LatinIME/java/src/com/android/inputmethod/latin/spellcheck/UserDictionaryLookup.java

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/*
* Copyright (C) 2015 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.android.inputmethod.latin.spellcheck;
import android.content.ContentResolver;
import android.content.Context;
import android.database.ContentObserver;
import android.database.Cursor;
import android.net.Uri;
import android.provider.UserDictionary;
import android.util.Log;
import com.android.inputmethod.annotations.UsedForTesting;
import com.android.inputmethod.latin.common.LocaleUtils;
import java.io.Closeable;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Locale;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;
/**
* UserDictionaryLookup provides the ability to lookup into the system-wide "Personal dictionary".
*
* Note, that the initial dictionary loading happens asynchronously so it is possible (hopefully
* rarely) that isValidWord is called before the initial load has started.
*
* The caller should explicitly call close() when the object is no longer needed, in order to
* release any resources and references to this object. A service should create this object in
* onCreate and close() it in onDestroy.
*/
public class UserDictionaryLookup implements Closeable {
private static final String TAG = UserDictionaryLookup.class.getSimpleName();
/**
* This guards the execution of any Log.d() logging, so that if false, they are not even
*/
private static final boolean DEBUG = false;
/**
* To avoid loading too many dictionary entries in memory, we cap them at this number. If
* that number is exceeded, the lowest-frequency items will be dropped. Note, there is no
* explicit cap on the number of locales in every entry.
*/
private static final int MAX_NUM_ENTRIES = 1000;
/**
* The delay (in milliseconds) to impose on reloads. Previously scheduled reloads will be
* cancelled if a new reload is scheduled before the delay expires. Thus, only the last
* reload in the series of frequent reloads will execute.
*
* Note, this value should be low enough to allow the "Add to dictionary" feature in the
* TextView correction (red underline) drop-down menu to work properly in the following case:
*
* 1. User types OOV (out-of-vocabulary) word.
* 2. The OOV is red-underlined.
* 3. User selects "Add to dictionary". The red underline disappears while the OOV is
* in a composing span.
* 4. The user taps space. The red underline should NOT reappear. If this value is very
* high and the user performs the space tap fast enough, the red underline may reappear.
*/
@UsedForTesting
static final int RELOAD_DELAY_MS = 200;
private final ContentResolver mResolver;
/**
* Executor on which to perform the initial load and subsequent reloads (after a delay).
*/
private final ScheduledExecutorService mLoadExecutor =
Executors.newSingleThreadScheduledExecutor();
/**
* Runnable that calls loadUserDictionary().
*/
private class UserDictionaryLoader implements Runnable {
@Override
public void run() {
if (DEBUG) {
Log.d(TAG, "Executing (re)load");
}
loadUserDictionary();
}
}
private final UserDictionaryLoader mLoader = new UserDictionaryLoader();
/**
* Content observer for UserDictionary changes. It has the following properties:
* 1. It spawns off a UserDictionary reload in another thread, after some delay.
* 2. It cancels previously scheduled reloads, and only executes the latest.
* 3. It may be called multiple times quickly in succession (and is in fact called so
* when UserDictionary is edited through its settings UI, when sometimes multiple
* notifications are sent for the edited entry, but also for the entire UserDictionary).
*/
private class UserDictionaryContentObserver extends ContentObserver {
public UserDictionaryContentObserver() {
super(null);
}
@Override
public boolean deliverSelfNotifications() {
return true;
}
// Support pre-API16 platforms.
@Override
public void onChange(boolean selfChange) {
onChange(selfChange, null);
}
@Override
public void onChange(boolean selfChange, Uri uri) {
if (DEBUG) {
Log.d(TAG, "Received content observer onChange notification for URI: " + uri);
}
// Cancel (but don't interrupt) any pending reloads (except the initial load).
if (mReloadFuture != null && !mReloadFuture.isCancelled() &&
!mReloadFuture.isDone()) {
// Note, that if already cancelled or done, this will do nothing.
boolean isCancelled = mReloadFuture.cancel(false);
if (DEBUG) {
if (isCancelled) {
Log.d(TAG, "Successfully canceled previous reload request");
} else {
Log.d(TAG, "Unable to cancel previous reload request");
}
}
}
if (DEBUG) {
Log.d(TAG, "Scheduling reload in " + RELOAD_DELAY_MS + " ms");
}
// Schedule a new reload after RELOAD_DELAY_MS.
mReloadFuture = mLoadExecutor.schedule(mLoader, RELOAD_DELAY_MS, TimeUnit.MILLISECONDS);
}
}
private final ContentObserver mObserver = new UserDictionaryContentObserver();
/**
* Indicates that a load is in progress, so no need for another.
*/
private AtomicBoolean mIsLoading = new AtomicBoolean(false);
/**
* Indicates that this lookup object has been close()d.
*/
private AtomicBoolean mIsClosed = new AtomicBoolean(false);
/**
* We store a map from a dictionary word to the set of locales it belongs
* in. We then iterate over the set of locales to find a match using
* LocaleUtils.
*/
private volatile HashMap<String, ArrayList<Locale>> mDictWords;
/**
* The last-scheduled reload future. Saved in order to cancel a pending reload if a new one
* is coming.
*/
private volatile ScheduledFuture<?> mReloadFuture;
/**
* @param context the context from which to obtain content resolver
*/
public UserDictionaryLookup(Context context) {
if (DEBUG) {
Log.d(TAG, "UserDictionaryLookup constructor with context: " + context);
}
// Obtain a content resolver.
mResolver = context.getContentResolver();
// Schedule the initial load to run immediately. It's possible that the first call to
// isValidWord occurs before the dictionary has actually loaded, so it should not
// assume that the dictionary has been loaded.
mLoadExecutor.schedule(mLoader, 0, TimeUnit.MILLISECONDS);
// Register the observer to be notified on changes to the UserDictionary and all individual
// items.
//
// If the user is interacting with the UserDictionary settings UI, or with the
// "Add to dictionary" drop-down option, duplicate notifications will be sent for the same
// edit: if a new entry is added, there is a notification for the entry itself, and
// separately for the entire dictionary. However, when used programmatically,
// only notifications for the specific edits are sent. Thus, the observer is registered to
// receive every possible notification, and instead has throttling logic to avoid doing too
// many reloads.
mResolver.registerContentObserver(
UserDictionary.Words.CONTENT_URI, true /* notifyForDescendents */, mObserver);
}
/**
* To be called by the garbage collector in the off chance that the service did not clean up
* properly. Do not rely on this getting called, and make sure close() is called explicitly.
*/
@Override
public void finalize() throws Throwable {
try {
if (DEBUG) {
Log.d(TAG, "Finalize called, calling close()");
}
close();
} finally {
super.finalize();
}
}
/**
* Cleans up UserDictionaryLookup: shuts down any extra threads and unregisters the observer.
*
* It is safe, but not advised to call this multiple times, and isValidWord would continue to
* work, but no data will be reloaded any longer.
*/
@Override
public void close() {
if (DEBUG) {
Log.d(TAG, "Close called (no pun intended), cleaning up executor and observer");
}
if (mIsClosed.compareAndSet(false, true)) {
// Shut down the load executor.
mLoadExecutor.shutdown();
// Unregister the content observer.
mResolver.unregisterContentObserver(mObserver);
}
}
/**
* Returns true if the initial load has been performed.
*
* @return true if the initial load is successful
*/
@UsedForTesting
boolean isLoaded() {
return mDictWords != null;
}
/**
* Determines if the given word is a valid word in the given locale based on the UserDictionary.
* It tries hard to find a match: for example, casing is ignored and if the word is present in a
* more general locale (e.g. en or all locales), and isValidWord is asking for a more specific
* locale (e.g. en_US), it will be considered a match.
*
* @param word the word to match
* @param locale the locale in which to match the word
* @return true iff the word has been matched for this locale in the UserDictionary.
*/
public boolean isValidWord(
final String word, final Locale locale) {
if (!isLoaded()) {
// This is a corner case in the event the initial load of UserDictionary has not
// been loaded. In that case, we assume the word is not a valid word in
// UserDictionary.
if (DEBUG) {
Log.d(TAG, "isValidWord invoked, but initial load not complete");
}
return false;
}
// Atomically obtain the current copy of mDictWords;
final HashMap<String, ArrayList<Locale>> dictWords = mDictWords;
if (DEBUG) {
Log.d(TAG, "isValidWord invoked for word [" + word +
"] in locale " + locale);
}
// Lowercase the word using the given locale. Note, that dictionary
// words are lowercased using their locale, and theoretically the
// lowercasing between two matching locales may differ. For simplicity
// we ignore that possibility.
final String lowercased = word.toLowerCase(locale);
final ArrayList<Locale> dictLocales = dictWords.get(lowercased);
if (null == dictLocales) {
if (DEBUG) {
Log.d(TAG, "isValidWord=false, since there is no entry for " +
"lowercased word [" + lowercased + "]");
}
return false;
} else {
if (DEBUG) {
Log.d(TAG, "isValidWord found an entry for lowercased word [" + lowercased +
"]; examining locales");
}
// Iterate over the locales this word is in.
for (final Locale dictLocale : dictLocales) {
final int matchLevel = LocaleUtils.getMatchLevel(dictLocale.toString(),
locale.toString());
if (DEBUG) {
Log.d(TAG, "matchLevel for dictLocale=" + dictLocale + ", locale=" +
locale + " is " + matchLevel);
}
if (LocaleUtils.isMatch(matchLevel)) {
if (DEBUG) {
Log.d(TAG, "isValidWord=true, since matchLevel " + matchLevel +
" is a match");
}
return true;
}
if (DEBUG) {
Log.d(TAG, "matchLevel " + matchLevel + " is not a match");
}
}
if (DEBUG) {
Log.d(TAG, "isValidWord=false, since none of the locales matched");
}
return false;
}
}
/**
* Loads the UserDictionary in the current thread.
*
* Only one reload can happen at a time. If already running, will exit quickly.
*/
private void loadUserDictionary() {
// Bail out if already in the process of loading.
if (!mIsLoading.compareAndSet(false, true)) {
if (DEBUG) {
Log.d(TAG, "Already in the process of loading UserDictionary, skipping");
}
return;
}
if (DEBUG) {
Log.d(TAG, "Loading UserDictionary");
}
HashMap<String, ArrayList<Locale>> dictWords =
new HashMap<String, ArrayList<Locale>>();
// Load the UserDictionary. Request that items be returned in the default sort order
// for UserDictionary, which is by frequency.
Cursor cursor = mResolver.query(UserDictionary.Words.CONTENT_URI,
null, null, null, UserDictionary.Words.DEFAULT_SORT_ORDER);
if (null == cursor || cursor.getCount() < 1) {
if (DEBUG) {
Log.d(TAG, "No entries found in UserDictionary");
}
} else {
// Iterate over the entries in the UserDictionary. Note, that iteration is in
// descending frequency by default.
while (dictWords.size() < MAX_NUM_ENTRIES && cursor.moveToNext()) {
// If there is no column for locale, skip this entry. An empty
// locale on the other hand will not be skipped.
final int dictLocaleIndex = cursor.getColumnIndex(
UserDictionary.Words.LOCALE);
if (dictLocaleIndex < 0) {
if (DEBUG) {
Log.d(TAG, "Encountered UserDictionary entry " +
"without LOCALE, skipping");
}
continue;
}
// If there is no column for word, skip this entry.
final int dictWordIndex = cursor.getColumnIndex(
UserDictionary.Words.WORD);
if (dictWordIndex < 0) {
if (DEBUG) {
Log.d(TAG, "Encountered UserDictionary entry without " +
"WORD, skipping");
}
continue;
}
// If the word is null, skip this entry.
final String rawDictWord = cursor.getString(dictWordIndex);
if (null == rawDictWord) {
if (DEBUG) {
Log.d(TAG, "Encountered null word");
}
continue;
}
// If the locale is null, that's interpreted to mean all locales. Note, the special
// zz locale for an Alphabet (QWERTY) layout will not match any actual language.
String localeString = cursor.getString(dictLocaleIndex);
if (null == localeString) {
if (DEBUG) {
Log.d(TAG, "Encountered null locale for word [" +
rawDictWord + "], assuming all locales");
}
// For purposes of LocaleUtils, an empty locale matches
// everything.
localeString = "";
}
final Locale dictLocale = LocaleUtils.constructLocaleFromString(
localeString);
// Lowercase the word before storing it.
final String dictWord = rawDictWord.toLowerCase(dictLocale);
if (DEBUG) {
Log.d(TAG, "Incorporating UserDictionary word [" + dictWord +
"] for locale " + dictLocale);
}
// Check if there is an existing entry for this word.
ArrayList<Locale> dictLocales = dictWords.get(dictWord);
if (null == dictLocales) {
// If there is no entry for this word, create one.
if (DEBUG) {
Log.d(TAG, "Word [" + dictWord +
"] not seen for other locales, creating new entry");
}
dictLocales = new ArrayList<Locale>();
dictWords.put(dictWord, dictLocales);
}
// Append the locale to the list of locales this word is in.
dictLocales.add(dictLocale);
}
}
// Atomically replace the copy of mDictWords.
mDictWords = dictWords;
// Allow other calls to loadUserDictionary to execute now.
mIsLoading.set(false);
}
}