date - Start week with SUNDAY format using Kotlin in android

Question

I am working on Calendar dates, where I am making 7 Days week value from below method. But I need to start my week days from SUNDAY specific only.

fun getWeekDay(): Array<String?>? {
        weekDaysCount--
        val now1 = Calendar.getInstance()
        now1.set(2021, 1, 29)
        val now = now1.clone() as Calendar

        val format = SimpleDateFormat("yyyy-MM-dd")
        val days = arrayOfNulls<String>(7)
        val delta = -now[GregorianCalendar.DAY_OF_WEEK] + 1
        now.add(Calendar.WEEK_OF_YEAR, weekDaysCount)
        now.add(Calendar.DAY_OF_MONTH, delta)
        for (i in 0..6) {
            days[i] = format.format(now.time)
            now.add(Calendar.DAY_OF_MONTH, 1)
        }

        return days
    }

I am getting an output like this:

I need to make a method where if i give any Date, it should adjust as per SUNDAY format.

As per Date 29/1/2021, output should be like:

24(Sun), 25 (Mon), 26 (Tue), 27 (Wed), 28 (Thur) 29 (Fri), 30 (Sat)

question from:https://stackoverflow.com/questions/65540656/start-week-with-sunday-format-using-kotlin-in-android

Answer 1

What you want to achieve is much easier using Java 8's date / time library (java.time) instead of Calendar.

import java.time.DayOfWeek
import java.time.LocalDate
import java.time.format.DateTimeFormatter
import java.time.temporal.TemporalAdjusters

fun getWeekDay(): Array<String?> {
    var date = LocalDate.of(2021, 1, 29)
    date = date.with(TemporalAdjusters.previousOrSame(DayOfWeek.SUNDAY))

    val formatter = DateTimeFormatter.ofPattern("dd (EEE)")

    val days = arrayOfNulls<String>(7)
    for (i in 0 until 7) {
        days[i] = formatter.format(date)
        date = date.plusDays(1)
    }

    return days
}

The code starts from a given date (I have hard-coded it here but you can adjust it), goes back to the previous or same Sunday and simply adds seven days.

---

To be able to use it in all android versions, add this dependency to your build.gradle file:

coreLibraryDesugaring 'com.android.tools:desugar_jdk_libs:1.1.1'

and these compile options:

android {
    ...
    compileOptions {
        coreLibraryDesugaringEnabled true
        targetCompatibility JavaVersion.VERSION_1_8
        sourceCompatibility JavaVersion.VERSION_1_8
    }
    ...

Now you will be able to use a lot of Java 8 features and libraries.