## Introduction Android's default localization uses `strings.xml` files, but many developers prefer JSON-based i18n for consistency across platforms. This guide covers both approaches and shows you how to implement robust localization in your Android app. Whether you're building a new app or maintaining an existing one, proper internationalization (i18n) is crucial for reaching global markets. Let's explore how to do it right. ## Prerequisites - Android Studio installed - Basic knowledge of Kotlin or Java - Understanding of Android resource system ## Understanding Android Localization Basics ### The Default Approach: strings.xml Android's built-in localization system uses XML files in the `res/values` directory: ```xml My App Welcome, %1$s! %d items ``` ```xml Meine App Willkommen, %1$s! %d Artikel ``` ### Why Consider JSON for Android i18n? JSON-based localization offers several advantages: 1. **Cross-platform consistency** - Same format as iOS, web, and backend 2. **Easier automation** - JSON is simpler to parse and generate 3. **Better tooling** - More translation management tools support JSON 4. **Nested structures** - Organize translations hierarchically ## Implementing JSON-Based i18n in Android ### Step 1: Create JSON Translation Files First, create your translation files in the `assets` directory: ```json // assets/i18n/en.json { "app": { "name": "My App", "welcome": "Welcome, {name}!", "items": { "one": "{count} item", "other": "{count} items" } }, "buttons": { "submit": "Submit", "cancel": "Cancel" } } ``` ```json // assets/i18n/de.json { "app": { "name": "Meine App", "welcome": "Willkommen, {name}!", "items": { "one": "{count} Artikel", "other": "{count} Artikel" } }, "buttons": { "submit": "Absenden", "cancel": "Abbrechen" } } ``` ### Step 2: Create a Translation Manager ```kotlin // TranslationManager.kt import android.content.Context import org.json.JSONObject import java.util.Locale object TranslationManager { private var translations: JSONObject? = null private var currentLocale: String = "en" fun init(context: Context, locale: String = Locale.getDefault().language) { currentLocale = locale loadTranslations(context) } private fun loadTranslations(context: Context) { try { val fileName = "i18n/$currentLocale.json" val jsonString = context.assets.open(fileName) .bufferedReader() .use { it.readText() } translations = JSONObject(jsonString) } catch (e: Exception) { // Fallback to English val jsonString = context.assets.open("i18n/en.json") .bufferedReader() .use { it.readText() } translations = JSONObject(jsonString) } } fun getString(key: String, params: Map = emptyMap()): String { val keys = key.split(".") var current: Any? = translations for (k in keys) { current = (current as? JSONObject)?.opt(k) } var result = current?.toString() ?: key // Replace placeholders params.forEach { (placeholder, value) -> result = result.replace("{$placeholder}", value.toString()) } return result } } ``` ### Step 3: Use Translations in Your App ```kotlin // MainActivity.kt class MainActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) // Initialize translations TranslationManager.init(this) // Use translations val welcomeText = TranslationManager.getString( "app.welcome", mapOf("name" to "John") ) // Result: "Welcome, John!" val itemsText = TranslationManager.getString( "app.items.other", mapOf("count" to 5) ) // Result: "5 items" } } ``` ## Handling Plurals in Android JSON i18n Android's default plurals system is powerful but complex. Here's how to implement it with JSON: ```kotlin // PluralHelper.kt object PluralHelper { fun getPlural( key: String, count: Int, params: Map = emptyMap() ): String { val pluralKey = when { count == 0 -> "$key.zero" count == 1 -> "$key.one" count == 2 -> "$key.two" count in 3..10 -> "$key.few" count in 11..99 -> "$key.many" else -> "$key.other" } // Try specific plural form, fallback to "other" val translation = TranslationManager.getString(pluralKey, params) return if (translation == pluralKey) { TranslationManager.getString("$key.other", params + ("count" to count)) } else { translation.replace("{count}", count.toString()) } } } ``` ## Best Practices for Android i18n ### 1. Placeholder Protection Always use consistent placeholder formats. The most common formats are: | Format | Example | Use Case | |--------|---------|----------| | `{name}` | `Hello, {name}!` | Named placeholders | | `%1$s` | `Hello, %1$s!` | Positional strings | | `%d` | `%d items` | Numbers | | `{{var}}` | `{{count}} items` | ICU format | ### 2. Organize by Feature ```json { "auth": { "login": { ... }, "register": { ... } }, "settings": { "profile": { ... }, "notifications": { ... } } } ``` ### 3. Include Context Comments ```json { "button_save": "Save", "_button_save_context": "Button label for saving user profile" } ``` ## Automating Android Translations Manually translating JSON files is time-consuming and error-prone. Here's how to automate the process: ### Using appstoretranslate.com 1. Export your base `en.json` file 2. Upload to [appstoretranslate.com](https://appstoretranslate.com) 3. Select target languages (29 available) 4. Download translated files The service automatically: - Preserves placeholders like `{name}` and `%1$s` - Maintains JSON structure - Handles plurals correctly - Uses Translation Memory for consistent updates ## Migrating from strings.xml to JSON If you have an existing app using strings.xml, here's a migration script: ```kotlin // StringsXmlToJson.kt import org.w3c.dom.Element import javax.xml.parsers.DocumentBuilderFactory import org.json.JSONObject fun convertStringsXmlToJson(xmlContent: String): String { val factory = DocumentBuilderFactory.newInstance() val builder = factory.newDocumentBuilder() val doc = builder.parse(xmlContent.byteInputStream()) val json = JSONObject() val strings = doc.getElementsByTagName("string") for (i in 0 until strings.length) { val element = strings.item(i) as Element val name = element.getAttribute("name") val value = element.textContent json.put(name, value) } return json.toString(2) } ``` ## Common Issues and Solutions ### Issue 1: Missing Translations at Runtime **Problem:** App crashes when translation key doesn't exist. **Solution:** Always implement fallback logic: ```kotlin fun getString(key: String, default: String = key): String { return try { // ... lookup logic result ?: default } catch (e: Exception) { default } } ``` ### Issue 2: RTL Language Support **Problem:** Right-to-left languages display incorrectly. **Solution:** Enable RTL support in your manifest: ```xml ``` ### Issue 3: Dynamic Language Switching **Problem:** User wants to change language without restarting app. **Solution:** Implement a language switcher: ```kotlin fun switchLanguage(context: Context, languageCode: String) { TranslationManager.init(context, languageCode) // Recreate activities to apply changes (context as? Activity)?.recreate() } ``` ## Conclusion JSON-based i18n in Android offers flexibility and cross-platform consistency. While strings.xml remains the default, JSON is excellent for: - Multi-platform apps (Android + iOS + Web) - Apps requiring frequent translation updates - Teams using translation management systems Ready to translate your Android app? [Try appstoretranslate.com](https://appstoretranslate.com) to automatically translate your JSON files to 29+ languages while preserving all placeholders and formatting. ## Related Resources - [Android Official Localization Guide](https://developer.android.com/guide/topics/resources/localization) - [React i18next Placeholder Guide](/blog/react-i18next-placeholder) - [Vue i18n in JavaScript Guide](/blog/vue-i18n-javascript)