Java Examples in a Nutshell, 3rd Edition

Defining a Complex Property Editor

There is another YesNoPanel property value that requires a property editor. The messageText property of YesNoPanel can specify a multiline message to be displayed in the panel. This property requires a property editor because simple beanbox programs like ShowBean don’t distinguish between single-line and multiline string types; the JTextField object it uses for text input doesn’t allow the user to enter multiple lines of text. For this reason, we define the YesNoPanelMessageEditor class and register it with the PropertyDescriptor for the message property, as shown in Example 15-6.

Example 15-8 shows the definition of this property editor. This is a more complex editor that supports the creation of a custom editor component and graphical display of the value. Note that this example implements PropertyEditor directly, which means that it must handle registration and notification of PropertyChangeListener objects. getCustomEditor( ) returns an editor component for multiline strings. Figure 15-1 shows this custom editor within a dialog box created by the ShowBean program. Note that the Ok button in this figure is part of the ShowBean dialog, not part of the property editor itself.

The paintValue( ) method displays the value of the messageText property. This multiline value doesn’t typically fit in the small rectangle of screen space allowed for the property, so paintValue( ) displays instructions for popping up the custom editor, which allows the ...