matter what I try... it gives me a default of 0 and GMT. My app just cannot seem to get the time zone (it should read -4 or ET, i.e. eastern USA time zones)
The strange thing is... my clock displays the correct time on my phone.
the "use automatic time zone" is checked in settings of my android device.
So why can't I get the local time in my app? how does the Android clock able to achieve this but not me?
I have checked online and cant seem to find anything. Is there at least a way to sync with the clock app and receive it's time to display on my app as well? Is there ANY way to get the correct time on my app?
System.getMilliseconds() return the time since epoch, which would only function as the current time in areas that use GMT. (As long as what you are using doesn't make it's own conversion)
To get local time in milliseconds since epoch, you can use this function:
// Kotlin
fun getLocalTime(): Long
{
val currentDate = Calendar.getInstance()
return currentDate.timeInMillis + TimeZone.getDefault().getOffset(currentDate.timeInMillis)
}
Which in Java would probably look like this:
// Java
static long getLocalTime()
{
Calendar currentDate = Calendar.getInstance();
return currentDate.getTimeInMillis() + TimeZone.getDefault().getOffset(currentDate.getTimeInMillis());
}
The function takes the time since epoch and adds to it the timezone offset of the phone's local timezone.
I am building an Android application that sets an alarm based on my application's server time.
By comparing GMT and application server time am trying to create an alarm.
for example: GMT = 10.30 am and server time = 4.30 am, so i need to set alarm after 1hour/2hour from server time.
Example code:
Calendar calender=Calendar.getInstance(TimeZone.getTimeZone("GMT"));
calender.set(Calendar.HOUR,-6); // my server running time is less than 6 hours of GMT time.
calender.set(Calendar.MINUTE,0);
calender.set(Calendar.SECOND,0);
can anyone has idea on how to set alarm
How do I set the alarm?
From what I understand, here is what you need to do.
Get Calendar object for GMT timezone.
Get current time.
Set current time to your calendar object.
Finally, add one hour to this calendar object.
Here is how you can achieve this:
Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone("GMT"));
long currentTime = System.currentTimeMillis();
calendar.setTimeInMillis(currentTime);
calendar.add(Calendar.HOUR, 1);
Hope this helps!
I am making a simple alarm clock application that mimics the default alarm app that comes with Android Lollipop.
The set*( ) methods of an AlarmManager require the date on which the alarm should be fired as a Unix epoch.
The UI is rather simple with a TimePicker.
So, given the current time and the time the user has selected from TimePicker, how do I figure out the time in milliseconds when the alarm should be fired?
Update:
There are two cases I run into:
Selecting the time that is after the current time:
Assume it is 11am and the user selects the time from the time picker as 03pm. In this case, I know that the alarm should be scheduled for the same day.
Selecting the time that is before the current time:
Assume it is 11am and the user selects the time from the time picker as 10am. In this case, I know that the alarm should be scheduled for the next day's 10am.
Ok here you go:
// Get the current time
final Date currentTime = new Date();
// Set the hours and minutes from the time picker against todays date
final Calendar selectedTime = Calendar.getInstance();
selectedTime.set(Calendar.HOUR_OF_DAY, hourFromTimePicker);
selectedTime.set(Calendar.MINUTE, minuteFromTimePicker);
// If the current date is greater than the hour and minute from time picker add one day
if (currentTime.getTime() > selectedTime.getTime().getTime()) {
selectedTime.add(Calendar.DAY_OF_YEAR, 1);
}
// Schedule the alarm
//AlarmManager.set(selectedTime.getTime().getTime());
if you store data in java Date object:
long getTime( )
Returns the number of milliseconds that have elapsed since January 1, 1970.just subtract.
Another way if you look only at time within day:
int ms = 1000*SECONDS + 1000*60*MINUTES + 1000*60*60*HOURS
I would use a android.text.format.Time class
call the setters on the Time class to set the Hour, Minute, Second, etc. The Hours are in 24H time, so if the current hour > selected hour then you know to increment days by 1
Finally, call Time#toMillis(boolean ignoreDst) to get the system time in millis, and pass that to AlarmManager
EDIT: GregorianCalendar should be used instead.