Layout Management and GUI Components - Learning Java Through Games - page 278

class NotepadFrame extends JFrame {
private static int WIDTH = 600;
private static int HEIGHT = 600;
public NotepadFrame () {
setDefaultCloseOperation(JFrame.DISPOSEON CLOSE) ;
setSize(WIDTH,HEIGHT);
final JTextArea textArea = new JTextArea () ;
add( new JScrollPane(textArea) ,BorderLayout.CENTER) ;
JPanel controlPanel = new JPanel () ;
controlPanel . setLayout( new FlowLayout(FlowLayout .LEFT) ) ;
String [ ] fontNames = GraphicsEnvironment .
getLocalGraphicsEnvironment () .
getAvailableFontFamilyNames () ;
final JComboBox fontComboBox = new JComboBox(fontNames) ;
fontComboBox. setSelectedItem( "SansSerif" );
final JComboBox sizeComboBox = new JComboBox ( ) ;
for ( int i=8;i < = 72; i++) {
sizeComboBox . addItem( i ) ;
sizeComboBox. setSelectedItem(12) ;
sizeComboBox . setEditable ( true );
ActionListener changeListener = new ActionListener () {
public void actionPerformed(ActionEvent e) {
textArea . setFont( new Font (( String ) fontComboBox .
getSelectedItem() ,Font.PLAIN,( Integer)sizeComboBox.
getSelectedItem())) ;
}
} ;
fontComboBox. addActionListener(changeListener) ;
sizeComboBox. addActionListener(changeListener) ;
controlPanel . add( fontComboBox) ;
controlPanel .add(sizeComboBox) ;
add( controlPanel , BorderLayout .NORTH) ;
}
}
The font of the text area is set by calling the setFont method.Notethatthevariable
textArea is defined as final because it is referenced in a local anonymous class. Note that
the setSelectedItem method is used to set a default font and default size for the text. The
method takes as input an object and selects that object in the combo box. Note as well that
there is a getSelectedItem method that returns the selected element of the combo box.
Since the method returns an object, a cast to the appropriate type is needed (in our case,
to String and to Integer ). The setEditable method can make the combo box editable
or not editable. If the combo box is editable, then the user can type text in the combo box.
Otherwise, they can just selected one of the available menu options. By default, a combo
box is not editable. By making the size combo box editable, we have allowed the user to
type in the size of the font.
Note that inside the actionPerformed method we directly referred to the combo box. If
we did not have access to the combo box, then we could have used the call e.getSource()
to get the source of the action listener event.