Java tutorial
/* * Copyright (c) 2000, 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.text; /** * <code>DocumentFilter</code>, as the name implies, is a filter for the * <code>Document</code> mutation methods. When a <code>Document</code> * containing a <code>DocumentFilter</code> is modified (either through * <code>insert</code> or <code>remove</code>), it forwards the appropriate * method invocation to the <code>DocumentFilter</code>. The * default implementation allows the modification to * occur. Subclasses can filter the modifications by conditionally invoking * methods on the superclass, or invoking the necessary methods on * the passed in <code>FilterBypass</code>. Subclasses should NOT call back * into the Document for the modification * instead call into the superclass or the <code>FilterBypass</code>. * <p> * When <code>remove</code> or <code>insertString</code> is invoked * on the <code>DocumentFilter</code>, the <code>DocumentFilter</code> * may callback into the * <code>FilterBypass</code> multiple times, or for different regions, but * it should not callback into the <code>FilterBypass</code> after returning * from the <code>remove</code> or <code>insertString</code> method. * <p> * By default, text related document mutation methods such as * <code>insertString</code>, <code>replace</code> and <code>remove</code> * in <code>AbstractDocument</code> use <code>DocumentFilter</code> when * available, and <code>Element</code> related mutation methods such as * <code>create</code>, <code>insert</code> and <code>removeElement</code> in * <code>DefaultStyledDocument</code> do not use <code>DocumentFilter</code>. * If a method doesn't follow these defaults, this must be explicitly stated * in the method documentation. * * @see javax.swing.text.Document * @see javax.swing.text.AbstractDocument * @see javax.swing.text.DefaultStyledDocument * * @since 1.4 */ public class DocumentFilter { /** * Invoked prior to removal of the specified region in the * specified Document. Subclasses that want to conditionally allow * removal should override this and only call supers implementation as * necessary, or call directly into the <code>FilterBypass</code> as * necessary. * * @param fb FilterBypass that can be used to mutate Document * @param offset the offset from the beginning >= 0 * @param length the number of characters to remove >= 0 * @exception BadLocationException some portion of the removal range * was not a valid part of the document. The location in the exception * is the first bad position encountered. */ public void remove(FilterBypass fb, int offset, int length) throws BadLocationException { fb.remove(offset, length); } /** * Invoked prior to insertion of text into the * specified Document. Subclasses that want to conditionally allow * insertion should override this and only call supers implementation as * necessary, or call directly into the FilterBypass. * * @param fb FilterBypass that can be used to mutate Document * @param offset the offset into the document to insert the content >= 0. * All positions that track change at or after the given location * will move. * @param string the string to insert * @param attr the attributes to associate with the inserted * content. This may be null if there are no attributes. * @exception BadLocationException the given insert position is not a * valid position within the document */ public void insertString(FilterBypass fb, int offset, String string, AttributeSet attr) throws BadLocationException { fb.insertString(offset, string, attr); } /** * Invoked prior to replacing a region of text in the * specified Document. Subclasses that want to conditionally allow * replace should override this and only call supers implementation as * necessary, or call directly into the FilterBypass. * * @param fb FilterBypass that can be used to mutate Document * @param offset Location in Document * @param length Length of text to delete * @param text Text to insert, null indicates no text to insert * @param attrs AttributeSet indicating attributes of inserted text, * null is legal. * @exception BadLocationException the given insert position is not a * valid position within the document */ public void replace(FilterBypass fb, int offset, int length, String text, AttributeSet attrs) throws BadLocationException { fb.replace(offset, length, text, attrs); } /** * Used as a way to circumvent calling back into the Document to * change it. Document implementations that wish to support * a DocumentFilter must provide an implementation that will * not callback into the DocumentFilter when the following methods * are invoked from the DocumentFilter. * @since 1.4 */ public abstract static class FilterBypass { /** * Returns the Document the mutation is occurring on. * * @return Document that remove/insertString will operate on */ public abstract Document getDocument(); /** * Removes the specified region of text, bypassing the * DocumentFilter. * * @param offset the offset from the beginning >= 0 * @param length the number of characters to remove >= 0 * @exception BadLocationException some portion of the removal range * was not a valid part of the document. The location in the * exception is the first bad position encountered. */ public abstract void remove(int offset, int length) throws BadLocationException; /** * Inserts the specified text, bypassing the * DocumentFilter. * @param offset the offset into the document to insert the * content >= 0. All positions that track change at or after the * given location will move. * @param string the string to insert * @param attr the attributes to associate with the inserted * content. This may be null if there are no attributes. * @exception BadLocationException the given insert position is not a * valid position within the document */ public abstract void insertString(int offset, String string, AttributeSet attr) throws BadLocationException; /** * Deletes the region of text from <code>offset</code> to * <code>offset + length</code>, and replaces it with * <code>text</code>. * * @param offset Location in Document * @param length Length of text to delete * @param string Text to insert, null indicates no text to insert * @param attrs AttributeSet indicating attributes of inserted text, * null is legal. * @exception BadLocationException the given insert is not a * valid position within the document */ public abstract void replace(int offset, int length, String string, AttributeSet attrs) throws BadLocationException; } }