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Comprehensive Guide to Language Changes in Kotlin for Android

August 16, 2024 • rlam20

During my time at OLE, one of my main tasks was supporting the languages myPlanet offers. At the time of this article, we support English, Spanish, French, Somali, Nepali, and Arabic.

This guide will help you understand how to manage language changes in Kotlin for Android. Even if you're new to Kotlin or Android development, this guide will walk you through the concepts step by step, providing best practices, code examples, and detailed explanations.

Part 1: Language Change Handling in Kotlin for Android

1. Introduction to Locale and Language Changes

What is a Locale?

In Android, a Locale refers to a specific geographical, political, or cultural region. It includes language and country codes that help format data such as numbers, dates, and strings.

  • Locale: A Locale object represents a specific language and region (e.g., English in the United States, Spanish in Mexico). The system uses locales to format various data types and display content appropriately based on the user's preferences.

Why handle Language Changes?

Many Android apps need to support multiple languages. Changing the language within an app involves setting a new Locale and updating the app’s configuration so that all UI elements display in the chosen language.

Given OLE's mission to provide educational support globally, it's especially important that we support multiple languages and that those translations are consistent and accurate.

2. Implementing Language Changes in Kotlin

a. Managing Locale with a Helper Class

We have a centralized LocaleHelper class to manage language changes effectively. This class encapsulates the logic required to update the Locale and refresh the app’s configuration.

import android.content.Context
import android.content.res.Configuration
import java.util.Locale

object LocaleHelper {

    // Method to set the locale of the app
    fun setLocale(context: Context, language: String): Context {
        return updateResources(context, language)
    }

    // Internal method to update the resources with the new locale
    private fun updateResources(context: Context, language: String): Context {
        val locale = Locale(language)  // Create a Locale object for the selected language
        Locale.setDefault(locale)      // Set it as the default locale for the app

        // Update the configuration with the new locale
        val configuration = Configuration(context.resources.configuration)
        configuration.setLocale(locale)
        configuration.setLayoutDirection(locale)  // Adjust layout direction for RTL languages

        // Return the updated context with the new configuration
        return context.createConfigurationContext(configuration)
    }
}

b. Applying Locale in the Application Class

To ensure the selected locale is consistently applied throughout your app, update the locale in the Application or MainApplication class, which serves as the entry point for your application.

import android.app.Application
import android.content.Context

class MyApp : Application() {

    // Override attachBaseContext to apply the locale when the app starts
    override fun attachBaseContext(base: Context?) {
        super.attachBaseContext(base?.let { LocaleHelper.setLocale(it, "en") }) // Default language is English
        //super.attachBaseContext(base?.let { LocaleHelper.setLocale(it, "ar") }) //Example for changing to Arabic
    }
}

c. Allowing Dynamic Language Changes

To allow users to change the language while the app is running, implement a method that updates the locale and restarts the application to apply the changes.

import android.content.Context
import android.content.Intent

fun changeLanguage(context: Context, language: String) {
    LocaleHelper.setLocale(context, language)

    // Restart the application to apply the new language
    val intent = context.packageManager.getLaunchIntentForPackage(context.packageName)
    intent?.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)
    context.startActivity(intent)
}

3. Managing Context and Configuration Updates

When changing the locale, it’s crucial to update the app’s Context and Configuration to reflect the new language settings.

What is Context?

In Android, Context is an interface to global information about an application environment. It allows access to resources, databases, and other services. Updating the context with the new Locale ensures that all parts of the app (activities, fragments, custom views) use the correct language.

Updating Context in an Activity

To update the context in an activity and apply the language change:

override fun attachBaseContext(newBase: Context?) {
    super.attachBaseContext(newBase?.let { LocaleHelper.setLocale(it, "es") }) // Set to Spanish
}

4. Configuring the Android Manifest for Language Support

The Android Manifest file is a configuration file where you declare essential information about your app, including its components and how it handles configurations like language changes.

Manifest Configuration for Multiple Languages

<application
    android:supportsRtl="true"  <!-- Support for Right-To-Left languages -->
    android:configChanges="locale|layoutDirection">  <!-- Handle locale and layout direction changes -->
</application>
<provider>
  <meta-data
    android:name="android.support.LANGUAGE"
    android:value="en,fr,es,ne,so" /> <!-- Support for different languages inside AndroidManifest.xml -->
</provider>
  • supportsRtl: Enables your app to support Right-To-Left (RTL) languages like Arabic and Hebrew.
  • configChanges: Including locale and layoutDirection prevents the activity from being recreated when the language changes, ensuring smooth transitions.

5. Handling Third-Party Libraries and Locale Changes

If your app uses third-party libraries, ensure they respect the app’s locale settings. Some libraries may cache configurations at startup, requiring re-initialization when the locale changes.

6. Best Practices for Language Handling

  • Persisting Locale: Store the user's language preference in persistent storage like SharedPreferences to ensure the language setting is retained even after the app restarts.
  • Localization Resources: Ensure all string resources are correctly localized. Place them in res/values-<language> directories (e.g., res/values-es for Spanish).
  • Testing: Test your application in all supported languages, including RTL languages, to verify that all UI elements adapt correctly to language changes.

7. Example Project Structure

Here's an example of how you might organize your project to handle localization:

- app/
    - src/
        - main/
            - java/
                - com/example/app/
                    - MyApp.kt
                    - MainActivity.kt
                    - LocaleHelper.kt
            - res/
                - values/
                    - strings.xml
                - values-es/
                    - strings.xml
                - values-ar/
                    - strings.xml  (for Arabic - RTL)

By following these guidelines, you can ensure your Android application effectively manages language changes, providing a seamless and localized experience to users across different regions and languages.