Jetpack Compose 生产级语言切换架构：ViewModel + Flow 的终极实现

最新推荐文章于 2025-06-16 08:04:13 发布

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最新推荐文章于 2025-06-16 08:04:13 发布

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分类专栏： Kotlin 文章标签： compose

本文链接：https://blog.youkuaiyun.com/tangweiguo03051987/article/details/147018482

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以下是对语言切换功能的深度优化方案，结合了现代 Android 开发的最佳实践和性能优化技巧：

1. LocaleManager (支持双向布局和系统回退)

@SuppressLint("AppBundleLocaleChanges")
object LocaleManager {
    private const val PREF_LANGUAGE_KEY = "app_language_preference"
    private val supportedLocales = mapOf(
        "en" to Locale("en"),
        "zh" to Locale("zh"),
        "es" to Locale("es"),
        "ar" to Locale("ar")  // 阿拉伯语测试RTL
    )

    // 使用内存缓存提升性能
    private var cachedLocale: Locale? = null

    fun getSupportedLanguages(): Map<String, String> = mapOf(
        "en" to "English",
        "zh" to "中文",
        "es" to "Español",
        "ar" to "العربية"
    )

    fun applyLocale(context: Context): Context {
        val locale = getSavedLocale(context)
        return updateContext(context, locale)
    }

    fun setAppLocale(context: Context, languageCode: String): Context {
        val locale = supportedLocales[languageCode] ?: Locale.getDefault()
        persistLocale(context, locale)
        cachedLocale = locale
        return updateContext(context, locale)
    }

    private fun updateContext(context: Context, locale: Locale): Context {
        Locale.setDefault(locale)
        
        val resources = context.resources
        val config = Configuration(resources.configuration).apply {
            if (Build.VERSION.SDK_INT >= 24) {
                setLocale(locale)
                setLayoutDirection(locale)
            } else {
                @Suppress("DEPRECATION")
                this.locale = locale
            }
        }

        return when {
            Build.VERSION.SDK_INT >= 24 -> {
                context.createConfigurationContext(config)
            }
            Build.VERSION.SDK_INT >= 17 -> {
                context.createConfigurationContext(config)
            }
            else -> {
                @Suppress("DEPRECATION")
                resources.updateConfiguration(config, resources.displayMetrics)
                context
            }
        }
    }

    private fun persistLocale(context: Context, locale: Locale) {
        context.getSharedPreferences("AppSettings", Context.MODE_PRIVATE).edit {
            putString(PREF_LANGUAGE_KEY, locale.language)
        }
    }

    private fun getSavedLocale(context: Context): Locale {
        return cachedLocale ?: run {
            val prefs = context.getSharedPreferences("AppSettings", Context.MODE_PRIVATE)
            val langCode = prefs.getString(PREF_LANGUAGE_KEY, null)
            supportedLocales[langCode] ?: getSystemLocale(context)
        }.also { cachedLocale = it }
    }

    private fun getSystemLocale(context: Context): Locale {
        return if (Build.VERSION.SDK_INT >= 24) {
            context.resources.configuration.locales[0]
        } else {
            @Suppress("DEPRECATION")
            context.resources.configuration.locale
        }
    }
}

2. 优化的 Activity 基类 (支持配置变更)

abstract class LocaleAwareActivity : ComponentActivity() {
    override fun attachBaseContext(newBase: Context) {
        super.attachBaseContext(LocaleManager.applyLocale(newBase))
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        observeLanguageChanges()
    }

    private fun observeLanguageChanges() {
        // 监听系统语言变化（可选）
        registerComponentActivityCallbacks(object : ComponentActivityCallbacks() {
            override fun onConfigurationChanged(newConfig: Configuration) {
                if (newConfig.locales[0] != LocaleManager.getSavedLocale(this@LocaleAwareActivity)) {
                    recreate()
                }
            }
        })
    }

    protected fun restartWithLocale(languageCode: String) {
        LocaleManager.setAppLocale(this, languageCode)
        startActivity(Intent(this, this::class.java).apply {
            flags = Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_CLEAR_TASK
        })
        overridePendingTransition(android.R.anim.fade_in, android.R.anim.fade_out)
    }
}

3. 使用 ViewModel + Flow 的状态管理

class LanguageViewModel(application: Application) : AndroidViewModel(application) {
    private val _currentLanguage = MutableStateFlow(
        LocaleManager.getSavedLocale(application).language
    )
    val currentLanguage: StateFlow<String> = _currentLanguage

    fun changeLanguage(languageCode: String) {
        _currentLanguage.value = languageCode
        LocaleManager.setAppLocale(getApplication(), languageCode)
    }
}

@Composable
fun rememberLanguageState(): LanguageViewModel {
    val factory = remember { 
        object : ViewModelProvider.Factory {
            override fun <T : ViewModel> create(modelClass: Class<T>): T {
                return LanguageViewModel(LocalContext.current.applicationContext as Application) as T
            }
        }
    }
    return viewModel(factory = factory)
}

4. 极致优化的 UI 实现

@OptIn(ExperimentalMaterial3Api::class)
@Composable
fun LanguageScreen(
    modifier: Modifier = Modifier,
    onBack: () -> Unit = {}
) {
    val viewModel = rememberLanguageState()
    val currentLanguage by viewModel.currentLanguage.collectAsState()
    val context = LocalContext.current
    
    Scaffold(
        modifier = modifier,
        topBar = {
            CenterAlignedTopAppBar(
                title = { Text(stringResource(R.string.language_settings)) },
                navigationIcon = {
                    IconButton(onClick = onBack) {
                        Icon(Icons.Default.ArrowBack, contentDescription = null)
                    }
                }
            )
        }
    ) { padding ->
        LanguageSelectionList(
            modifier = Modifier.padding(padding),
            currentLanguage = currentLanguage,
            onLanguageSelected = { lang ->
                viewModel.changeLanguage(lang)
                (context as? Activity)?.let {
                    it.restartWithLocale(lang)
                }
            }
        )
    }
}

@Composable
private fun LanguageSelectionList(
    modifier: Modifier = Modifier,
    currentLanguage: String,
    onLanguageSelected: (String) -> Unit
) {
    val languages = LocaleManager.getSupportedLanguages()
    
    LazyColumn(modifier = modifier) {
        items(languages.keys.toList()) { langCode ->
            LanguageListItem(
                languageName = languages[langCode] ?: "",
                isSelected = langCode == currentLanguage,
                onClick = { onLanguageSelected(langCode) }
            )
        }
    }
}

@Composable
private fun LanguageListItem(
    languageName: String,
    isSelected: Boolean,
    onClick: () -> Unit
) {
    ListItem(
        headlineContent = { Text(languageName) },
        trailingContent = {
            if (isSelected) {
                Icon(
                    imageVector = Icons.Default.Check,
                    contentDescription = stringResource(R.string.selected)
                )
            }
        },
        modifier = Modifier.clickable(onClick = onClick)
    )
}

5. 扩展函数简化调用

fun Context.restartApp() {
    val intent = Intent(this, MainActivity::class.java).apply {
        flags = Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_CLEAR_TASK
    }
    startActivity(intent)
    if (this is Activity) {
        overridePendingTransition(android.R.anim.fade_in, android.R.anim.fade_out)
        finish()
    }
}

fun Fragment.restartApp() {
    requireActivity().restartApp()
}