feat: 添加布局和路由组件

lib/views/HomePage.dart

@@ -0,0 +1,10 @@
+import 'package:flutter/material.dart';
+
+class HomePage extends StatelessWidget {
+  const HomePage({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(body: Center(child: Text("Home")));
+  }
+}

lib/views/LoginPage.dart

@@ -0,0 +1,66 @@
+import 'package:flutter/material.dart';
+import 'package:flutter/widget_previews.dart';
+import 'package:go_router/go_router.dart';
+
+class LoginPage extends StatelessWidget {
+  const LoginPage({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(title: Text('登录')),
+      body: Padding(
+        padding: const EdgeInsets.all(16),
+        child: Column(
+          crossAxisAlignment: CrossAxisAlignment.center,
+          children: [
+            const Text('登录', style: TextStyle(fontSize: 24)),
+            const SizedBox(height: 16),
+            Row(
+              children: [
+                Expanded(flex: 1, child: const Text('用户名：')),
+                const SizedBox(width: 8),
+                Expanded(
+                  flex: 4,
+                  child: TextField(
+                    decoration: const InputDecoration(hintText: '请输入用户名'),
+                  ),
+                ),
+              ],
+            ),
+            Row(
+              children: [
+                Expanded(flex: 1, child: const Text('密码：')),
+                const SizedBox(width: 8),
+                Expanded(
+                  flex: 4,
+                  child: TextField(
+                    decoration: const InputDecoration(hintText: '请输入密码'),
+                    obscureText: true,
+                  ),
+                ),
+              ],
+            ),
+
+            const SizedBox(height: 16),
+
+            ElevatedButton(
+              onPressed: () {
+                context.go('/home');
+              },
+              style: ElevatedButton.styleFrom(
+                minimumSize: const Size(double.infinity, 48),
+              ),
+              child: const Text('登录'),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+}
+
+// ========== 组件预览（顶层函数） ==========
+
+@Preview(name: 'LoginPage 默认状态')
+Widget loginPagePreview() => const LoginPage();

lib/views/main.dart

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+import 'package:flutter/material.dart';
+import 'package:go_router/go_router.dart';
+
+import 'HomePage.dart';
+import 'LoginPage.dart';
+
+void main() {
+  runApp(MainApp());
+}
+
+class MainApp extends StatelessWidget {
+  MainApp({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp.router(routerConfig: _route);
+  }
+
+  final _route = GoRouter(
+    initialLocation: '/login',
+    routes: <RouteBase>[
+      GoRoute(path: '/login', builder: (context, state) => const LoginPage()),
+      StatefulShellRoute.indexedStack(
+        builder: (context, state, navigationShell) => Scaffold(
+          body: navigationShell,
+          bottomNavigationBar: BottomNavigationBar(
+            items: const [
+              BottomNavigationBarItem(icon: Icon(Icons.home), label: 'Home'),
+              BottomNavigationBarItem(
+                icon: Icon(Icons.settings),
+                label: 'Settings',
+              ),
+            ],
+            onTap: (index) {
+              navigationShell.goBranch(index); // 跳转到GoRoute中定义的分支
+            },
+          ),
+        ),
+        branches: <StatefulShellBranch>[
+          StatefulShellBranch(
+            routes: <RouteBase>[
+              GoRoute(
+                path: '/home',
+                builder: (context, state) => const HomePage(),
+              ),
+            ],
+          ),
+          StatefulShellBranch(
+            routes: <RouteBase>[
+              GoRoute(
+                path: '/settings',
+                builder: (context, state) => const Text('Settings'),
+              ),
+            ],
+          ),
+        ],
+      ),
+    ],
+  );
+}