Setting component focus in JOptionPane.showOptionDialog()

问题

In order to have custom button captions in an input dialog, I created the following code:

String key = null;
JTextField txtKey = new JTextField();        
int answerKey = JOptionPane.showOptionDialog(this, new Object[] {pleaseEnterTheKey, txtKey}, decryptionKey, JOptionPane.OK_CANCEL_OPTION, JOptionPane.QUESTION_MESSAGE, null, new Object[] {okCaption, cancelCaption}, okCaption);        
if (answerKey == JOptionPane.OK_OPTION && txtKey.getText() != null) {
  key = txtKey.getText();
}

How can I move the focus (cursor) to the text field as the dialog is displayed?

UPDATE

This does not work for me, I mean the textfield has no focus: OS: Fedora - Gnome

public class Test {
  public static void main(String[] args) {
    String key = null;
    JTextField txtKey = new JTextField();
    txtKey.addAncestorListener(new RequestFocusListener());
    int answerKey = JOptionPane.showOptionDialog(null, new Object[]{"Please enter the key:", txtKey}, "Title", JOptionPane.OK_CANCEL_OPTION, JOptionPane.QUESTION_MESSAGE, null, new Object[]{"OKKK", "CANCELLLL"}, "OKKK");
    if (answerKey == JOptionPane.OK_OPTION && txtKey.getText() != null) {
      key = txtKey.getText();
    }
  }
}

回答1:

Dialog Focus shows how you can easily set the focus on any component in a modal dialog.

回答2:

    public static String getPassword(String title) {
        JPanel panel = new JPanel();
        final JPasswordField passwordField = new JPasswordField(10);
        panel.add(new JLabel("Password"));
        panel.add(passwordField);
        JOptionPane pane = new JOptionPane(panel, JOptionPane.QUESTION_MESSAGE, JOptionPane.OK_CANCEL_OPTION) {
            @Override
            public void selectInitialValue() {
                passwordField.requestFocusInWindow();
            }
        };
        pane.createDialog(null, title).setVisible(true);
        return passwordField.getPassword().length == 0 ? null : new String(passwordField.getPassword());
    }

回答3:

passing null as the last argument is the solution. At least it worked for me.

String key = null;
JTextField txtKey = new JTextField();        
int answerKey = JOptionPane.showOptionDialog(this, new Object[] {pleaseEnterTheKey, txtKey}, decryptionKey, JOptionPane.OK_CANCEL_OPTION, JOptionPane.QUESTION_MESSAGE, null, new Object[] {okCaption, cancelCaption}, null);        
if (answerKey == JOptionPane.OK_OPTION && txtKey.getText() != null) {
  key = txtKey.getText();
}

But even this solution bring another problem:

Focused component and Default component are different. Default component or default button is the button which its onclick fires if you press ENTER KEY.The last argument define the default component which gets the focus too and passing null brings the problem of having no default component! I solved it for my code this way but I guess it is not a best practice:

String key = null;
    final JTextField txtKey = new JTextField();
    txtKey.addKeyListener(new KeyAdapter() {

      @Override
      public void keyPressed(KeyEvent e) {
        int keyCode = e.getKeyCode();
        if (keyCode == 10) { //enter key
          Container parent = txtKey.getParent();              
          while (!(parent instanceof JOptionPane)) {
            parent = parent.getParent();
          }

          JOptionPane pane = (JOptionPane) parent;
          final JPanel pnlBottom = (JPanel) pane.getComponent(pane.getComponentCount() - 1);
          for (int i = 0; i < pnlBottom.getComponents().length; i++) {
            Component component = pnlBottom.getComponents()[i];
            if (component instanceof JButton) {
              final JButton okButton = ((JButton)component);
              if (okButton.getText().equalsIgnoreCase(okCaption)) {
                ActionListener[] actionListeners = okButton.getActionListeners();
                if (actionListeners.length > 0) {
                  actionListeners[0].actionPerformed(null);
                }
              }
            }
          }
        }
      }

    });

回答4:

I had the same problem with the RequestFocusListener() not working on Linux, after following the discussion on http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=5018574 I found that adding an invokeLater fixed it for now...

public class RequestFocusListener implements AncestorListener
{
public void ancestorAdded(final AncestorEvent e)
{
    final AncestorListener al= this;   
    SwingUtilities.invokeLater(new Runnable(){

        @Override
        public void run() {
            JComponent component = (JComponent)e.getComponent();
            component.requestFocusInWindow();
            component.removeAncestorListener( al );
        }
    });
}

public void ancestorMoved(AncestorEvent e) {}
public void ancestorRemoved(AncestorEvent e) {}
}

回答5:

The trick is to (a) use an AncestorListener on the text component to request focus, and when the focus is lost again (given to the default button), ask for focus a second time using a FocusListener on the text component (but don't keep asking for focus after that):

final JPasswordField accessPassword = new JPasswordField();

accessPassword.addAncestorListener( new AncestorListener()
{
  @Override
  public void ancestorRemoved( final AncestorEvent event )
  {
  }
  @Override
  public void ancestorMoved( final AncestorEvent event )
  {
  }
  @Override
  public void ancestorAdded( final AncestorEvent event )
  {
    // Ask for focus (we'll lose it again)
    accessPassword.requestFocusInWindow();
  }
} );

accessPassword.addFocusListener( new FocusListener()
{
  @Override
  public void focusGained( final FocusEvent e )
  {
  }
  @Override
  public void focusLost( final FocusEvent e )
  {
    if( isFirstTime )
    {
      // When we lose focus, ask for it back but only once
      accessPassword.requestFocusInWindow();
      isFirstTime = false;
    }
  }
  private boolean isFirstTime = true;
} );

回答6:

Try this

String key = null;
JTextField txtKey = new JTextField();
Object[] foo = {pleaseEnterTheKey, txtKey};      
int answerKey = JOptionPane.showOptionDialog(this, foo, decryptionKey, JOptionPane.OK_CANCEL_OPTION, JOptionPane.QUESTION_MESSAGE, null, new Object[] {okCaption, cancelCaption}, foo[1]);        
if (answerKey == JOptionPane.OK_OPTION && txtKey.getText() != null) {
  key = txtKey.getText();
}

回答7:

Better way to do it: create the JOptionPane using the constructor, override selectInitialValue to set the focus, and then build the dialog using createDialog.

// Replace by the constructor you want
JOptionPane pane = new JOptionPane(panel, JOptionPane.PLAIN_MESSAGE, JOptionPane.OK_CANCEL_OPTION) {
  @Override
  public void selectInitialValue() {
    textArea.requestFocusInWindow();
  }
};

JDialog dialog = pane.createDialog(owner, title);
dialog.setVisible(true);

回答8:

I found a solution ! Very primitive, but works.

Just jump to the field by java.awt.Robot using key "Tab". For example:

Robot robot = new Robot();
robot.keyPress(KeyEvent.VK_TAB);
robot.delay(100);
robot.keyRelease(KeyEvent.VK_TAB);

If you should press multiple times on "Tab" to get your Component you can use below method:

GUIUtils.pressTab(3);

Definition:

public static void pressTab(int amountOfClickes)
{
    SwingUtilities.invokeLater(new Runnable()
    {
        public void run()
        {
            try
            {
                Robot robot = new Robot();
                int i = amountOfClickes;
                while (i-- > 0)
                {
                    robot.keyPress(KeyEvent.VK_TAB);
                    robot.delay(100);
                    robot.keyRelease(KeyEvent.VK_TAB);
                }
            }
            catch (AWTException e)
            {
                System.out.println("Failed to use Robot, got exception: " + e.getMessage());
            }
        }
    });
}

If your Component location is dynamic, you can run over the while loop without limitation, but add some focus listener on the component, to stop the loop once arrived to it.

来源：https://stackoverflow.com/questions/6251665/setting-component-focus-in-joptionpane-showoptiondialog

标签

java

swing

focus

joptionpane