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November 11, 2009

Groovy Goodness: Building a GUI with SwingBuilder

Groovy has some very nice builders to quickly make for example XML. The SwingBuilder class makes it possible to use a builder syntax to make a GUI. We define the components we want to display, bindings, and event handlers. Groovy adds the TableLayout as a layout manger to define a simple table-like layout.

import groovy.swing.SwingBuilder  
import groovy.beans.Bindable  
import static javax.swing.JFrame.EXIT_ON_CLOSE  
import java.awt.*
 
@Bindable
class Address {  
    String street, number, city
    String toString() { "address[street=$street,number=$number,city=$city]" }
}
  
def address = new Address(street: 'Evergreen Terrace', number: '742', city: 'Springfield')
  
def swingBuilder = new SwingBuilder()
swingBuilder.edt {  // edt method makes sure UI is build on Event Dispatch Thread.
    lookAndFeel 'nimbus'  // Simple change in look and feel.
    frame(title: 'Address', size: [350, 230], 
            show: true, locationRelativeTo: null, 
            defaultCloseOperation: EXIT_ON_CLOSE) { 
        borderLayout(vgap: 5)
        
        panel(constraints: BorderLayout.CENTER, 
                border: compoundBorder([emptyBorder(10), titledBorder('Enter your address:')])) {
            tableLayout {
                tr {
                    td {
                        label 'Street:'  // text property is default, so it is implicit.
                    }
                    td {
                        textField address.street, id: 'streetField', columns: 20
                    }
                }
                tr {
                    td {
                        label 'Number:'
                    }
                    td {
                        textField id: 'numberField', columns: 5, text: address.number
                    }
                }
                tr {
                    td {
                        label 'City:'
                    }
                    td {
                        textField id: 'cityField', columns: 20, address.city
                    }
                }
            }
            
        }
        
        panel(constraints: BorderLayout.SOUTH) {
            button text: 'Save', actionPerformed: {
                println address
            }
        }
        
        // Binding of textfield's to address object.
        bean address, 
            street: bind { streetField.text }, 
            number: bind { numberField.text }, 
            city: bind { cityField.text }
    }  
}

When we run the script we get the following output:

If we change the input field and click on the Save button we get the following output:

address[street=Main St.,number=1,city=Hometown]