Java tutorial
/* * Copyright (c) 1997, 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 java.awt.Font; import java.awt.event.InputEvent; import java.awt.event.KeyEvent; import java.awt.Color; import java.awt.Component; import java.awt.SystemColor; import java.awt.Toolkit; import sun.awt.SunToolkit; import javax.swing.text.*; import javax.swing.border.*; import javax.swing.plaf.*; import java.net.URL; import sun.swing.SwingUtilities2; import sun.swing.DefaultLayoutStyle; import sun.swing.ImageIconUIResource; import java.util.StringTokenizer; /** * {@code LookAndFeel}, as the name implies, encapsulates a look and * feel. Beyond installing a look and feel most developers never need to * interact directly with {@code LookAndFeel}. In general only developers * creating a custom look and feel need to concern themselves with this class. * <p> * Swing is built upon the foundation that each {@code JComponent} * subclass has an implementation of a specific {@code ComponentUI} * subclass. The {@code ComponentUI} is often referred to as "the ui", * "component ui", or "look and feel delegate". The {@code ComponentUI} * subclass is responsible for providing the look and feel specific * functionality of the component. For example, {@code JTree} requires * an implementation of the {@code ComponentUI} subclass {@code * TreeUI}. The implementation of the specific {@code * ComponentUI} subclass is provided by the {@code LookAndFeel}. Each * {@code JComponent} subclass identifies the {@code ComponentUI} * subclass it requires by way of the {@code JComponent} method {@code * getUIClassID}. * <p> * Each {@code LookAndFeel} implementation must provide * an implementation of the appropriate {@code ComponentUI} subclass by * specifying a value for each of Swing's ui class ids in the {@code * UIDefaults} object returned from {@code getDefaults}. For example, * {@code BasicLookAndFeel} uses {@code BasicTreeUI} as the concrete * implementation for {@code TreeUI}. This is accomplished by {@code * BasicLookAndFeel} providing the key-value pair {@code * "TreeUI"-"javax.swing.plaf.basic.BasicTreeUI"}, in the * {@code UIDefaults} returned from {@code getDefaults}. Refer to * {@link UIDefaults#getUI(JComponent)} for details on how the implementation * of the {@code ComponentUI} subclass is obtained. * <p> * When a {@code LookAndFeel} is installed the {@code UIManager} does * not check that an entry exists for all ui class ids. As such, * random exceptions will occur if the current look and feel has not * provided a value for a particular ui class id and an instance of * the {@code JComponent} subclass is created. * * <h2>Recommendations for Look and Feels</h2> * * As noted in {@code UIManager} each {@code LookAndFeel} has the opportunity * to provide a set of defaults that are layered in with developer and * system defaults. Some of Swing's components require the look and feel * to provide a specific set of defaults. These are documented in the * classes that require the specific default. * * <h3><a id="defaultRecommendation">ComponentUIs and defaults</a></h3> * * All {@code ComponentUIs} typically need to set various properties * on the {@code JComponent} the {@code ComponentUI} is providing the * look and feel for. This is typically done when the {@code * ComponentUI} is installed on the {@code JComponent}. Setting a * property should only be done if the developer has not set the * property. For non-primitive values it is recommended that the * {@code ComponentUI} only change the property on the {@code * JComponent} if the current value is {@code null} or implements * {@code UIResource}. If the current value is {@code null} or * implements {@code UIResource} it indicates the property has not * been set by the developer, and the ui is free to change it. For * example, {@code BasicButtonUI.installDefaults} only changes the * font on the {@code JButton} if the return value from {@code * button.getFont()} is {@code null} or implements {@code * UIResource}. On the other hand if {@code button.getFont()} returned * a {@code non-null} value that did not implement {@code UIResource} * then {@code BasicButtonUI.installDefaults} would not change the * {@code JButton}'s font. * <p> * For primitive values, such as {@code opaque}, the method {@code * installProperty} should be invoked. {@code installProperty} only changes * the corresponding property if the value has not been changed by the * developer. * <p> * {@code ComponentUI} implementations should use the various install methods * provided by this class as they handle the necessary checking and install * the property using the recommended guidelines. * * <h3><a id="exceptions"></a>Exceptions</h3> * * All of the install methods provided by {@code LookAndFeel} need to * access the defaults if the value of the property being changed is * {@code null} or a {@code UIResource}. For example, installing the * font does the following: * <pre> * JComponent c; * Font font = c.getFont(); * if (font == null || (font instanceof UIResource)) { * c.setFont(UIManager.getFont("fontKey")); * } * </pre> * If the font is {@code null} or a {@code UIResource}, the * defaults table is queried with the key {@code fontKey}. All of * {@code UIDefault's} get methods throw a {@code * NullPointerException} if passed in {@code null}. As such, unless * otherwise noted each of the various install methods of {@code * LookAndFeel} throw a {@code NullPointerException} if the current * value is {@code null} or a {@code UIResource} and the supplied * defaults key is {@code null}. In addition, unless otherwise specified * all of the {@code install} methods throw a {@code NullPointerException} if * a {@code null} component is passed in. * * @author Tom Ball * @author Hans Muller * @since 1.2 */ public abstract class LookAndFeel { /** * Convenience method for setting a component's foreground * and background color properties with values from the * defaults. The properties are only set if the current * value is either {@code null} or a {@code UIResource}. * * @param c component to set the colors on * @param defaultBgName key for the background * @param defaultFgName key for the foreground * * @see #installColorsAndFont * @see UIManager#getColor * @throws NullPointerException as described in * <a href="#exceptions">exceptions</a> */ public static void installColors(JComponent c, String defaultBgName, String defaultFgName) { Color bg = c.getBackground(); if (bg == null || bg instanceof UIResource) { c.setBackground(UIManager.getColor(defaultBgName)); } Color fg = c.getForeground(); if (fg == null || fg instanceof UIResource) { c.setForeground(UIManager.getColor(defaultFgName)); } } /** * Convenience method for setting a component's foreground, * background and font properties with values from the * defaults. The properties are only set if the current * value is either {@code null} or a {@code UIResource}. * * @param c component set to the colors and font on * @param defaultBgName key for the background * @param defaultFgName key for the foreground * @param defaultFontName key for the font * @throws NullPointerException as described in * <a href="#exceptions">exceptions</a> * * @see #installColors * @see UIManager#getColor * @see UIManager#getFont */ public static void installColorsAndFont(JComponent c, String defaultBgName, String defaultFgName, String defaultFontName) { Font f = c.getFont(); if (f == null || f instanceof UIResource) { c.setFont(UIManager.getFont(defaultFontName)); } installColors(c, defaultBgName, defaultFgName); } /** * Convenience method for setting a component's border property with * a value from the defaults. The border is only set if the border is * {@code null} or an instance of {@code UIResource}. * * @param c component to set the border on * @param defaultBorderName key specifying the border * @throws NullPointerException as described in * <a href="#exceptions">exceptions</a> */ public static void installBorder(JComponent c, String defaultBorderName) { Border b = c.getBorder(); if (b == null || b instanceof UIResource) { c.setBorder(UIManager.getBorder(defaultBorderName)); } } /** * Convenience method for uninstalling a border. If the border of * the component is a {@code UIResource}, it is set to {@code * null}. * * @param c component to uninstall the border on * @throws NullPointerException if {@code c} is {@code null} */ public static void uninstallBorder(JComponent c) { if (c.getBorder() instanceof UIResource) { c.setBorder(null); } } /** * Convenience method for installing a property with the specified name * and value on a component if that property has not already been set * by the developer. This method is intended to be used by * ui delegate instances that need to specify a default value for a * property of primitive type (boolean, int, ..), but do not wish * to override a value set by the client. Since primitive property * values cannot be wrapped with the {@code UIResource} marker, this method * uses private state to determine whether the property has been set * by the client. * * @throws IllegalArgumentException if the specified property is not * one which can be set using this method * @throws ClassCastException if the property value has not been set * by the developer and the type does not match the property's type * @throws NullPointerException if {@code c} is {@code null}, or the * named property has not been set by the developer and * {@code propertyValue} is {@code null} * @param c target component to set the property on * @param propertyName name of the property to set * @param propertyValue value of the property * @since 1.5 */ public static void installProperty(JComponent c, String propertyName, Object propertyValue) { // this is a special case because the JPasswordField's ancestor hierarchy // includes a class outside of javax.swing, thus we cannot call setUIProperty // directly. if (SunToolkit.isInstanceOf(c, "javax.swing.JPasswordField")) { if (!((JPasswordField) c).customSetUIProperty(propertyName, propertyValue)) { c.setUIProperty(propertyName, propertyValue); } } else { c.setUIProperty(propertyName, propertyValue); } } /** * Convenience method for building an array of {@code * KeyBindings}. While this method is not deprecated, developers * should instead use {@code ActionMap} and {@code InputMap} for * supplying key bindings. * <p> * This method returns an array of {@code KeyBindings}, one for each * alternating {@code key-action} pair in {@code keyBindingList}. * A {@code key} can either be a {@code String} in the format * specified by the <code>KeyStroke.getKeyStroke</code> method, or * a {@code KeyStroke}. The {@code action} part of the pair is a * {@code String} that corresponds to the name of the {@code * Action}. * <p> * The following example illustrates creating a {@code KeyBinding} array * from six alternating {@code key-action} pairs: * <pre> * JTextComponent.KeyBinding[] multilineBindings = makeKeyBindings( new Object[] { * "UP", DefaultEditorKit.upAction, * "DOWN", DefaultEditorKit.downAction, * "PAGE_UP", DefaultEditorKit.pageUpAction, * "PAGE_DOWN", DefaultEditorKit.pageDownAction, * "ENTER", DefaultEditorKit.insertBreakAction, * "TAB", DefaultEditorKit.insertTabAction * }); * </pre> * If {@code keyBindingList's} length is odd, the last element is * ignored. * <p> * Supplying a {@code null} value for either the {@code key} or * {@code action} part of the {@code key-action} pair results in * creating a {@code KeyBinding} with the corresponding value * {@code null}. As other parts of Swing's expect {@code non-null} values * in a {@code KeyBinding}, you should avoid supplying {@code null} as * either the {@code key} or {@code action} part of the {@code key-action} * pair. * * @param keyBindingList an array of {@code key-action} pairs * @return an array of {@code KeyBindings} * @throws NullPointerException if {@code keyBindingList} is {@code null} * @throws ClassCastException if the {@code key} part of the pair is * not a {@code KeyStroke} or {@code String}, or the * {@code action} part of the pair is not a {@code String} * @see ActionMap * @see InputMap * @see KeyStroke#getKeyStroke */ public static JTextComponent.KeyBinding[] makeKeyBindings(Object[] keyBindingList) { JTextComponent.KeyBinding[] rv = new JTextComponent.KeyBinding[keyBindingList.length / 2]; for (int i = 0; i < rv.length; i++) { Object o = keyBindingList[2 * i]; KeyStroke keystroke = (o instanceof KeyStroke) ? (KeyStroke) o : KeyStroke.getKeyStroke((String) o); String action = (String) keyBindingList[2 * i + 1]; rv[i] = new JTextComponent.KeyBinding(keystroke, action); } return rv; } /** * Creates an {@code InputMapUIResource} from <code>keys</code>. This is * a convenience method for creating a new {@code InputMapUIResource}, * invoking {@code loadKeyBindings(map, keys)}, and returning the * {@code InputMapUIResource}. * * @param keys alternating pairs of {@code keystroke-action key} * pairs as described in {@link #loadKeyBindings} * @return newly created and populated {@code InputMapUIResource} * @see #loadKeyBindings * * @since 1.3 */ public static InputMap makeInputMap(Object[] keys) { InputMap retMap = new InputMapUIResource(); loadKeyBindings(retMap, keys); return retMap; } /** * Creates a {@code ComponentInputMapUIResource} from * <code>keys</code>. This is a convenience method for creating a * new {@code ComponentInputMapUIResource}, invoking {@code * loadKeyBindings(map, keys)}, and returning the {@code * ComponentInputMapUIResource}. * * @param c component to create the {@code ComponentInputMapUIResource} * with * @param keys alternating pairs of {@code keystroke-action key} * pairs as described in {@link #loadKeyBindings} * @return newly created and populated {@code InputMapUIResource} * @throws IllegalArgumentException if {@code c} is {@code null} * * @see #loadKeyBindings * @see ComponentInputMapUIResource * * @since 1.3 */ public static ComponentInputMap makeComponentInputMap(JComponent c, Object[] keys) { ComponentInputMap retMap = new ComponentInputMapUIResource(c); loadKeyBindings(retMap, keys); return retMap; } /** * Populates an {@code InputMap} with the specified bindings. * The bindings are supplied as a list of alternating * {@code keystroke-action key} pairs. The {@code keystroke} is either * an instance of {@code KeyStroke}, or a {@code String} * that identifies the {@code KeyStroke} for the binding. Refer * to {@code KeyStroke.getKeyStroke(String)} for the specific * format. The {@code action key} part of the pair is the key * registered in the {@code InputMap} for the {@code KeyStroke}. * <p> * The following illustrates loading an {@code InputMap} with two * {@code key-action} pairs: * <pre> * LookAndFeel.loadKeyBindings(inputMap, new Object[] { * "control X", "cut", * "control V", "paste" * }); * </pre> * <p> * Supplying a {@code null} list of bindings ({@code keys}) does not * change {@code retMap} in any way. * <p> * Specifying a {@code null} {@code action key} results in * removing the {@code keystroke's} entry from the {@code InputMap}. * A {@code null} {@code keystroke} is ignored. * * @param retMap {@code InputMap} to add the {@code key-action} * pairs to * @param keys bindings to add to {@code retMap} * @throws NullPointerException if {@code keys} is * {@code non-null}, not empty, and {@code retMap} is * {@code null} * * @see KeyStroke#getKeyStroke(String) * @see InputMap * * @since 1.3 */ public static void loadKeyBindings(InputMap retMap, Object[] keys) { if (keys != null) { for (int counter = 0, maxCounter = keys.length; counter < maxCounter; counter++) { Object keyStrokeO = keys[counter++]; KeyStroke ks = (keyStrokeO instanceof KeyStroke) ? (KeyStroke) keyStrokeO : KeyStroke.getKeyStroke((String) keyStrokeO); retMap.put(ks, keys[counter]); } } } /** * Creates and returns a {@code UIDefault.LazyValue} that loads an * image. The returned value is an implementation of {@code * UIDefaults.LazyValue}. When {@code createValue} is invoked on * the returned object, the image is loaded. If the image is {@code * non-null}, it is then wrapped in an {@code Icon} that implements {@code * UIResource}. The image is loaded using {@code * Class.getResourceAsStream(gifFile)}. * <p> * This method does not check the arguments in any way. It is * strongly recommended that {@code non-null} values are supplied else * exceptions may occur when {@code createValue} is invoked on the * returned object. * * @param baseClass {@code Class} used to load the resource * @param gifFile path to the image to load * @return a {@code UIDefaults.LazyValue}; when resolved the * {@code LazyValue} loads the specified image * @see UIDefaults.LazyValue * @see Icon * @see Class#getResourceAsStream(String) */ public static Object makeIcon(final Class<?> baseClass, final String gifFile) { return SwingUtilities2.makeIcon_Unprivileged(baseClass, baseClass, gifFile); } /** * Returns the <code>LayoutStyle</code> for this look * and feel. This never returns {@code null}. * <p> * You generally don't use the <code>LayoutStyle</code> from * the look and feel, instead use the <code>LayoutStyle</code> * method <code>getInstance</code>. * * @see LayoutStyle#getInstance * @return the <code>LayoutStyle</code> for this look and feel * @since 1.6 */ public LayoutStyle getLayoutStyle() { return DefaultLayoutStyle.getInstance(); } /** * Invoked when the user attempts an invalid operation, * such as pasting into an uneditable <code>JTextField</code> * that has focus. The default implementation beeps. Subclasses * that wish different behavior should override this and provide * the additional feedback. * * @param component the <code>Component</code> the error occurred in, * may be <code>null</code> * indicating the error condition is not directly * associated with a <code>Component</code> * @since 1.4 */ public void provideErrorFeedback(Component component) { Toolkit toolkit = null; if (component != null) { toolkit = component.getToolkit(); } else { toolkit = Toolkit.getDefaultToolkit(); } toolkit.beep(); } // provideErrorFeedback() /** * Returns the value of the specified system desktop property by * invoking <code>Toolkit.getDefaultToolkit().getDesktopProperty()</code>. * If the value of the specified property is {@code null}, * {@code fallbackValue} is returned. * * @param systemPropertyName the name of the system desktop property being queried * @param fallbackValue the object to be returned as the value if the system value is null * @return the current value of the desktop property * * @see java.awt.Toolkit#getDesktopProperty * * @since 1.4 */ public static Object getDesktopPropertyValue(String systemPropertyName, Object fallbackValue) { Object value = Toolkit.getDefaultToolkit().getDesktopProperty(systemPropertyName); if (value == null) { return fallbackValue; } else if (value instanceof Color) { return new ColorUIResource((Color) value); } else if (value instanceof Font) { return new FontUIResource((Font) value); } return value; } /** * Returns an <code>Icon</code> with a disabled appearance. * This method is used to generate a disabled <code>Icon</code> when * one has not been specified. For example, if you create a * <code>JButton</code> and only specify an <code>Icon</code> via * <code>setIcon</code> this method will be called to generate the * disabled <code>Icon</code>. If {@code null} is passed as * <code>icon</code> this method returns {@code null}. * <p> * Some look and feels might not render the disabled {@code Icon}, in which * case they will ignore this. * * @param component {@code JComponent} that will display the {@code Icon}, * may be {@code null} * @param icon {@code Icon} to generate the disabled icon from * @return disabled {@code Icon}, or {@code null} if a suitable * {@code Icon} can not be generated * @since 1.5 */ public Icon getDisabledIcon(JComponent component, Icon icon) { if (icon instanceof ImageIcon) { return new ImageIconUIResource(GrayFilter.createDisabledImage(((ImageIcon) icon).getImage())); } return null; } /** * Returns an <code>Icon</code> for use by disabled * components that are also selected. This method is used to generate an * <code>Icon</code> for components that are in both the disabled and * selected states but do not have a specific <code>Icon</code> for this * state. For example, if you create a <code>JButton</code> and only * specify an <code>Icon</code> via <code>setIcon</code> this method * will be called to generate the disabled and selected * <code>Icon</code>. If {@code null} is passed as <code>icon</code> this * methods returns {@code null}. * <p> * Some look and feels might not render the disabled and selected * {@code Icon}, in which case they will ignore this. * * @param component {@code JComponent} that will display the {@code Icon}, * may be {@code null} * @param icon {@code Icon} to generate disabled and selected icon from * @return disabled and selected icon, or {@code null} if a suitable * {@code Icon} can not be generated. * @since 1.5 */ public Icon getDisabledSelectedIcon(JComponent component, Icon icon) { return getDisabledIcon(component, icon); } /** * Return a short string that identifies this look and feel, e.g. * "CDE/Motif". This string should be appropriate for a menu item. * Distinct look and feels should have different names, e.g. * a subclass of MotifLookAndFeel that changes the way a few components * are rendered should be called "CDE/Motif My Way"; something * that would be useful to a user trying to select a L&F from a list * of names. * * @return short identifier for the look and feel */ public abstract String getName(); /** * Return a string that identifies this look and feel. This string * will be used by applications/services that want to recognize * well known look and feel implementations. Presently * the well known names are "Motif", "Windows", "Mac", "Metal". Note * that a LookAndFeel derived from a well known superclass * that doesn't make any fundamental changes to the look or feel * shouldn't override this method. * * @return identifier for the look and feel */ public abstract String getID(); /** * Return a one line description of this look and feel implementation, * e.g. "The CDE/Motif Look and Feel". This string is intended for * the user, e.g. in the title of a window or in a ToolTip message. * * @return short description for the look and feel */ public abstract String getDescription(); /** * Returns {@code true} if the <code>LookAndFeel</code> returned * <code>RootPaneUI</code> instances support providing {@code Window} * decorations in a <code>JRootPane</code>. * <p> * The default implementation returns {@code false}, subclasses that * support {@code Window} decorations should override this and return * {@code true}. * * @return {@code true} if the {@code RootPaneUI} instances created by * this look and feel support client side decorations * @see JDialog#setDefaultLookAndFeelDecorated * @see JFrame#setDefaultLookAndFeelDecorated * @see JRootPane#setWindowDecorationStyle * @since 1.4 */ public boolean getSupportsWindowDecorations() { return false; } /** * If the underlying platform has a "native" look and feel, and * this is an implementation of it, return {@code true}. For * example, when the underlying platform is Solaris running CDE * a CDE/Motif look and feel implementation would return {@code * true}. * * @return {@code true} if this look and feel represents the underlying * platform look and feel */ public abstract boolean isNativeLookAndFeel(); /** * Return {@code true} if the underlying platform supports and or permits * this look and feel. This method returns {@code false} if the look * and feel depends on special resources or legal agreements that * aren't defined for the current platform. * * * @return {@code true} if this is a supported look and feel * @see UIManager#setLookAndFeel */ public abstract boolean isSupportedLookAndFeel(); /** * Initializes the look and feel. While this method is public, * it should only be invoked by the {@code UIManager} when a * look and feel is installed as the current look and feel. This * method is invoked before the {@code UIManager} invokes * {@code getDefaults}. This method is intended to perform any * initialization for the look and feel. Subclasses * should do any one-time setup they need here, rather than * in a static initializer, because look and feel class objects * may be loaded just to discover that {@code isSupportedLookAndFeel()} * returns {@code false}. * * @see #uninitialize * @see UIManager#setLookAndFeel */ public void initialize() { } /** * Uninitializes the look and feel. While this method is public, * it should only be invoked by the {@code UIManager} when * the look and feel is uninstalled. For example, * {@code UIManager.setLookAndFeel} invokes this when the look and * feel is changed. * <p> * Subclasses may choose to free up some resources here. * * @see #initialize * @see UIManager#setLookAndFeel */ public void uninitialize() { } /** * Returns the look and feel defaults. While this method is public, * it should only be invoked by the {@code UIManager} when the * look and feel is set as the current look and feel and after * {@code initialize} has been invoked. * * @return the look and feel defaults * @see #initialize * @see #uninitialize * @see UIManager#setLookAndFeel */ public UIDefaults getDefaults() { return null; } /** * Returns a string that displays and identifies this * object's properties. * * @return a String representation of this object */ public String toString() { return "[" + getDescription() + " - " + getClass().getName() + "]"; } }