Java tutorial
/* * Copyright (c) 2005, 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.Container; import javax.swing.plaf.ComponentUI; import sun.awt.AppContext; /** * <code>LayoutStyle</code> provides information about how to position * components. This class is primarily useful for visual tools and * layout managers. Most developers will not need to use this class. * <p> * You typically don't set or create a * <code>LayoutStyle</code>. Instead use the static method * <code>getInstance</code> to obtain the current instance. * * @since 1.6 */ public abstract class LayoutStyle { /** * Sets the shared instance of <code>LayoutStyle</code>. Specifying * <code>null</code> results in using the <code>LayoutStyle</code> from * the current <code>LookAndFeel</code>. * * @param style the <code>LayoutStyle</code>, or <code>null</code> * @see #getInstance */ public static void setInstance(LayoutStyle style) { synchronized (LayoutStyle.class) { if (style == null) { AppContext.getAppContext().remove(LayoutStyle.class); } else { AppContext.getAppContext().put(LayoutStyle.class, style); } } } /** * Returns the shared instance of <code>LayoutStyle</code>. If an instance * has not been specified in <code>setInstance</code>, this will return * the <code>LayoutStyle</code> from the current <code>LookAndFeel</code>. * * @see LookAndFeel#getLayoutStyle * @return the shared instance of <code>LayoutStyle</code> */ public static LayoutStyle getInstance() { LayoutStyle style; synchronized (LayoutStyle.class) { style = (LayoutStyle) AppContext.getAppContext().get(LayoutStyle.class); } if (style == null) { return UIManager.getLookAndFeel().getLayoutStyle(); } return style; } /** * <code>ComponentPlacement</code> is an enumeration of the * possible ways two components can be placed relative to each * other. <code>ComponentPlacement</code> is used by the * <code>LayoutStyle</code> method <code>getPreferredGap</code>. Refer to * <code>LayoutStyle</code> for more information. * * @see LayoutStyle#getPreferredGap(JComponent,JComponent, * ComponentPlacement,int,Container) * @since 1.6 */ public enum ComponentPlacement { /** * Enumeration value indicating the two components are * visually related and will be placed in the same parent. * For example, a <code>JLabel</code> providing a label for a * <code>JTextField</code> is typically visually associated * with the <code>JTextField</code>; the constant <code>RELATED</code> * is used for this. */ RELATED, /** * Enumeration value indicating the two components are * visually unrelated and will be placed in the same parent. * For example, groupings of components are usually visually * separated; the constant <code>UNRELATED</code> is used for this. */ UNRELATED, /** * Enumeration value indicating the distance to indent a component * is being requested. For example, often times the children of * a label will be horizontally indented from the label. To determine * the preferred distance for such a gap use the * <code>INDENT</code> type. * <p> * This value is typically only useful with a direction of * <code>EAST</code> or <code>WEST</code>. */ INDENT; } /** * Creates a new <code>LayoutStyle</code>. You generally don't * create a <code>LayoutStyle</code>. Instead use the method * <code>getInstance</code> to obtain the current * <code>LayoutStyle</code>. */ public LayoutStyle() { } /** * Returns the amount of space to use between two components. * The return value indicates the distance to place * <code>component2</code> relative to <code>component1</code>. * For example, the following returns the amount of space to place * between <code>component2</code> and <code>component1</code> * when <code>component2</code> is placed vertically above * <code>component1</code>: * <pre> * int gap = getPreferredGap(component1, component2, * ComponentPlacement.RELATED, * SwingConstants.NORTH, parent); * </pre> * The <code>type</code> parameter indicates the relation between * the two components. If the two components will be contained in * the same parent and are showing similar logically related * items, use <code>RELATED</code>. If the two components will be * contained in the same parent but show logically unrelated items * use <code>UNRELATED</code>. Some look and feels may not * distinguish between the <code>RELATED</code> and * <code>UNRELATED</code> types. * <p> * The return value is not intended to take into account the * current size and position of <code>component2</code> or * <code>component1</code>. The return value may take into * consideration various properties of the components. For * example, the space may vary based on font size, or the preferred * size of the component. * * @param component1 the <code>JComponent</code> * <code>component2</code> is being placed relative to * @param component2 the <code>JComponent</code> being placed * @param position the position <code>component2</code> is being placed * relative to <code>component1</code>; one of * <code>SwingConstants.NORTH</code>, * <code>SwingConstants.SOUTH</code>, * <code>SwingConstants.EAST</code> or * <code>SwingConstants.WEST</code> * @param type how the two components are being placed * @param parent the parent of <code>component2</code>; this may differ * from the actual parent and it may be <code>null</code> * @return the amount of space to place between the two components * @throws NullPointerException if <code>component1</code>, * <code>component2</code> or <code>type</code> is * <code>null</code> * @throws IllegalArgumentException if <code>position</code> is not * one of <code>SwingConstants.NORTH</code>, * <code>SwingConstants.SOUTH</code>, * <code>SwingConstants.EAST</code> or * <code>SwingConstants.WEST</code> * @see LookAndFeel#getLayoutStyle * @since 1.6 */ public abstract int getPreferredGap(JComponent component1, JComponent component2, ComponentPlacement type, int position, Container parent); /** * Returns the amount of space to place between the component and specified * edge of its parent. * * @param component the <code>JComponent</code> being positioned * @param position the position <code>component</code> is being placed * relative to its parent; one of * <code>SwingConstants.NORTH</code>, * <code>SwingConstants.SOUTH</code>, * <code>SwingConstants.EAST</code> or * <code>SwingConstants.WEST</code> * @param parent the parent of <code>component</code>; this may differ * from the actual parent and may be <code>null</code> * @return the amount of space to place between the component and specified * edge * @throws IllegalArgumentException if <code>position</code> is not * one of <code>SwingConstants.NORTH</code>, * <code>SwingConstants.SOUTH</code>, * <code>SwingConstants.EAST</code> or * <code>SwingConstants.WEST</code> */ public abstract int getContainerGap(JComponent component, int position, Container parent); }