Making a JFileChooser select the text of the file name but not the extension

Question

I'd like the text in the file name field of the JFileChooser save dialog to select just the file name and not the extension.

I currently have this:

And want it to look like this:

This is a simple change, but one that makes saving a file much easier, in my opinion, since the user can start typing the file name right away without erasing the extension accidentally.

I know I can forcefully add the extension if it's missing, but I'd rather not do this because the extension isn't mandatory and I don't feel it should be enforced.

So, is there any way I could achieve this?

Answer 1

The API does not offer that directly but one simple way to do it is to scan the component hierarchy, looking for a JTextField and then change the selection of that textfield.

Here is an example of that solution:

import java.awt.Component;
import java.awt.Container;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;

import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;

public class TestJFileChooser {

    public TestJFileChooser() {

    }

    protected void initUI() {
        JFrame frame = new JFrame(TestJFileChooser.class.getSimpleName());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        final JButton button = new JButton("Click me");
        button.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                JFileChooser chooser = new JFileChooser();
                chooser.setSelectedFile(new File(chooser.getCurrentDirectory(), "save.dat"));
                final JTextField textField = getTexField(chooser);
                if (textField != null) {
                    SwingUtilities.invokeLater(new Runnable() {
                        @Override
                        public void run() {
                            String text = textField.getText();
                            if (text != null) {
                                int index = text.lastIndexOf('.');
                                if (index > -1) {
                                    textField.setSelectionStart(0);
                                    textField.setSelectionEnd(index);
                                }
                            }
                        }
                    });
                }
                chooser.showSaveDialog(button);
            }

            private JTextField getTexField(Container container) {
                for (int i = 0; i < container.getComponentCount(); i++) {
                    Component child = container.getComponent(i);
                    if (child instanceof JTextField) {
                        return (JTextField) child;
                    } else if (child instanceof Container) {
                        JTextField field = getTexField((Container) child);
                        if (field != null) {
                            return field;
                        }
                    }
                }
                return null;
            }
        });
        frame.add(button);
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                TestJFileChooser fc = new TestJFileChooser();
                fc.initUI();
            }
        });
    }
}