Android example source code file (RootElement.java)

This example Android source code file (RootElement.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

attributes, badxmlexception, children, defaulthandler, element, encountered, got, handler, locator, override, rootelement, sax, saxexception, string, stringbuilder

The RootElement.java Android example source code

/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.sax;

import org.xml.sax.helpers.DefaultHandler;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.ContentHandler;
import org.xml.sax.Locator;

/**
 * The root XML element. The entry point for this API. Not safe for concurrent
 * use.
 *
 * <p>For example, passing this XML:
 *
 * <pre>
 * <feed xmlns='http://www.w3.org/2005/Atom'>
 *   <entry>
 *     <id>bob</id>
 *   </entry>
 * </feed>
 * </pre>
 *
 * to this code:
 *
 * <pre>
 * static final String ATOM_NAMESPACE = "http://www.w3.org/2005/Atom";
 *
 * ...
 * 
 * RootElement root = new RootElement(ATOM_NAMESPACE, "feed");
 * Element entry = root.getChild(ATOM_NAMESPACE, "entry");
 * entry.getChild(ATOM_NAMESPACE, "id").setEndTextElementListener(
 *   new EndTextElementListener() {
 *     public void end(String body) {
 *       System.out.println("Entry ID: " + body);
 *     }
 *   });
 *
 * XMLReader reader = ...;
 * reader.setContentHandler(root.getContentHandler());
 * reader.parse(...);
 * </pre>
 *
 * would output:
 *
 * <pre>
 * Entry ID: bob
 * </pre>
 */
public class RootElement extends Element {

    final Handler handler = new Handler();

    /**
     * Constructs a new root element with the given name.
     *
     * @param uri the namespace
     * @param localName the local name
     */
    public RootElement(String uri, String localName) {
        super(null, uri, localName, 0);
    }

    /**
     * Constructs a new root element with the given name. Uses an empty string
     * as the namespace.
     *
     * @param localName the local name
     */
    public RootElement(String localName) {
        this("", localName);
    }

    /**
     * Gets the SAX {@code ContentHandler}. Pass this to your SAX parser.
     */
    public ContentHandler getContentHandler() {
        return this.handler;
    }

    class Handler extends DefaultHandler {

        Locator locator;
        int depth = -1;
        Element current = null;
        StringBuilder bodyBuilder = null;

        @Override
        public void setDocumentLocator(Locator locator) {
            this.locator = locator;
        }

        @Override
        public void startElement(String uri, String localName, String qName,
                Attributes attributes) throws SAXException {
            int depth = ++this.depth;

            if (depth == 0) {
                // This is the root element.
                startRoot(uri, localName, attributes);
                return;
            }

            // Prohibit mixed text and elements.
            if (bodyBuilder != null) {
                throw new BadXmlException("Encountered mixed content"
                        + " within text element named " + current + ".",
                        locator);
            }

            // If we're one level below the current element.
            if (depth == current.depth + 1) {
                // Look for a child to push onto the stack.
                Children children = current.children;
                if (children != null) {
                    Element child = children.get(uri, localName);
                    if (child != null) {
                        start(child, attributes);
                    }
                }
            }
        }

        void startRoot(String uri, String localName, Attributes attributes)
                throws SAXException {
            Element root = RootElement.this;
            if (root.uri.compareTo(uri) != 0
                    || root.localName.compareTo(localName) != 0) {
                throw new BadXmlException("Root element name does"
                        + " not match. Expected: " + root + ", Got: "
                        + Element.toString(uri, localName), locator);
            }

            start(root, attributes);
        }

        void start(Element e, Attributes attributes) {
            // Push element onto the stack.
            this.current = e;

            if (e.startElementListener != null) {
                e.startElementListener.start(attributes);
            }

            if (e.endTextElementListener != null) {
                this.bodyBuilder = new StringBuilder();
            }
            
            e.resetRequiredChildren();
            e.visited = true;
        }

        @Override
        public void characters(char[] buffer, int start, int length)
                throws SAXException {
            if (bodyBuilder != null) {
                bodyBuilder.append(buffer, start, length);
            }
        }

        @Override
        public void endElement(String uri, String localName, String qName)
                throws SAXException {
            Element current = this.current;

            // If we've ended the current element...
            if (depth == current.depth) {
                current.checkRequiredChildren(locator);

                // Invoke end element listener.
                if (current.endElementListener != null) {
                    current.endElementListener.end();
                }

                // Invoke end text element listener.
                if (bodyBuilder != null) {
                    String body = bodyBuilder.toString();
                    bodyBuilder = null;

                    // We can assume that this listener is present.
                    current.endTextElementListener.end(body);
                }

                // Pop element off the stack.
                this.current = current.parent;
            }

            depth--;
        }
    }
}