adjust selected File to FileFilter in a JFileChooser

Question

I\'m writing a diagram editor in java. This app has the option to export to various standard image formats such as .jpg, .png etc. When the user clicks File->Export, you get

Answer 1

You can also use a PropertyChangeListener on the SELECTED_FILE_CHANGED_PROPERTY prior to attaching your suffix. When the selected file gets checked against the new filter (and subsequently set to null), the SELECTED_FILE_CHANGED_PROPERTY event is actually fired before the FILE_FILTER_CHANGED_PROPERTY event.

If the evt.getOldValue() != null and the evt.getNewValue() == null, you know that the JFileChooser has blasted your file. You can then grab the old file's name (using ((File)evt.getOldValue()).getName() as described above), pull off the extension using standard string parsing functions, and stash it into a named member variable within your class.

That way, when the FILE_FILTER_CHANGED event is triggered (immediately afterwards, as near as I can determine), you can pull that stashed root name from the named member variable, apply the extension for the new file filter type, and set the JFileChooser's selected file accordingly.

Answer 2

Here is my solution and it works fine. It maybe helps someone. You sould create your own "MyExtensionFileFilter" class, otherwise you have to modify the code.

public class MyFileChooser extends JFileChooser {
    private File file = new File("");

    public MyFileChooser() {
        addPropertyChangeListener(JFileChooser.FILE_FILTER_CHANGED_PROPERTY, new PropertyChangeListener() {
            public void propertyChange(PropertyChangeEvent e) {
                String filename = MyFileChooser.this.file.getName();
                String extold = null;
                String extnew = null;
                if (e.getOldValue() == null || !(e.getOldValue() instanceof MyExtensionFileFilter)) {
                    return;
                }
                if (e.getNewValue() == null || !(e.getNewValue() instanceof MyExtensionFileFilter)) {
                    return;
                }
                MyExtensionFileFilter oldValue = ((MyExtensionFileFilter) e.getOldValue());
                MyExtensionFileFilter newValue = ((MyExtensionFileFilter) e.getNewValue());
                extold = oldValue.getExtension();
                extnew = newValue.getExtension();

                if (filename.endsWith(extold)) {
                    filename = filename.replace(extold, extnew);
                } else {
                    filename += ("." + extnew);
                }
                setSelectedFile(new File(filename));
            }
        });
    }

    @Override
    public void setSelectedFile(File file) {
        super.setSelectedFile(file);
        if(getDialogType() == SAVE_DIALOG) {
            if(file != null) {
                super.setSelectedFile(file);
                this.file = file;
            }
        }
    }

    @Override
    public void approveSelection() { 
        if(getDialogType() == SAVE_DIALOG) {
            File f = getSelectedFile();  
            if (f.exists()) {  
                String msg = "File existes ...";  
                msg = MessageFormat.format(msg, new Object[] { f.getName() });  
                int option = JOptionPane.showConfirmDialog(this, msg, "", JOptionPane.YES_NO_OPTION);
                if (option == JOptionPane.NO_OPTION ) {  
                    return;  
                }
            }
        }
        super.approveSelection();   
    }

    @Override
    public void setVisible(boolean visible) {
        super.setVisible(visible);
        if(!visible) {
            resetChoosableFileFilters();
        }
    }
}