Back to index...

	/*
	* 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.Component;
	import java.awt.Container;
	import java.awt.ComponentOrientation;
	import java.util.Comparator;
	import java.io.*;
	import sun.awt.SunToolkit;


	/**
	* A SortingFocusTraversalPolicy which sorts Components based on their size,
	* position, and orientation. Based on their size and position, Components are
	* roughly categorized into rows and columns. For a Container with horizontal
	* orientation, columns run left-to-right or right-to-left, and rows run top-
	* to-bottom. For a Container with vertical orientation, columns run top-to-
	* bottom and rows run left-to-right or right-to-left. See
	* <code>ComponentOrientation</code> for more information. All columns in a
	* row are fully traversed before proceeding to the next row.
	*
	* @author David Mendenhall
	*
	* @see java.awt.ComponentOrientation
	* @since 1.4
	*/
	public class LayoutFocusTraversalPolicy extends SortingFocusTraversalPolicy
	implements Serializable
	{
	// Delegate most of our fitness test to Default so that we only have to
	// code the algorithm once.
	private static final SwingDefaultFocusTraversalPolicy fitnessTestPolicy =
	new SwingDefaultFocusTraversalPolicy();

	/**
	* Constructs a LayoutFocusTraversalPolicy.
	*/
	public LayoutFocusTraversalPolicy() {
	super(new LayoutComparator());
	}

	/**
	* Constructs a LayoutFocusTraversalPolicy with the passed in
	* <code>Comparator</code>.
	*/
	LayoutFocusTraversalPolicy(Comparator<? super Component> c) {
	super(c);
	}

	/**
	* Returns the Component that should receive the focus after aComponent.
	* aContainer must be a focus cycle root of aComponent.
	* <p>
	* By default, LayoutFocusTraversalPolicy implicitly transfers focus down-
	* cycle. That is, during normal 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>
	* If aContainer is <a href="../../java/awt/doc-files/FocusSpec.html#FocusTraversalPolicyProviders">focus
	* traversal policy provider</a>, the focus is always transferred down-cycle.
	*
	* @param aContainer a focus cycle root of aComponent or a focus traversal policy provider
	* @param aComponent a (possibly indirect) child of aContainer, or
	* aContainer itself
	* @return the Component that should receive the focus after aComponent, or
	* null if no suitable Component can be found
	* @throws IllegalArgumentException if aContainer is not a focus cycle
	* root of aComponent or a focus traversal policy provider, or if either aContainer or
	* aComponent is null
	*/
	public Component getComponentAfter(Container aContainer,
	Component aComponent) {
	if (aContainer == null \|\| aComponent == null) {
	throw new IllegalArgumentException("aContainer and aComponent cannot be null");
	}
	Comparator comparator = getComparator();
	if (comparator instanceof LayoutComparator) {
	((LayoutComparator)comparator).
	setComponentOrientation(aContainer.
	getComponentOrientation());
	}
	return super.getComponentAfter(aContainer, aComponent);
	}

	/**
	* Returns the Component that should receive the focus before aComponent.
	* aContainer must be a focus cycle root of aComponent.
	* <p>
	* By default, LayoutFocusTraversalPolicy implicitly transfers focus down-
	* cycle. That is, during normal 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>
	* If aContainer is <a href="../../java/awt/doc-files/FocusSpec.html#FocusTraversalPolicyProviders">focus
	* traversal policy provider</a>, the focus is always transferred down-cycle.
	*
	* @param aContainer a focus cycle root of aComponent or a focus traversal policy provider
	* @param aComponent a (possibly indirect) child of aContainer, or
	* aContainer itself
	* @return the Component that should receive the focus before aComponent,
	* or null if no suitable Component can be found
	* @throws IllegalArgumentException if aContainer is not a focus cycle
	* root of aComponent or a focus traversal policy provider, or if either aContainer or
	* aComponent is null
	*/
	public Component getComponentBefore(Container aContainer,
	Component aComponent) {
	if (aContainer == null \|\| aComponent == null) {
	throw new IllegalArgumentException("aContainer and aComponent cannot be null");
	}
	Comparator comparator = getComparator();
	if (comparator instanceof LayoutComparator) {
	((LayoutComparator)comparator).
	setComponentOrientation(aContainer.
	getComponentOrientation());
	}
	return super.getComponentBefore(aContainer, aComponent);
	}

	/**
	* Returns the first Component in the traversal cycle. This method is used
	* to determine the next Component to focus when traversal wraps in the
	* forward direction.
	*
	* @param aContainer a focus cycle root of aComponent or a focus traversal policy provider whose
	* first Component is to be returned
	* @return the first Component in the traversal cycle of aContainer,
	* or null if no suitable Component can be found
	* @throws IllegalArgumentException if aContainer is null
	*/
	public Component getFirstComponent(Container aContainer) {
	if (aContainer == null) {
	throw new IllegalArgumentException("aContainer cannot be null");
	}
	Comparator comparator = getComparator();
	if (comparator instanceof LayoutComparator) {
	((LayoutComparator)comparator).
	setComponentOrientation(aContainer.
	getComponentOrientation());
	}
	return super.getFirstComponent(aContainer);
	}

	/**
	* Returns the last Component in the traversal cycle. This method is used
	* to determine the next Component to focus when traversal wraps in the
	* reverse direction.
	*
	* @param aContainer a focus cycle root of aComponent or a focus traversal policy provider whose
	* last Component is to be returned
	* @return the last Component in the traversal cycle of aContainer,
	* or null if no suitable Component can be found
	* @throws IllegalArgumentException if aContainer is null
	*/
	public Component getLastComponent(Container aContainer) {
	if (aContainer == null) {
	throw new IllegalArgumentException("aContainer cannot be null");
	}
	Comparator comparator = getComparator();
	if (comparator instanceof LayoutComparator) {
	((LayoutComparator)comparator).
	setComponentOrientation(aContainer.
	getComponentOrientation());
	}
	return super.getLastComponent(aContainer);
	}

	/**
	* Determines whether the specified <code>Component</code>
	* is an acceptable choice as the new focus owner.
	* This method performs the following sequence of operations:
	* <ol>
	* <li>Checks whether <code>aComponent</code> is visible, displayable,
	* enabled, and focusable. If any of these properties is
	* <code>false</code>, this method returns <code>false</code>.
	* <li>If <code>aComponent</code> is an instance of <code>JTable</code>,
	* returns <code>true</code>.
	* <li>If <code>aComponent</code> is an instance of <code>JComboBox</code>,
	* then returns the value of
	* <code>aComponent.getUI().isFocusTraversable(aComponent)</code>.
	* <li>If <code>aComponent</code> is a <code>JComponent</code>
	* with a <code>JComponent.WHEN_FOCUSED</code>
	* <code>InputMap</code> that is neither <code>null</code>
	* nor empty, returns <code>true</code>.
	* <li>Returns the value of
	* <code>DefaultFocusTraversalPolicy.accept(aComponent)</code>.
	* </ol>
	*
	* @param aComponent the <code>Component</code> whose fitness
	* as a focus owner is to be tested
	* @see java.awt.Component#isVisible
	* @see java.awt.Component#isDisplayable
	* @see java.awt.Component#isEnabled
	* @see java.awt.Component#isFocusable
	* @see javax.swing.plaf.ComboBoxUI#isFocusTraversable
	* @see javax.swing.JComponent#getInputMap
	* @see java.awt.DefaultFocusTraversalPolicy#accept
	* @return <code>true</code> if <code>aComponent</code> is a valid choice
	* for a focus owner;
	* otherwise <code>false</code>
	*/
	protected boolean accept(Component aComponent) {
	if (!super.accept(aComponent)) {
	return false;
	} else if (SunToolkit.isInstanceOf(aComponent, "javax.swing.JTable")) {
	// JTable only has ancestor focus bindings, we thus force it
	// to be focusable by returning true here.
	return true;
	} else if (SunToolkit.isInstanceOf(aComponent, "javax.swing.JComboBox")) {
	JComboBox box = (JComboBox)aComponent;
	return box.getUI().isFocusTraversable(box);
	} else if (aComponent instanceof JComponent) {
	JComponent jComponent = (JComponent)aComponent;
	InputMap inputMap = jComponent.getInputMap(JComponent.WHEN_FOCUSED,
	false);
	while (inputMap != null && inputMap.size() == 0) {
	inputMap = inputMap.getParent();
	}
	if (inputMap != null) {
	return true;
	}
	// Delegate to the fitnessTestPolicy, this will test for the
	// case where the developer has overriden isFocusTraversable to
	// return true.
	}
	return fitnessTestPolicy.accept(aComponent);
	}

	private void writeObject(ObjectOutputStream out) throws IOException {
	out.writeObject(getComparator());
	out.writeBoolean(getImplicitDownCycleTraversal());
	}
	private void readObject(ObjectInputStream in)
	throws IOException, ClassNotFoundException
	{
	setComparator((Comparator)in.readObject());
	setImplicitDownCycleTraversal(in.readBoolean());
	}
	}

	// Create our own subclass and change accept to public so that we can call
	// accept.
	class SwingDefaultFocusTraversalPolicy
	extends java.awt.DefaultFocusTraversalPolicy
	{
	public boolean accept(Component aComponent) {
	return super.accept(aComponent);
	}
	}

Back to index...