Java example source code file (LegacyGlueFocusTraversalPolicy.java)

This example Java source code file (LegacyGlueFocusTraversalPolicy.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

awt, classnotfoundexception, component, container, defaultfocusmanager, hashmap, hashset, ioexception, legacygluefocustraversalpolicy, serializable, util, window

The LegacyGlueFocusTraversalPolicy.java Java example source code

/*
 * Copyright (c) 2000, 2008, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package javax.swing;

import java.awt.FocusTraversalPolicy;
import java.awt.Component;
import java.awt.Container;
import java.awt.Window;
import java.util.HashMap;
import java.util.HashSet;
import java.io.*;


/**
 * A FocusTraversalPolicy which provides support for legacy applications which
 * handle focus traversal via JComponent.setNextFocusableComponent or by
 * installing a custom DefaultFocusManager. If a specific traversal has not
 * been hard coded, then that traversal is provided either by the custom
 * DefaultFocusManager, or by a wrapped FocusTraversalPolicy instance.
 *
 * @author David Mendenhall
 */
final class LegacyGlueFocusTraversalPolicy extends FocusTraversalPolicy
    implements Serializable
{
    private transient FocusTraversalPolicy delegatePolicy;
    private transient DefaultFocusManager delegateManager;

    private HashMap<Component, Component> forwardMap = new HashMap(),
        backwardMap = new HashMap<Component, Component>();

    LegacyGlueFocusTraversalPolicy(FocusTraversalPolicy delegatePolicy) {
        this.delegatePolicy = delegatePolicy;
    }
    LegacyGlueFocusTraversalPolicy(DefaultFocusManager delegateManager) {
        this.delegateManager = delegateManager;
    }

    void setNextFocusableComponent(Component left, Component right) {
        forwardMap.put(left, right);
        backwardMap.put(right, left);
    }
    void unsetNextFocusableComponent(Component left, Component right) {
        forwardMap.remove(left);
        backwardMap.remove(right);
    }

    public Component getComponentAfter(Container focusCycleRoot,
                                       Component aComponent) {
        Component hardCoded = aComponent, prevHardCoded;
        HashSet<Component> sanity = new HashSet();

        do {
            prevHardCoded = hardCoded;
            hardCoded = forwardMap.get(hardCoded);
            if (hardCoded == null) {
                if (delegatePolicy != null &&
                    prevHardCoded.isFocusCycleRoot(focusCycleRoot)) {
                    return delegatePolicy.getComponentAfter(focusCycleRoot,
                                                            prevHardCoded);
                } else if (delegateManager != null) {
                    return delegateManager.
                        getComponentAfter(focusCycleRoot, aComponent);
                } else {
                    return null;
                }
            }
            if (sanity.contains(hardCoded)) {
                // cycle detected; bail
                return null;
            }
            sanity.add(hardCoded);
        } while (!accept(hardCoded));

        return hardCoded;
    }
    public Component getComponentBefore(Container focusCycleRoot,
                                        Component aComponent) {
        Component hardCoded = aComponent, prevHardCoded;
        HashSet<Component> sanity = new HashSet();

        do {
            prevHardCoded = hardCoded;
            hardCoded = backwardMap.get(hardCoded);
            if (hardCoded == null) {
                if (delegatePolicy != null &&
                    prevHardCoded.isFocusCycleRoot(focusCycleRoot)) {
                    return delegatePolicy.getComponentBefore(focusCycleRoot,
                                                       prevHardCoded);
                } else if (delegateManager != null) {
                    return delegateManager.
                        getComponentBefore(focusCycleRoot, aComponent);
                } else {
                    return null;
                }
            }
            if (sanity.contains(hardCoded)) {
                // cycle detected; bail
                return null;
            }
            sanity.add(hardCoded);
        } while (!accept(hardCoded));

        return hardCoded;
    }
    public Component getFirstComponent(Container focusCycleRoot) {
        if (delegatePolicy != null) {
            return delegatePolicy.getFirstComponent(focusCycleRoot);
        } else if (delegateManager != null) {
            return delegateManager.getFirstComponent(focusCycleRoot);
        } else {
            return null;
        }
    }
    public Component getLastComponent(Container focusCycleRoot) {
        if (delegatePolicy != null) {
            return delegatePolicy.getLastComponent(focusCycleRoot);
        } else if (delegateManager != null) {
            return delegateManager.getLastComponent(focusCycleRoot);
        } else {
            return null;
        }
    }
    public Component getDefaultComponent(Container focusCycleRoot) {
        if (delegatePolicy != null) {
            return delegatePolicy.getDefaultComponent(focusCycleRoot);
        } else {
            return getFirstComponent(focusCycleRoot);
        }
    }
    private boolean accept(Component aComponent) {
        if (!(aComponent.isVisible() && aComponent.isDisplayable() &&
              aComponent.isFocusable() && aComponent.isEnabled())) {
            return false;
        }

        // Verify that the Component is recursively enabled. Disabling a
        // heavyweight Container disables its children, whereas disabling
        // a lightweight Container does not.
        if (!(aComponent instanceof Window)) {
            for (Container enableTest = aComponent.getParent();
                 enableTest != null;
                 enableTest = enableTest.getParent())
            {
                if (!(enableTest.isEnabled() || enableTest.isLightweight())) {
                    return false;
                }
                if (enableTest instanceof Window) {
                    break;
                }
            }
        }

        return true;
    }
    private void writeObject(ObjectOutputStream out) throws IOException {
        out.defaultWriteObject();

        if (delegatePolicy instanceof Serializable) {
            out.writeObject(delegatePolicy);
        } else {
            out.writeObject(null);
        }

        if (delegateManager instanceof Serializable) {
            out.writeObject(delegateManager);
        } else {
            out.writeObject(null);
        }
    }
    private void readObject(ObjectInputStream in)
        throws IOException, ClassNotFoundException
    {
        in.defaultReadObject();
        delegatePolicy = (FocusTraversalPolicy)in.readObject();
        delegateManager = (DefaultFocusManager)in.readObject();
    }
}