Android example source code file (AutoText.java)

This example Android source code file (AutoText.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, aug, autotext, content, increment, io, locale, object, runtimeexception, string, stringbuilder, trie_child, trie_next, trie_null, trie_off, trie_root, trie_sizeof, ui, util, view

The AutoText.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.text;

import android.content.res.Resources;
import android.content.res.XmlResourceParser;

import com.android.internal.util.XmlUtils;

import android.view.View;

import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserException;

import java.io.IOException;
import java.util.Locale;

/**
 * This class accesses a dictionary of corrections to frequent misspellings.
 */
public class AutoText {
    // struct trie {
    //     char c;
    //     int off;
    //     struct trie *child;
    //     struct trie *next;
    // };

    private static final int TRIE_C = 0;
    private static final int TRIE_OFF = 1;
    private static final int TRIE_CHILD = 2;
    private static final int TRIE_NEXT = 3;

    private static final int TRIE_SIZEOF = 4;
    private static final char TRIE_NULL = (char) -1;
    private static final int TRIE_ROOT = 0;

    private static final int INCREMENT = 1024;

    private static final int DEFAULT = 14337; // Size of the Trie 13 Aug 2007

    private static final int RIGHT = 9300; // Size of 'right' 13 Aug 2007

    private static AutoText sInstance = new AutoText(Resources.getSystem());
    private static Object sLock = new Object();

    // TODO:
    //
    // Note the assumption that the destination strings total less than
    // 64K characters and that the trie for the source side totals less
    // than 64K chars/offsets/child pointers/next pointers.
    //
    // This seems very safe for English (currently 7K of destination,
    // 14K of trie) but may need to be revisited.

    private char[] mTrie;
    private char mTrieUsed;
    private String mText;
    private Locale mLocale;
    private int mSize;

    private AutoText(Resources resources) {
        mLocale = resources.getConfiguration().locale;
        init(resources);
    }

    /**
     * Returns the instance of AutoText. If the locale has changed, it will create a new
     * instance of AutoText for the locale.
     * @param view to get the resources from
     * @return the single instance of AutoText
     */
    private static AutoText getInstance(View view) {
        Resources res = view.getContext().getResources();
        Locale locale = res.getConfiguration().locale;
        AutoText instance;

        synchronized (sLock) {
            instance = sInstance;

            if (!locale.equals(instance.mLocale)) {
                instance = new AutoText(res);
                sInstance = instance;
            }
        }
        
        return instance;
    }
    
    /**
     * Retrieves a possible spelling correction for the specified range
     * of text.  Returns null if no correction can be found.
     * The View is used to get the current Locale and Resources.
     */
    public static String get(CharSequence src, final int start, final int end,
                             View view) {
        return getInstance(view).lookup(src, start, end);
    }

    /**
     * Returns the size of the auto text dictionary. The return value can be zero if there is
     * no auto correction data available for the current locale.
     * @param view used to retrieve the current Locale and Resources.
     * @return the number of entries in the auto text dictionary
     */
    public static int getSize(View view) {

        return getInstance(view).getSize(); 
    }

    /**
     * Returns the size of the dictionary.
     */
    private int getSize() {
        return mSize;
    }

    private String lookup(CharSequence src, final int start, final int end) {
        int here = mTrie[TRIE_ROOT];

        for (int i = start; i < end; i++) {
            char c = src.charAt(i);

            for (; here != TRIE_NULL; here = mTrie[here + TRIE_NEXT]) {
                if (c == mTrie[here + TRIE_C]) {
                    if ((i == end - 1) 
                            && (mTrie[here + TRIE_OFF] != TRIE_NULL)) {
                        int off = mTrie[here + TRIE_OFF];
                        int len = mText.charAt(off);

                        return mText.substring(off + 1, off + 1 + len);
                    }

                    here = mTrie[here + TRIE_CHILD];
                    break;
                }
            }

            if (here == TRIE_NULL) {
                return null;
            }
        }

        return null;
    }

    private void init(Resources r) {
        XmlResourceParser parser = r.getXml(com.android.internal.R.xml.autotext);

        StringBuilder right = new StringBuilder(RIGHT);
        mTrie = new char[DEFAULT];
        mTrie[TRIE_ROOT] = TRIE_NULL;
        mTrieUsed = TRIE_ROOT + 1;

        try {
            XmlUtils.beginDocument(parser, "words");
            String odest = "";
            char ooff = 0;

            while (true) {
                XmlUtils.nextElement(parser);

                String element = parser.getName(); 
                if (element == null || !(element.equals("word"))) {
                    break;
                }

                String src = parser.getAttributeValue(null, "src");
                if (parser.next() == XmlPullParser.TEXT) {
                    String dest = parser.getText();
                    char off;

                    if (dest.equals(odest)) {
                        off = ooff;
                    } else {
                        off = (char) right.length();
                        right.append((char) dest.length());
                        right.append(dest);
                    }

                    add(src, off);
                }
            }

            // Don't let Resources cache a copy of all these strings.
            r.flushLayoutCache();
        } catch (XmlPullParserException e) {
            throw new RuntimeException(e);
        } catch (IOException e) {
            throw new RuntimeException(e);
        } finally {
            parser.close();
        }

        mText = right.toString();
    }

    private void add(String src, char off) {
        int slen = src.length();
        int herep = TRIE_ROOT;
        // Keep track of the size of the dictionary
        mSize++;
        
        for (int i = 0; i < slen; i++) {
            char c = src.charAt(i);
            boolean found = false;

            for (; mTrie[herep] != TRIE_NULL;
                    herep = mTrie[herep] + TRIE_NEXT) {
                if (c == mTrie[mTrie[herep] + TRIE_C]) {
                    // There is a node for this letter, and this is the
                    // end, so fill in the right hand side fields.

                    if (i == slen - 1) {
                        mTrie[mTrie[herep] + TRIE_OFF] = off;
                        return;
                    }

                    // There is a node for this letter, and we need
                    // to go deeper into it to fill in the rest.

                    herep = mTrie[herep] + TRIE_CHILD;
                    found = true;
                    break;
                }
            }

            if (!found) {
                // No node for this letter yet.  Make one.

                char node = newTrieNode();
                mTrie[herep] = node;

                mTrie[mTrie[herep] + TRIE_C] = c;
                mTrie[mTrie[herep] + TRIE_OFF] = TRIE_NULL;
                mTrie[mTrie[herep] + TRIE_NEXT] = TRIE_NULL;
                mTrie[mTrie[herep] + TRIE_CHILD] = TRIE_NULL;

                // If this is the end of the word, fill in the offset.

                if (i == slen - 1) {
                    mTrie[mTrie[herep] + TRIE_OFF] = off;
                    return;
                }

                // Otherwise, step in deeper and go to the next letter.

                herep = mTrie[herep] + TRIE_CHILD;
            }
        }
    }

    private char newTrieNode() {
        if (mTrieUsed + TRIE_SIZEOF > mTrie.length) {
            char[] copy = new char[mTrie.length + INCREMENT];
            System.arraycopy(mTrie, 0, copy, 0, mTrie.length);
            mTrie = copy;
        }

        char ret = mTrieUsed;
        mTrieUsed += TRIE_SIZEOF;

        return ret;
    }
}