Improved example app. Extracted loading page to a separate file.

example/lib/loading_page.dart

@@ -0,0 +1,45 @@
+import 'package:flutter/material.dart';
+
+class LoadingPage extends StatefulWidget {
+  @override
+  _LoadingPageState createState() => _LoadingPageState();
+}
+
+class _LoadingPageState extends State<LoadingPage> {
+  bool _loading = true;
+
+  @override
+  void initState() {
+    Future.delayed(Duration(seconds: 1)).then((e) {
+      setState(() {
+        _loading = false;
+      });
+    });
+    super.initState();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Center(
+      child: _loading
+          ? Container(
+              child: Text(
+                "Loading....",
+                style: TextStyle(
+                  fontSize: 30.0,
+                  color: Colors.blue,
+                ),
+              ),
+            )
+          : Container(
+              child: Text(
+                "Loaded",
+                style: TextStyle(
+                  fontSize: 30.0,
+                  color: Colors.green,
+                ),
+              ),
+            ),
+    );
+  }
+}

example/lib/main.dart

@@ -2,27 +2,19 @@ import 'package:flutter/material.dart';
 
 import 'package:lazy_indexed_stack/lazy_indexed_stack.dart';
 
+import 'loading_page.dart';
+
 void main() => runApp(MyApp());
 
 class MyApp extends StatelessWidget {
-  // This widget is the root of your application.
   @override
   Widget build(BuildContext context) {
     return MaterialApp(
       title: 'Flutter Demo',
       theme: ThemeData(
-        // This is the theme of your application.
-        //
-        // Try running your application with "flutter run". You'll see the
-        // application has a blue toolbar. Then, without quitting the app, try
-        // changing the primarySwatch below to Colors.green and then invoke
-        // "hot reload" (press "r" in the console where you ran "flutter run",
-        // or simply save your changes to "hot reload" in a Flutter IDE).
-        // Notice that the counter didn't reset back to zero; the application
-        // is not restarted.
         primarySwatch: Colors.blue,
       ),
-      home: MyHomePage(title: 'Flutter Demo Home Page'),
+      home: MyHomePage(title: 'LazyIndexedStack demo'),
     );
   }
 }
@@ -36,78 +28,50 @@ class MyHomePage extends StatefulWidget {
   _MyHomePageState createState() => _MyHomePageState();
 }
 
-class LoadingPage extends StatefulWidget {
-  @override
-  _LoadingPageState createState() => _LoadingPageState();
-}
-
-class _LoadingPageState extends State<LoadingPage> {
-  bool loading = true;
-
-  @override
-  void initState() {
-    Future.delayed(new Duration(seconds: 2)).then((e) {
-      setState(() {
-        loading = false;
-      });
-    });
-    super.initState();
-  }
-
-  @override
-  Widget build(BuildContext context) {
-    return loading
-        ? new Container(
-            child: new Text("loading...."),
-          )
-        : Container(
-            child: new Text("load success"),
-          );
-  }
-}
-
 class _MyHomePageState extends State<MyHomePage> {
-  int _counter = 0;
-  int index = 0;
+  int _selectedIndex = 0;
 
   @override
   Widget build(BuildContext context) {
     return Scaffold(
       appBar: AppBar(
-        // Here we take the value from the MyHomePage object that was created by
-        // the App.build method, and use it to set our appbar title.
         title: Text(widget.title),
       ),
-      body: new LazyIndexedStack(
+      body: LazyIndexedStack(
         reuse: false,
-        index: index,
+        index: _selectedIndex,
         itemBuilder: (c, i) {
           return LoadingPage();
         },
         itemCount: 4,
       ),
-      bottomNavigationBar: new BottomNavigationBar(
+      bottomNavigationBar: BottomNavigationBar(
+        type: BottomNavigationBarType.fixed,
+        backgroundColor: Colors.blueGrey,
+        selectedItemColor: Colors.amber,
+        unselectedItemColor: Colors.white70,
         items: [
-          new BottomNavigationBarItem(
-              icon: new Icon(
-                Icons.add,
-                color: Colors.black38,
-              ),
-              title: new Text("add")),
-          new BottomNavigationBarItem(
-              icon: new Icon(Icons.add, color: Colors.black38),
-              title: new Text("add")),
-          new BottomNavigationBarItem(
-              icon: new Icon(Icons.add, color: Colors.black38),
-              title: new Text("add")),
-          new BottomNavigationBarItem(
-              icon: new Icon(Icons.add, color: Colors.black38),
-              title: new Text("add")),
+          BottomNavigationBarItem(
+            icon: Icon(Icons.add, color: Colors.white),
+            title: Text("one"),
+          ),
+          BottomNavigationBarItem(
+            icon: Icon(Icons.add, color: Colors.white),
+            title: Text("two"),
+          ),
+          BottomNavigationBarItem(
+            icon: Icon(Icons.add, color: Colors.white),
+            title: Text("three"),
+          ),
+          BottomNavigationBarItem(
+            icon: Icon(Icons.add, color: Colors.white),
+            title: Text("four"),
+          ),
         ],
-        currentIndex: index,
+        currentIndex: _selectedIndex,
         onTap: (i) {
           setState(() {
-            index = i;
+            _selectedIndex = i;
           });
         },
       ),