Java – disable the open button in Jfilechooser?

I extended a Jfilechooser and overridden the approveselection method so that when the user selects an invalid directory and clicks the open button, an error message in joptionpane will be displayed But I want to make my Jfilechooser more user-friendly, and when the user clicks the invalid directory and then re enables it when the user clicks the valid directory, the button will open Can I further customize my Jfilechooser and access the open button so that I can change the status of the button accordingly (possibly the listener selected by listening directory)?

public class MyFileChooser extends JFileChooser {

  private final JFrame mainFrame;

  public MyFileChooser(JFrame mainFrame) {
    this.mainFrame = mainFrame;
    setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY);
  }

  @Override
  public void approveSelection() {
    if (/* directory is valid */) {
      super.approveSelection();
      return;
    }
    JOptionPane.showMessageDialog(mainFrame,"Invalid directory","Error",JOptionPane.ERROR_MESSAGE);
  }

}

Solution

You can call chooser. When any selection change on the file / directory is detected Setcontrolbuttonsareshown (false) to hide the accept / Cancel button:

myChooser.setFileSelectionMode(JFileChooser.FILES_AND_DIRECTORIES);
myChooser.addPropertychangelistener(new Propertychangelistener() {
  public void propertyChange(PropertyChangeEvent evt) {
        if (JFileChooser.SELECTED_FILE_CHANGED_PROPERTY.equals(evt.getPropertyName())) {
            File file = (File) evt.getNewValue();
            if (file != null && file.isFile()) {    // your condition                  
                myChooser.setControlButtonsAreShown(false);
            }
            else if ( file != null ) {
                System.out.println(file.getName());
                myChooser.setControlButtonsAreShown(true);
            }
        }

        myChooser.repaint();
    }
});

However, it may confuse users, better make a custom filefilter and display only the files / directories you need:

public static class MyDirectoryFilter extends javax.swing.filechooser.FileFilter {
  @Override
  public boolean accept( File file ) {
    return file.isDirectory() && customeCondition(file) ;
  }

  @Override
  public String getDescription() {
    return "this only my custom dir";
  }
}

myChooser.setFileFilter( new MyDirectoryFilter () );

Edit: I found a way to disable the button by iterating over the component and getting the handle to open the button: http://www.coderanch.com/t/468663/GUI/java/Disabling-Enabling-level-button-folder

Example:

myChooser.setFileSelectionMode(JFileChooser.FILES_AND_DIRECTORIES);
myChooser.addPropertychangelistener(new Propertychangelistener() {
public void propertyChange(PropertyChangeEvent evt) {
    if (JFileChooser.SELECTED_FILE_CHANGED_PROPERTY.equals(evt.getPropertyName())) {
           File file = (File) evt.getNewValue();

           if (file != null && file.isFile()) { 
                setOpenButtonState(myChooser,false);

           }
           else if ( file != null ) {
                setOpenButtonState(myChooser,true);
                System.out.println(file.getName());
           }
        }

        myChooser.repaint();
    }
});

public static void setOpenButtonState(Container c,boolean flag) {
    int len = c.getComponentCount();
    for (int i = 0; i < len; i++) {
      Component comp = c.getComponent(i);

      if (comp instanceof JButton) {
        JButton b = (JButton) comp;

        if ( "Open".equals(b.getText()) ) {
            b.setEnabled(flag);
        }

      } else if (comp instanceof Container) {
          setOpenButtonState((Container) comp,flag);
      }
    }     
}