ColorPicker

ColorPicker selects a color through a 2-D hue×saturation matrix plus a brightness slider. It follows the picker pattern (see Picker) and returns an ARGB Integer without an alpha channel.

🟡 · Package: dev.crossfly.ui.picker · Extends: Picker · Selection: internal ColorMatrix

When to use

Let the user choose a color (theme, accent, label).

Appearance

An 80%×80% window with the hue×saturation matrix filling the body, a brightness slider, and the Cancel and Select buttons (Select shows the hex and is painted with the chosen color itself).

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 cor");
      // Uses the chosen color itself as the button background
      abrir.onAction(c ->
      {
         ColorPicker cp = new ColorPicker(0xFF3366CC);
         cp.show(answer ->
         {
            int argb = 0xFF000000 | (Integer) answer;  // adds alpha (color without alpha)
            abrir.style(abrir.getStyle().copy().backColor(argb));
         });
      });
      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

ColorPicker cp = new ColorPicker(0xFF3366CC);
cp.show(answer ->
{
   int rgb = (Integer) answer;    // 0x00RRGGBB (no alpha)
   int argb = 0xFF000000 | rgb;   // add alpha to use it as an opaque color
   botao.style(botao.getStyle().copy().backColor(argb));
});

Constructors

Constructor	Description
`ColorPicker(int defaultColor)`	Initial ARGB color shown on opening.

Properties and customization

Member	Type	What it does
`choosenColor`	`int` (public)	Current color (RGB without alpha); `-1` if canceled.
`ColorPicker.selectStr` (static)	`String`	Prefix of the Select button label (`"Select color "`).

Callbacks and events

Callback	When it fires
`show(onAnswer)`	on confirming (Select), delivers the `Integer` (RGB without alpha).

Result (important)

getAnswer() returns Integer (RGB color without alpha, masked with & 0x00FFFFFF), or null if canceled. The type is Integer (not int) precisely so it can be null.

⚠️ The color has no alpha channel. Apply 0xFF000000 | if you need an opaque color.

States

Select → answer = choosenColor and closes.
Cancel → answer = null, choosenColor = -1 and closes (the onAnswer does not fire).

Use the chosen color as a button’s background

ColorPicker cp = new ColorPicker(0xFF3366CC);
cp.show(answer ->
{
   int argb = 0xFF000000 | (Integer) answer;
   botao.style(botao.getStyle().copy().backColor(argb));
});

Best practices

Remember to add alpha (0xFF000000 |) when using the result as an opaque color.
Cast to Integer (not int) so as not to lose the null semantics on cancellation.

Common mistakes

Using the result without alpha — it comes out transparent (0x00RRGGBB).
Expecting onAnswer on cancellation — it does not fire (answer = null).