StandardColoursEx.kt

package com.zetcode

import java.awt.Color
import java.awt.Dimension
import java.awt.EventQueue
import javax.swing.GroupLayout
import javax.swing.JFrame
import javax.swing.JLabel
import javax.swing.SwingConstants.LEADING


class StandardColoursEx(title: String) : JFrame() {

    init {
        createUI(title)
    }

    private fun createUI(title: String) {

        val stdCols = arrayOf<Color>(
            Color.black, Color.blue, Color.cyan,
            Color.darkGray, Color.gray, Color.green, Color.lightGray, Color.magenta,
            Color.orange, Color.pink, Color.red, Color.white, Color.yellow
        )

        val labels = stdCols.map {
            JLabel("", null, LEADING).apply {

                minimumSize = Dimension(90, 40)
                background = it
                isOpaque = true
            }
        }

        createLayout(labels)

        setTitle(title)
        defaultCloseOperation = EXIT_ON_CLOSE
        setLocationRelativeTo(null)
    }

    private fun createLayout(labels: List<JLabel>) {

        val gl = GroupLayout(contentPane)
        contentPane.layout = gl

        gl.autoCreateContainerGaps = true
        gl.autoCreateGaps = true


        gl.setHorizontalGroup(
            gl.createParallelGroup()
                .addGroup(
                    gl.createSequentialGroup()
                        .addComponent(labels[0])
                        .addComponent(labels[1])
                        .addComponent(labels[2])
                        .addComponent(labels[3])
                )
                .addGroup(
                    gl.createSequentialGroup()
                        .addComponent(labels[4])
                        .addComponent(labels[5])
                        .addComponent(labels[6])
                        .addComponent(labels[7])
                )
                .addGroup(
                    gl.createSequentialGroup()
                        .addComponent(labels[8])
                        .addComponent(labels[9])
                        .addComponent(labels[10])
                        .addComponent(labels[11])
                )
                .addComponent(labels[12])
        )

        gl.setVerticalGroup(
            gl.createSequentialGroup()
                .addGroup(
                    gl.createParallelGroup()
                        .addComponent(labels[0])
                        .addComponent(labels[1])
                        .addComponent(labels[2])
                        .addComponent(labels[3])
                )
                .addGroup(
                    gl.createParallelGroup()
                        .addComponent(labels[4])
                        .addComponent(labels[5])
                        .addComponent(labels[6])
                        .addComponent(labels[7])
                )
                .addGroup(
                    gl.createParallelGroup()
                        .addComponent(labels[8])
                        .addComponent(labels[9])
                        .addComponent(labels[10])
                        .addComponent(labels[11])
                )
                .addComponent(labels[12])
        )

        pack()
    }
}

private fun createAndShowGUI() {

    val frame = StandardColoursEx("Standard colours")
    frame.isVisible = true
}

fun main() {
    EventQueue.invokeLater(::createAndShowGUI)
}