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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
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* 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
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package java.awt;
import java.awt.peer.ComponentPeer;
/**
* 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>
* If client code has explicitly set the focusability of a Component by either
* overriding <code>Component.isFocusTraversable()</code> or
* <code>Component.isFocusable()</code>, or by calling
* <code>Component.setFocusable()</code>, then a DefaultFocusTraversalPolicy
* behaves exactly like a ContainerOrderFocusTraversalPolicy. If, however, the
* Component is relying on default focusability, then a
* DefaultFocusTraversalPolicy will reject all Components with non-focusable
* peers. This is the default FocusTraversalPolicy for all AWT Containers.
* <p>
* The focusability of a peer is implementation-dependent. Sun recommends that
* all implementations for a particular native platform construct peers with
* the same focusability. The recommendations for Windows and Unix are that
* Canvases, Labels, Panels, Scrollbars, ScrollPanes, Windows, and lightweight
* Components have non-focusable peers, and all other Components have focusable
* peers. These recommendations are used in the Sun AWT implementations. Note
* that the focusability of a Component's peer is different from, and does not
* impact, the focusability of the Component itself.
* <p>
* Please see
* <a href="http://java.sun.com/docs/books/tutorial/uiswing/misc/focus.html">
* How to Use the Focus Subsystem</a>,
* a section in <em>The Java Tutorial</em>, and the
* <a href="../../java/awt/doc-files/FocusSpec.html">Focus Specification</a>
* for more information.
*
* @author David Mendenhall
*
* @see Container#getComponents
* @see Component#isFocusable
* @see Component#setFocusable
* @since 1.4
*/
public class DefaultFocusTraversalPolicy
extends ContainerOrderFocusTraversalPolicy
{
/*
* serialVersionUID
*/
private static final long serialVersionUID = 8876966522510157497L;
/**
* Determines whether a Component is an acceptable choice as the new
* focus owner. The Component must be visible, displayable, and enabled
* to be accepted. If client code has explicitly set the focusability
* of the Component by either overriding
* <code>Component.isFocusTraversable()</code> or
* <code>Component.isFocusable()</code>, or by calling
* <code>Component.setFocusable()</code>, then the Component will be
* accepted if and only if it is focusable. If, however, the Component is
* relying on default focusability, then all Canvases, Labels, Panels,
* Scrollbars, ScrollPanes, Windows, and lightweight Components will be
* rejected.
*
* @param aComponent the Component whose fitness as a focus owner is to
* be tested
* @return <code>true</code> if aComponent meets the above requirements;
* <code>false</code> otherwise
*/
protected boolean accept(Component aComponent) {
if (!(aComponent.isVisible() && aComponent.isDisplayable() &&
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;
}
}
}
boolean focusable = aComponent.isFocusable();
if (aComponent.isFocusTraversableOverridden()) {
return focusable;
}
ComponentPeer peer = aComponent.getPeer();
return (peer != null && peer.isFocusable());
}
}