adding packages

deprecated/responsive_scaffold/example/lib/main.dart

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+import 'dart:io';
+
+import 'package:flutter/material.dart';
+
+import 'package:flutter/foundation.dart';
+import 'examples/index.dart';
+
+/// main is entry point of Flutter application
+void main() {
+  // Desktop platforms aren't a valid platform.
+  if (!kIsWeb) _setTargetPlatformForDesktop();
+  return runApp(MyApp());
+}
+
+/// If the current platform is desktop, override the default platform to
+/// a supported platform (iOS for macOS, Android for Linux and Windows).
+/// Otherwise, do nothing.
+void _setTargetPlatformForDesktop() {
+  TargetPlatform targetPlatform;
+  if (Platform.isMacOS) {
+    targetPlatform = TargetPlatform.iOS;
+  } else if (Platform.isLinux || Platform.isWindows) {
+    targetPlatform = TargetPlatform.android;
+  }
+  if (targetPlatform != null) {
+    debugDefaultTargetPlatformOverride = targetPlatform;
+  }
+}
+
+class MyApp extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      theme: ThemeData.light().copyWith(accentColor: Colors.red),
+      debugShowCheckedModeBanner: false,
+      home: HomePage(),
+    );
+  }
+}
+
+class HomePage extends StatelessWidget {
+  const HomePage({
+    Key key,
+  }) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        title: Text('Responsive Examples'),
+      ),
+      body: ListView(
+        children: <Widget>[
+          ListTile(
+            title: Text('Responsive List'),
+            onTap: () => _goToScreen(context, ListExample()),
+          ),
+          ListTile(
+            title: Text('Responsive Layout'),
+            onTap: () => _goToScreen(context, LayoutExample()),
+          ),
+          ListTile(
+            title: Text('Multi Column Layout'),
+            onTap: () => _goToScreen(context, MultiColumnNavigationExample()),
+          ),
+        ],
+      ),
+    );
+  }
+
+  void _goToScreen(BuildContext context, Widget child) =>
+      Navigator.of(context).pushReplacement(
+        MaterialPageRoute(builder: (_) => child),
+      );
+}