Java tutorial
/* * Copyright (c) 1998, 2017, 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 javax.swing.*; import javax.swing.event.*; import javax.swing.border.*; import java.awt.Component; import java.awt.Color; import java.awt.Rectangle; import java.io.Serializable; import sun.swing.DefaultLookup; import sun.swing.SwingUtilities2; /** * Renders an item in a list. * <p> * <strong><a id="override">Implementation Note:</a></strong> * This class overrides * <code>invalidate</code>, * <code>validate</code>, * <code>revalidate</code>, * <code>repaint</code>, * <code>isOpaque</code>, * and * <code>firePropertyChange</code> * solely to improve performance. * If not overridden, these frequently called methods would execute code paths * that are unnecessary for the default list cell renderer. * If you write your own renderer, * take care to weigh the benefits and * drawbacks of overriding these methods. * * <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}. * * @author Philip Milne * @author Hans Muller * @since 1.2 */ @SuppressWarnings("serial") // Same-version serialization only public class DefaultListCellRenderer extends JLabel implements ListCellRenderer<Object>, Serializable { /** * An empty <code>Border</code>. This field might not be used. To change the * <code>Border</code> used by this renderer override the * <code>getListCellRendererComponent</code> method and set the border * of the returned component directly. */ private static final Border SAFE_NO_FOCUS_BORDER = new EmptyBorder(1, 1, 1, 1); private static final Border DEFAULT_NO_FOCUS_BORDER = new EmptyBorder(1, 1, 1, 1); /** * No focus border */ protected static Border noFocusBorder = DEFAULT_NO_FOCUS_BORDER; /** * Constructs a default renderer object for an item * in a list. */ public DefaultListCellRenderer() { super(); setOpaque(true); setBorder(getNoFocusBorder()); setName("List.cellRenderer"); } private Border getNoFocusBorder() { Border border = DefaultLookup.getBorder(this, ui, "List.cellNoFocusBorder"); if (System.getSecurityManager() != null) { if (border != null) return border; return SAFE_NO_FOCUS_BORDER; } else { if (border != null && (noFocusBorder == null || noFocusBorder == DEFAULT_NO_FOCUS_BORDER)) { return border; } return noFocusBorder; } } public Component getListCellRendererComponent(JList<?> list, Object value, int index, boolean isSelected, boolean cellHasFocus) { setComponentOrientation(list.getComponentOrientation()); Color bg = null; Color fg = null; JList.DropLocation dropLocation = list.getDropLocation(); if (dropLocation != null && !dropLocation.isInsert() && dropLocation.getIndex() == index) { bg = DefaultLookup.getColor(this, ui, "List.dropCellBackground"); fg = DefaultLookup.getColor(this, ui, "List.dropCellForeground"); isSelected = true; } if (isSelected) { setBackground(bg == null ? list.getSelectionBackground() : bg); setForeground(fg == null ? list.getSelectionForeground() : fg); } else { setBackground(list.getBackground()); setForeground(list.getForeground()); } if (value instanceof Icon) { setIcon((Icon) value); setText(""); } else { setIcon(null); setText((value == null) ? "" : value.toString()); } setEnabled(list.isEnabled()); setFont(list.getFont()); Border border = null; if (cellHasFocus) { if (isSelected) { border = DefaultLookup.getBorder(this, ui, "List.focusSelectedCellHighlightBorder"); } if (border == null) { border = DefaultLookup.getBorder(this, ui, "List.focusCellHighlightBorder"); } } else { border = getNoFocusBorder(); } setBorder(border); return this; } /** * Overridden for performance reasons. * See the <a href="#override">Implementation Note</a> * for more information. * * @since 1.5 * @return <code>true</code> if the background is completely opaque * and differs from the JList's background; * <code>false</code> otherwise */ @Override public boolean isOpaque() { Color back = getBackground(); Component p = getParent(); if (p != null) { p = p.getParent(); } // p should now be the JList. boolean colorMatch = (back != null) && (p != null) && back.equals(p.getBackground()) && p.isOpaque(); return !colorMatch && super.isOpaque(); } /** * Overridden for performance reasons. * See the <a href="#override">Implementation Note</a> * for more information. */ @Override public void validate() { } /** * Overridden for performance reasons. * See the <a href="#override">Implementation Note</a> * for more information. * * @since 1.5 */ @Override public void invalidate() { } /** * Overridden for performance reasons. * See the <a href="#override">Implementation Note</a> * for more information. * * @since 1.5 */ @Override public void repaint() { } /** * Overridden for performance reasons. * See the <a href="#override">Implementation Note</a> * for more information. */ @Override public void revalidate() { } /** * Overridden for performance reasons. * See the <a href="#override">Implementation Note</a> * for more information. */ @Override public void repaint(long tm, int x, int y, int width, int height) { } /** * Overridden for performance reasons. * See the <a href="#override">Implementation Note</a> * for more information. */ @Override public void repaint(Rectangle r) { } /** * Overridden for performance reasons. * See the <a href="#override">Implementation Note</a> * for more information. */ @Override protected void firePropertyChange(String propertyName, Object oldValue, Object newValue) { // Strings get interned... if (propertyName == "text" || ((SwingUtilities2.isScaleChanged(propertyName, oldValue, newValue) || propertyName == "font" || propertyName == "foreground") && oldValue != newValue && getClientProperty(javax.swing.plaf.basic.BasicHTML.propertyKey) != null)) { super.firePropertyChange(propertyName, oldValue, newValue); } } /** * Overridden for performance reasons. * See the <a href="#override">Implementation Note</a> * for more information. */ @Override public void firePropertyChange(String propertyName, byte oldValue, byte newValue) { } /** * Overridden for performance reasons. * See the <a href="#override">Implementation Note</a> * for more information. */ @Override public void firePropertyChange(String propertyName, char oldValue, char newValue) { } /** * Overridden for performance reasons. * See the <a href="#override">Implementation Note</a> * for more information. */ @Override public void firePropertyChange(String propertyName, short oldValue, short newValue) { } /** * Overridden for performance reasons. * See the <a href="#override">Implementation Note</a> * for more information. */ @Override public void firePropertyChange(String propertyName, int oldValue, int newValue) { } /** * Overridden for performance reasons. * See the <a href="#override">Implementation Note</a> * for more information. */ @Override public void firePropertyChange(String propertyName, long oldValue, long newValue) { } /** * Overridden for performance reasons. * See the <a href="#override">Implementation Note</a> * for more information. */ @Override public void firePropertyChange(String propertyName, float oldValue, float newValue) { } /** * Overridden for performance reasons. * See the <a href="#override">Implementation Note</a> * for more information. */ @Override public void firePropertyChange(String propertyName, double oldValue, double newValue) { } /** * Overridden for performance reasons. * See the <a href="#override">Implementation Note</a> * for more information. */ @Override public void firePropertyChange(String propertyName, boolean oldValue, boolean newValue) { } /** * A subclass of DefaultListCellRenderer that implements UIResource. * DefaultListCellRenderer doesn't implement UIResource * directly so that applications can safely override the * cellRenderer property with DefaultListCellRenderer subclasses. * <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") // Same-version serialization only public static class UIResource extends DefaultListCellRenderer implements javax.swing.plaf.UIResource { } }