android kotlin - DatePicker example

MainActivity.kt

package com.cfsuman.kotlintutorials

import android.os.Bundle
import android.widget.*
import androidx.appcompat.app.AppCompatActivity
import java.text.DateFormat
import java.util.*
import kotlin.random.Random


class MainActivity : AppCompatActivity() {
    private lateinit var calendar:Calendar

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        // Get the widgets reference from XML layout
        val textView = findViewById<TextView>(R.id.textView)
        val datePicker = findViewById<DatePicker>(R.id.datePicker)
        val buttonGet = findViewById<Button>(R.id.buttonGet)
        val buttonSet = findViewById<Button>(R.id.buttonSet)


        // Initialize a new calendar instance
        calendar = Calendar.getInstance()

        // Get the Calendar current year, month and day of month
        val thisYear = calendar.get(Calendar.YEAR)
        val month = calendar.get(Calendar.MONTH)
        val day = calendar.get(Calendar.DAY_OF_MONTH)


        // Initialize the date picker widget with system current date
        datePicker.init(
            thisYear,
            month,
            day
        ) { view, year, monthOfYear, dayOfMonth ->
            // Do something when the date changed in date picker object
            // Display the date picker selected date on text view
            textView.text = "Date changed : " +
                    "${formatDate(year, monthOfYear, dayOfMonth)}"
        }


        // Set date programmatically
        buttonSet.setOnClickListener{
            // Update the date picker date by a random date
            // Kotlin Random range(inclusive,exclusive)
            val year = Random.nextInt(1999,2026)
            val month = Random.nextInt(0,12)
            val day = Random.nextInt(0,28)

            // Update the date picker with random date
            datePicker.updateDate(
                year, // Year
                month, // The month which is starting from zero.
                day // Day of month
            )
        }


        // Get date programmatically
        buttonGet.setOnClickListener{
            // Get the date picker widget selected date
            val selectedDate = formatDate(datePicker.year,
                datePicker.month,datePicker.dayOfMonth)
            // Display the date picker selected formatted date
            textView.text = "Selected date : $selectedDate"
        }
    }


    // Custom method to format date
    private fun formatDate(year:Int, month:Int, day:Int):String{
        // Create a Date variable/object with user chosen date
        calendar.set(year, month, day, 0, 0, 0)
        val chosenDate = calendar.time

        // Format the date picker selected date
        val df = DateFormat.getDateInstance(DateFormat.MEDIUM)
        return df.format(chosenDate)
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/rootLayout"
    android:background="#DCDCDC"
    android:padding="24dp">

    <TextView
        android:id="@+id/textView"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:padding="16dp"
        android:background="#E6E5E5"
        android:fontFamily="sans-serif"
        android:textSize="20sp"
        android:textAlignment="center"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <DatePicker
        android:id="@+id/datePicker"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:calendarViewShown="false"
        android:datePickerMode="spinner"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView" />

    <Button
        android:id="@+id/buttonGet"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:text="Get Date"
        app:layout_constraintStart_toStartOf="@+id/datePicker"
        app:layout_constraintTop_toBottomOf="@+id/datePicker" />

    <Button
        android:id="@+id/buttonSet"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:text="Set Date"
        app:layout_constraintBottom_toBottomOf="@+id/buttonGet"
        app:layout_constraintStart_toEndOf="@+id/buttonGet" />

</androidx.constraintlayout.widget.ConstraintLayout>