mathtool2/lib/main.dart

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

import 'calculator_page.dart';
import 'console_page.dart';
import 'symja.dart';
import 'tools_page.dart';

void main() => runApp(const CalApp());

class CalApp extends StatelessWidget {
  const CalApp({super.key});

  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider(
      create: (_) => SymjaSession(),
      child: MaterialApp(
        title: '某人的计算器2',
        debugShowCheckedModeBanner: false,
        theme: ThemeData(colorSchemeSeed: Colors.indigo, useMaterial3: true),
        home: const ShellPage(),
      ),
    );
  }
}

/// 三个界面（Q16 的「双界面」+ 插件页）：
///   计算器 —— 默认入口，卡西欧式按键
///   工具   —— 16 个插件的网格入口
///   控制台 —— 表达式 REPL
///
/// 用 IndexedStack 保住各页状态：切回来时控制台的历史、计算器正在输入的
/// 表达式都还在。
class ShellPage extends StatefulWidget {
  const ShellPage({super.key});

  @override
  State<ShellPage> createState() => _ShellPageState();
}

class _ShellPageState extends State<ShellPage> {
  int _index = 0;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: IndexedStack(
        index: _index,
        children: const [
          CalculatorPage(),
          ToolsPage(),
          ConsolePage(),
        ],
      ),
      bottomNavigationBar: NavigationBar(
        selectedIndex: _index,
        onDestinationSelected: (i) => setState(() => _index = i),
        destinations: const [
          NavigationDestination(
            icon: Icon(Icons.calculate_outlined),
            selectedIcon: Icon(Icons.calculate),
            label: '计算器',
          ),
          NavigationDestination(
            icon: Icon(Icons.widgets_outlined),
            selectedIcon: Icon(Icons.widgets),
            label: '工具',
          ),
          NavigationDestination(
            icon: Icon(Icons.terminal_outlined),
            selectedIcon: Icon(Icons.terminal),
            label: '控制台',
          ),
        ],
      ),
    );
  }
}