containerorderfocustraversalpolicy.java

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/*
 * 
 * Copyright  1990-2008 Sun Microsystems, Inc. All Rights Reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
 * 
 * This program 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. 
 * 
 * This program 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 at /legal/license.txt). 
 * 
 * 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 Sun Microsystems, Inc., 4150 Network Circle, Santa
 * Clara, CA 95054 or visit www.sun.com if you need additional
 * information or have any questions. 
 */
package java.awt;

/**
 * A FocusTraversalPolicy that determines traversal order based on the order
 * of child Components in a Container. From a particular focus cycle root, the
 * policy makes a pre-order traversal of the Component hierarchy, and traverses
 * a Container's children according to the ordering of the array returned by
 * <code>Container.getComponents()</code>. Portions of the hierarchy that are
 * not visible and displayable will not be searched.
 * <p>
 * By default, ContainerOrderFocusTraversalPolicy implicitly transfers focus
 * down-cycle. That is, during normal forward focus traversal, the Component
 * traversed after a focus cycle root will be the focus-cycle-root's default
 * Component to focus. This behavior can be disabled using the
 * <code>setImplicitDownCycleTraversal</code> method.
 * <p>
 * By default, methods of this class with return a Component only if it is
 * visible, displayable, enabled, and focusable. Subclasses can modify this
 * behavior by overriding the <code>accept</code> method.
 *
 * @author David Mendenhall
 * @version 1.3, 01/23/03
 *
 * @see Container#getComponents
 * @since 1.4
 */
public class ContainerOrderFocusTraversalPolicy extends FocusTraversalPolicy
    implements java.io.Serializable {

    private static class MutableBoolean {
        boolean value = false;
    }

    private static final MutableBoolean found = new MutableBoolean();
    private boolean implicitDownCycleTraversal = true;
    /**
     * Returns the Component that should receive the focus after aComponent.
     * focusCycleRoot must be a focus cycle root of aComponent.
     * <p>
     * By default, ContainerOrderFocusTraversalPolicy implicitly transfers
     * focus down-cycle. That is, during normal forward focus traversal, the
     * Component traversed after a focus cycle root will be the focus-cycle-
     * root's default Component to focus. This behavior can be disabled using
     * the <code>setImplicitDownCycleTraversal</code> method.
     *
     * @param focusCycleRoot a focus cycle root of aComponent
     * @param aComponent a (possibly indirect) child of focusCycleRoot, or
     *        focusCycleRoot itself
     * @return the Component that should receive the focus after aComponent, or
     *         null if no suitable Component can be found
     * @throws IllegalArgumentException if focusCycleRoot is not a focus cycle
     *         root of aComponent, or if either focusCycleRoot or aComponent is
     *         null
     */
    public Component getComponentAfter(Container focusCycleRoot,
            Component aComponent) {
        if (focusCycleRoot == null || aComponent == null) {
            throw new IllegalArgumentException("focusCycleRoot and aComponent cannot be null");
        }
        if (!aComponent.isFocusCycleRoot(focusCycleRoot)) {
            throw new IllegalArgumentException("focusCycleRoot is not a focus cyle root of aComponent");
        }
        synchronized (focusCycleRoot.getTreeLock()) {
            found.value = false;
            Component retval = getComponentAfter(focusCycleRoot, aComponent,
                    found);
            if (retval != null) {
                return retval;
            } else if (found.value) {
                return getFirstComponent(focusCycleRoot);
            } else {
                return null;
            }
        }
    }

    private Component getComponentAfter(Container aContainer,
            Component aComponent,
            MutableBoolean found) {
        if (!(aContainer.isVisible() && aContainer.isDisplayable())) {
            return null;
        }
        if (found.value) {
            if (accept(aContainer)) {
                return aContainer;
            }
        } else if (aContainer == aComponent) {
            found.value = true;
        }
        for (int i = 0; i < aContainer.ncomponents; i++) {
            Component comp = aContainer.component[i];
            if ((comp instanceof Container)
                    && !((Container) comp).isFocusCycleRoot()) {
                Component retval = getComponentAfter((Container) comp,
                        aComponent, found);
                if (retval != null) {
                    return retval;
                }
            } else if (found.value) {
                if (accept(comp)) {
                    return comp;
                }
            } else if (comp == aComponent) {
                found.value = true;
            }
            if (found.value && getImplicitDownCycleTraversal()
                    && (comp instanceof Container)
                    && ((Container) comp).isFocusCycleRoot()) {
                Container cont = (Container) comp;
                Component retval = cont.getFocusTraversalPolicy().getDefaultComponent(cont);
                if (retval != null) {
                    return retval;
                }
            }
        }
        return null;
    }

    /**
     * Returns the Component that should receive the focus before aComponent.
     * focusCycleRoot must be a focus cycle root of aComponent.
     *
     * @param focusCycleRoot a focus cycle root of aComponent
     * @param aComponent a (possibly indirect) child of focusCycleRoot, or
     *        focusCycleRoot itself
     * @return the Component that should receive the focus before aComponent,
     *         or null if no suitable Component can be found
     * @throws IllegalArgumentException if focusCycleRoot is not a focus cycle
     *         root of aComponent, or if either focusCycleRoot or aComponent is
     *         null
     */
    public Component getComponentBefore(Container focusCycleRoot,
            Component aComponent) {
        if (focusCycleRoot == null || aComponent == null) {
            throw new IllegalArgumentException("focusCycleRoot and aComponent cannot be null");
        }
        if (!aComponent.isFocusCycleRoot(focusCycleRoot)) {
            throw new IllegalArgumentException("focusCycleRoot is not a focus cyle root of aComponent");
        }
        synchronized (focusCycleRoot.getTreeLock()) {
            found.value = false;
            Component retval = getComponentBefore(focusCycleRoot, aComponent,
                    found);
            if (retval != null) {
                return retval;
            } else if (found.value) {
                return getLastComponent(focusCycleRoot);
            } else {
                return null;
            }
        }
    }

    private Component getComponentBefore(Container aContainer,
            Component aComponent,
            MutableBoolean found) {
        if (!(aContainer.isVisible() && aContainer.isDisplayable())) {
            return null;
        }
        for (int i = aContainer.ncomponents - 1; i >= 0; i--) {
            Component comp = aContainer.component[i];
            if (comp == aComponent) {
                found.value = true;
            } else if ((comp instanceof Container)
                    && !((Container) comp).isFocusCycleRoot()) {