Feature/#220 language menu (#7070)

* For #220
- Added advanced header + locale settings item in the settings fragment

* For #220
- Added locale selection page with lib state + handling of locale changes

* For #220
- Removed registering for locale changes in the manifest, allow system
to restart activity in that scenario

* For #220
- Added unit tests for locale settings page

* For #220: fixed an outdated unit test
ga-a

Co-authored-by: Severin Rudie <Baron-Severin@users.noreply.github.com>

app/build.gradle

@@ -429,6 +429,7 @@ dependencies {
     implementation Deps.mozilla_support_ktx
     implementation Deps.mozilla_support_rustlog
     implementation Deps.mozilla_support_utils
+    implementation Deps.mozilla_support_locale
 
     // We only care about support-migration in builds that will be overwriting Fennec.
     fennecProductionImplementation Deps.mozilla_support_migration
@@ -602,6 +603,23 @@ task printVariants {
     }
 }
 
+task buildTranslationArray {
+    def foundLocales = new StringBuilder()
+    foundLocales.append("new String[]{")
+
+    fileTree("src/main/res").visit { FileVisitDetails details ->
+        if(details.file.path.endsWith("/strings.xml")){
+            def languageCode = details.file.parent.tokenize('/').last().replaceAll('values-','').replaceAll('-r','-')
+            languageCode = (languageCode == "values") ? "en-US" : languageCode
+            foundLocales.append("\"").append(languageCode).append("\"").append(",")
+        }
+    }
+
+    foundLocales.append("}")
+    def foundLocalesString = foundLocales.toString().replaceAll(',}','}')
+    android.defaultConfig.buildConfigField "String[]", "SUPPORTED_LOCALE_ARRAY", foundLocalesString
+}
+
 def glean_android_components_tag = (
         Versions.mozilla_android_components.endsWith('-SNAPSHOT') ?
                 'master' :

app/src/main/AndroidManifest.xml

@@ -50,7 +50,7 @@
 
         <activity
             android:name=".HomeActivity"
-            android:configChanges="keyboard|keyboardHidden|mcc|mnc|orientation|screenSize|locale|layoutDirection|smallestScreenSize|screenLayout"
+            android:configChanges="keyboard|keyboardHidden|mcc|mnc|orientation|screenSize|layoutDirection|smallestScreenSize|screenLayout"
             android:launchMode="singleTask"
             android:windowSoftInputMode="adjustResize">
             <intent-filter>
@@ -81,7 +81,7 @@
         <activity
             android:name=".customtabs.ExternalAppBrowserActivity"
             android:autoRemoveFromRecents="false"
-            android:configChanges="keyboard|keyboardHidden|mcc|mnc|orientation|screenSize|locale|layoutDirection|smallestScreenSize|screenLayout"
+            android:configChanges="keyboard|keyboardHidden|mcc|mnc|orientation|screenSize|layoutDirection|smallestScreenSize|screenLayout"
             android:exported="false"
             android:label="@string/app_name"
             android:persistableMode="persistNever"
@@ -151,7 +151,7 @@
         <activity
             android:name=".settings.account.AuthCustomTabActivity"
             android:autoRemoveFromRecents="false"
-            android:configChanges="keyboard|keyboardHidden|mcc|mnc|orientation|screenSize|locale|layoutDirection|smallestScreenSize|screenLayout"
+            android:configChanges="keyboard|keyboardHidden|mcc|mnc|orientation|screenSize|layoutDirection|smallestScreenSize|screenLayout"
             android:exported="false"
             android:taskAffinity=""
             android:windowSoftInputMode="adjustResize|stateAlwaysHidden" />

app/src/main/java/org/mozilla/fenix/FenixApplication.kt

@@ -5,19 +5,18 @@
 package org.mozilla.fenix
 
 import android.annotation.SuppressLint
-import android.app.Application
 import android.os.Build
 import android.os.Build.VERSION.SDK_INT
 import android.os.StrictMode
 import androidx.annotation.CallSuper
 import androidx.appcompat.app.AppCompatDelegate
 import androidx.core.content.getSystemService
-import kotlinx.coroutines.async
-import kotlinx.coroutines.launch
-import kotlinx.coroutines.runBlocking
 import kotlinx.coroutines.Deferred
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.GlobalScope
+import kotlinx.coroutines.async
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.runBlocking
 import mozilla.appservices.Megazord
 import mozilla.components.concept.push.PushProcessor
 import mozilla.components.service.experiments.Experiments
@@ -29,6 +28,7 @@ import mozilla.components.support.base.log.logger.Logger
 import mozilla.components.support.base.log.sink.AndroidLogSink
 import mozilla.components.support.ktx.android.content.isMainProcess
 import mozilla.components.support.ktx.android.content.runOnlyInMainProcess
+import mozilla.components.support.locale.LocaleAwareApplication
 import mozilla.components.support.rusthttp.RustHttpConfig
 import mozilla.components.support.rustlog.RustLog
 import org.mozilla.fenix.GleanMetrics.ExperimentsMetrics
@@ -40,7 +40,7 @@ import java.io.File
 
 @SuppressLint("Registered")
 @Suppress("TooManyFunctions")
-open class FenixApplication : Application() {
+open class FenixApplication : LocaleAwareApplication() {
     lateinit var fretboard: Fretboard
     lateinit var experimentLoader: Deferred<Boolean>
 

app/src/main/java/org/mozilla/fenix/HomeActivity.kt

@@ -13,7 +13,6 @@ import androidx.annotation.CallSuper
 import androidx.annotation.IdRes
 import androidx.annotation.VisibleForTesting
 import androidx.annotation.VisibleForTesting.PROTECTED
-import androidx.appcompat.app.AppCompatActivity
 import androidx.appcompat.widget.Toolbar
 import androidx.lifecycle.lifecycleScope
 import androidx.navigation.NavDestination
@@ -30,6 +29,7 @@ import mozilla.components.service.fxa.sync.SyncReason
 import mozilla.components.support.base.feature.UserInteractionHandler
 import mozilla.components.support.ktx.kotlin.isUrl
 import mozilla.components.support.ktx.kotlin.toNormalizedUrl
+import mozilla.components.support.locale.LocaleAwareAppCompatActivity
 import mozilla.components.support.utils.SafeIntent
 import mozilla.components.support.utils.toSafeIntent
 import org.mozilla.fenix.browser.UriOpenedObserver
@@ -62,7 +62,7 @@ import org.mozilla.fenix.theme.DefaultThemeManager
 import org.mozilla.fenix.theme.ThemeManager
 
 @SuppressWarnings("TooManyFunctions", "LargeClass")
-open class HomeActivity : AppCompatActivity() {
+open class HomeActivity : LocaleAwareAppCompatActivity() {
 
     lateinit var themeManager: ThemeManager
     lateinit var browsingModeManager: BrowsingModeManager
@@ -239,8 +239,9 @@ open class HomeActivity : AppCompatActivity() {
     }
 
     fun openToBrowser(from: BrowserDirection, customTabSessionId: String? = null) {
-        if (sessionObserver == null)
+        if (sessionObserver == null) {
             sessionObserver = UriOpenedObserver(this)
+        }
 
         if (navHost.navController.alreadyOnDestination(R.id.browserFragment)) return
         @IdRes val fragmentId = if (from.fragmentId != 0) from.fragmentId else null

app/src/main/java/org/mozilla/fenix/library/bookmarks/BookmarkFragmentStore.kt

@@ -11,9 +11,9 @@ import mozilla.components.lib.state.State
 import mozilla.components.lib.state.Store
 
 class BookmarkFragmentStore(
-    initalState: BookmarkFragmentState
+    initialState: BookmarkFragmentState
 ) : Store<BookmarkFragmentState, BookmarkFragmentAction>(
-    initalState, ::bookmarkFragmentStateReducer
+    initialState, ::bookmarkFragmentStateReducer
 )
 
 /**

app/src/main/java/org/mozilla/fenix/settings/SettingsFragment.kt

@@ -62,7 +62,6 @@ import org.mozilla.fenix.ext.settings
 import org.mozilla.fenix.ext.showToolbar
 import org.mozilla.fenix.settings.account.AccountAuthErrorPreference
 import org.mozilla.fenix.settings.account.AccountPreference
-import org.mozilla.fenix.utils.ItsNotBrokenSnack
 
 @Suppress("LargeClass")
 class SettingsFragment : PreferenceFragmentCompat() {
@@ -210,9 +209,7 @@ class SettingsFragment : PreferenceFragmentCompat() {
                 SettingsFragmentDirections.actionSettingsFragmentToAccessibilityFragment()
             }
             resources.getString(pref_key_language) -> {
-                // TODO #220
+                SettingsFragmentDirections.actionSettingsFragmentToLocaleSettingsFragment()
-                ItsNotBrokenSnack(requireContext()).showSnackbar(issueNumber = "220")
-                null
             }
             resources.getString(pref_key_make_default_browser) -> {
                 SettingsFragmentDirections.actionSettingsFragmentToDefaultBrowserSettingsFragment()

app/src/main/java/org/mozilla/fenix/settings/advanced/DefaultLocaleSettingsController.kt

@@ -0,0 +1,41 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.fenix.settings.advanced
+
+import android.app.Activity
+import android.content.Context
+import mozilla.components.support.locale.LocaleManager
+import java.util.Locale
+
+interface LocaleSettingsController {
+    fun handleLocaleSelected(locale: Locale)
+    fun handleSearchQueryTyped(query: String)
+    fun handleDefaultLocaleSelected()
+}
+
+class DefaultLocaleSettingsController(
+    private val context: Context,
+    private val localeSettingsStore: LocaleSettingsStore
+) : LocaleSettingsController {
+
+    override fun handleLocaleSelected(locale: Locale) {
+        if (localeSettingsStore.state.selectedLocale == locale) {
+            return
+        }
+        localeSettingsStore.dispatch(LocaleSettingsAction.Select(locale))
+        LocaleManager.setNewLocale(context, locale.toLanguageTag())
+        (context as Activity).recreate()
+    }
+
+    override fun handleDefaultLocaleSelected() {
+        localeSettingsStore.dispatch(LocaleSettingsAction.Select(localeSettingsStore.state.localeList[0]))
+        LocaleManager.resetToSystemDefault(context)
+        (context as Activity).recreate()
+    }
+
+    override fun handleSearchQueryTyped(query: String) {
+        localeSettingsStore.dispatch(LocaleSettingsAction.Search(query))
+    }
+}

app/src/main/java/org/mozilla/fenix/settings/advanced/LocaleAdapter.kt

@@ -0,0 +1,150 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.fenix.settings.advanced
+
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import androidx.core.view.isVisible
+import androidx.recyclerview.widget.DiffUtil
+import androidx.recyclerview.widget.RecyclerView
+import kotlinx.android.synthetic.main.locale_settings_item.view.locale_selected_icon
+import kotlinx.android.synthetic.main.locale_settings_item.view.locale_subtitle_text
+import kotlinx.android.synthetic.main.locale_settings_item.view.locale_title_text
+import org.mozilla.fenix.R
+import java.util.Locale
+
+class LocaleAdapter(private val interactor: LocaleSettingsViewInteractor) :
+    RecyclerView.Adapter<BaseLocaleViewHolder>() {
+
+    private var localeList: List<Locale> = listOf()
+    private var selectedLocale: Locale = Locale.getDefault()
+
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): BaseLocaleViewHolder {
+        val view =
+            LayoutInflater.from(parent.context)
+                .inflate(R.layout.locale_settings_item, parent, false)
+
+        return when (viewType) {
+            ItemType.DEFAULT.ordinal -> SystemLocaleViewHolder(
+                view,
+                interactor,
+                selectedLocale
+            )
+            ItemType.LOCALE.ordinal -> LocaleViewHolder(
+                view,
+                interactor,
+                selectedLocale
+            )
+            else -> throw IllegalStateException("ViewType $viewType does not match to a ViewHolder")
+        }
+    }
+
+    override fun getItemCount(): Int {
+        return localeList.size
+    }
+
+    override fun onBindViewHolder(holder: BaseLocaleViewHolder, position: Int) {
+        holder.bind(localeList[position])
+    }
+
+    override fun getItemViewType(position: Int): Int {
+        return when (position) {
+            0 -> ItemType.DEFAULT
+            else -> ItemType.LOCALE
+        }.ordinal
+    }
+
+    fun updateData(localeList: List<Locale>, selectedLocale: Locale) {
+        val diffUtil = DiffUtil.calculateDiff(
+            LocaleDiffUtil(
+                this.localeList,
+                localeList,
+                this.selectedLocale,
+                selectedLocale
+            )
+        )
+        this.localeList = localeList
+        this.selectedLocale = selectedLocale
+
+        diffUtil.dispatchUpdatesTo(this)
+    }
+
+    inner class LocaleDiffUtil(
+        private val old: List<Locale>,
+        private val new: List<Locale>,
+        private val oldSelectedLocale: Locale,
+        private val newSelectedLocale: Locale
+    ) : DiffUtil.Callback() {
+
+        override fun areItemsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean {
+            val selectionChanged =
+                old[oldItemPosition] == oldSelectedLocale && oldSelectedLocale != newSelectedLocale
+            return old[oldItemPosition] == new[newItemPosition] && !selectionChanged
+        }
+
+        override fun areContentsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean =
+            old[oldItemPosition].toLanguageTag() == new[newItemPosition].toLanguageTag()
+
+        override fun getOldListSize(): Int = old.size
+        override fun getNewListSize(): Int = new.size
+    }
+
+    enum class ItemType {
+        DEFAULT, LOCALE;
+    }
+}
+
+class LocaleViewHolder(
+    view: View,
+    private val interactor: LocaleSettingsViewInteractor,
+    private val selectedLocale: Locale
+) : BaseLocaleViewHolder(view) {
+    private val icon = view.locale_selected_icon
+    private val title = view.locale_title_text
+    private val subtitle = view.locale_subtitle_text
+
+    override fun bind(locale: Locale) {
+        // capitalisation is done using the rules of the appropriate locale (endonym and exonym)
+        title.text = locale.getDisplayName(locale).capitalize(locale)
+        subtitle.text = locale.displayName.capitalize(Locale.getDefault())
+        icon.isVisible = locale === selectedLocale
+
+        itemView.setOnClickListener {
+            interactor.onLocaleSelected(locale)
+        }
+    }
+}
+
+class SystemLocaleViewHolder(
+    view: View,
+    private val interactor: LocaleSettingsViewInteractor,
+    private val selectedLocale: Locale
+) : BaseLocaleViewHolder(view) {
+    private val icon = view.locale_selected_icon
+    private val title = view.locale_title_text
+    private val subtitle = view.locale_subtitle_text
+
+    override fun bind(locale: Locale) {
+        title.text = itemView.context.getString(R.string.default_locale_text)
+        subtitle.visibility = View.GONE
+        icon.isVisible = locale === selectedLocale
+
+        itemView.setOnClickListener {
+            interactor.onDefaultLocaleSelected()
+        }
+    }
+}
+
+abstract class BaseLocaleViewHolder(view: View) : RecyclerView.ViewHolder(view) {
+    abstract fun bind(locale: Locale)
+}
+
+/**
+ * Similar to Kotlin's capitalize with locale parameter, but that method is currently experimental
+ */
+private fun String.capitalize(locale: Locale): String {
+    return substring(0, 1).toUpperCase(locale) + substring(1)
+}

app/src/main/java/org/mozilla/fenix/settings/advanced/LocaleManagerExtension.kt

@@ -0,0 +1,49 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.fenix.settings.advanced
+
+import android.content.Context
+import mozilla.components.support.locale.LocaleManager
+import mozilla.components.support.locale.toLocale
+import org.mozilla.fenix.BuildConfig
+import java.util.Locale
+
+/**
+ * Returns a list of currently supported locales, with the system default set as the first one
+ */
+fun LocaleManager.getSupportedLocales(): List<Locale> {
+    val resultLocaleList: MutableList<Locale> = ArrayList()
+    resultLocaleList.add(0, getSystemDefault() ?: Locale.getDefault())
+
+    resultLocaleList.addAll(BuildConfig.SUPPORTED_LOCALE_ARRAY
+        .toList()
+        .map {
+            it.toLocale()
+        }.sortedWith(compareBy(
+            { it.displayLanguage },
+            { it.displayCountry }
+        )))
+    return resultLocaleList
+}
+
+/**
+ * Returns the locale that corresponds to the language stored locally by us. If no suitable one is found,
+ * return default.
+ */
+fun LocaleManager.getSelectedLocale(
+    context: Context,
+    localeList: List<Locale> = getSupportedLocales()
+): Locale {
+    val selectedLocale = getCurrentLocale(context)?.toLanguageTag()
+    val defaultLocale = getSystemDefault() ?: Locale.getDefault()
+
+    return if (selectedLocale == null) {
+        defaultLocale
+    } else {
+        val supportedMatch = localeList
+            .firstOrNull { it.toLanguageTag() == selectedLocale }
+        supportedMatch ?: defaultLocale
+    }
+}

app/src/main/java/org/mozilla/fenix/settings/advanced/LocaleSettingsFragment.kt

@@ -0,0 +1,78 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.fenix.settings.advanced
+
+import android.os.Bundle
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import androidx.fragment.app.Fragment
+import kotlinx.android.synthetic.main.fragment_locale_settings.view.locale_container
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import mozilla.components.lib.state.ext.consumeFrom
+import mozilla.components.support.ktx.android.view.hideKeyboard
+import mozilla.components.support.locale.LocaleManager
+import org.mozilla.fenix.R
+import org.mozilla.fenix.components.StoreProvider
+import org.mozilla.fenix.ext.showToolbar
+
+class LocaleSettingsFragment : Fragment() {
+
+    private lateinit var store: LocaleSettingsStore
+    private lateinit var interactor: LocaleSettingsInteractor
+    private lateinit var localeView: LocaleSettingsView
+
+    override fun onCreateView(
+        inflater: LayoutInflater,
+        container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View? {
+        val view = inflater.inflate(R.layout.fragment_locale_settings, container, false)
+
+        store = getStore()
+        interactor = LocaleSettingsInteractor(
+            controller = DefaultLocaleSettingsController(
+                context = requireContext(),
+                localeSettingsStore = store
+            )
+        )
+        localeView = LocaleSettingsView(view.locale_container, interactor)
+        return view
+    }
+
+    override fun onResume() {
+        super.onResume()
+        localeView.onResume()
+        showToolbar(getString(R.string.preferences_language))
+    }
+
+    override fun onPause() {
+        view?.hideKeyboard()
+        super.onPause()
+    }
+
+    @ExperimentalCoroutinesApi
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        super.onViewCreated(view, savedInstanceState)
+        consumeFrom(store) {
+            localeView.update(it)
+        }
+    }
+
+    private fun getStore(): LocaleSettingsStore {
+        val supportedLocales = LocaleManager.getSupportedLocales()
+        val selectedLocale = LocaleManager.getSelectedLocale(requireContext())
+
+        return StoreProvider.get(this) {
+            LocaleSettingsStore(
+                LocaleSettingsState(
+                    supportedLocales,
+                    supportedLocales,
+                    selectedLocale
+                )
+            )
+        }
+    }
+}

app/src/main/java/org/mozilla/fenix/settings/advanced/LocaleSettingsInteractor.kt

@@ -0,0 +1,23 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.fenix.settings.advanced
+
+import java.util.Locale
+
+class LocaleSettingsInteractor(private val controller: LocaleSettingsController) :
+    LocaleSettingsViewInteractor {
+
+    override fun onLocaleSelected(locale: Locale) {
+        controller.handleLocaleSelected(locale)
+    }
+
+    override fun onDefaultLocaleSelected() {
+        controller.handleDefaultLocaleSelected()
+    }
+
+    override fun onSearchQueryTyped(query: String) {
+        controller.handleSearchQueryTyped(query)
+    }
+}

app/src/main/java/org/mozilla/fenix/settings/advanced/LocaleSettingsStore.kt

@@ -0,0 +1,61 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.fenix.settings.advanced
+
+import mozilla.components.lib.state.Action
+import mozilla.components.lib.state.State
+import mozilla.components.lib.state.Store
+import java.util.Locale
+
+class LocaleSettingsStore(
+    initialState: LocaleSettingsState
+) : Store<LocaleSettingsState, LocaleSettingsAction>(
+    initialState, ::localeSettingsStateReducer
+)
+
+/**
+ * The state of the language selection page
+ * @property localeList The full list of locales available
+ * @property searchedLocaleList The list of locales starting with a search query
+ * @property selectedLocale The current selected locale
+ */
+data class LocaleSettingsState(
+    val localeList: List<Locale>,
+    val searchedLocaleList: List<Locale>,
+    val selectedLocale: Locale
+) : State
+
+/**
+ * Actions to dispatch through the `LocaleSettingsStore` to modify `LocaleSettingsState` through the reducer.
+ */
+sealed class LocaleSettingsAction : Action {
+    data class Select(val selectedItem: Locale) : LocaleSettingsAction()
+    data class Search(val query: String) : LocaleSettingsAction()
+}
+
+/**
+ * Reduces the locale state from the current state and an action performed on it.
+ * @param state the current locale state
+ * @param action the action to perform
+ * @return the new locale state
+ */
+private fun localeSettingsStateReducer(
+    state: LocaleSettingsState,
+    action: LocaleSettingsAction
+): LocaleSettingsState {
+    return when (action) {
+        is LocaleSettingsAction.Select -> {
+            state.copy(selectedLocale = action.selectedItem)
+        }
+        is LocaleSettingsAction.Search -> {
+            val searchedItems = state.localeList.filter {
+                it.getDisplayLanguage(it).startsWith(action.query, ignoreCase = true) ||
+                        it.displayLanguage.startsWith(action.query, ignoreCase = true) ||
+                        it === state.localeList[0]
+            }
+            state.copy(searchedLocaleList = searchedItems)
+        }
+    }
+}

app/src/main/java/org/mozilla/fenix/settings/advanced/LocaleSettingsView.kt

@@ -0,0 +1,62 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.fenix.settings.advanced
+
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import android.widget.SearchView
+import androidx.recyclerview.widget.LinearLayoutManager
+import kotlinx.android.synthetic.main.component_locale_settings.view.locale_list
+import kotlinx.android.synthetic.main.component_locale_settings.view.toolbar_container
+import org.mozilla.fenix.R
+import java.util.Locale
+
+interface LocaleSettingsViewInteractor {
+
+    fun onLocaleSelected(locale: Locale)
+
+    fun onDefaultLocaleSelected()
+
+    fun onSearchQueryTyped(query: String)
+}
+
+class LocaleSettingsView(
+    container: ViewGroup,
+    val interactor: LocaleSettingsViewInteractor
+) {
+
+    val view: View = LayoutInflater.from(container.context)
+        .inflate(R.layout.component_locale_settings, container, true)
+
+    private val localeAdapter: LocaleAdapter
+
+    init {
+        view.locale_list.apply {
+            localeAdapter = LocaleAdapter(interactor)
+            adapter = localeAdapter
+            layoutManager = LinearLayoutManager(context)
+        }
+        val searchView: SearchView = view.toolbar_container
+        searchView.setOnQueryTextListener(object : SearchView.OnQueryTextListener {
+            override fun onQueryTextSubmit(query: String): Boolean {
+                return false
+            }
+
+            override fun onQueryTextChange(newText: String): Boolean {
+                interactor.onSearchQueryTyped(newText)
+                return false
+            }
+        })
+    }
+
+    fun update(state: LocaleSettingsState) {
+        localeAdapter.updateData(state.searchedLocaleList, state.selectedLocale)
+    }
+
+    fun onResume() {
+        view.requestFocus()
+    }
+}

app/src/main/java/org/mozilla/fenix/widget/VoiceSearchActivity.kt

@@ -9,6 +9,7 @@ import android.content.Intent
 import android.os.Bundle
 import android.speech.RecognizerIntent
 import androidx.appcompat.app.AppCompatActivity
+import mozilla.components.support.locale.LocaleManager
 import org.mozilla.fenix.HomeActivity
 import org.mozilla.fenix.IntentReceiverActivity
 import org.mozilla.fenix.components.metrics.Event
@@ -57,6 +58,7 @@ class VoiceSearchActivity : AppCompatActivity() {
     private fun displaySpeechRecognizer() {
         val intentSpeech = Intent(RecognizerIntent.ACTION_RECOGNIZE_SPEECH).apply {
             putExtra(RecognizerIntent.EXTRA_LANGUAGE_MODEL, RecognizerIntent.LANGUAGE_MODEL_FREE_FORM)
+            putExtra(RecognizerIntent.EXTRA_LANGUAGE, LocaleManager.getCurrentLocale(this@VoiceSearchActivity))
         }
         metrics.track(Event.SearchWidgetVoiceSearchPressed)
 

app/src/main/res/drawable/locale_search_background.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<shape xmlns:android="http://schemas.android.com/apk/res/android">
+    <solid android:color="?foundation" />
+</shape>

app/src/main/res/layout/component_locale_settings.xml

@@ -0,0 +1,36 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:focusable="true"
+    android:focusableInTouchMode="true">
+
+    <SearchView
+        android:id="@+id/toolbar_container"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_margin="@dimen/locale_search_bar_margin"
+        android:background="@drawable/search_url_background"
+        android:closeIcon="@drawable/ic_close"
+        android:iconifiedByDefault="false"
+        android:paddingStart="@dimen/locale_search_bar_padding_start"
+        android:paddingEnd="0dp"
+        android:queryBackground="@android:color/transparent"
+        android:queryHint="@string/locale_search_hint"
+        android:searchIcon="@drawable/ic_search"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent" />
+
+    <androidx.recyclerview.widget.RecyclerView
+        android:id="@+id/locale_list"
+        android:layout_width="match_parent"
+        android:layout_height="0dp"
+        android:layout_margin="@dimen/locale_list_margin"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/toolbar_container" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>

app/src/main/res/layout/fragment_locale_settings.xml

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <FrameLayout
+        android:id="@+id/locale_container"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>

app/src/main/res/layout/locale_settings_item.xml

@@ -0,0 +1,52 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content">
+
+    <ImageView
+        android:id="@+id/locale_selected_icon"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_marginTop="@dimen/locale_item_vertical_margin"
+        android:layout_marginBottom="@dimen/locale_item_vertical_margin"
+        android:contentDescription="@string/a11y_selected_locale_content_description"
+        android:src="@drawable/mozac_ic_check"
+        android:tint="?primaryText"
+        android:visibility="gone"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent" />
+
+    <TextView
+        android:id="@+id/locale_title_text"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_marginStart="@dimen/locale_item_text_margin_start"
+        android:layout_marginTop="@dimen/locale_item_vertical_margin"
+        android:textColor="?primaryText"
+        app:layout_goneMarginStart="@dimen/locale_item_text_margin_gone_start"
+        android:textSize="@dimen/locale_item_title_size"
+        app:layout_constraintBottom_toTopOf="@+id/locale_subtitle_text"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toEndOf="@+id/locale_selected_icon"
+        app:layout_constraintTop_toTopOf="parent"
+        app:layout_constraintVertical_chainStyle="packed"
+        app:layout_goneMarginBottom="@dimen/locale_item_vertical_margin" />
+
+    <TextView
+        android:id="@+id/locale_subtitle_text"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_marginStart="@dimen/locale_item_text_margin_start"
+        android:layout_marginBottom="@dimen/locale_item_vertical_margin"
+        android:textColor="?secondaryText"
+        android:textSize="@dimen/locale_item_subtitle_size"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_goneMarginStart="@dimen/locale_item_text_margin_gone_start"
+        app:layout_constraintStart_toEndOf="@+id/locale_selected_icon"
+        app:layout_constraintTop_toBottomOf="@+id/locale_title_text"
+        app:layout_constraintVertical_chainStyle="packed" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>

app/src/main/res/navigation/nav_graph.xml

@@ -397,6 +397,9 @@
         <action
             android:id="@+id/action_settingsFragment_to_toolbarSettingsFragment"
             app:destination="@id/toolbarSettingsFragment" />
+        <action
+            android:id="@+id/action_settingsFragment_to_localeSettingsFragment"
+            app:destination="@id/localeSettingsFragment" />
     </fragment>
     <fragment
         android:id="@+id/dataChoicesFragment"
@@ -687,4 +690,8 @@
         android:id="@+id/toolbarSettingsFragment"
         android:name="org.mozilla.fenix.settings.ToolbarSettingsFragment"
         android:label="ToolbarSettingsFragment" />
+    <fragment
+        android:id="@+id/localeSettingsFragment"
+        android:name="org.mozilla.fenix.settings.advanced.LocaleSettingsFragment"
+        android:label="LanguageSettingsFragment" />
 </navigation>

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

@@ -93,4 +93,15 @@
     <dimen name="about_items_text_size">16sp</dimen>
     <dimen name="about_header_text_line_spacing_extra">4dp</dimen>
 
+    <!-- Locale Settings Fragment -->
+    <dimen name="locale_search_bar_margin">8dp</dimen>
+    <dimen name="locale_search_bar_padding_start">-12dp</dimen>
+    <dimen name="locale_list_margin">16dp</dimen>
+    <dimen name="locale_item_vertical_margin">8dp</dimen>
+    <dimen name="locale_item_text_margin_start">16dp</dimen>
+    <dimen name="locale_item_text_margin_gone_start">40dp</dimen>
+    <dimen name="locale_item_title_size">16sp</dimen>
+    <dimen name="locale_item_subtitle_size">12sp</dimen>
+
+
 </resources>

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

@@ -108,6 +108,16 @@
     <!-- Browser menu button to configure reader mode appearance e.g. the used font type and size -->
     <string name="browser_menu_read_appearance">Appearance</string>
 
+    <!-- Locale Settings Fragment -->
+    <!-- Content description for tick mark on selected language -->
+    <string name="a11y_selected_locale_content_description">Selected language</string>
+    <!-- Content description for search icon -->
+    <string name="a11y_search_icon_content_description">Search</string>
+    <!-- Text for default locale item -->
+    <string name="default_locale_text">Follow device language</string>
+    <!-- Placeholder text shown in the search bar before a user enters text -->
+    <string name="locale_search_hint">Search language</string>
+
     <!-- Search Fragment -->
     <!-- Button in the search view that lets a user search by scanning a QR code -->
     <string name="search_scan_button">Scan</string>

app/src/main/res/xml/preferences.xml

@@ -101,6 +101,15 @@
             app:isPreferenceVisible="@bool/IS_DEBUG" />
     </androidx.preference.PreferenceCategory>
 
+    <PreferenceCategory
+        android:title="@string/preferences_category_advanced"
+        app:iconSpaceReserved="false">
+        <androidx.preference.Preference
+            android:icon="@drawable/ic_language"
+            android:key="@string/pref_key_language"
+            android:title="@string/preferences_language" />
+    </PreferenceCategory>
+
     <PreferenceCategory
         android:title="@string/developer_tools_category"
         app:iconSpaceReserved="false">

app/src/test/java/org/mozilla/fenix/settings/advanced/LocaleManagerExtensionTest.kt

@@ -0,0 +1,76 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+* License, v. 2.0. If a copy of the MPL was not distributed with this
+* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.fenix.settings.advanced
+
+import android.content.Context
+import io.mockk.every
+import io.mockk.mockk
+import io.mockk.mockkObject
+import io.mockk.mockkStatic
+import mozilla.components.support.locale.LocaleManager
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Before
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.mozilla.fenix.BuildConfig
+import org.mozilla.fenix.TestApplication
+import org.robolectric.RobolectricTestRunner
+import org.robolectric.annotation.Config
+import java.util.Locale
+
+@RunWith(RobolectricTestRunner::class)
+@Config(application = TestApplication::class)
+class LocaleManagerExtensionTest {
+
+    @Before
+    fun setup() {
+        mockkStatic("org.mozilla.fenix.settings.advanced.LocaleManagerExtensionKt")
+    }
+
+    @Test
+    @Config(qualifiers = "en-rUS")
+    fun `build supported locale list`() {
+        val list = LocaleManager.getSupportedLocales()
+
+        // Expect all supported locales + 'follow default option'
+        val expectedSize = BuildConfig.SUPPORTED_LOCALE_ARRAY.size + 1
+
+        assertEquals(expectedSize, list.size)
+        assertTrue(list.isNotEmpty())
+    }
+
+    @Test
+    @Config(qualifiers = "en-rUS")
+    fun `match current stored locale string with a Locale from our list`() {
+        val context: Context = mockk()
+        mockkObject(LocaleManager)
+        val otherLocale = Locale("fr")
+        val selectedLocale = Locale("en", "UK")
+        val localeList = ArrayList<Locale>()
+        localeList.add(otherLocale)
+        localeList.add(selectedLocale)
+
+        every { LocaleManager.getCurrentLocale(context) } returns selectedLocale
+
+        assertEquals(selectedLocale, LocaleManager.getSelectedLocale(context, localeList))
+    }
+
+    @Test
+    @Config(qualifiers = "en-rUS")
+    fun `match null stored locale with the default Locale from our list`() {
+        val context: Context = mockk()
+        mockkObject(LocaleManager)
+        val firstLocale = Locale("fr")
+        val secondLocale = Locale("en", "UK")
+        val localeList = ArrayList<Locale>()
+        localeList.add(firstLocale)
+        localeList.add(secondLocale)
+
+        every { LocaleManager.getCurrentLocale(context) } returns null
+
+        assertEquals("en-US", LocaleManager.getSelectedLocale(context, localeList).toLanguageTag())
+    }
+}

app/src/test/java/org/mozilla/fenix/settings/advanced/LocaleSettingsControllerTest.kt

@@ -0,0 +1,85 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.fenix.settings.advanced
+
+import android.app.Activity
+import android.content.Context
+import io.mockk.Runs
+import io.mockk.every
+import io.mockk.just
+import io.mockk.mockk
+import io.mockk.mockkObject
+import io.mockk.verify
+import mozilla.components.support.locale.LocaleManager
+import mozilla.components.support.test.mock
+import org.junit.Before
+import org.junit.Test
+import java.util.Locale
+
+class LocaleSettingsControllerTest {
+
+    private val context: Context = mockk<Activity>(relaxed = true)
+    private val localeSettingsStore: LocaleSettingsStore = mockk(relaxed = true)
+
+    private lateinit var controller: LocaleSettingsController
+
+    @Before
+    fun setup() {
+        controller = DefaultLocaleSettingsController(context, localeSettingsStore)
+    }
+
+    @Test
+    fun `set a new locale from the list`() {
+        val selectedLocale = Locale("en", "UK")
+        val otherLocale: Locale = mock()
+        every { localeSettingsStore.state } returns LocaleSettingsState(
+            mockk(),
+            mockk(),
+            otherLocale
+        )
+        mockkObject(LocaleManager)
+        every {
+            LocaleManager.setNewLocale(
+                context,
+                selectedLocale.toLanguageTag()
+            )
+        } returns context
+
+        controller.handleLocaleSelected(selectedLocale)
+
+        verify { localeSettingsStore.dispatch(LocaleSettingsAction.Select(selectedLocale)) }
+        verify { LocaleManager.setNewLocale(context, selectedLocale.toLanguageTag()) }
+        verify { (context as Activity).recreate() }
+    }
+
+    @Test
+    fun `set the default locale as the new locale`() {
+        val selectedLocale = Locale("en", "UK")
+        val localeList = ArrayList<Locale>()
+        localeList.add(selectedLocale)
+        every { localeSettingsStore.state } returns LocaleSettingsState(
+            localeList,
+            mockk(),
+            mockk()
+        )
+        mockkObject(LocaleManager)
+        every { LocaleManager.resetToSystemDefault(context) } just Runs
+
+        controller.handleDefaultLocaleSelected()
+
+        verify { localeSettingsStore.dispatch(LocaleSettingsAction.Select(selectedLocale)) }
+        verify { LocaleManager.resetToSystemDefault(context) }
+        verify { (context as Activity).recreate() }
+    }
+
+    @Test
+    fun `handle search query typed`() {
+        val query = "Eng"
+
+        controller.handleSearchQueryTyped(query)
+
+        verify { localeSettingsStore.dispatch(LocaleSettingsAction.Search(query)) }
+    }
+}

app/src/test/java/org/mozilla/fenix/settings/advanced/LocaleSettingsInteractorTest.kt

@@ -0,0 +1,47 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.fenix.settings.advanced
+
+import io.mockk.mockk
+import io.mockk.verify
+import org.junit.Before
+import org.junit.Test
+import java.util.Locale
+
+class LocaleSettingsInteractorTest {
+
+    private lateinit var interactor: LocaleSettingsInteractor
+    private val controller: LocaleSettingsController = mockk(relaxed = true)
+
+    @Before
+    fun setup() {
+        interactor = LocaleSettingsInteractor(controller)
+    }
+
+    @Test
+    fun `locale was selected from list`() {
+        val locale: Locale = mockk()
+
+        interactor.onLocaleSelected(locale)
+
+        verify { controller.handleLocaleSelected(locale) }
+    }
+
+    @Test
+    fun `default locale was selected from list`() {
+        interactor.onDefaultLocaleSelected()
+
+        verify { controller.handleDefaultLocaleSelected() }
+    }
+
+    @Test
+    fun `search query was typed`() {
+        val query = "Eng"
+
+        interactor.onSearchQueryTyped(query)
+
+        verify { controller.handleSearchQueryTyped(query) }
+    }
+}

app/src/test/java/org/mozilla/fenix/settings/advanced/LocaleSettingsStoreTest.kt

@@ -0,0 +1,44 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.fenix.settings.advanced
+
+import kotlinx.coroutines.runBlocking
+import org.junit.Assert.assertEquals
+import org.junit.Before
+import org.junit.Test
+import java.util.Locale
+
+class LocaleSettingsStoreTest {
+
+    private lateinit var localeSettingsStore: LocaleSettingsStore
+    private val selectedLocale = Locale("en", "UK")
+    private val otherLocale = Locale("fr")
+
+    @Before
+    fun setup() {
+        val localeList = ArrayList<Locale>()
+        localeList.add(Locale("fr")) // default
+        localeList.add(otherLocale)
+        localeList.add(selectedLocale)
+
+        localeSettingsStore =
+            LocaleSettingsStore(LocaleSettingsState(localeList, localeList, selectedLocale))
+    }
+
+    @Test
+    fun `change selected locale`() = runBlocking {
+        localeSettingsStore.dispatch(LocaleSettingsAction.Select(otherLocale)).join()
+
+        assertEquals(otherLocale, localeSettingsStore.state.selectedLocale)
+    }
+
+    @Test
+    fun `change selected list by search query`() = runBlocking {
+        localeSettingsStore.dispatch(LocaleSettingsAction.Search("Eng")).join()
+
+        assertEquals(2, (localeSettingsStore.state.searchedLocaleList as ArrayList).size)
+        assertEquals(selectedLocale, localeSettingsStore.state.searchedLocaleList[1])
+    }
+}

buildSrc/src/main/java/Dependencies.kt

@@ -147,6 +147,7 @@ object Deps {
     const val mozilla_support_utils = "org.mozilla.components:support-utils:${Versions.mozilla_android_components}"
     const val mozilla_support_test = "org.mozilla.components:support-test:${Versions.mozilla_android_components}"
     const val mozilla_support_migration = "org.mozilla.components:support-migration:${Versions.mozilla_android_components}"
+    const val mozilla_support_locale = "org.mozilla.components:support-locale:${Versions.mozilla_android_components}"
 
     const val sentry = "io.sentry:sentry-android:${Versions.sentry}"
     const val leakcanary = "com.squareup.leakcanary:leakcanary-android:${Versions.leakcanary}"