附录H：2025年Android开发趋势¶

// 数据对象（Data Objects）
sealed interface Error  // interface定义类型契约
data object NetworkError : Error  // 自动生成equals/hashCode

// 改进的类型推导
val list = buildList {  // 自动推导为MutableList<String>
    add("item")
}

// 模式匹配
when (result) {
    is Success -> process(result.data)
    is Error -> handle(result.exception)
}

// Navigation 2.8.0+ 类型安全导航
@Serializable
object Home
@Serializable
data class Detail(val id: String)

// 使用
navController.navigate(Detail(id = "123"))

// Room 2.6+ 支持Kotlin序列化
@Entity
data class User(
    @PrimaryKey val id: String,
    val name: String
)

// ML Kit设备端推理
val options = ObjectDetectorOptions.Builder()
    .setDetectorMode(ObjectDetectorOptions.SINGLE_IMAGE_MODE)
    .enableMultipleObjects()
    .enableClassification()
    .build()

val objectDetector = ObjectDetection.getClient(options)

// Gemini Nano本地模型
val generativeModel = GenerativeModel(
    modelName = "gemini-nano",
    context = applicationContext
)

// 共享业务逻辑
expect class Platform() {
    val name: String
}

// Android实现
actual class Platform actual constructor() {
    actual val name: String = "Android ${android.os.Build.VERSION.SDK_INT}"
}

// iOS实现
actual class Platform actual constructor() {
    actual val name: String = UIDevice.currentDevice.systemName()
}

// 延迟初始化
@HiltAndroidApp
class MyApplication : Application(), Initializer {
    override fun onCreate() {
        super.onCreate()
        // 异步初始化非关键组件
        ProcessLifecycleOwner.get().lifecycle.addObserver(this)
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_START)
    fun onAppForeground() {
        // 延迟初始化
    }
}

// Baseline Profiles
@Module
@InstallIn(SingletonComponent::class)
object BaselineProfileModule {
    @Provides
    @Singleton
    fun provideBaselineProfile() {
        // 使用Baseline Profile优化启动
    }
}

// 使用WeakReference避免内存泄漏
class ImageLoader {
    private val cache = WeakHashMap<String, Bitmap>()

    fun load(url: String): Bitmap? {
        return cache.getOrPut(url) {
            downloadImage(url)
        }
    }
}

// 协程作用域管理
class MyViewModel : ViewModel() {
    private val scope = CoroutineScope(SupervisorJob() + Dispatchers.Main)

    override fun onCleared() {
        super.onCleared()
        scope.cancel() // 自动清理协程
    }
}

// 使用WorkManager进行后台任务
val constraints = Constraints.Builder()
    .setRequiredNetworkType(NetworkType.CONNECTED)
    .setRequiresBatteryNotLow(true)
    .build()

val workRequest = PeriodicWorkRequestBuilder<SyncWorker>(
    15, TimeUnit.MINUTES
).setConstraints(constraints).build()

WorkManager.getInstance(context).enqueueUniquePeriodicWork(
    "sync",
    ExistingPeriodicWorkPolicy.KEEP,
    workRequest
)

// 加密敏感数据
class SecureStorage @Inject constructor(
    @ApplicationContext context: Context
) {
    private val masterKey = MasterKey.Builder(context)
        .setKeyScheme(MasterKey.KeyScheme.AES256_GCM)
        .build()

    private val encryptedPrefs = EncryptedSharedPreferences.create(
        context,
        "secure_prefs",
        masterKey,
        EncryptedSharedPreferences.PrefKeyEncryptionScheme.AES256_SIV,
        EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM
    )

    fun saveToken(token: String) {
        encryptedPrefs.edit().putString("auth_token", token).apply()
    }
}