Merge pull request #7 from colonal/force_reload_indexes

Add `autoDisposeIndexes` to dispose unused IndexedStack children and rebuild them when needed

Author: okaryo

README.md

@@ -3,23 +3,25 @@
 
 # lazy_load_indexed_stack
 
-A package that extends IndexedStack to allow for lazy loading.
+A package that extends IndexedStack to allow for lazy loading and provides enhanced control for reloading specific child widgets.
 
 ## Motivation
 
-If you use the IndexedStack with bottom navigation, all the widgets specified in the children of the IndexedStack will be built.
+If you use the IndexedStack with bottom navigation, all the widgets specified in the children of the IndexedStack will be built.  
 
-Moreover, if the widget requires API requests or database access, or has a complex UI, the IndexedStack build time will be significant.
+Moreover, if the widget requires API requests or database access, or has a complex UI, the IndexedStack build time will be significant.  
 
-Therefore, we created an extended IndexedStack that builds the required widget only when it is needed, and returns the pre-built widget when it is needed again.
+Therefore, we created an extended IndexedStack that builds the required widget only when it is needed and returns the pre-built widget when it is needed again.
 
 ## Features
 * **Lazy Loading**: The main feature of `LazyLoadIndexedStack` is to build children widgets only when they are needed, reducing initial load time.
 * **Preloading**: With the `preloadIndexes` parameter, you can specify indexes of children that should be built in advance, even if they are not currently visible. This is useful for preloading widgets that are likely to be needed soon.
+* **Auto Disposal**: The `autoDisposeIndexes` parameter allows specific children to be automatically disposed of when they are no longer visible. When these children are accessed again, they will be rebuilt from scratch. This is useful for cases where widgets hold significant state or require resetting when revisited.
 
 ## Usage
-You can use `LazyLoadIndexedStack` in the same way as `IndexedStack`.
+You can use `LazyLoadIndexedStack` in the same way as `IndexedStack`, with additional options for preloading and auto dispose.
 
+### Basic Example
 ```dart
 class MainPage extends StatefulWidget {
   @override
@@ -36,11 +38,12 @@ class _MainPageState extends State<MainPage> {
         body: LazyLoadIndexedStack(
           index: _index,
           preloadIndexes: const [3],
+          autoDisposeIndexes: const [1, 2],
           children: [
             Page1(),
-            Page2(),
-            Page3(),
-            Page4(), // index3 is preloaded
+            Page2(), // index 1 will be auto dispose
+            Page3(), // index 2 will also auto dispose
+            Page4(), // index 3 is preloaded
           ],
         ),
         bottomNavigationBar: BottomNavigationBar(

lib/lazy_load_indexed_stack.dart

@@ -1,5 +1,3 @@
-library lazy_load_indexed_stack;
-
 import 'package:flutter/widgets.dart';
 
 /// An extended IndexedStack that builds the required widget only when it is needed, and returns the pre-built widget when it is needed again.
@@ -10,6 +8,9 @@ class LazyLoadIndexedStack extends StatefulWidget {
   /// The indexes of children that should be preloaded.
   final List<int> preloadIndexes;
 
+  /// The indexes of children that should be automatically disposed and rebuilt when accessed again.
+  final List<int> autoDisposeIndexes;
+
   /// Same as alignment attribute of original IndexedStack.
   final AlignmentGeometry alignment;
 
@@ -33,6 +34,7 @@ class LazyLoadIndexedStack extends StatefulWidget {
     super.key,
     Widget? unloadWidget,
     this.preloadIndexes = const [],
+    this.autoDisposeIndexes = const [],
     this.alignment = AlignmentDirectional.topStart,
     this.sizing = StackFit.loose,
     this.textDirection,
@@ -65,6 +67,8 @@ class LazyLoadIndexedStackState extends State<LazyLoadIndexedStack> {
       _children = _initialChildren();
     }
 
+    _children = _updateChildrenForAutoDispose();
+
     _children[widget.index] = widget.children[widget.index];
   }
 
@@ -92,4 +96,17 @@ class LazyLoadIndexedStackState extends State<LazyLoadIndexedStack> {
       }
     }).toList();
   }
+
+  List<Widget> _updateChildrenForAutoDispose() {
+    return widget.children.asMap().entries.map((entry) {
+      final index = entry.key;
+      final childWidget = entry.value;
+
+      if (index != widget.index && widget.autoDisposeIndexes.contains(index)) {
+        return widget.unloadWidget;
+      } else {
+        return childWidget;
+      }
+    }).toList();
+  }
 }