Develop Reference

How get the first day of a week index in Flutter

I try to get the first day of the week index on a flutter app by using :
var firstDayOfWeekIndex =
MaterialLocalizations.of(context).firstDayOfWeekIndex;
It's work done to get the first day of the week based on Language and region settings but not with the calendar phone settings.
For exemple, on locale "en_US" first day of week is sunday, but my phone settings calendar is monday. The previous code get Sunday not monday.
How can achieve this ? (I would like a compatibility iOS/Android) ?

Take a look at this answer :
enter link description here
In few words, make this:
DateTime findFirstDateOfTheWeek(DateTime dateTime) {
return dateTime.subtract(Duration(days: dateTime.weekday - 1)); }

Android: How to set first day of week in DateRangePicker?

How to set first day of week to monday or saturday ?
I can't find method or variable to change it. Like picture example below, first day of week is monday. Thanks in advance.
link github DateRangePicker https://github.com/savvisingh/DateRangePicker
Thanks for the answer. I finally figure it out. You need to initialize Locale and Timezone to change first day of week. Not calendar that you have to change. Don't need to break the library code too.
new CalendarPickerView.init(date1, date1, TimeZone.getDefault(), Locale.UK, new SimpleDateFormat("MMMM, YYYY", Locale.getDefault())) //
.inMode(CalendarPickerView.SelectionMode.MULTIPLE)
.withSelectedDates(listDate);

The first day of week is determined by your locale.
Set it to something like English (UK) or German and you will have Monday as first day of week.
Then if it dosen't work you can change by code, like :
datePickerDialog.setFirstDayOfWeek(int weekStart);
If you want monday weekStart = 2
I hope it will help you!

As per you using the DateRangePicker library :
For Example:
Use this code in your project.
// create a calendar
Calendar cal = Calendar.getInstance();
// set first day of the week as something else
cal.setFirstDayOfWeek(Calendar.WEDNESDAY);
or it will not run then required for you to change in library code with create method and put above code then used it in your project.

I have looked at that repository. The library creates days from 0 to 7 in a loop and gets days. See this.
The calendar here in use is created in init method in CalendarPickerView. Look at CalendarPickerView.
today = Calendar.getInstance(timeZone, locale);
I think if you change first day of week of calendar or default locale/timezone, you can do what you want.

Wrong data return from calender

I am trying to retrieve the number of week in a month.. actually today is the second week in november but I am getting it as 3
The code I am using is
Log.e("dfhkdjfk", Calendar.getInstance().get(Calendar.WEEK_OF_MONTH)+"");
please help me to figure it out.
Reference Time:
3:45 AM
Monday, November 9, 2015
Coordinated Universal Time (UTC)

Wrong.
For some country like France where Monday is the first day of the week, today is really the first day of the third week of November, as the first of november was a Sunday ( so the first week of november had one day... ).
You might use DAY_OF_WEEK_IN_MONTH which give you the number of time a day already happened starting from the beginning of the current month.
Otherwise check which day is considered as the first of the week and implement some logic to adapt it to your need.

You need to try below code with TimeZone which give correct Calendar.WEEK_OF_MONTH
Calendar calUs = Calendar.getInstance(TimeZone.getTimeZone("US/Eastern"), Locale.US);
int weekOfMonthUs = calUs.get(Calendar.WEEK_OF_MONTH);
System.out.println("Week of month is " + weekOfMonthUs);
O/P

Week of month is the week within the current month starting from Sunday to how many weeks have there been.
WEEK_OF_MONTH depends on the first day of the week. Not all calendars have Sunday has beginning of the week. For ex: France has Monday as first day of the week. So Before getting into this check the locale of the phone.

calendarview highlights wrong week

I have a CalendarView in my app, when the user selects a date by touching that date in the monthview, the correct date is selected (verified by adding debug statements in the code), but the week before is highlighted, so it looks as if the wrong date is selected.
I have found a work-around: if I set 'firstDayInWeek' to 1 the problem is solved, but by default the firstDayInweek is 2 (monday), and then this problem occurs.
Thank you very much!
Samsung S4 with API 21

I have had the same issue as you, using a Samsung S5 running API 21.
There are two workarounds that I have found, none of them is a good experience for our users :(
Force first day of the week to Sunday
calendarView.setFirstDayOfTheWeek(Calendar.SUNDAY);
Set a minimum and a maximum date for the calendar (be careful because not all of the dates work here). I was able to make it work properly setting a minimum date 2 months before the current date and maximum date 2 years after the current date. You can play with these values and find a good compromise between the limits and your user experience.
Calendar calendar = Calendar.getInstance();
calendar.set(Calendar.MONTH, calendar.get(Calendar.MONTH) - 2);
calendarView.setMinDate(calendar.getTimeInMillis());
calendar.set(Calendar.YEAR, calendar.get(Calendar.YEAR) + 2);
calendarView.setMaxDate(calendar.getTimeInMillis());
Unfortunately, this is the only way I could fix this issue, I hope it is useful for you.

Repeat scheduled tasks on selected days in Android sdk alarm manager

I have tried to do this without bothering the experts and have read numerous threads here and on other sites. It is clearly my brain not understanding what needs to be done in order for this to work.
My goal is that the app allows the user to enter a time and one or more days in a week. All of the GUI side and storing of the dates and times I have done, however to get the alarm manager to repeat, lets say every Monday at 14:00 and then can send at 14:02 . I have used the java Calendar object to hold the times and days of the week or even used date and day of the week of the month. These are then , as needed, converted to milliseconds for it to be read in by the alarm manager.
I then have used either the alarm manager set or set repeat methods to repeat the event. All I am able to do is get it to occur once and then if I change the emulator date and time to another Monday nothing happens.
The GUI holds the hours and minutes in required variables and then these are used against the calendar objects.
The alarm manager calls a broadcast receiver for the event to occur.
Please can someone simply give an example on how to set specific days such as Monday , Wednesday Friday. I know that separate alarm managers are needed for each day and at the moment I have just focused on Monday as my main test.
Links viewed:
How can i Repeat the Alarm in android for only Monday, Tuesday and Friday
How to repeat the alarm for "n" days at a particular time
how to repeat alarm after 1 day in android
Managed to figure this out now and so follows my answer:
The following code calculates the remaining days between now and the day needed for the scheduled task. the variable whichday is passed via parameter from the method this code belongs to. In the understanding of this whichday represents days of the week 1 through to 7 where 1 is Sunday , 2 is Monday and so .
//This gets the current day of the week as of TODAY / NOW
int checkcurrentday = getcurtime.get(Calendar.DAY_OF_WEEK);
// This calculates the days between now and the day needed which is represented by whichday.
int numberofdays = Calendar.SATURDAY + whichday - checkcurrentday;
//Now add NOT set the difference of the days to your Calendar object
tMondayOn.add(Calendar.DATE, numberofdays);

Well, you need to first use the Java Calendar API (or Joda!) to figure out when the next monday is. Set the alarm to to that time in milliseconds then use setRepeating and pass in a long that represents the interval of one week.