Java Swing Focus installJComponentRepainterOnWindowFocusChanged( JComponent component)

Description

Installs a listener on the given JComponent 's parent Window that repaints the given component when the parent window's focused state changes.

License

Apache License

Parameter

Parameter	Description
component	the JComponent to add the repaint focus listener to.

Declaration

public static void installJComponentRepainterOnWindowFocusChanged(
        JComponent component) 

Method Source Code

//package com.java2s;
/*/*from  w ww.j  a  v  a 2 s  . c  o  m*/
 * Copyright (c) 2009 Kathryn Huxtable and Kenneth Orr.
 *
 * This file is part of the SeaGlass Pluggable Look and Feel.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * 
 * $Id$
 */

import java.awt.Window;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.event.WindowFocusListener;
import java.awt.event.WindowListener;
import java.lang.ref.WeakReference;

import javax.swing.JComponent;
import javax.swing.SwingUtilities;
import javax.swing.event.AncestorEvent;
import javax.swing.event.AncestorListener;

public class Main {
    /**
     * Installs a listener on the given {@link JComponent}'s parent
     * {@link Window} that repaints the given component when the parent window's
     * focused state changes. If the given component does not have a parent at
     * the time this method is called, then an ancestor listener will be
     * installed that installs a window listener when the components parent
     * changes.
     * 
     * @param component
     *            the {@code JComponent} to add the repaint focus listener to.
     */
    public static void installJComponentRepainterOnWindowFocusChanged(
            JComponent component) {
        // TODO check to see if the component already has an ancestor.
        WindowListener windowListener = createWeakWindowFocusListener(createRepaintWindowListener(component));
        AncestorListener ancestorListener = createAncestorListener(
                component, windowListener);
        component.addAncestorListener(ancestorListener);
    }

    private static WindowListener createWeakWindowFocusListener(
            WindowFocusListener windowFocusListener) {
        final WeakReference<WindowFocusListener> weakReference = new WeakReference<WindowFocusListener>(
                windowFocusListener);
        return new WindowAdapter() {
            public void windowActivated(WindowEvent e) {
                // TODO if the WeakReference's object is null, remove the
                // WeakReference as a FocusListener.
                if (weakReference.get() != null) {
                    weakReference.get().windowGainedFocus(e);
                }
            }

            public void windowDeactivated(WindowEvent e) {
                if (weakReference.get() != null) {
                    weakReference.get().windowLostFocus(e);
                }
            }
        };
    }

    private static WindowFocusListener createRepaintWindowListener(
            final JComponent component) {
        return new WindowAdapter() {
            public void windowActivated(WindowEvent e) {
                component.repaint();
            }

            public void windowDeactivated(WindowEvent e) {
                component.repaint();
            }
        };
    }

    private static AncestorListener createAncestorListener(
            JComponent component, final WindowListener windowListener) {
        final WeakReference<JComponent> weakReference = new WeakReference<JComponent>(
                component);
        return new AncestorListener() {
            public void ancestorAdded(AncestorEvent event) {
                // TODO if the WeakReference's object is null, remove the
                // WeakReference as an AncestorListener.
                Window window = weakReference.get() == null ? null
                        : SwingUtilities.getWindowAncestor(weakReference
                                .get());
                if (window != null) {
                    window.removeWindowListener(windowListener);
                    window.addWindowListener(windowListener);
                }
            }

            public void ancestorRemoved(AncestorEvent event) {
                Window window = weakReference.get() == null ? null
                        : SwingUtilities.getWindowAncestor(weakReference
                                .get());
                if (window != null) {
                    window.removeWindowListener(windowListener);
                }
            }

            public void ancestorMoved(AncestorEvent event) {
                // no implementation.
            }
        };
    }
}

Related

1. getPermanentFocusOwner()
2. hasFocus(Component component)
3. hasFocusOwner(final Component component)
4. installDefaultFocusHandling(Container c)
5. installFocusCycleRoot(Container c, FocusTraversalPolicy cyclePolicy)
6. installJComponentRepainterOnWindowFocusChanged(JComponent component)
7. installJComponentRepainterOnWindowFocusChanged(JComponent component)
8. isDescendingFrom(Component focusOwner, Component parent)
9. isFocusable(Component component)