give focus to a panel that is not a child of the focused Window?

Question

I'm working in Java to create an internal tool. The two consists of two JPanels which are anticipated to run on two separate screens. I want to be able to click a JButton which is part of JFrame A which will send a keyboard action to JFrame B.

Unfortunately I can't seem to do this because JFrame B doesn't have the focus and I can't use any of the request Focus methods because JFrame B is not a child of the Focus Window (JFrame A is).

So how can I either give JFrame B focus despite it not being a child of the Focus Window or send Keyboard Events to JFrame B that it will respond to without having focus?

Answer 1

is so hard to manage Focus between two JFrames, better would be create only one JFrame and other Top-level Containers would be JDialogs, create one/two JDialog(s) and reuse that by removing all JComponents

basicaly it would be :

EventQueue.invokeLater(new Runnable() {

   @Override
     public void run() {
         someComponent.grabFocus();
         someComponent.requestFocus();//or inWindow depends if Swing or Awt
     }
});

but between two JFrames is things little bit complicated, just basic and uncompleted example (based on code from old.good.sun.forums.com)

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class PMDialog extends JDialog {

    private static final long serialVersionUID = 1L;
    private boolean modal = false;
    private WindowAdapter parentWindowListener;
    private Window owner;
    private JFrame blockedFrame = new JFrame("Blocked Frame");
    private JFrame noBlockedFrame = new JFrame("No Blocked Frame");

    public PMDialog() {
        noBlockedFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        noBlockedFrame.getContentPane().add(new JButton(new AbstractAction("Test button") {

            private static final long serialVersionUID = 1L;

            @Override
            public void actionPerformed(ActionEvent evt) {
                System.out.println("Non blocked button pushed");
                /*if (blockedFrame.isVisible()) {
                noBlockedFrame.setVisible(false);
                } else {
                blockedFrame.setVisible(true);
                }*/
                noBlockedFrame.setVisible(true);
                blockedFrame.setVisible(true);
            }
        }));
        noBlockedFrame.setSize(200, 200);
        noBlockedFrame.setVisible(true);
        blockedFrame.setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);
        blockedFrame.getContentPane().add(new JButton(new AbstractAction("Test Button") {

            private static final long serialVersionUID = 1L;

            @Override
            public void actionPerformed(ActionEvent evt) {
                final PMDialog pmd = new PMDialog(blockedFrame, "Partial Modal Dialog", true);
                pmd.setSize(200, 100);
                pmd.setLocationRelativeTo(blockedFrame);
                pmd.getContentPane().add(new JButton(new AbstractAction("Test button") {

                    private static final long serialVersionUID = 1L;

                    @Override
                    public void actionPerformed(ActionEvent evt) {
                        System.out.println("Blocked button pushed");
                        pmd.setVisible(false);
                        blockedFrame.setVisible(false);
                        noBlockedFrame.setVisible(true);
                    }
                }));
                pmd.setDefaultCloseOperation(PMDialog.DISPOSE_ON_CLOSE);
                pmd.setVisible(true);
                System.out.println("Returned from Dialog");
            }
        }));
        blockedFrame.setSize(200, 200);
        blockedFrame.setLocation(300, 0);
        blockedFrame.setVisible(false);
    }

    public PMDialog(JDialog parent, String title, boolean isModal) {
        super(parent, title, false);
        initDialog(parent, title, isModal);
    }

    public PMDialog(JFrame parent, String title, boolean isModal) {
        super(parent, title, false);
        initDialog(parent, title, isModal);
    }

    private void initDialog(Window parent, String title, boolean isModal) {
        owner = parent;
        modal = isModal;
        parentWindowListener = new WindowAdapter() {

            @Override
            public void windowActivated(WindowEvent e) {
                if (isVisible()) {
                    System.out.println("Dialog.getFocusBack()");
                    getFocusBack();
                }
            }
        };
    }

    private void getFocusBack() {
        Toolkit.getDefaultToolkit().beep();
        super.setVisible(false);
        super.pack();
        super.setLocationRelativeTo(owner);
        super.setVisible(true);
        super.toFront();
    }

    @Override
    public void dispose() {
        owner.setEnabled(true);
        owner.setFocusableWindowState(true);
        super.dispose();
    }

    @Override
    @SuppressWarnings("deprecation")
    public void hide() {
        owner.setEnabled(true);
        owner.setFocusableWindowState(true);
        super.hide();
    }

    @Override
    public void setVisible(boolean visible) {
        boolean blockParent = (visible && modal);
        owner.setEnabled(!blockParent);
        owner.setFocusableWindowState(!blockParent);
        super.setVisible(visible);
        if (blockParent) {
            System.out.println("Adding listener to parent ...");
            owner.addWindowListener(parentWindowListener);
            try {
                if (SwingUtilities.isEventDispatchThread()) {
                    System.out.println("EventDispatchThread");
                    EventQueue theQueue = getToolkit().getSystemEventQueue();
                    while (isVisible()) {
                        AWTEvent event = theQueue.getNextEvent();
                        Object src = event.getSource();
                        if (event instanceof ActiveEvent) {
                            ((ActiveEvent) event).dispatch();
                        } else if (src instanceof Component) {
                            ((Component) src).dispatchEvent(event);
                        }
                    }
                } else {
                    System.out.println("OUTSIDE EventDispatchThread");
                    synchronized (getTreeLock()) {
                        while (isVisible()) {
                            try {
                                getTreeLock().wait();
                            } catch (InterruptedException e) {
                                break;
                            }
                        }
                    }
                }
            } catch (Exception ex) {
                ex.printStackTrace();
                System.out.println("Error from EDT ... : " + ex);
            }
        } else {
            System.out.println("Removing listener from parent ...");
            owner.removeWindowListener(parentWindowListener);
            owner.setEnabled(true);
            owner.setFocusableWindowState(true);
        }
    }

    @Override
    public void setModal(boolean modal) {
        this.modal = modal;
    }

    public static void main(String args[]) {
        PMDialog pMDialog = new PMDialog();
    }
}

EDIT: for How to adds Focus to the JDialog is there excelent Woodoo by camickr Dialog Focus but AncestorListener isn't my cup of Java and too much abstract for me

Answer 2

Is this a Swing GUI (you don't mention or add a tag to a gui library)? If so, consider using Key Bindings which can be more flexible about focus compared with KeyListeners.

Answer 3

Nothing says you can't have one Action send a message to another. In this example, Enter also needs to Clear, so it forwards the ActionEvent. Note also that each NumberButton binds two keystrokes to Click. In your case, you may have to to remove an existing binding and perhaps call toFront() on the other window. Note the caveats that lend support to @mKorbel's answer.