How to open a numeric keyboard

Purpose. Make the field open a numbers-only keyboard when it receives focus — the system’s native numeric keyboard, CrossFly’s built-in Keypad, or the calculator variant.

APIs used

• campo.keyboard(Keyboard.NUMERIC) — fluent shortcut (equivalent to setKeyboard). Available types (enum Keyboard): NONE, DEFAULT, NUMERIC, KEYPAD, CALCULATOR, DATE, TIME.
• campo.setKeyboard(Keyboard kbd) — sets the keyboard. Passing Keyboard.DEFAULT makes the field adopt the keyboard implied by the current EditMode (mode.getKeyboard()).
• campo.<TextFieldStyle>getStyle().mode(EditMode.NUMERIC) — sets the numeric mode; as a side effect, mode(...) always derives the keyboard from the mode (NUMERIC → NUMERIC). To override it, call keyboard(...) AFTER mode(...).

Which one to choose:

On desktop (Device.platform.isDesktop()), NUMERIC is automatically converted to KEYPAD in showInput(), since there is no native virtual keyboard.

Complete example (copy, paste, and run)

package com.exemplo;

import dev.crossfly.ui.*;
import dev.crossfly.ui.layout.*;
import dev.crossfly.ui.style.*;   // TextFieldStyle (config on the style)

/** 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());

      // 1) Native numeric keyboard (KEYPAD on desktop)
      TextField idade = new TextField("");
      idade.caption("Idade");
      idade.<TextFieldStyle>getStyle().mode(EditMode.NUMERIC);

      // 2) Force the built-in Keypad, regardless of mode
      TextField pin = new TextField("");
      pin.caption("PIN");
      pin.keyboard(Keyboard.KEYPAD);

      // 3) Calculator
      TextField total = new TextField("");
      total.caption("Total");
      total.keyboard(Keyboard.CALCULATOR);

      Label resultado = new Label("");

      Button enviar = new Button("Enviar");
      enviar.onAction(o ->
         resultado.setText("Idade: " + idade.getText()
            + " · PIN: " + pin.getText()
            + " · Total: " + total.getText()));

      add(LAY_FILL, idade);
      add(LAY_FILL, pin);
      add(LAY_FILL, total);
      add(LAY_AUTO, enviar);
      add(LAY_FILL, resultado);
   }
}

The snippet below shows only the core. To run it, place it in the MainWindow skeleton above.

Minimal snippet

import dev.crossfly.ui.*;
import dev.crossfly.ui.style.*;
import static dev.crossfly.ui.UIConstants.EditMode;
import static dev.crossfly.ui.UIConstants.Keyboard;

// 1) Native numeric keyboard (KEYPAD on desktop)
TextField idade = new TextField("");
idade.caption("Idade");
idade.<TextFieldStyle>getStyle().mode(EditMode.NUMERIC);

// 2) Force the built-in Keypad, regardless of mode
TextField pin = new TextField("");
pin.caption("PIN");
pin.keyboard(Keyboard.KEYPAD);

// 3) Calculator
TextField total = new TextField("");
total.keyboard(Keyboard.CALCULATOR);

To restrict input to digits in addition to opening the keyboard, combine it with validChars (see Validate a field):

idade.<TextFieldStyle>getStyle()
   .mode(EditMode.NUMERIC)
   .validChars("0123456789")
   .maxLength(3);

Dig deeper

• Masks and keyboards · Keypad
• Sibling recipes: Currency mask · Validate a field
• Canonical source: Chapter 14 — Basic widgets · Enums (UIConstants)