Android example source code file (ExtendedWikiHelper.java)

This example Android source code file (ExtendedWikiHelper.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

android, formatrule, hashset, jsonobject, matcher, net, network, parseexception, pattern, random_tries, regex, simplewikihelper, string, stringbuilder, style_sheet, text, util, wiki_authority, wiki_lookup_host, wiktionary_random

The ExtendedWikiHelper.java Android example source code

/*
 * Copyright (C) 2009 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 com.example.android.wiktionary;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.net.Uri;
import android.text.TextUtils;
import android.webkit.WebView;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Extended version of {@link SimpleWikiHelper}. This version adds methods to
 * pick a random word, and to format generic wiki-style text into HTML.
 */
public class ExtendedWikiHelper extends SimpleWikiHelper {
    /**
     * HTML style sheet to include with any {@link #formatWikiText(String)} HTML
     * results. It formats nicely for a mobile screen, and hides some content
     * boxes to keep things tidy.
     */
    private static final String STYLE_SHEET = "<style>h2 {font-size:1.2em;font-weight:normal;} " +
            "a {color:#6688cc;} ol {padding-left:1.5em;} blockquote {margin-left:0em;} " +
            ".interProject, .noprint {display:none;} " +
            "li, blockquote {margin-top:0.5em;margin-bottom:0.5em;}</style>";

    /**
     * Pattern of section titles we're interested in showing. This trims out
     * extra sections that can clutter things up on a mobile screen.
     */
    private static final Pattern sValidSections =
        Pattern.compile("(verb|noun|adjective|pronoun|interjection)", Pattern.CASE_INSENSITIVE);

    /**
     * Pattern that can be used to split a returned wiki page into its various
     * sections. Doesn't treat children sections differently.
     */
    private static final Pattern sSectionSplit =
        Pattern.compile("^=+(.+?)=+.+?(?=^=)", Pattern.MULTILINE | Pattern.DOTALL);

    /**
     * When picking random words in {@link #getRandomWord()}, we sometimes
     * encounter special articles or templates. This pattern ignores any words
     * like those, usually because they have ":" or other punctuation.
     */
    private static final Pattern sInvalidWord = Pattern.compile("[^A-Za-z0-9 ]");

    /**
     * {@link Uri} authority to use when creating internal links.
     */
    public static final String WIKI_AUTHORITY = "wiktionary";

    /**
     * {@link Uri} host to use when creating internal links.
     */
    public static final String WIKI_LOOKUP_HOST = "lookup";

    /**
     * Mime-type to use when showing parsed results in a {@link WebView}.
     */
    public static final String MIME_TYPE = "text/html";

    /**
     * Encoding to use when showing parsed results in a {@link WebView}.
     */
    public static final String ENCODING = "utf-8";

    /**
     * {@link Uri} to use when requesting a random page.
     */
    private static final String WIKTIONARY_RANDOM =
        "http://en.wiktionary.org/w/api.php?action=query&list=random&format=json";

    /**
     * Fake section to insert at the bottom of a wiki response before parsing.
     * This ensures that {@link #sSectionSplit} will always catch the last
     * section, as it uses section headers in its searching.
     */
    private static final String STUB_SECTION = "\n=Stub section=";

    /**
     * Number of times to try finding a random word in {@link #getRandomWord()}.
     * These failures are usually when the found word fails the
     * {@link #sInvalidWord} test, or when a network error happens.
     */
    private static final int RANDOM_TRIES = 3;

    /**
     * Internal class to hold a wiki formatting rule. It's mostly a wrapper to
     * simplify {@link Matcher#replaceAll(String)}.
     */
    private static class FormatRule {
        private Pattern mPattern;
        private String mReplaceWith;

        /**
         * Create a wiki formatting rule.
         *
         * @param pattern Search string to be compiled into a {@link Pattern}.
         * @param replaceWith String to replace any found occurances with. This
         *            string can also include back-references into the given
         *            pattern.
         * @param flags Any flags to compile the {@link Pattern} with.
         */
        public FormatRule(String pattern, String replaceWith, int flags) {
            mPattern = Pattern.compile(pattern, flags);
            mReplaceWith = replaceWith;
        }

        /**
         * Create a wiki formatting rule.
         *
         * @param pattern Search string to be compiled into a {@link Pattern}.
         * @param replaceWith String to replace any found occurances with. This
         *            string can also include back-references into the given
         *            pattern.
         */
        public FormatRule(String pattern, String replaceWith) {
            this(pattern, replaceWith, 0);
        }

        /**
         * Apply this formatting rule to the given input string, and return the
         * resulting new string.
         */
        public String apply(String input) {
            Matcher m = mPattern.matcher(input);
            return m.replaceAll(mReplaceWith);
        }

    }

    /**
     * List of internal formatting rules to apply when parsing wiki text. These
     * include indenting various bullets, apply italic and bold styles, and
     * adding internal linking.
     */
    private static final List<FormatRule> sFormatRules = new ArrayList();

    static {
        // Format header blocks and wrap outside content in ordered list
        sFormatRules.add(new FormatRule("^=+(.+?)=+", "</ol>
$1
",
                Pattern.MULTILINE));

        // Indent quoted blocks, handle ordered and bullet lists
        sFormatRules.add(new FormatRule("^#+\\*?:(.+?)$", "<blockquote>$1",
                Pattern.MULTILINE));
        sFormatRules.add(new FormatRule("^#+:?\\*(.+?)$", "<ul>
$1
",
                Pattern.MULTILINE));
        sFormatRules.add(new FormatRule("^#+(.+?)$", "<li>$1",
                Pattern.MULTILINE));

        // Add internal links
        sFormatRules.add(new FormatRule("\\[\\[([^:\\|\\]]+)\\]\\]",
                String.format("<a href=\"%s://%s/$1\">$1", WIKI_AUTHORITY, WIKI_LOOKUP_HOST)));
        sFormatRules.add(new FormatRule("\\[\\[([^:\\|\\]]+)\\|([^\\]]+)\\]\\]",
                String.format("<a href=\"%s://%s/$1\">$2", WIKI_AUTHORITY, WIKI_LOOKUP_HOST)));

        // Add bold and italic formatting
        sFormatRules.add(new FormatRule("'''(.+?)'''", "<b>$1"));
        sFormatRules.add(new FormatRule("([^'])''([^'].*?[^'])''([^'])", "$1<i>$2$3"));

        // Remove odd category links and convert remaining links into flat text
        sFormatRules.add(new FormatRule("(\\{+.+?\\}+|\\[\\[[^:]+:[^\\\\|\\]]+\\]\\]|" +
                "\\[http.+?\\]|\\[\\[Category:.+?\\]\\])", "", Pattern.MULTILINE | Pattern.DOTALL));
        sFormatRules.add(new FormatRule("\\[\\[([^\\|\\]]+\\|)?(.+?)\\]\\]", "$2",
                Pattern.MULTILINE));

    }

    /**
     * Query the Wiktionary API to pick a random dictionary word. Will try
     * multiple times to find a valid word before giving up.
     *
     * @return Random dictionary word, or null if no valid word was found.
     * @throws ApiException If any connection or server error occurs.
     * @throws ParseException If there are problems parsing the response.
     */
    public static String getRandomWord() throws ApiException, ParseException {
        // Keep trying a few times until we find a valid word
        int tries = 0;
        while (tries++ < RANDOM_TRIES) {
            // Query the API for a random word
            String content = getUrlContent(WIKTIONARY_RANDOM);
            try {
                // Drill into the JSON response to find the returned word
                JSONObject response = new JSONObject(content);
                JSONObject query = response.getJSONObject("query");
                JSONArray random = query.getJSONArray("random");
                JSONObject word = random.getJSONObject(0);
                String foundWord = word.getString("title");

                // If we found an actual word, and it wasn't rejected by our invalid
                // filter, then accept and return it.
                if (foundWord != null &&
                        !sInvalidWord.matcher(foundWord).find()) {
                    return foundWord;
                }
            } catch (JSONException e) {
                throw new ParseException("Problem parsing API response", e);
            }
        }

        // No valid word found in number of tries, so return null
        return null;
    }

    /**
     * Format the given wiki-style text into formatted HTML content. This will
     * create headers, lists, internal links, and style formatting for any wiki
     * markup found.
     *
     * @param wikiText The raw text to format, with wiki-markup included.
     * @return HTML formatted content, ready for display in {@link WebView}.
     */
    public static String formatWikiText(String wikiText) {
        if (wikiText == null) {
            return null;
        }

        // Insert a fake last section into the document so our section splitter
        // can correctly catch the last section.
        wikiText = wikiText.concat(STUB_SECTION);

        // Read through all sections, keeping only those matching our filter,
        // and only including the first entry for each title.
        HashSet<String> foundSections = new HashSet();
        StringBuilder builder = new StringBuilder();

        Matcher sectionMatcher = sSectionSplit.matcher(wikiText);
        while (sectionMatcher.find()) {
            String title = sectionMatcher.group(1);
            if (!foundSections.contains(title) &&
                    sValidSections.matcher(title).matches()) {
                String sectionContent = sectionMatcher.group();
                foundSections.add(title);
                builder.append(sectionContent);
            }
        }

        // Our new wiki text is the selected sections only
        wikiText = builder.toString();

        // Apply all formatting rules, in order, to the wiki text
        for (FormatRule rule : sFormatRules) {
            wikiText = rule.apply(wikiText);
        }

        // Return the resulting HTML with style sheet, if we have content left
        if (!TextUtils.isEmpty(wikiText)) {
            return STYLE_SHEET + wikiText;
        } else {
            return null;
        }
    }

}