Creating Menus and Button Arrays Using the Abstract Windows Toolkit - Java Programming: Comprehensive Concepts and Techniques - page 406

To Enter Code to Search for the About Command

1. Enter lines 170 through 175 as shown in Figure 6-26.
The TextPad window displays the remainder of the if statement to determine
which menu command the user clicked (Figure 6-27). If the user clicked the
About Calculator command, the program will display information about the
program in a message box (Figure 6-27).

tests if
the About
command
was clicked

code to
display About
Calculator
message box

FIGURE 6-27

Recall that the arguments for the showMessageDialog() include placement of
the message box (null defaults to centered), a message, a title bar caption, and an
intrinsic constant representing one of the message icons.

Searching the Numeric Buttons

Figure 6-28 displays the code to search the array of buttons to determine
which button the user clicked and to add functionality to the numeric buttons
and the decimal point in the actionPerformed() method.

176 // test for button clicks

177 foundKey = false ;

178
179 // search for the clicked key

180 for ( int i=0; i<keys.length && !foundKey; i++ )

181 {

182 if ( e.getSource () == keys [ i ])

183 {

184 foundKey = true ;

185 switch ( i )

186 {

187 // number and decimal point buttons

188 case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7: case 8:

case 9: case 15:

189 if ( clearText )

190 {

191 lcd.setText ( "" ) ;

192 clearText = false ;

193 }

194 lcd.setText ( lcd.getText () + keys [ i ] .getLabel ()) ;

195 break ;

196

FIGURE 6-28