/*
* Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
*
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*
*/
package javax.swing;
import java.awt.*;
import javax.swing.plaf.*;
import javax.accessibility.*;
import java.io.
Serializable;
import java.io.
ObjectOutputStream;
import java.io.
ObjectInputStream;
import java.io.
IOException;
/**
* <code>JPanel</code> is a generic lightweight container.
* For examples and task-oriented documentation for JPanel, see
* <a
href="https://docs.oracle.com/javase/tutorial/uiswing/components/panel.html">How to Use Panels</a>,
* a section in <em>The Java Tutorial</em>.
* <p>
* <strong>Warning:</strong> Swing is not thread safe. For more
* information see <a
* href="package-summary.html#threading">Swing's Threading
* Policy</a>.
* <p>
* <strong>Warning:</strong>
* Serialized objects of this class will not be compatible with
* future Swing releases. The current serialization support is
* appropriate for short term storage or RMI between applications running
* the same version of Swing. As of 1.4, support for long term storage
* of all JavaBeans™
* has been added to the <code>java.beans</code> package.
* Please see {@link java.beans.XMLEncoder}.
*
* @beaninfo
* description: A generic lightweight container.
*
* @author Arnaud Weber
* @author Steve Wilson
*/
public class
JPanel extends
JComponent implements
Accessible
{
/**
* @see #getUIClassID
* @see #readObject
*/
private static final
String uiClassID = "PanelUI";
/**
* Creates a new JPanel with the specified layout manager and buffering
* strategy.
*
* @param layout the LayoutManager to use
* @param isDoubleBuffered a boolean, true for double-buffering, which
* uses additional memory space to achieve fast, flicker-free
* updates
*/
public
JPanel(
LayoutManager layout, boolean
isDoubleBuffered) {
setLayout(
layout);
setDoubleBuffered(
isDoubleBuffered);
setUIProperty("opaque",
Boolean.
TRUE);
updateUI();
}
/**
* Create a new buffered JPanel with the specified layout manager
*
* @param layout the LayoutManager to use
*/
public
JPanel(
LayoutManager layout) {
this(
layout, true);
}
/**
* Creates a new <code>JPanel</code> with <code>FlowLayout</code>
* and the specified buffering strategy.
* If <code>isDoubleBuffered</code> is true, the <code>JPanel</code>
* will use a double buffer.
*
* @param isDoubleBuffered a boolean, true for double-buffering, which
* uses additional memory space to achieve fast, flicker-free
* updates
*/
public
JPanel(boolean
isDoubleBuffered) {
this(new
FlowLayout(),
isDoubleBuffered);
}
/**
* Creates a new <code>JPanel</code> with a double buffer
* and a flow layout.
*/
public
JPanel() {
this(true);
}
/**
* Resets the UI property with a value from the current look and feel.
*
* @see JComponent#updateUI
*/
public void
updateUI() {
setUI((
PanelUI)
UIManager.
getUI(this));
}
/**
* Returns the look and feel (L&F) object that renders this component.
*
* @return the PanelUI object that renders this component
* @since 1.4
*/
public
PanelUI getUI() {
return (
PanelUI)
ui;
}
/**
* Sets the look and feel (L&F) object that renders this component.
*
* @param ui the PanelUI L&F object
* @see UIDefaults#getUI
* @since 1.4
* @beaninfo
* bound: true
* hidden: true
* attribute: visualUpdate true
* description: The UI object that implements the Component's LookAndFeel.
*/
public void
setUI(
PanelUI ui) {
super.setUI(
ui);
}
/**
* Returns a string that specifies the name of the L&F class
* that renders this component.
*
* @return "PanelUI"
* @see JComponent#getUIClassID
* @see UIDefaults#getUI
* @beaninfo
* expert: true
* description: A string that specifies the name of the L&F class.
*/
public
String getUIClassID() {
return
uiClassID;
}
/**
* See readObject() and writeObject() in JComponent for more
* information about serialization in Swing.
*/
private void
writeObject(
ObjectOutputStream s) throws
IOException {
s.
defaultWriteObject();
if (
getUIClassID().
equals(
uiClassID)) {
byte
count =
JComponent.
getWriteObjCounter(this);
JComponent.
setWriteObjCounter(this, --
count);
if (
count == 0 &&
ui != null) {
ui.
installUI(this);
}
}
}
/**
* Returns a string representation of this JPanel. This method
* is intended to be used only for debugging purposes, and the
* content and format of the returned string may vary between
* implementations. The returned string may be empty but may not
* be <code>null</code>.
*
* @return a string representation of this JPanel.
*/
protected
String paramString() {
return super.paramString();
}
/////////////////
// Accessibility support
////////////////
/**
* Gets the AccessibleContext associated with this JPanel.
* For JPanels, the AccessibleContext takes the form of an
* AccessibleJPanel.
* A new AccessibleJPanel instance is created if necessary.
*
* @return an AccessibleJPanel that serves as the
* AccessibleContext of this JPanel
*/
public
AccessibleContext getAccessibleContext() {
if (
accessibleContext == null) {
accessibleContext = new
AccessibleJPanel();
}
return
accessibleContext;
}
/**
* This class implements accessibility support for the
* <code>JPanel</code> class. It provides an implementation of the
* Java Accessibility API appropriate to panel user-interface
* elements.
* <p>
* <strong>Warning:</strong>
* Serialized objects of this class will not be compatible with
* future Swing releases. The current serialization support is
* appropriate for short term storage or RMI between applications running
* the same version of Swing. As of 1.4, support for long term storage
* of all JavaBeans™
* has been added to the <code>java.beans</code> package.
* Please see {@link java.beans.XMLEncoder}.
*/
protected class
AccessibleJPanel extends
AccessibleJComponent {
/**
* Get the role of this object.
*
* @return an instance of AccessibleRole describing the role of the
* object
*/
public
AccessibleRole getAccessibleRole() {
return
AccessibleRole.
PANEL;
}
}
}