Fix locale not applied outside activities

app/src/main/java/eu/kanade/tachiyomi/App.kt

@@ -34,7 +34,7 @@ open class App : Application() {
         setupAcra()
         setupJobManager()
 
-        LocaleHelper.updateCfg(this, baseContext.resources.configuration)
+        LocaleHelper.updateConfiguration(this, resources.configuration)
     }
 
     override fun attachBaseContext(base: Context) {
@@ -46,7 +46,7 @@ open class App : Application() {
 
     override fun onConfigurationChanged(newConfig: Configuration) {
         super.onConfigurationChanged(newConfig)
-        LocaleHelper.updateCfg(this, newConfig)
+        LocaleHelper.updateConfiguration(this, newConfig, true)
     }
 
     protected open fun setupAcra() {

app/src/main/java/eu/kanade/tachiyomi/ui/base/activity/BaseActivity.kt

@@ -6,7 +6,7 @@ import eu.kanade.tachiyomi.util.LocaleHelper
 abstract class BaseActivity : AppCompatActivity(), ActivityMixin {
 
     init {
-        LocaleHelper.updateCfg(this)
+        LocaleHelper.updateConfiguration(this)
     }
 
     override fun getActivity() = this

app/src/main/java/eu/kanade/tachiyomi/ui/base/activity/BaseRxActivity.kt

@@ -9,7 +9,7 @@ import nucleus.view.NucleusAppCompatActivity
 abstract class BaseRxActivity<P : BasePresenter<*>> : NucleusAppCompatActivity<P>(), ActivityMixin {
 
     init {
-        LocaleHelper.updateCfg(this)
+        LocaleHelper.updateConfiguration(this)
     }
 
     override fun onCreate(savedState: Bundle?) {

app/src/main/java/eu/kanade/tachiyomi/ui/setting/SettingsGeneralFragment.kt

@@ -115,7 +115,8 @@ class SettingsGeneralFragment : SettingsFragment(),
         langPreference.setOnPreferenceChangeListener { preference, newValue ->
             (activity as SettingsActivity).parentFlags = SettingsActivity.FLAG_LANG_CHANGED
             LocaleHelper.changeLocale(newValue.toString())
-            LocaleHelper.updateCfg(activity.application, activity.baseContext.resources.configuration)
+            val app = activity.application
+            LocaleHelper.updateConfiguration(app, app.resources.configuration)
             activity.recreate()
             true
         }

app/src/main/java/eu/kanade/tachiyomi/util/LocaleHelper.kt

@@ -3,6 +3,7 @@ package eu.kanade.tachiyomi.util
 import android.app.Application
 import android.content.res.Configuration
 import android.os.Build
+import android.os.LocaleList
 import android.view.ContextThemeWrapper
 import eu.kanade.tachiyomi.data.preference.PreferencesHelper
 import uy.kohesive.injekt.injectLazy
@@ -20,12 +21,9 @@ object LocaleHelper {
     private val preferences: PreferencesHelper by injectLazy()
 
     /**
-     * In API 16 and below the application's configuration has to be changed, so we need a copy of
-     * the initial locale. The only problem is that if the system locale changes while the app is
-     * running, it won't change until an application restart.
+     * The system's locale.
      */
-    private var v16SystemLocale = if (Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN_MR1)
-        preferences.context.resources.configuration.locale else null
+    private var systemLocale: Locale? = null
 
     /**
      * The application's locale. When it's null, the system locale is used.
@@ -57,9 +55,9 @@ object LocaleHelper {
     }
 
     /**
-     * Updates the app's language from API 17.
+     * Updates the app's language to an activity.
      */
-    fun updateCfg(wrapper: ContextThemeWrapper) {
+    fun updateConfiguration(wrapper: ContextThemeWrapper) {
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1 && appLocale != null) {
             val config = Configuration(preferences.context.resources.configuration)
             config.setLocale(appLocale)
@@ -68,16 +66,36 @@ object LocaleHelper {
     }
 
     /**
-     * Updates the app's language for API 16 and lower.
+     * Updates the app's language to the application.
      */
-    fun updateCfg(app: Application, config: Configuration) {
-        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN_MR1) {
-            val configCopy = Configuration(config)
-            val displayMetrics = app.baseContext.resources.displayMetrics
-            configCopy.locale = appLocale ?: v16SystemLocale
-            app.baseContext.resources.updateConfiguration(configCopy, displayMetrics)
+    fun updateConfiguration(app: Application, config: Configuration, configChange: Boolean = false) {
+        if (systemLocale == null) {
+            systemLocale = getConfigLocale(config)
         }
+        // In API 16 and lower the system locale can't be changed.
+        if (configChange && Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
+            val newLocale = getConfigLocale(config)
+            if (systemLocale == newLocale) {
+                return
+            }
+            systemLocale = newLocale
+        }
+        val newConfig = Configuration(config)
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.N) {
+            newConfig.locale = appLocale ?: systemLocale
+        } else {
+            newConfig.locales = LocaleList(appLocale ?: systemLocale)
+        }
+        val resources = app.resources
+        resources.updateConfiguration(newConfig, resources.displayMetrics)
     }
 
+    private fun getConfigLocale(config: Configuration): Locale {
+        return if (Build.VERSION.SDK_INT < Build.VERSION_CODES.N) {
+            config.locale
+        } else {
+            config.locales[0]
+        }
+    }
 
 }