DatePicker

DatePicker selects a date in a monthly calendar, with navigation by month, by year and quick month/year selection grids. It follows the picker pattern: it returns the value via getAnswer() consumed by show(onAnswer) on close (see Picker).

🟡 · Package: dev.crossfly.ui.picker · Extends: Picker · Style: DatePickerStyle

When to use

Collect a date (birthday, scheduling, due date) with a calendar UI.

When NOT to use

Collect a time → use TimePicker.

Appearance

A card with a title bar, a month row (< Name >), a year row (< 2026 >) and a 6×7 grid of day cells. It sizes at ~90% of Screen.minSize.

Complete example (copy, paste and run)

package com.exemplo;

import dev.crossfly.ui.*;
import dev.crossfly.ui.layout.*;
import dev.crossfly.ui.picker.*;

/** Runnable main screen. Point the launcher (classname) and run: gradlew :lwjgl3:run */
public class MainWindow extends Window
{
   @Override
   public void onShow() throws Exception
   {
      super.onShow();
      setLayout(new VerticalLayout());

      Button abrir = new Button("Escolher data");
      abrir.onAction(c ->
      {
         DatePicker dp = new DatePicker().title("Data de nascimento");
         dp.show(answer -> Hint.show("Data: " + (String) answer, 2000));
      });
      add(LAY_AUTO, abrir);
   }
}

The snippets below show only the core (what goes inside onShow()). To run them, place them in the MainWindow skeleton above.

Basic usage

DatePicker dp = new DatePicker();
dp.show(answer -> campoData.setText((String) answer));

Constructors

Constructor	Description
`DatePicker()`	No parameters; starts at today’s date.

Properties and customization (fluent)

Method	Type	Default	What it does
`setDate(int year, int month, int day)`	year, 0-based month, 1-based day	today	Pre-selects the date.
`title(String)`	`String`	`"Date Picker"`	Title bar text.
`yearRange(int before, int after)`	`int`, `int`	30, 10	Years before/after for the year grid.
`style(DatePickerStyle)`	style	skin	Custom style.
`getSelectedDay()`	`int`	—	Selected day (1-based).
`getDisplayYear()` / `getDisplayMonth()`	`int`	—	Displayed year / month (0-based month).

Callbacks and events

Callback	When it fires
`onSelect(Action)`	on tapping a day (receives the `DatePicker` itself).
`show(onAnswer)`	on close, delivers the date `String` (if confirmed).

getAnswer() returns the date in the format of DateTimeUtils.formatDate — the order (DMY/MDY/YMD) and the separator depend on LocaleFormats, it is not a fixed dd/MM/yyyy.

States

Navigating between months resets selectedDay to -1 (no day marked until the user chooses).
Per-state styles: today, selected, other month, normal (via DatePickerStyle).

Birthday

DatePicker dp = new DatePicker()
   .title("Data de nascimento")
   .yearRange(100, 0)     // up to 100 years ago, none in the future
   .setDate(2000, 0, 1);  // 01/Jan/2000 (month 0-based!)

dp.onSelect(p ->
{
   DatePicker d = (DatePicker) p;
   Debug.log("dia=" + d.getSelectedDay() + " mes=" + (d.getDisplayMonth() + 1));
});

dp.show(answer ->
{
   String data = (String) answer; // e.g.: "01/01/2000" per LocaleFormats
   campoData.setText(data);
});

Best practices

Remember that month is 0-based in setDate.
To localize month/day names, reassign the public constants MONTH_NAMES/MONTH_SHORT.

Common mistakes

Passing a 1-based month in setDate — January is 0.
Expecting a fixed format — the output follows LocaleFormats.dateFormat/dateSeparator.
yearRange as a selection clamp — it only limits year navigation; any day of the displayed month is selectable.