indexd_stack_dev 0.1.3

A high-performance lazy-loading IndexedStack for Flutter that initializes pages only when needed.

indexd_stack_dev

A high-performance lazy-loading IndexedStack for Flutter with a custom RenderObject pipeline and native tab transitions. Pages are initialized only when accessed, and inactive tabs consume zero layout or paint resources.

Features

• 🚀 Custom RenderObject: Only the active child participates in layout — inactive cached pages are completely skipped
• ⚡ Native Animations: Fade, FadeThrough, SharedAxis transitions built without external dependencies
• 💾 LRU Cache: Configurable maxCachedPages with automatic least-recently-used eviction
• 🧹 Memory Pressure: Automatic cache flush on OS memory warnings via WidgetsBindingObserver
• 🔄 TickerMode: Animations in background tabs are automatically paused
• 🎯 Zero Overhead: When animation: IndexdAnimationType.none, no AnimationController is allocated

Installation

dependencies:
  indexd_stack_dev: ^0.1.0

flutter pub get

Quick Start

import 'package:indexd_stack_dev/indexd_stack_dev.dart';

class MyApp extends StatefulWidget {
  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  late LazyStackController controller;
  
  @override
  void initState() {
    super.initState();
    controller = LazyStackController(
      initialIndex: 0,
      maxCachedPages: 3,
      disposeUnused: true,
      isListenMemoryPressure: true,
    );
  }
  
  @override
  void dispose() {
    controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: LazyLoadIndexedStack(
        controller: controller,
        animation: IndexdAnimationType.fadeThrough, // or .none for zero overhead
        children: [
          HomePage(),
          ProfilePage(),
          SettingsPage(),
        ],
      ),
      bottomNavigationBar: BottomNavigationBar(
        currentIndex: controller.currentIndex,
        onTap: (index) => controller.switchTo(index, 3),
        items: const [
          BottomNavigationBarItem(icon: Icon(Icons.home), label: 'Home'),
          BottomNavigationBarItem(icon: Icon(Icons.person), label: 'Profile'),
          BottomNavigationBarItem(icon: Icon(Icons.settings), label: 'Settings'),
        ],
      ),
    );
  }
}

Animations

Pass IndexdAnimationType to control tab transitions:

LazyLoadIndexedStack(
  controller: controller,
  animation: IndexdAnimationType.sharedAxisHorizontal,
  animationDuration: const Duration(milliseconds: 300),
  children: [...],
)

Type	Description
none	Instant switch, zero allocation (default)
fade	Simple crossfade
fadeThrough	Material Design fade through (scale + fade)
sharedAxisHorizontal	Slide + fade on the X axis
sharedAxisVertical	Slide + fade on the Y axis

Animation type can be changed dynamically at runtime. Switching to none immediately disposes the AnimationController.

API Reference

LazyStackController

LazyStackController({
  int initialIndex = 0,
  List<int> preloadIndexes = const [],
  bool disposeUnused = false,
  int maxCachedPages = 3,
  bool isListenMemoryPressure = false,
})

Property	Type	Description
currentIndex	int	Currently visible page
loadedIndexes	Set<int>	Pages currently in memory
canGoBack	bool	Whether current index > 0

Method	Description
switchTo(index, totalPages)	Switch to a page with automatic cache management
disposePage(index)	Remove a specific page from memory
disposePages(indexes)	Remove multiple pages from memory
reset()	Clear all pages except current and preloaded
preloadPage(index, totalPages)	Eagerly load a page into cache
preloadAdjacentPages(totalPages, [range])	Preload pages adjacent to current
isLoaded(index)	Check if a page is in memory
didHaveMemoryPressure()	Manually trigger memory flush

LazyLoadIndexedStack

LazyLoadIndexedStack({
  required LazyStackController controller,
  required List<Widget> children,
  IndexdAnimationType animation = IndexdAnimationType.none,
  Duration animationDuration = const Duration(milliseconds: 300),
  AlignmentGeometry alignment = AlignmentDirectional.topStart,
  TextDirection? textDirection,
})

Architecture

LazyLoadIndexedStack (StatefulWidget)
  └── AnimationController? (null when animation == none)
  └── _LazyRenderStack (MultiChildRenderObjectWidget)
       └── _RenderLazyStack (RenderBox)
            ├── performLayout: only active + transitioning child
            ├── paint: outgoing first, incoming on top
            └── hitTest: only active child receives touches

License

MIT

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.