SwingBuilder 中佈建 panel

Groovy 使用 SwingBuilder 進行 panel 佈置可有 3 種手法:
(1) 逐一佈建

import groovy.swing.SwingBuilder
import java.awt.*
import javax.swing.*

def swing = new SwingBuilder()

swing.edt {
 frame (
  title: "Ex",
  defaultCloseOperation: JFrame.EXIT_ON_CLOSE,
  pack: true,
  show: true ) {
  
  borderLayout()
  panel(constraints: BorderLayout.CENTER) {
   
   borderLayout()
   panel(constraints: BorderLayout.PAGE_START) {
    label(text: 'header')
   }
   panel(constraints: BorderLayout.CENTER) {
    label(text: 'center 1')
   }
   panel(constraints: BorderLayout.PAGE_END) {
    label(text: 'footer')
   }
   
  }
 }
}

(2) 先簡單的佈建, 接著再佈置主要的 panel (以避免擁擠、縮排過深)

import groovy.swing.SwingBuilder
import java.awt.*
import javax.swing.*

def swing = new SwingBuilder()

swing.edt {
 frame (
  title: "Ex",
  defaultCloseOperation: JFrame.EXIT_ON_CLOSE,
  pack: true,
  show: true ) {
  
  borderLayout()
  panel(constraints: BorderLayout.PAGE_START) {
   
   borderLayout()
   panel(constraints: BorderLayout.PAGE_START) {
    label(text: 'header')
   }
   panel(constraints: BorderLayout.PAGE_END) {
    label(text: 'footer')
   }
   
  }.add(
   panel(constraints: BorderLayout.CENTER) {
    label(text: 'center 2')
   })
 }
}

(3) 先簡單的佈建, 事後再佈置主要的 panel

import groovy.swing.SwingBuilder
import java.awt.*
import javax.swing.*

def swing = new SwingBuilder()
def thePanel

swing.edt {
 frame (
  title: "Ex",
  defaultCloseOperation: JFrame.EXIT_ON_CLOSE,
  pack: true,
  show: true ) {
  
  borderLayout()
  thePanel = panel(constraints: BorderLayout.CENTER) {
   
   borderLayout()
   panel(constraints: BorderLayout.PAGE_START) {
    label(text: 'header')
   }
   panel(constraints: BorderLayout.PAGE_END) {
    label(text: 'footer')
   }
   
  }
...
...
  thePanel.add(
   panel(constraints: BorderLayout.CENTER) {
    label(text: 'center 3')
   })

 }
}