Disable Open button in JFileChooser?

问题:

I extended a JFileChooser and overrode the approveSelection method so that when a user chooses an invalid directory and then clicks on the Open button, an error message in a JOptionPane will be displayed. But I want to make my JFileChooser more user-friendly and make the Open button become disabled when a user clicks on an invalid directory and then become re-enabled when a user clicks on a valid directory. Is it possible to customize my JFileChooser even further and get access to the Open button so that I can change the status of the button accordingly (possibly via a listener that listens for a directory selection)?

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);
  }

}

回答1:

you can hide the accept/cancel buttons by calling chooser.setControlButtonsAreShown(false) when detect any selecting change on files/directories:

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();
    }
});

but it may confuse the user, its better to make custom FileFilter and showing 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 components and getting handle to Open 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);
      }
    }     
}

回答2:

As Wajdy Essam already answered you can usually hide/show the controlbuttons using

javax.swing.JFileChooser#setControlButtonsAreShown(boolean)

but this method does not work for all Look&Feel out there, at least not the ones I'm using.

I wrote a quick workaround which will work in most cases.

Further you have full access to the cancel and approveButton of the FileChooser.

public class JFileChooserTest extends JFileChooser {

private JButton approveButton, cancelButton;

public JFileChooserTest() {
    // Lookup the Buttons
    if (approveButton == null) {
        approveButton = lookupButton(JFileChooserTest.this, getUI().getApproveButtonText(this));
    }
    if (cancelButton == null) {
        cancelButton = lookupButton(JFileChooserTest.this, UIManager.getString("FileChooser.cancelButtonText"));
    }

    setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY);

    //Creating the Listener
    PropertyChangeListener propertyChangeListener = new PropertyChangeListener() {
        @Override
        public void propertyChange(PropertyChangeEvent evt) {
            //Do action only if the selected file changed
            if (evt.getPropertyName().equals(JFileChooser.SELECTED_FILE_CHANGED_PROPERTY)) {
                File newFile = (File) evt.getNewValue();
                //Validate the new File
                boolean validate = validateFile(newFile);

                //Enable/Disable the buttons
                if (approveButton != null) {
                    approveButton.setEnabled(validate);
                }
                if (cancelButton != null) {
                    cancelButton.setEnabled(validate);
                }
            }
        }
    };

    //Adding the listeners
    addPropertyChangeListener(SELECTED_FILE_CHANGED_PROPERTY, propertyChangeListener);
}

public static void main(String[] args) {
    SwingUtilities.invokeLater(new Runnable() {
        @Override
        public void run() {
            try {
                UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                JFileChooserTest test = new JFileChooserTest();
                test.showOpenDialog(null);
            } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                Logger.getLogger(JFileChooserTest.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
    });

}

/**
 * Simple validation method; only for testing purpose
 *
 * @param f
 * @return
 */
private boolean validateFile(File f) {
    return f != null && !f.getName().startsWith("A");
}

/**
 * Looksup the first JButton in the specific Container (and sub-containers)
 * with the given text.
 *
 * @param c
 * @param text
 * @return
 */
private JButton lookupButton(Container c, String text) {
    JButton temp = null;
    for (Component comp : c.getComponents()) {
        if (comp == null) {
            continue;
        }
        if (comp instanceof JButton && (temp = (JButton) comp).getText() != null && temp.getText().equals(text)) {
            return temp;
        } else if (comp instanceof Container) {
            if ((temp = lookupButton((Container) comp, text)) != null) {
                return temp;
            }
        }
    }
    return temp;
}
}

I also recommend using javax.swing.filechooser.FileFilter to validate selected files rather then overriding approveSelection()

回答3:

Disable Open button in JFileChooser?

Even better, install a custom FileSystemView that hides the invalid directories. Look into overriding isHiddenFile(File) for that.