# Android Native Architecture The Android implementation provides native navigation using Views and ViewGroups (not Fragments), coordinated through a TurboModule that receives commands from JavaScript. ## App Integration ### NavigationApplication **File**: `NavigationApplication.java` Abstract Application class that user's MainApplication must extend: ```kotlin // MainApplication.kt - User extends NavigationApplication class MainApplication : NavigationApplication() { override val reactNativeHost: ReactNativeHost get() = NavigationReactNativeHost(this) // Must use NavigationReactNativeHost } ``` **What NavigationApplication does:** - Initializes SoLoader - Provides `ReactGateway` singleton for React lifecycle - Offers `registerExternalComponent()` for native screens ### NavigationActivity **File**: `NavigationActivity.java` Base Activity that user's MainActivity must extend: ```kotlin // MainActivity.kt - User extends NavigationActivity class MainActivity : NavigationActivity() { // No getMainComponentName() needed - navigation handles root } ``` **What NavigationActivity does:** - Creates `Navigator` with root, modal, and overlay layouts - Manages back press via `OnBackPressedCallback` - Coordinates React lifecycle with activity lifecycle ### NavigationReactNativeHost **File**: `react/NavigationReactNativeHost.kt` Custom ReactNativeHost that integrates with navigation: - Used instead of `DefaultReactNativeHost` - Provides proper module registration for navigation ### Autolink Script (`npx rnn-link`) The `autolink/postlink/postLinkAndroid.js` script automates setup: | Linker | What it does | |--------|--------------| | `ApplicationLinker` | Changes MainApplication to extend `NavigationApplication`, uses `NavigationReactNativeHost`, removes SoLoader.init() | | `ActivityLinker` | Changes MainActivity to extend `NavigationActivity`, removes `getMainComponentName()` | | `GradleLinker` | Updates build.gradle if needed | **ApplicationLinker transformations:** - `class MainApplication : Application(), ReactApplication` → `class MainApplication : NavigationApplication()` - `DefaultReactNativeHost(this)` → `NavigationReactNativeHost(this)` - Removes `SoLoader.init()` (NavigationApplication handles it) - Removes new architecture entry point load block **ActivityLinker transformations:** - `class MainActivity : ReactActivity()` → `class MainActivity : NavigationActivity()` - Removes `getMainComponentName()` override - Removes `createReactActivityDelegate()` override ## Directory Structure ``` android/src/main/java/com/reactnativenavigation/ ├── NavigationActivity.java # Main Activity entry point ├── NavigationApplication.java # Application class ├── NavigationPackage.kt # React package registration ├── react/ # React bridge layer │ ├── NavigationTurboModule.kt # TurboModule implementation │ ├── ReactGateway.java # React lifecycle management │ └── events/ │ └── EventEmitter.java # Event emission to JS ├── options/ # Options parsing and factories │ ├── LayoutFactory.java # Creates ViewControllers from layout nodes │ └── Options.java # Options model ├── viewcontrollers/ # ViewController hierarchy │ ├── ViewController.java # Base class │ ├── ChildController.java # With presenter support │ ├── ParentController.java # Container controllers │ ├── stack/ # Stack navigation │ ├── bottomtabs/ # Bottom tabs │ ├── toptabs/ # Top tabs (lowercase) │ ├── sidemenu/ # Side menu/drawer │ ├── modal/ # Modal management │ └── externalcomponent/ # Native component support ├── views/ # UI View implementations ├── utils/ # Utilities └── hierarchy/ # Root layout management ``` ## Bridge Architecture ``` ┌────────────────────────────────────────────────────────────┐ │ JavaScript (TurboModule) │ └─────────────────────────┬──────────────────────────────────┘ │ ┌─────────────────────────▼──────────────────────────────────┐ │ NavigationTurboModule.kt │ │ - setRoot, push, pop, showModal, dismissModal, etc. │ └─────────────────────────┬──────────────────────────────────┘ │ ┌─────────────────────────▼──────────────────────────────────┐ │ Navigator (Root ViewController) │ │ - Manages root, modals, overlays │ │ - Coordinates LayoutFactory │ └──────┬──────────────┬──────────────┬──────────────┬────────┘ │ │ │ │ ┌──────▼─────┐ ┌──────▼─────┐ ┌──────▼─────┐ ┌─────▼──────┐ │ModalStack │ │OverlayMgr │ │LayoutFactory│ │EventEmitter│ └────────────┘ └────────────┘ └────────────┘ └────────────┘ ``` ## Entry Points ### NavigationApplication Abstract Application class that apps extend: - Manages `ReactGateway` singleton - Initializes SoLoader - Provides `registerExternalComponent()` for native screens ### NavigationActivity Main Activity containing all navigation: - Creates `Navigator` with three CoordinatorLayouts: - `rootLayout` - Main navigation content - `modalsLayout` - Modal stack - `overlaysLayout` - Overlays (highest z-order) - Handles back press via `OnBackPressedCallback` - Coordinates activity lifecycle with React ### NavigationTurboModule TurboModule implementation (Kotlin, ~300 lines): ```kotlin @ReactMethod fun setRoot(commandId: String, layout: ReadableMap, promise: Promise) @ReactMethod fun push(commandId: String, componentId: String, layout: ReadableMap, promise: Promise) @ReactMethod fun showModal(commandId: String, layout: ReadableMap, promise: Promise) ``` All commands execute on UI thread via `UiThread.post()`. ## ViewController Hierarchy **Note**: Android implementation does NOT use Fragments - it's purely View-based. ``` ViewController (abstract) │ - Base for all navigation controllers │ - Manages view creation and lifecycle │ - Handles options and back press │ ├── ChildController │ │ - Adds Presenter support │ │ │ ├── ComponentViewController │ │ - Renders React components via ReactView │ │ │ └── ExternalComponentViewController │ - Wraps native Android views │ └── ParentController (extends ChildController) - Container for child controllers │ ├── StackController │ - Push/pop navigation │ - Uses IdStack │ ├── BottomTabsController │ - UITabBarController equivalent │ - Uses AHBottomNavigation │ ├── TopTabsController │ - Horizontal ViewPager tabs │ ├── SideMenuController │ - DrawerLayout-based drawer │ └── Navigator - Root controller - Manages modals and overlays ``` ## Core Classes ### ViewController (Base) **File**: `viewcontrollers/viewcontroller/ViewController.java` (~500 lines) Abstract base for all navigation controllers: ```java public abstract class ViewController { protected abstract T createView(); // Subclasses create views public void onViewWillAppear() { } public void onViewDidAppear() { } public void onViewDisappear() { } public void mergeOptions(Options options) { } public void applyOptions(Options options) { } public boolean handleBack(CommandListener listener) { } public void destroy() { } } ``` ### Navigator (Root) **File**: `viewcontrollers/navigator/Navigator.java` Root ViewController managing: - Root content hierarchy - Modal stack (`ModalStack`) - Overlay manager (`OverlayManager`) - Component lookup by ID ### LayoutFactory **File**: `options/LayoutFactory.java` Factory creating ViewControllers from LayoutNode. Owned by `NavigationTurboModule` and used to build the view controller hierarchy when commands are received from JavaScript. ```java public ViewController create(LayoutNode node) { switch (node.type) { case Component: return createComponent(node); case Stack: return createStack(node); case BottomTabs: return createBottomTabs(node); case SideMenuRoot: return createSideMenuRoot(node); case SideMenuCenter: return createSideMenuContent(node); case SideMenuLeft: return createSideMenuLeft(node); case SideMenuRight: return createSideMenuRight(node); case TopTabs: return createTopTabs(node); // Note: SplitView is iOS-only, not implemented on Android } } ``` ## Navigation Types ### Stack Navigation (StackController) **Files**: `viewcontrollers/stack/` - View: `StackLayout` (CoordinatorLayout with TopBar) - Internal stack: `IdStack>` - Components: `TopBarController`, `StackAnimator`, `StackPresenter`, `FabPresenter` Operations: - `push(viewController, listener)` - `pop(options, listener)` - `popTo(target, options, listener)` - `popToRoot(options, listener)` - `setRoot(children, listener)` ### Bottom Tabs (BottomTabsController) **Files**: `viewcontrollers/bottomtabs/` - View: `BottomTabsLayout` (CoordinatorLayout with BottomTabs) - Uses `AHBottomNavigation` library - Components: `BottomTabsPresenter`, `BottomTabPresenter`, `BottomTabsAnimator` Attachment Modes: - `TogetherAttacher` - Load all tabs immediately - `OnSwitchToTabAttacher` - Lazy load on selection - `AfterInitialTabAttacher` - Load initial + others in background ### Side Menu (SideMenuController) **Files**: `viewcontrollers/sidemenu/` - View: `SideMenuRoot` (DrawerLayout-based) - Children: Center, Left, Right controllers - `SideMenuPresenter` for styling ### Top Tabs (TopTabsController) **Files**: `viewcontrollers/toptabs/` - View: `TopTabsViewPager` (ViewPager-based) - `TopTabsLayoutCreator` for view creation ### Modals (ModalStack) **Files**: `viewcontrollers/modal/` Not a ViewController - manages modal presentation: - `ModalPresenter` - Show/dismiss with animations - `ModalAnimator` (Kotlin) - Animation handling - Stack of modals with lifecycle management ### Overlays (OverlayManager) **File**: `viewcontrollers/overlay/OverlayManager.kt` Registry of active overlays: - Show/dismiss by component ID - Configuration change handling - Host pause/resume lifecycle ## React Component Rendering ### ComponentViewController Manages React component lifecycle: - Creates `ComponentLayout` view - Initializes `ReactView` with ReactSurface - Emits lifecycle events to JS - Handles scroll events and status bar ### ReactView **File**: `react/ReactView.java` Extends FrameLayout, wraps `ReactSurface`: - `start()` - Attach surface to React instance - `destroy()` - Clean up React surface - `sendComponentWillStart()` - Emit event to JS - `isReady()` - Check surface attachment ## Event Emission ### EventEmitter **File**: `react/events/EventEmitter.java` Events sent to JavaScript: | Event | Description | |-------|-------------| | `RNN.AppLaunched` | App initialization complete | | `RNN.ComponentDidAppear` | Component visible | | `RNN.ComponentWillAppear` | About to become visible | | `RNN.ComponentDidDisappear` | Component hidden | | `RNN.NavigationButtonPressed` | TopBar button tapped | | `RNN.BottomTabSelected` | Tab selection changed | | `RNN.BottomTabPressed` | Tab pressed (even if selected) | | `RNN.ModalDismissed` | Modal was dismissed | | `RNN.ScreenPopped` | Screen removed from stack | | `RNN.CommandCompleted` | Navigation command finished | ## Options System ### Options Class **File**: `options/Options.java` ```java public class Options { public TopBarOptions topBar; public TopTabsOptions topTabs; public BottomTabsOptions bottomTabsOptions; public BottomTabOptions bottomTabOptions; public OverlayOptions overlayOptions; public FabOptions fabOptions; public AnimationsOptions animations; public SideMenuRootOptions sideMenuRootOptions; public ModalOptions modal; public StatusBarOptions statusBar; public NavigationBarOptions navigationBar; public LayoutOptions layout; public HardwareBackButtonOptions hardwareBack; } ``` ### Options Flow 1. **Parse**: JSON from JS → Options object via JSONParser 2. **Merge**: Default → Screen → Component options 3. **Apply**: Presenter applies to views ## Presenter Pattern Each ViewController has a Presenter: | ViewController | Presenter | |---------------|-----------| | StackController | StackPresenter | | BottomTabsController | BottomTabsPresenter + BottomTabPresenter | | ComponentViewController | ComponentPresenter | | SideMenuController | SideMenuPresenter | | Navigator | RootPresenter | ### Presenter Base **File**: `viewcontrollers/viewcontroller/Presenter.java` Handles: - Orientation changes - Status bar styling - Navigation bar styling - Layout parameters ## Animation System ### Animators (Kotlin) - `StackAnimator.kt` - Push, pop, setRoot animations - `ModalAnimator.kt` - Modal show/dismiss - `BottomTabsAnimator.kt` - Tab transitions - `TopBarAppearanceAnimator.kt` - Top bar changes ### Element Transitions Via `TransitionAnimatorCreator.kt`: - Position, scale, rotation animations - Color transitions - Corner radius animations - Shared element support ## Activity Lifecycle ```java onCreate() // Create Navigator, initialize React onPostCreate() // Set content layout onResume() // React host resume, event emitter setup onPause() // React host pause onDestroy() // Clean up Navigator onConfigurationChanged() // Handle orientation, locale onNewIntent() // Process deep links onActivityResult() // Handle permissions ``` ## ViewController Lifecycle ``` View creation ↓ onViewWillAppear() // Register with registry ↓ onViewDidAppear() // Emit event to JS ↓ [visible] ↓ onViewWillDisappear() ↓ onViewDisappear() // Unregister from registry ↓ destroy() // Complete cleanup ``` ## Key Files Reference All paths relative to `android/src/main/java/com/reactnativenavigation/`: | File | Path | Purpose | |------|------|---------| | NavigationActivity.java | `.` | Main Activity | | NavigationApplication.java | `.` | Application class | | NavigationTurboModule.kt | `react/` | JS bridge | | Navigator.java | `viewcontrollers/navigator/` | Root controller | | ViewController.java | `viewcontrollers/viewcontroller/` | Base class | | StackController.java | `viewcontrollers/stack/` | Stack navigation | | BottomTabsController.java | `viewcontrollers/bottomtabs/` | Tab navigation | | LayoutFactory.java | `options/` | Controller factory | | Options.java | `options/` | Options model | | Presenter.java | `viewcontrollers/viewcontroller/` | Base presenter | | EventEmitter.java | `react/events/` | JS events | | ReactView.java | `react/` | React component wrapper | | StackAnimator.kt | `viewcontrollers/stack/` | Stack animations | | ModalStack.java | `viewcontrollers/modal/` | Modal management |