Refactor (Android Architecture Aligned)

Refactor existing code to align with the official Android architecture. No external behavior changes.

Principles

• •No behavior changes: Refactoring improves internal structure only
• •Incremental steps: Avoid large changes at once
• •Build verification at each step: Revert immediately if broken

Refactoring Patterns

Layer Separation (Highest Priority)

When business logic exists in Activity/Fragment:

1. •Extract UI State as a data class
2. •Create a ViewModel and move logic into it
3. •Expose state via StateFlow<UiState>
4. •UI collects with collectAsStateWithLifecycle()
5. •Define user actions as sealed interface

Introducing Repository Pattern:

1. •Extract data access into a Repository interface
2. •Create implementation class (inject DataSource)
3. •ViewModel depends only on Repository

ViewModel Improvements

• •Consolidate multiple MutableState → single UiState data class
• •Migrate LiveData → StateFlow
• •Apply stateIn(SharingStarted.WhileSubscribed(5_000))
• •Convert one-off events to state (event → state pattern)

Compose Improvements

• •Split large Composables (one Composable ≈ one responsibility)
• •Apply state hoisting (make Composables stateless)
• •Optimize with remember / derivedStateOf
• •Add @Preview functions
• •Replace NavController passing with callback pattern

DI Introduction/Improvement

• •Migrate Manual DI → Hilt
• •@HiltViewModel + @Inject constructor
• •Use @Binds for interface bindings
• •Optimize scopes

Kotlin Idioms

• •Use when expressions
• •Convert to sealed class/sealed interface
• •Leverage extension functions
• •Remove unnecessary !! (use ?.let, requireNotNull, defaults)
• •Use data class appropriately

Build Configuration Improvements

• •Consolidate into Version Catalog (libs.versions.toml)
• •Introduce Convention Plugins (for multi-module projects)
• •Remove unused dependencies

Procedure

Step 1: Current State Analysis

• •List issues in the target code
• •Create a refactoring plan (tracked with TodoWrite)

Step 2: Incremental Execution

• •Execute one step at a time following the plan
• •After each step: ./gradlew assembleDebug

Step 3: Final Verification

./gradlew assembleDebug
./gradlew test
./gradlew lint

Step 4: Change Summary

Report before/after architecture comparison and improvements made.

Target

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