Tech Stack Migration (技術遷移)

Name: Tech Stack Migration
Rating: 92
Author: BryantChi

Instructions

•僅在需要漸進式遷移時使用
•依照下方章節順序套用
•一次只替換一個技術棧
•完成後對照 Quick Checklist

When to Use

•Scenario C：舊專案現代化

Example Prompts

•"請依照 View → Compose 章節，幫我嵌入 ComposeView"
•"用 RxJava → Flow 對照表，改寫這段 stream"
•"請用 LiveData → StateFlow 的步驟規劃遷移"

Workflow

•先確認要遷移的技術棧與範圍
•依序套用對應章節的範例與對照表
•最後用 Quick Checklist 驗收

Practical Notes (2026)

•遷移必先有可驗證的測試安全網
•一次只遷移一個維度（UI 或 Data 或 DI）
•指標回歸後才能推進下一步

Minimal Template

code

目標: 
遷移範圍: 
測試安全網: 
回歸指標: 
驗收: Quick Checklist

View → Compose Interoperability

Compose in XML

xml

<!-- layout/activity_main.xml -->
<androidx.compose.ui.platform.ComposeView
    android:id="@+id/compose_view"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" />

kotlin

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        
        findViewById<ComposeView>(R.id.compose_view).setContent {
            AppTheme {
                NewFeatureCard()
            }
        }
    }
}

XML in Compose

kotlin

@Composable
fun LegacyMapView(modifier: Modifier = Modifier) {
    AndroidView(
        modifier = modifier,
        factory = { context ->
            MapView(context).apply {
                onCreate(null)
            }
        },
        update = { mapView ->
            mapView.getMapAsync { /* configure */ }
        },
        onRelease = { mapView ->
            mapView.onDestroy()
        }
    )
}

Fragment in Compose

kotlin

@Composable
fun LegacyFragmentContainer() {
    AndroidViewBinding(LegacyFragmentContainerBinding::inflate) {
        val fragment = LegacyFragment()
        fragmentContainerView.getFragment<Fragment>() ?: run {
            (LocalContext.current as FragmentActivity)
                .supportFragmentManager
                .beginTransaction()
                .replace(fragmentContainerView.id, fragment)
                .commit()
        }
    }
}

RxJava → Coroutines/Flow

Operator Mapping

RxJava	Coroutines/Flow	備註
`Observable`	`Flow`	Cold stream
`Single`	`suspend fun`	單值
`Completable`	`suspend fun`	無回傳
`flatMap`	`flatMapLatest`	取消前一個
`flatMap`	`flatMapConcat`	依序執行
`switchMap`	`flatMapLatest`	等同
`debounce`	`debounce`	相同
`combineLatest`	`combine`	相同
`zip`	`zip`	相同
`observeOn(main)`	`flowOn(Dispatchers.Main)`	注意位置不同
`subscribeOn(io)`	`flowOn(Dispatchers.IO)`	影響上游

範例：Search with Debounce

kotlin

// Before (RxJava)
searchEditText.textChanges()
    .debounce(300, TimeUnit.MILLISECONDS)
    .switchMap { query -> api.search(query) }
    .observeOn(AndroidSchedulers.mainThread())
    .subscribe { results -> updateUI(results) }

// After (Flow)
searchFlow
    .debounce(300)
    .flatMapLatest { query -> api.search(query) }
    .flowOn(Dispatchers.IO)
    .collect { results -> updateUI(results) }

Error Handling 差異

kotlin

// RxJava: onError 終止 stream
observable
    .onErrorReturn { defaultValue }
    .subscribe()

// Flow: catch 不終止 stream
flow
    .catch { emit(defaultValue) }
    .collect()

// Flow: 重試
flow
    .retry(3) { e -> e is IOException }
    .collect()

LiveData → StateFlow

漸進式替換

kotlin

// Step 1: ViewModel 內部用 StateFlow
private val _uiState = MutableStateFlow(UiState())
val uiState: StateFlow<UiState> = _uiState.asStateFlow()

// Step 2: 暴露 LiveData 給舊 UI (過渡期)
val uiStateLiveData: LiveData<UiState> = uiState.asLiveData()

// Step 3: 新 UI 直接 collect StateFlow
@Composable
fun Screen(viewModel: MyViewModel) {
    val uiState by viewModel.uiState.collectAsStateWithLifecycle()
}

Dagger → Hilt

漸進式遷移

kotlin

// 1. 保留 Dagger Component，加入 Hilt
@HiltAndroidApp
class MyApp : Application() {
    // 保留舊的 Dagger component (過渡期)
    val legacyComponent by lazy { DaggerLegacyComponent.create() }
}

// 2. 新模組用 Hilt
@Module
@InstallIn(SingletonComponent::class)
object NewModule { }

// 3. 橋接舊模組
@Module
@InstallIn(SingletonComponent::class)
object LegacyBridgeModule {
    @Provides
    fun provideLegacyService(): LegacyService {
        return (application as MyApp).legacyComponent.legacyService()
    }
}

Quick Checklist

• Compose 與 View 的生命週期對齊
• AndroidView 正確處理 onRelease
• Flow operator 對照 RxJava 正確
• StateFlow 使用 collectAsStateWithLifecycle
• Hilt 遷移維持向後相容