Java tutorial
/* * Copyright (c) 1997, 2015, 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.*; import java.beans.JavaBean; import java.beans.BeanProperty; import java.beans.ConstructorProperties; import javax.accessibility.*; /** * A lightweight container * that uses a BoxLayout object as its layout manager. * Box provides several class methods * that are useful for containers using BoxLayout -- * even non-Box containers. * * <p> * The <code>Box</code> class can create several kinds * of invisible components * that affect layout: * glue, struts, and rigid areas. * If all the components your <code>Box</code> contains * have a fixed size, * you might want to use a glue component * (returned by <code>createGlue</code>) * to control the components' positions. * If you need a fixed amount of space between two components, * try using a strut * (<code>createHorizontalStrut</code> or <code>createVerticalStrut</code>). * If you need an invisible component * that always takes up the same amount of space, * get it by invoking <code>createRigidArea</code>. * <p> * If you are implementing a <code>BoxLayout</code> you * can find further information and examples in * <a href="https://docs.oracle.com/javase/tutorial/uiswing/layout/box.html">How to Use BoxLayout</a>, * a section in <em>The Java Tutorial.</em> * <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}. * * @see BoxLayout * * @author Timothy Prinzing * @since 1.2 */ @JavaBean(defaultProperty = "accessibleContext") @SuppressWarnings("serial") public class Box extends JComponent implements Accessible { /** * Creates a <code>Box</code> that displays its components * along the specified axis. * * @param axis can be {@link BoxLayout#X_AXIS}, * {@link BoxLayout#Y_AXIS}, * {@link BoxLayout#LINE_AXIS} or * {@link BoxLayout#PAGE_AXIS}. * @throws AWTError if the <code>axis</code> is invalid * @see #createHorizontalBox * @see #createVerticalBox */ public Box(int axis) { super(); super.setLayout(new BoxLayout(this, axis)); } /** * Creates a <code>Box</code> that displays its components * from left to right. If you want a <code>Box</code> that * respects the component orientation you should create the * <code>Box</code> using the constructor and pass in * <code>BoxLayout.LINE_AXIS</code>, eg: * <pre> * Box lineBox = new Box(BoxLayout.LINE_AXIS); * </pre> * * @return the box */ public static Box createHorizontalBox() { return new Box(BoxLayout.X_AXIS); } /** * Creates a <code>Box</code> that displays its components * from top to bottom. If you want a <code>Box</code> that * respects the component orientation you should create the * <code>Box</code> using the constructor and pass in * <code>BoxLayout.PAGE_AXIS</code>, eg: * <pre> * Box lineBox = new Box(BoxLayout.PAGE_AXIS); * </pre> * * @return the box */ public static Box createVerticalBox() { return new Box(BoxLayout.Y_AXIS); } /** * Creates an invisible component that's always the specified size. * <!-- WHEN WOULD YOU USE THIS AS OPPOSED TO A STRUT? --> * * @param d the dimensions of the invisible component * @return the component * @see #createGlue * @see #createHorizontalStrut * @see #createVerticalStrut */ public static Component createRigidArea(Dimension d) { return new Filler(d, d, d); } /** * Creates an invisible, fixed-width component. * In a horizontal box, * you typically use this method * to force a certain amount of space between two components. * In a vertical box, * you might use this method * to force the box to be at least the specified width. * The invisible component has no height * unless excess space is available, * in which case it takes its share of available space, * just like any other component that has no maximum height. * * @param width the width of the invisible component, in pixels >= 0 * @return the component * @see #createVerticalStrut * @see #createGlue * @see #createRigidArea */ public static Component createHorizontalStrut(int width) { return new Filler(new Dimension(width, 0), new Dimension(width, 0), new Dimension(width, Short.MAX_VALUE)); } /** * Creates an invisible, fixed-height component. * In a vertical box, * you typically use this method * to force a certain amount of space between two components. * In a horizontal box, * you might use this method * to force the box to be at least the specified height. * The invisible component has no width * unless excess space is available, * in which case it takes its share of available space, * just like any other component that has no maximum width. * * @param height the height of the invisible component, in pixels >= 0 * @return the component * @see #createHorizontalStrut * @see #createGlue * @see #createRigidArea */ public static Component createVerticalStrut(int height) { return new Filler(new Dimension(0, height), new Dimension(0, height), new Dimension(Short.MAX_VALUE, height)); } /** * Creates an invisible "glue" component * that can be useful in a Box * whose visible components have a maximum width * (for a horizontal box) * or height (for a vertical box). * You can think of the glue component * as being a gooey substance * that expands as much as necessary * to fill the space between its neighboring components. * * <p> * * For example, suppose you have * a horizontal box that contains two fixed-size components. * If the box gets extra space, * the fixed-size components won't become larger, * so where does the extra space go? * Without glue, * the extra space goes to the right of the second component. * If you put glue between the fixed-size components, * then the extra space goes there. * If you put glue before the first fixed-size component, * the extra space goes there, * and the fixed-size components are shoved against the right * edge of the box. * If you put glue before the first fixed-size component * and after the second fixed-size component, * the fixed-size components are centered in the box. * * <p> * * To use glue, * call <code>Box.createGlue</code> * and add the returned component to a container. * The glue component has no minimum or preferred size, * so it takes no space unless excess space is available. * If excess space is available, * then the glue component takes its share of available * horizontal or vertical space, * just like any other component that has no maximum width or height. * * @return the component */ public static Component createGlue() { return new Filler(new Dimension(0, 0), new Dimension(0, 0), new Dimension(Short.MAX_VALUE, Short.MAX_VALUE)); } /** * Creates a horizontal glue component. * * @return the component */ public static Component createHorizontalGlue() { return new Filler(new Dimension(0, 0), new Dimension(0, 0), new Dimension(Short.MAX_VALUE, 0)); } /** * Creates a vertical glue component. * * @return the component */ public static Component createVerticalGlue() { return new Filler(new Dimension(0, 0), new Dimension(0, 0), new Dimension(0, Short.MAX_VALUE)); } /** * Throws an AWTError, since a Box can use only a BoxLayout. * * @param l the layout manager to use */ public void setLayout(LayoutManager l) { throw new AWTError("Illegal request"); } /** * Paints this <code>Box</code>. If this <code>Box</code> has a UI this * method invokes super's implementation, otherwise if this * <code>Box</code> is opaque the <code>Graphics</code> is filled * using the background. * * @param g the <code>Graphics</code> to paint to * @throws NullPointerException if <code>g</code> is null * @since 1.6 */ protected void paintComponent(Graphics g) { if (ui != null) { // On the off chance some one created a UI, honor it super.paintComponent(g); } else if (isOpaque()) { g.setColor(getBackground()); g.fillRect(0, 0, getWidth(), getHeight()); } } /** * An implementation of a lightweight component that participates in * layout but has no view. * <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}. */ @SuppressWarnings("serial") public static class Filler extends JComponent implements Accessible { /** * Constructor to create shape with the given size ranges. * * @param min Minimum size * @param pref Preferred size * @param max Maximum size */ @ConstructorProperties({ "minimumSize", "preferredSize", "maximumSize" }) public Filler(Dimension min, Dimension pref, Dimension max) { setMinimumSize(min); setPreferredSize(pref); setMaximumSize(max); } /** * Change the size requests for this shape. An invalidate() is * propagated upward as a result so that layout will eventually * happen with using the new sizes. * * @param min Value to return for getMinimumSize * @param pref Value to return for getPreferredSize * @param max Value to return for getMaximumSize */ public void changeShape(Dimension min, Dimension pref, Dimension max) { setMinimumSize(min); setPreferredSize(pref); setMaximumSize(max); revalidate(); } // ---- Component methods ------------------------------------------ /** * Paints this <code>Filler</code>. If this * <code>Filler</code> has a UI this method invokes super's * implementation, otherwise if this <code>Filler</code> is * opaque the <code>Graphics</code> is filled using the * background. * * @param g the <code>Graphics</code> to paint to * @throws NullPointerException if <code>g</code> is null * @since 1.6 */ protected void paintComponent(Graphics g) { if (ui != null) { // On the off chance some one created a UI, honor it super.paintComponent(g); } else if (isOpaque()) { g.setColor(getBackground()); g.fillRect(0, 0, getWidth(), getHeight()); } } ///////////////// // Accessibility support for Box$Filler //////////////// /** * Gets the AccessibleContext associated with this Box.Filler. * For box fillers, the AccessibleContext takes the form of an * AccessibleBoxFiller. * A new AccessibleAWTBoxFiller instance is created if necessary. * * @return an AccessibleBoxFiller that serves as the * AccessibleContext of this Box.Filler. */ public AccessibleContext getAccessibleContext() { if (accessibleContext == null) { accessibleContext = new AccessibleBoxFiller(); } return accessibleContext; } /** * This class implements accessibility support for the * <code>Box.Filler</code> class. */ @SuppressWarnings("serial") protected class AccessibleBoxFiller extends AccessibleAWTComponent { // AccessibleContext methods // /** * Gets the role of this object. * * @return an instance of AccessibleRole describing the role of * the object (AccessibleRole.FILLER) * @see AccessibleRole */ public AccessibleRole getAccessibleRole() { return AccessibleRole.FILLER; } } } ///////////////// // Accessibility support for Box //////////////// /** * Gets the AccessibleContext associated with this Box. * For boxes, the AccessibleContext takes the form of an * AccessibleBox. * A new AccessibleAWTBox instance is created if necessary. * * @return an AccessibleBox that serves as the * AccessibleContext of this Box */ @BeanProperty(bound = false) public AccessibleContext getAccessibleContext() { if (accessibleContext == null) { accessibleContext = new AccessibleBox(); } return accessibleContext; } /** * This class implements accessibility support for the * <code>Box</code> class. */ @SuppressWarnings("serial") protected class AccessibleBox extends AccessibleAWTContainer { // AccessibleContext methods // /** * Gets the role of this object. * * @return an instance of AccessibleRole describing the role of the * object (AccessibleRole.FILLER) * @see AccessibleRole */ public AccessibleRole getAccessibleRole() { return AccessibleRole.FILLER; } } // inner class AccessibleBox }