Dialogues - An Introduction to Graphical User Interfaces with Java Swing - page 111

Figure 12.1 A file selection dialogue

indicates that the 'Open' (or 'Save', in case of a save dialogue) button of the
dialogue has been clicked. CANCEL_OPTION indicates that the 'Cancel' button
of the dialogue has been clicked.

showSaveDialog(Component parent) displays the file selection dialogue for sav-
ing files; the rest is as for showOpenDialog .
getSelectedFile() returns the selected file in a variable of type File if AP-
PROVE_OPTION has been selected.

Methods that display a file selection dialogue receive a Component parent as an
argument. Class Component from the AWT library is the mother class of all graph-
ical components in Java. The reference to the parent is needed because a JFile-
Chooser is modal. The parent component is blocked as long as it is visible itself.
Only after the dialogue is closed can the parent component be used again. This is
to avoid unwanted interactions such as modifying a file in the parent frame while
it is being saved.
Figure 12.1 shows the result of creating a JFileChooser with the TestData
directory of the ITS package, a start directory, and then making it visible by
showOpenDialog .

12.2.2 Adding the file chooser to the editor

We declare a variable chooser of type JFileChooser and a variable selectedFile
of type File in class EditorFrame by

private JFileChooser chooser;
private File selectedFile;