How to get day of week name from selected date month and year in Android?

问题

I tried the below code but it gives me the name of the day of week two days ago.

  DatePicker picker;
  int date = picker.DayOfMonth;
  int month = (picker.Month + 1);//month is 0 based
  int year = picker.Year;

  SimpleDateFormat simpledateformat = new SimpleDateFormat("EEE");
  Date dt = new Date(year, month, date);

回答1:

First convert your Date in to specific Date format using SimpleDateFormat

Use SimpleDateFormat simpleDateFormat = new SimpleDateFormat("EEEE"); to get Day name in week

WHERE EEEE -> Day name in week

SAMPLE CODE

 SimpleDateFormat inFormat = new SimpleDateFormat("dd-MM-yyyy");
 try {
       Date myDate = inFormat.parse(date+"-"+month+"-"+year);
       SimpleDateFormat simpleDateFormat = new SimpleDateFormat("EEEE");
       String dayName=simpleDateFormat.format(myDate);
 } catch (ParseException e) {
     e.printStackTrace();
}

回答2:

SimpleDateFormat dateFormat = new SimpleDateFormat("EEE", Locale.US); 
String asWeek = dateFormat.format(dt);

回答3:

    DateTimeFormatter dayOfWeekFormatter 
            = DateTimeFormatter.ofPattern("EEE", Locale.ENGLISH);
    LocalDate date = LocalDate.of(
            picker.getYear(), picker.getMonth(), picker.getDayOfMonth());
    System.out.println(date.format(dayOfWeekFormatter));

Picking 2018-04-09 this printed

Mon

I am using and recommending java.time, the modern Java date and time API. The Date class is long outdated, and you are using a deprecated constructor. It was deprecated because it works unreliably across time zones, so you shouldn’t. SimpleDateFormat is not only outdated, it is also notoriously troublesome. I recommend you avoid those classes altogether. The modern API is so much nicer to work with.

What went wrong in your code?

You’ve got two bugs apart from using the deprecated Date constructor and the outdated classes:

It’s the Date’s month that is 0-based (not that of DatePicker), so you need to subtract 1, not add 1 (or maybe they are both 0-based??).
The deprecated Date constructor’s year is “1900-based”. This may have seemed a good idea when the class was designed in the 1990’s: you could just specify 95 to get 1995. When you pass 2018 to the constructor, you get year 3918. That’s right. :-(

Question: Can I use java.time on Android?

Yes, java.time works nicely on older and newer Android devices. It just requires at least Java 6.

In Java 8 and later and on newer Android devices (from API level 26, I’m told) the modern API comes built-in.
In Java 6 and 7 get the ThreeTen Backport, the backport of the new classes (ThreeTen for JSR 310; see the links at the bottom).
On (older) Android use the Android edition of ThreeTen Backport. It’s called ThreeTenABP. And make sure you import the date and time classes from org.threeten.bp with subpackages.