Java tutorial
/* * Copyright (c) 2005, 2013, 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.Graphics2D; /** * <p>A painting delegate. The Painter interface defines exactly one method, * <code>paint</code>. It is used in situations where the developer can change * the painting routine of a component without having to resort to subclassing * the component. It is also generically useful when doing any form of painting * delegation.</p> * * <p><code>Painter</code>s are simply encapsulations of Java2D code and make * it fairly trivial to reuse existing <code>Painter</code>s or to combine * them together. Implementations of this interface are also trivial to write, * such that if you can't find a <code>Painter</code> that does what you need, * you can write one with minimal effort. Writing a <code>Painter</code> requires * knowledge of Java2D.</p> * * <p>A <code>Painter</code> may be created with a type parameter. This type will be * expected in the <code>paint</code> method. For example, you may wish to write a * <code>Painter</code> that only works with subclasses of {@link java.awt.Component}. * In that case, when the <code>Painter</code> is declared, you may declare that * it requires a <code>Component</code>, allowing the paint method to be type safe. Ex: * <pre> * {@code * Painter<Component> p = new Painter<Component>() { * public void paint(Graphics2D g, Component c, int width, int height) { * g.setColor(c.getBackground()); * //and so forth * } * } * } * </pre> * * <p>This interface makes no guarantees of threadsafety.</p> * * @author rbair * @since 1.7 */ public interface Painter<T> { /** * <p>Renders to the given {@link java.awt.Graphics2D} object. Implementations * of this method <em>may</em> modify state on the <code>Graphics2D</code>, and are not * required to restore that state upon completion. In most cases, it is recommended * that the caller pass in a scratch graphics object. The <code>Graphics2D</code> * must never be null.</p> * * <p>State on the graphics object may be honored by the <code>paint</code> method, * but may not be. For instance, setting the antialiasing rendering hint on the * graphics may or may not be respected by the <code>Painter</code> implementation.</p> * * <p>The supplied object parameter acts as an optional configuration argument. * For example, it could be of type <code>Component</code>. A <code>Painter</code> * that expected it could then read state from that <code>Component</code> and * use the state for painting. For example, an implementation may read the * backgroundColor and use that.</p> * * <p>Generally, to enhance reusability, most standard <code>Painter</code>s ignore * this parameter. They can thus be reused in any context. The <code>object</code> * may be null. Implementations must not throw a NullPointerException if the object * parameter is null.</p> * * <p>Finally, the <code>width</code> and <code>height</code> arguments specify the * width and height that the <code>Painter</code> should paint into. More * specifically, the specified width and height instruct the painter that it should * paint fully within this width and height. Any specified clip on the * <code>g</code> param will further constrain the region.</p> * * <p>For example, suppose I have a <code>Painter</code> implementation that draws * a gradient. The gradient goes from white to black. It "stretches" to fill the * painted region. Thus, if I use this <code>Painter</code> to paint a 500 x 500 * region, the far left would be black, the far right would be white, and a smooth * gradient would be painted between. I could then, without modification, reuse the * <code>Painter</code> to paint a region that is 20x20 in size. This region would * also be black on the left, white on the right, and a smooth gradient painted * between.</p> * * @param g The Graphics2D to render to. This must not be null. * @param object an optional configuration parameter. This may be null. * @param width width of the area to paint. * @param height height of the area to paint. */ public void paint(Graphics2D g, T object, int width, int height); }