DatePicker.kt

import android.app.Dialog
import android.os.Bundle
import android.view.View
import android.view.ViewGroup
import android.widget.DatePicker
import androidx.appcompat.app.AlertDialog
import androidx.core.os.bundleOf
import androidx.fragment.app.DialogFragment
import androidx.fragment.app.activityViewModels
import dagger.hilt.android.AndroidEntryPoint
import java.time.LocalDate
import java.time.ZoneOffset


@AndroidEntryPoint
class DatePickerDialogFragment private constructor() : DialogFragment(), DatePicker.OnDateChangedListener {

    private val preselectedDate: LocalDate by lazy { (requireArguments().getSerializable(ARG_PRESELECTED_DATE) as? LocalDate) ?: LocalDate.now() }
    private val minDate: LocalDate? by lazy { (requireArguments().getSerializable(ARG_MIN_DATE) as? LocalDate) }
    private val maxDate: LocalDate? by lazy { (requireArguments().getSerializable(ARG_MAX_DATE) as? LocalDate) }

    private val caller: String by lazy { requireNotNull(requireArguments().getString(ARG_REQUEST_KEY)) }

    private val viewModel: DatePickerDialogViewModel by activityViewModels()
    private var selectedDate: LocalDate? = null

    override fun onCreateDialog(savedInstanceState: Bundle?): Dialog {
        val dialogView = View.inflate(requireContext(), R.layout.view_date_picker, null)
        val datePicker = dialogView.findViewById<DatePicker>(R.id.date_picker)
        val alertDialog = AlertDialog.Builder(requireContext()).create()

        datePicker.init(preselectedDate.year, preselectedDate.legacyCalendarMonth, preselectedDate.dayOfMonth, this)
        minDate?.let { datePicker.minDate = it.toEpochMilli(ZoneOffset.UTC) }
        maxDate?.let { datePicker.maxDate = it.toEpochMilli(ZoneOffset.UTC) }

        dialogView.findViewById<View>(R.id.btn_ok).setOnClickListener {
            selectedDate?.let { viewModel.onDateSelected(requestKey = caller, date = it) }
            alertDialog.dismiss()
        }

        dialogView.findViewById<View>(R.id.btn_cancel).setOnClickListener {
            alertDialog.dismiss()
        }

        alertDialog.setView(dialogView)
        alertDialog.window?.decorView?.addOnLayoutChangeListener { v, _, _, _, _, _, _, _, _ ->
            if (doesDatePickerTakeAllScreenSpace(datePicker, dialogView)) {
                dialog?.window?.setLayout(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT)
            }
        }
        return alertDialog
    }

    private fun doesDatePickerTakeAllScreenSpace(datePicker: DatePicker, dialogView: View) = datePicker.height >= dialogView.height

    override fun onDateChanged(view: DatePicker?, year: Int, monthOfYear: Int, dayOfMonth: Int) {
        selectedDate = localDateOfCalendar(year, monthOfYear, dayOfMonth)
    }

    companion object {

        private const val ARG_PRESELECTED_DATE = "preselectedDate"
        private const val ARG_MIN_DATE = "minDate"
        private const val ARG_MAX_DATE = "maxDate"
        private const val ARG_REQUEST_KEY = "requestKey"

        fun newInstance(preselectedDate: LocalDate?, requestKey: String, minDate: LocalDate? = null, maxDate: LocalDate? = null) =
            DatePickerDialogFragment().apply {
                arguments = bundleOf(
                    ARG_PRESELECTED_DATE to preselectedDate,
                    ARG_MIN_DATE to minDate,
                    ARG_MAX_DATE to maxDate,
                    ARG_REQUEST_KEY to requestKey,
                )
            }
    }
}

view_date_picker

<?xml version="1.0" encoding="utf-8"?>
<ScrollView 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="wrap_content">

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <DatePicker
            android:id="@+id/date_picker"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:calendarViewShown="true"
            android:spinnersShown="false"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

        <TextView
            android:id="@+id/btn_ok"
            style="@style/Widget.AppCompat.Button.ButtonBar.AlertDialog"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginEnd="12dp"
            android:text="@string/ok"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintTop_toBottomOf="@id/date_picker" />

        <TextView
            android:id="@+id/btn_cancel"
            style="@style/Widget.AppCompat.Button.ButtonBar.AlertDialog"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginEnd="4dp"
            android:text="@string/cancel"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toStartOf="@id/btn_ok"
            app:layout_constraintTop_toBottomOf="@id/date_picker" />
    </androidx.constraintlayout.widget.ConstraintLayout>
</ScrollView>