allow users to select dictionaries

https://github.com/openboard-team/openboard/pull/569
https://github.com/openboard-team/openboard/pull/578
modified so dictionaries use the correct type instead of always main

README.md

@@ -9,8 +9,8 @@ Plan / to do:
 * ~upgrade dependencies~
 * upgrade NDK, https://github.com/openboard-team/openboard/issues/782
 * maybe: rename (package, app, icon), so it can be installed parallel to OpenBoard, and published on F-Droid
-* user-selectable dictionaries, https://github.com/openboard-team/openboard/pull/578
-  * make additional dictionaries available for download, and link from app
+* ~user-selectable dictionaries, https://github.com/openboard-team/openboard/pull/578~
+  * make additional dictionaries available for download (from OpenBoard PRs)
 * multi-lingual typing, https://github.com/openboard-team/openboard/pull/593
 * suggestion fixes, https://github.com/openboard-team/openboard/pull/694, https://github.com/openboard-team/openboard/issues/795, https://github.com/openboard-team/openboard/issues/660
 * improve auto-space insertion, https://github.com/openboard-team/openboard/pull/576
@@ -23,6 +23,10 @@ Plan / to do:
 Changes:
 * Updated dependencies
 * Debug version can be installed along OpenBoard
+* Allow users to add and replace built-in dictionaries
+  * modified / improved from https://github.com/openboard-team/openboard/pull/569 and https://github.com/openboard-team/openboard/pull/578
+  * dictionaries are available at https://github.com/Helium314/openboard/dictionaries/dict
+  * dictionary files starting with "main_" replace the built-in dictionary for the language, all other names work as add-on dictionaries
 
 -----
 

app/build.gradle

@@ -42,7 +42,8 @@ android {
 
     ndkVersion '23.2.8568313'
     androidResources {
-        noCompress 'dict'
+        noCompress 'main.dict'
+        noCompress 'empty.dict'
     }
 }
 

app/src/main/java/org/dslul/openboard/inputmethod/latin/BinaryDictionaryGetter.java

@@ -21,6 +21,7 @@ import android.content.SharedPreferences;
 import android.content.res.AssetFileDescriptor;
 import android.util.Log;
 
+import org.dslul.openboard.inputmethod.latin.common.FileUtils;
 import org.dslul.openboard.inputmethod.latin.common.LocaleUtils;
 import org.dslul.openboard.inputmethod.latin.define.DecoderSpecificConstants;
 import org.dslul.openboard.inputmethod.latin.makedict.DictionaryHeader;
@@ -62,6 +63,8 @@ final public class BinaryDictionaryGetter {
     public static final String MAIN_DICTIONARY_CATEGORY = "main";
     public static final String ID_CATEGORY_SEPARATOR = ":";
 
+    public static final String ASSETS_DICTIONARY_FOLDER = "dicts";
+
     // The key considered to read the version attribute in a dictionary file.
     private static String VERSION_KEY = "version";
 
@@ -170,8 +173,8 @@ final public class BinaryDictionaryGetter {
         for (File directory : directoryList) {
             if (!directory.isDirectory()) continue;
             final String dirLocale =
-                    DictionaryInfoUtils.getWordListIdFromFileName(directory.getName());
-            final int matchLevel = LocaleUtils.getMatchLevel(dirLocale, locale);
+                    DictionaryInfoUtils.getWordListIdFromFileName(directory.getName()).toLowerCase(Locale.ENGLISH);
+            final int matchLevel = LocaleUtils.getMatchLevel(dirLocale, locale.toLowerCase(Locale.ENGLISH));
             if (LocaleUtils.isMatch(matchLevel)) {
                 final File[] wordLists = directory.listFiles();
                 if (null != wordLists) {
@@ -265,9 +268,16 @@ final public class BinaryDictionaryGetter {
         }
 
         if (!foundMainDict && dictPackSettings.isWordListActive(mainDictId)) {
+            final File dict = loadDictionaryFromAssets(locale.toString(), context);
+            final AssetFileAddress fallbackAsset;
+            if (dict == null) {
+                // fall back to the old way (maybe remove? will not work if files are compressed)
                 final int fallbackResId =
                         DictionaryInfoUtils.getMainDictionaryResourceId(context.getResources(), locale);
-            final AssetFileAddress fallbackAsset = loadFallbackResource(context, fallbackResId);
+                fallbackAsset = loadFallbackResource(context, fallbackResId);
+            } else {
+                fallbackAsset = AssetFileAddress.makeFromFileName(dict.getPath());
+            }
             if (null != fallbackAsset) {
                 fileList.add(fallbackAsset);
             }
@@ -275,4 +285,75 @@ final public class BinaryDictionaryGetter {
 
         return fileList;
     }
+
+    /**
+     * Returns the best matching main dictionary from assets.
+     *
+     * Actually copies the dictionary to cache folder, and then returns that file. This allows
+     * the dictionaries to be stored in a compressed way, reducing APK size.
+     * On next load, the dictionary in cache folder is found by getCachedWordLists
+     *
+     * Returns null on IO errors or if no matching dictionary is found
+     */
+    public static File loadDictionaryFromAssets(final String locale, final Context context) {
+        final String[] dictionaryList = getAssetsDictionaryList(context);
+        if (null == dictionaryList) return null;
+        String bestMatchName = null;
+        int bestMatchLevel = 0;
+        for (String dictionary : dictionaryList) {
+            final String dictLocale =
+                    extractLocaleFromAssetsDictionaryFile(dictionary);
+            if (dictLocale == null) continue;
+            // assets files may contain the locale in lowercase, but dictionary headers usually
+            //  have an upper case country code, so we compare lowercase here
+            final int matchLevel = LocaleUtils.getMatchLevel(dictLocale.toLowerCase(Locale.ENGLISH), locale.toLowerCase(Locale.ENGLISH));
+            if (LocaleUtils.isMatch(matchLevel) && matchLevel > bestMatchLevel) {
+                bestMatchName = dictionary;
+            }
+        }
+        if (bestMatchName == null) return null;
+
+        // we have a match, now copy contents of the dictionary to cached word lists folder
+        final String bestMatchLocale = extractLocaleFromAssetsDictionaryFile(bestMatchName);
+        if (bestMatchLocale == null) return null;
+        File dictFile = new File(DictionaryInfoUtils.getCacheDirectoryForLocale(bestMatchLocale, context) +
+                File.separator + DictionaryInfoUtils.getMainDictFilename(bestMatchLocale));
+        try {
+            FileUtils.copyStreamToNewFile(
+                    context.getAssets().open(ASSETS_DICTIONARY_FOLDER + File.separator + bestMatchName),
+                    dictFile);
+            return dictFile;
+        } catch (IOException e) {
+            Log.e(TAG, "exception while looking for locale " + locale, e);
+            return null;
+        }
+    }
+
+    /**
+     * Returns the locale for a dictionary file name stored in assets.
+     *
+     * Assumes file name main_[locale].dict
+     *
+     * Returns the locale, or null if file name does not match the pattern
+     */
+    public static String extractLocaleFromAssetsDictionaryFile(final String dictionaryFileName) {
+        if (dictionaryFileName.startsWith(DictionaryInfoUtils.MAIN_DICT_PREFIX)
+                && dictionaryFileName.endsWith(".dict")) {
+            return dictionaryFileName.substring(
+                    DictionaryInfoUtils.MAIN_DICT_PREFIX.length(),
+                    dictionaryFileName.lastIndexOf('.')
+            );
+        }
+        return null;
+    }
+
+    public static String[] getAssetsDictionaryList(final Context context) {
+        final String[] dictionaryList;
+        try {
+            dictionaryList = context.getAssets().list(ASSETS_DICTIONARY_FOLDER);
+        } catch (IOException e) {
+            return null;
+        }
+        return dictionaryList;
+    }
 }

app/src/main/java/org/dslul/openboard/inputmethod/latin/common/FileUtils.java

@@ -17,7 +17,10 @@
 package org.dslul.openboard.inputmethod.latin.common;
 
 import java.io.File;
+import java.io.FileOutputStream;
 import java.io.FilenameFilter;
+import java.io.IOException;
+import java.io.InputStream;
 
 /**
  * A simple class to help with removing directories recursively.
@@ -58,4 +61,19 @@ public class FileUtils {
         toFile.delete();
         return fromFile.renameTo(toFile);
     }
+
+    public static void copyStreamToNewFile(InputStream in, File outfile) throws IOException {
+        File parentFile = outfile.getParentFile();
+        if (parentFile == null || (!parentFile.exists() && !parentFile.mkdirs())) {
+            throw new IOException("could not create parent folder");
+        }
+        FileOutputStream out = new FileOutputStream(outfile);
+        byte[] buf = new byte[1024];
+        int len;
+        while ((len = in.read(buf)) > 0) {
+            out.write(buf, 0, len);
+        }
+        out.flush();
+    }
+
 }

app/src/main/java/org/dslul/openboard/inputmethod/latin/settings/DictionarySettingsFragment.kt

@@ -0,0 +1,329 @@
+package org.dslul.openboard.inputmethod.latin.settings
+
+import android.app.Activity
+import android.app.AlertDialog
+import android.content.Intent
+import android.os.Build
+import android.os.Bundle
+import android.preference.Preference
+import android.text.Html
+import android.text.method.LinkMovementMethod
+import android.util.TypedValue
+import android.view.Menu
+import android.view.MenuInflater
+import android.view.MenuItem
+import android.view.View
+import android.widget.TextView
+import android.widget.Toast
+import org.dslul.openboard.inputmethod.dictionarypack.DictionaryPackConstants
+import org.dslul.openboard.inputmethod.latin.BinaryDictionaryGetter
+import org.dslul.openboard.inputmethod.latin.R
+import org.dslul.openboard.inputmethod.latin.common.FileUtils
+import org.dslul.openboard.inputmethod.latin.common.LocaleUtils
+import org.dslul.openboard.inputmethod.latin.utils.DialogUtils
+import org.dslul.openboard.inputmethod.latin.utils.DictionaryInfoUtils
+import java.io.File
+import java.io.IOException
+import java.util.*
+
+class DictionarySettingsFragment : SubScreenFragment() {
+
+    // dict for which dialog is currently open (if any)
+    private var currentDictLocale: Locale? = null
+    private var currentDictState: Int? = null
+
+    private val cachedDictionaryFile by lazy { File(activity.cacheDir.path + File.separator + "temp_dict") }
+    private val currentDictExistsForUser get() = currentDictState == DICT_INTERNAL_AND_USER || currentDictState == DICT_USER_ONLY
+    private val currentDictExistsInternal get() = currentDictState == DICT_INTERNAL_AND_USER || currentDictState == DICT_INTERNAL_ONLY
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        addPreferencesFromResource(R.xml.additional_subtype_settings)
+        reloadDictionaries()
+        // + button to add dictionary
+        setHasOptionsMenu(true)
+        activity.actionBar?.setTitle(R.string.dictionary_settings_category)
+    }
+
+    // shows existing dictionaries as preferences
+    private fun reloadDictionaries() {
+        val screen = preferenceScreen ?: return
+        screen.removeAll()
+        val userDicts = mutableSetOf<Locale>()
+        val internalDicts = mutableSetOf<Locale>()
+        // get available dictionaries
+        // cached (internal in use and user dicts)
+        DictionaryInfoUtils.getCachedDirectoryList(activity)?.forEach { dir ->
+            if (!dir.isDirectory)
+                return@forEach
+            dir.list()?.forEach {
+                if (it.endsWith(USER_DICTIONARY_SUFFIX))
+                    userDicts.add(dir.name.toLocale())
+                else if (it.startsWith(DictionaryInfoUtils.MAIN_DICT_PREFIX))
+                    internalDicts.add(dir.name.toLocale())
+            }
+        }
+        // internal only
+        BinaryDictionaryGetter.getAssetsDictionaryList(activity)?.forEach { dictFile ->
+            BinaryDictionaryGetter.extractLocaleFromAssetsDictionaryFile(dictFile)?.let {
+                internalDicts.add(it.toLocale())
+            }
+        }
+
+        // first show user-added dictionaries
+        userDicts.sortedBy { it.displayName() }.forEach { dict ->
+            val pref = Preference(activity).apply {
+                title = dict.displayName()
+                setSummary(R.string.user_dictionary_summary)
+                setOnPreferenceClickListener {
+                    // open dialog for update or delete / reset
+                    currentDictLocale = dict
+                    currentDictState = if (internalDicts.contains(dict)) DICT_INTERNAL_AND_USER else DICT_USER_ONLY
+                    showUpdateDialog()
+                    true
+                }
+            }
+            screen.addPreference(pref)
+        }
+
+        // TODO: only show if language is actually used?
+        internalDicts.sortedBy { it.displayName() }.forEach { dict ->
+            if (userDicts.contains(dict)) return@forEach // don't show a second time
+            val pref = Preference(activity).apply {
+                title = dict.displayName()
+                setSummary(R.string.internal_dictionary_summary)
+                setOnPreferenceClickListener {
+                    // open dialog for update, maybe disabling if i can make it work?
+                    currentDictLocale = dict
+                    currentDictState = DICT_INTERNAL_ONLY
+                    showUpdateDialog()
+                    true
+                }
+            }
+            screen.addPreference(pref)
+        }
+    }
+
+    private fun showUpdateDialog() {
+        // -1: adding new dict, don't know where it may exist
+        // 0: user only -> offer delete
+        // 1: internal only -> only update (and maybe later: disable)
+        // 2: user and internal -> offer reset to internal
+
+        if (currentDictState == null) return
+        if (currentDictLocale == null && currentDictState != DICT_NEW)
+            return
+
+        val link = "<a href='$DICTIONARY_URL'>" +
+                resources.getString(R.string.dictionary_link_text) + "</a>"
+        val message = if (currentDictState == DICT_NEW)
+            Html.fromHtml(resources.getString(R.string.add_new_dictionary, link))
+        else
+            Html.fromHtml(resources.getString(R.string.update_dictionary, link))
+        val title = if (currentDictState == DICT_NEW) R.string.add_new_dictionary_title
+            else R.string.dictionary_settings_category
+        val updateButtonTitle = if (currentDictExistsForUser) R.string.update_dictionary_button
+        else R.string.user_dict_settings_add_menu_title
+
+        val builder = AlertDialog.Builder(DialogUtils.getPlatformDialogThemeContext(activity))
+            .setNegativeButton(R.string.cancel, null)
+            .setMessage(message)
+            .setTitle(title)
+            .setPositiveButton(updateButtonTitle) { _, _ ->
+                val intent = Intent(Intent.ACTION_OPEN_DOCUMENT)
+                    .addCategory(Intent.CATEGORY_OPENABLE)
+                    .setType("application/octet-stream")
+                startActivityForResult(intent, DICTIONARY_REQUEST_CODE)
+            }
+
+        // allow removing dictionaries
+        if (currentDictExistsForUser) {
+            builder.setNeutralButton(if (currentDictExistsInternal) R.string.reset_dictionary else R.string.delete_dict) { _, _ ->
+                AlertDialog.Builder(DialogUtils.getPlatformDialogThemeContext(activity))
+                    .setTitle(R.string.remove_dictionary_title)
+                    .setMessage(resources.getString(R.string.remove_dictionary_message, currentDictLocale?.displayName()))
+                    .setNegativeButton(R.string.cancel, null)
+                    .setPositiveButton(R.string.delete_dict) { _,_ ->
+                        currentDictLocale?.getUserDictFilenames()?.let { files ->
+                            var parent: File? = null
+                            files.forEach {
+                                val f = File(it)
+                                parent = f.parentFile
+                                f.delete()
+                            }
+                            if (parent?.list()?.isEmpty() == true)
+                                parent?.delete()
+                        }
+                        reloadDictionaries()
+                    }
+                    .show()
+            }
+        }
+
+        val dialog = builder.create()
+        dialog.show()
+        // make links in the HTML text work
+        (dialog.findViewById<View>(android.R.id.message) as TextView).movementMethod =
+            LinkMovementMethod.getInstance()
+    }
+
+    // copied from CustomInputStyleSettingsFragment
+    override fun onCreateOptionsMenu(menu: Menu, inflater: MenuInflater) {
+        inflater.inflate(R.menu.add_style, menu)
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
+            val value = TypedValue()
+            activity.theme.resolveAttribute(android.R.attr.colorForeground, value, true)
+            menu.findItem(R.id.action_add_style).icon?.setTint(value.data)
+        }
+    }
+
+    override fun onOptionsItemSelected(item: MenuItem): Boolean {
+        val itemId = item.itemId
+        if (itemId == R.id.action_add_style) {
+            currentDictLocale = null
+            currentDictState = DICT_NEW
+            showUpdateDialog()
+        }
+        return super.onOptionsItemSelected(item)
+    }
+
+    override fun onActivityResult(requestCode: Int, resultCode: Int, resultData: Intent?) {
+        if (requestCode == DICTIONARY_REQUEST_CODE) onDictionaryFileSelected(resultCode, resultData)
+    }
+
+    private fun onDictionaryFileSelected(resultCode: Int, resultData: Intent?) {
+        if (resultCode != Activity.RESULT_OK || resultData == null) {
+            onDictionaryLoadingError(R.string.dictionary_load_error.resString())
+            return
+        }
+        val uri = resultData.data ?: return onDictionaryLoadingError(R.string.dictionary_load_error.resString())
+
+        cachedDictionaryFile.delete()
+        try {
+            FileUtils.copyStreamToNewFile(
+                activity.contentResolver.openInputStream(uri),
+                cachedDictionaryFile
+            )
+        } catch (e: IOException) {
+            onDictionaryLoadingError(R.string.dictionary_load_error.resString())
+            return
+        }
+
+        val newHeader = DictionaryInfoUtils.getDictionaryFileHeaderOrNull(cachedDictionaryFile, 0, cachedDictionaryFile.length())
+        if (newHeader == null) {
+            cachedDictionaryFile.delete()
+            onDictionaryLoadingError(R.string.dictionary_file_error.resString())
+            return
+        }
+        val locale = newHeader.mLocaleString.toLocale()
+        if (currentDictLocale != null && locale != currentDictLocale) {
+            cachedDictionaryFile.delete()
+            onDictionaryLoadingError(resources.getString(R.string.dictionary_file_wrong_locale, locale.displayName(), currentDictLocale?.displayName()))
+            return
+        }
+        // idString is content of 'dictionary' key, in format <type>:<locale>
+        val dictionaryType = newHeader.mIdString.substringBefore(":")
+
+        val userDictFile = File(locale.getUserDictFilename(dictionaryType))
+        // ask for user confirmation if it would be a version downgrade or if user pressed add new,
+        //  but we already have a user dictionary for the same locale
+        val shouldAskMessageId = if (userDictFile.exists()) {
+            val oldHeader = DictionaryInfoUtils.getDictionaryFileHeaderOrNull(userDictFile, 0, userDictFile.length())
+            if (oldHeader != null && oldHeader.mVersionString.toInt() > newHeader.mVersionString.toInt())
+                R.string.overwrite_old_dicitonary_messsage
+            else if (currentDictState == DICT_NEW && currentDictLocale == null)
+                R.string.replace_dictionary_message
+            else 0
+        } else 0
+        if (shouldAskMessageId != 0)
+            showConfirmReplaceDialog(locale, dictionaryType, shouldAskMessageId)
+        else
+            moveCachedFileToDictionaries(locale, dictionaryType)
+    }
+
+    private fun showConfirmReplaceDialog(locale: Locale, dictionaryType: String, messageId: Int) {
+        AlertDialog.Builder(DialogUtils.getPlatformDialogThemeContext(activity))
+            .setTitle(R.string.replace_dictionary)
+            .setMessage(resources.getString(messageId, locale.displayName()))
+            .setCancelable(false)
+            .setNegativeButton(R.string.cancel, ) { _,_ ->
+                cachedDictionaryFile.delete()
+            }
+            .setPositiveButton(R.string.replace_dictionary) { _,_ ->
+                moveCachedFileToDictionaries(locale, dictionaryType)
+            }
+            .show()
+    }
+
+    private fun moveCachedFileToDictionaries(locale: Locale, dictionaryType: String) {
+        val dictFile = File(locale.getUserDictFilename(dictionaryType))
+        if (!cachedDictionaryFile.renameTo(dictFile)) {
+            cachedDictionaryFile.delete()
+            onDictionaryLoadingError(R.string.dictionary_load_error.resString())
+            return
+        }
+
+        // success, now remove internal dictionary file if a main dictionary was added
+        if (dictionaryType == DictionaryInfoUtils.DEFAULT_MAIN_DICT)
+            File(locale.getInternalDictFilename()).delete()
+
+        // inform user about success
+        val successMessageForLocale = resources
+            .getString(R.string.dictionary_load_success, locale.displayName())
+        Toast.makeText(activity, successMessageForLocale, Toast.LENGTH_LONG).show()
+
+        // inform LatinIME about new dictionary
+        val newDictBroadcast = Intent(DictionaryPackConstants.NEW_DICTIONARY_INTENT_ACTION)
+        activity.sendBroadcast(newDictBroadcast)
+        reloadDictionaries()
+    }
+
+    private fun onDictionaryLoadingError(message: String) {
+        AlertDialog.Builder(DialogUtils.getPlatformDialogThemeContext(activity))
+            .setNegativeButton(android.R.string.ok, null)
+            .setMessage(message)
+            .setTitle("loading error")
+            .show()
+    }
+
+    private fun Locale.getUserDictFilename(dictionaryType: String) =
+        DictionaryInfoUtils.getCacheDirectoryForLocale(this.toString(), activity) + File.separator + dictionaryType + "_" + USER_DICTIONARY_SUFFIX
+
+    private fun Locale.getUserDictFilenames(): List<String> {
+        val dicts = mutableListOf<String>()
+        val p = DictionaryInfoUtils.getCacheDirectoryForLocale(this.toString(), activity)
+        DictionaryInfoUtils.getCachedDirectoryList(activity)?.forEach { dir ->
+            if (!dir.isDirectory)
+                return@forEach
+            dir.list()?.forEach {
+                if (it.endsWith(USER_DICTIONARY_SUFFIX))
+                    dicts.add(p + File.separator + it)
+            }
+        }
+        return dicts
+    }
+
+    private fun Locale.getInternalDictFilename() =
+        DictionaryInfoUtils.getCacheDirectoryForLocale(this.toString(), activity) + File.separator + DictionaryInfoUtils.getMainDictFilename(this.toString())
+
+    private fun String.displayName() = LocaleUtils.constructLocaleFromString(this).displayName()
+
+    private fun String.toLocale() = LocaleUtils.constructLocaleFromString(this)
+
+    private fun Locale.displayName() = getDisplayName(resources.configuration.locale)
+
+    private fun Int.resString() = resources.getString(this)
+
+    companion object {
+        private const val DICTIONARY_REQUEST_CODE = 96834
+        private const val DICTIONARY_URL =
+            "https://github.com/Helium314/openboard/dictionaries/dict"
+        private const val USER_DICTIONARY_SUFFIX = "user.dict"
+
+        private const val DICT_INTERNAL_AND_USER = 2
+        private const val DICT_INTERNAL_ONLY = 1
+        private const val DICT_USER_ONLY = 0
+        private const val DICT_NEW = -1
+
+    }
+}

app/src/main/java/org/dslul/openboard/inputmethod/latin/settings/Settings.java

@@ -65,6 +65,7 @@ public final class Settings implements SharedPreferences.OnSharedPreferenceChang
     public static final String PREF_VOICE_INPUT_KEY = "pref_voice_input_key";
     public static final String PREF_CLIPBOARD_CLIPBOARD_KEY = "pref_clipboard_clipboard_key";
     public static final String PREF_EDIT_PERSONAL_DICTIONARY = "edit_personal_dictionary";
+    public static final String PREF_ADD_DICTIONARY = "add_dictionary";
     public static final String PREF_AUTO_CORRECTION = "pref_key_auto_correction";
     public static final String PREF_AUTO_CORRECTION_CONFIDENCE = "pref_key_auto_correction_confidence";
     // PREF_SHOW_SUGGESTIONS_SETTING_OBSOLETE is obsolete. Use PREF_SHOW_SUGGESTIONS instead.

app/src/main/java/org/dslul/openboard/inputmethod/latin/utils/DictionaryInfoUtils.java

@@ -52,8 +52,9 @@ import javax.annotation.Nullable;
 public class DictionaryInfoUtils {
     private static final String TAG = DictionaryInfoUtils.class.getSimpleName();
     public static final String RESOURCE_PACKAGE_NAME = R.class.getPackage().getName();
-    private static final String DEFAULT_MAIN_DICT = "main";
-    private static final String MAIN_DICT_PREFIX = "main_";
+    public static final String DEFAULT_MAIN_DICT = "main";
+    public static final String MAIN_DICT_PREFIX = DEFAULT_MAIN_DICT + "_";
+    private static final String DICTIONARY_CATEGORY_SEPARATOR_EXPRESSION = "[" + BinaryDictionaryGetter.ID_CATEGORY_SEPARATOR + "_]";
     private static final String DECODER_DICT_SUFFIX = DecoderSpecificConstants.DECODER_DICT_SUFFIX;
     // 6 digits - unicode is limited to 21 bits
     private static final int MAX_HEX_DIGITS_FOR_CODEPOINT = 6;
@@ -151,7 +152,7 @@ public class DictionaryInfoUtils {
     /**
      * Helper method to get the top level cache directory.
      */
-    private static String getWordListCacheDirectory(final Context context) {
+    public static String getWordListCacheDirectory(final Context context) {
         return context.getFilesDir() + File.separator + "dicts";
     }
 
@@ -212,10 +213,12 @@ public class DictionaryInfoUtils {
     @Nullable
     public static String getCategoryFromFileName(@Nonnull final String fileName) {
         final String id = getWordListIdFromFileName(fileName);
-        final String[] idArray = id.split(BinaryDictionaryGetter.ID_CATEGORY_SEPARATOR);
+        final String[] idArray = id.split(DICTIONARY_CATEGORY_SEPARATOR_EXPRESSION);
         // An id is supposed to be in format category:locale, so splitting on the separator
         // should yield a 2-elements array
-        if (2 != idArray.length) {
+        // Also allow '_' as separator, this is ok for locales like pt_br because
+        // we're interested in the part before first separator anyway
+        if (1 == idArray.length) {
             return null;
         }
         return idArray[0];
@@ -225,7 +228,7 @@ public class DictionaryInfoUtils {
      * Find out the cache directory associated with a specific locale.
      */
     public static String getCacheDirectoryForLocale(final String locale, final Context context) {
-        final String relativeDirectoryName = replaceFileNameDangerousCharacters(locale);
+        final String relativeDirectoryName = replaceFileNameDangerousCharacters(locale).toLowerCase(Locale.ENGLISH);
         final String absoluteDirectoryName = getWordListCacheDirectory(context) + File.separator
                 + relativeDirectoryName;
         final File directory = new File(absoluteDirectoryName);
@@ -238,10 +241,12 @@ public class DictionaryInfoUtils {
     }
 
     public static boolean isMainWordListId(final String id) {
-        final String[] idArray = id.split(BinaryDictionaryGetter.ID_CATEGORY_SEPARATOR);
+        final String[] idArray = id.split(DICTIONARY_CATEGORY_SEPARATOR_EXPRESSION);
         // An id is supposed to be in format category:locale, so splitting on the separator
         // should yield a 2-elements array
-        if (2 != idArray.length) {
+        // Also allow '_' as separator, this is ok for locales like pt_br because
+        // we're interested in the part before first separator anyway
+        if (1 == idArray.length) {
             return false;
         }
         return BinaryDictionaryGetter.MAIN_DICTIONARY_CATEGORY.equals(idArray[0]);
@@ -318,6 +323,10 @@ public class DictionaryInfoUtils {
                 BinaryDictionaryGetter.ID_CATEGORY_SEPARATOR + locale.toString().toLowerCase();
     }
 
+    public static String getMainDictFilename(@Nonnull final String locale) {
+        return MAIN_DICT_PREFIX + locale.toLowerCase(Locale.ENGLISH) + ".dict";
+    }
+
     public static DictionaryHeader getDictionaryFileHeaderOrNull(final File file,
             final long offset, final long length) {
         try {

app/src/main/res/values/strings.xml

@@ -467,6 +467,44 @@ disposition rather than other common dispositions for Latin languages. [CHAR LIM
     <string name="dictionary_settings_title">Add-on dictionaries</string>
     <!-- Title for the prompt dialog which informs the user that a dictionary is available for the current language and asks to decide whether to download it over 3g -->
     <string name="dictionary_settings_summary">Settings for dictionaries</string>
+    <!-- Title for dictionaries preference screen -->
+    <string name="dictionary_settings_category">Dictionaries</string>
+    <!-- Summary text for dictionary added by user -->
+    <string name="user_dictionary_summary">User-added dictionary</string>
+    <!-- Summary text for built-in dictionary -->
+    <string name="internal_dictionary_summary">Built-in dictionary</string>
+    <!-- Title for the adding new user dictionary dialog -->
+    <string name="add_new_dictionary_title">"Add dictionary from file"</string>
+    <!-- Button text for updating a dictionary -->
+    <string name="update_dictionary_button">"Update"</string>
+    <!-- Message for user dictionary replacement dialog -->
+    <string name="replace_dictionary_message">"Really replace existing user-added dictionary for %s?"</string>
+    <!-- Message when trying to replace user dictionary with older version -->
+    <string name="overwrite_old_dicitonary_messsage">"New dictionary file contains older version code than current file. Really replace current dictionary for %s?"</string>
+    <!-- Title and confirm button text for user dictionary replacement dialog -->
+    <string name="replace_dictionary">"Replace dictionary"</string>
+    <!-- Message for user dictionary remove dialog -->
+    <string name="remove_dictionary_message">"Really remove user-added dictionaries for %s?"</string>
+    <!-- Title for user dictionary remove dialog -->
+    <string name="remove_dictionary_title">"Remove dictionary"</string>
+    <!-- Button text in user dictionary remove dialog for resetting to default -->
+    <string name="reset_dictionary">"Reset to default"</string>
+    <!-- Message for the user dictionary selection dialog. This string will be interpreted as HTML -->
+    <string name="update_dictionary">"Select a dictionary to replace the current main dictionary. Dictionaries can be downloaded at %s."</string>
+    <!-- Message for the user dictionary selection dialog. This string will be interpreted as HTML -->
+    <string name="add_new_dictionary">"Select a new dictionary to be added to the list. Dictionaries can be downloaded at the %s."</string>
+    <!-- Title of the link to the download page inserted into selection message (above) -->
+    <string name="dictionary_link_text">"project repository"</string>
+    <!-- Button text for dictionary file selection -->
+    <string name="load_dictionary_file">"Load dictionary"</string>
+    <!-- Toast text shown when dictionary file for a locale was added successfully -->
+    <string name="dictionary_load_success">"Dictionary for %s added"</string>
+    <!-- Text shown when dictionary file could not be read -->
+    <string name="dictionary_file_error">"Error: Selected file is not a valid dictionary file"</string>
+    <!-- Text shown when dictionary file is not for the selected locale -->
+    <string name="dictionary_file_wrong_locale">"Error: Selected file is for %1$s, but %2$s was expected"</string>
+    <!-- Text shown on other errors when loading dictionary file -->
+    <string name="dictionary_load_error">"Error loading dictionary file"</string>
     <!-- Name of the user dictionaries settings category -->
     <string name="user_dictionaries">User dictionaries</string>
     <!-- Name for the "user dictionary" preference item when there is only one -->

app/src/main/res/xml/prefs.xml

@@ -36,6 +36,11 @@
         android:title="@string/settings_screen_correction"
         android:key="screen_correction"
         android:icon="@drawable/ic_settings_correction"/>
+    <PreferenceScreen
+        android:fragment="org.dslul.openboard.inputmethod.latin.settings.DictionarySettingsFragment"
+        android:title="@string/dictionary_settings_category"
+        android:key="add_dictionary"
+        android:icon="@drawable/ic_notify_dictionary"/>
     <PreferenceScreen
         android:fragment="org.dslul.openboard.inputmethod.latin.settings.AdvancedSettingsFragment"
         android:title="@string/settings_screen_advanced"