Swing Interfaces with Sorting and Searching - Java Programming: Comprehensive Concepts and Techniques - page 461

getActionCommand() versus getSource()
The getActionCommand() method is preferred over the
getSource() method for objects that can have multiple states,
such as menus and buttons.

Coding the actionPerformed() Method

In the Classics on DVD program, several objects may be clicked. Previously,
action Strings were assigned to each of the menu commands. Besides the menu
commands, a user also can click the JComboBox. On any of those occasions, the
program should perform the correct operation.
Figure 7-26 displays the code for the actionPerformed() event.

188 //event to process user clicks

189 public void actionPerformed ( ActionEvent e )

190 {

191 String arg = e.getActionCommand () ;

192
193 //user clicks the sort by combo box

194 if ( e.getSource () == fieldCombo )

195 {

196 switch ( fieldCombo.getSelectedIndex ())

197 {

198 case 0:

199 sort ( title ) ;

200 break ;

201 case 1:

202 sort ( studio ) ;

203 break ;

204 case 2:

205 sort ( year ) ;

206 break ;

207 }

208 }

209
210 //user clicks Exit on the File menu

211 if ( arg == "Exit" )

212 System .exit ( 0 ) ;

213
214 //user clicks Insert New DVD on the Edit menu

215 if ( arg == "Insert" )

216 {

217 //accept new data

218 String newTitle = JOptionPane.showInputDialog ( null ,

"Please enter the new movie's title" ) ;

219 String newStudio = JOptionPane.showInputDialog ( null ,

"Please enter the studio for " + newTitle ) ;

220 String newYear = JOptionPane.showInputDialog ( null ,

"Please enter the year for " + newTitle ) ;

221
222

//enlarge arrays

223

title = enlargeArray ( title ) ;

224

studio = enlargeArray ( studio ) ;

225 year = enlargeArray ( year ) ;

226
227

//add new data to arrays

228 title [ title.length-1 ] = newTitle;

229 studio [ studio.length-1 ] = newStudio;

230 year [ year.length-1 ] = newYear;

231

FIGURE 7-26

(continued)