Flutter学习记录——29.完整实践——实现一个简易日记本应用

1.知识整理

本篇练习看似简单，但是已经将应用编写的大部分需要用的功能都贯穿起来进行了实践、并提供了比较好的解决方案，将开发中可能会遇到的很多问题和难点进行了一一解决。

在进行综合实践编写前，我们先整理下我们这节课里用到的一些知识点：

• 引导页（PageView）
• 顶部 ToolBar（AppBar）
• 列表（CustomScrollView）
• 日历（三方库：fluttercustomcalendar）
• 权重（Flexible、Expanded）
• 导航组件（CupertinoTabBar）
• 弹窗（BottomSheet、SnackBar）
• 输入框（TextField）
• 通信（EventBut）
• 路由
• 下拉刷新（RefreshIndicator）
• 数据库（官方库：sqflite）
• 时间格式化
• 生命周期监听
• 返回键拦截
• List 的操作
• 复杂布局实现
• 其他

那么我们这节综合实践课，就通过以上我们学过的一些 Widget 和技术进行实现一个完整的日记本应用，过程不复杂，但是可以检验一下我们的开发实战水平。

2.项目实现

2.1 效果展示

本节课将要实现的日记本应用，效果图和功能展示如下：









我们先简单介绍下我们要实现的应用的功能： 日记本有引导页，具备列表显示功能、日记的新建、查看阅读、编辑功能，并加入了搜索功能。日记的数据存储的本地手机数据库内，提供3个页面进行切换。

1. 首先是引导页：引导页作为应用的一个基本的功能，会为大家实现并提供解决方案
2. 应用页面基本框架：包括一个底部导航栏，带三个页面切换，并在切换时保持页面数据状态
3. 日记的增删改查功能：存储在手机自带数据库中。
4. 日记的搜索功能
5. 关于页面
6. 列表时时通知更新功能
7. 复制剪贴板功能等

由于功能比较完善、比较多，所以这里就挑选比较常见和重要的技术点来进行代码讲解。

2.2 项目概览

1. 项目的dart代码结构如下：
   
2. 使用到的第三方库如下：
   • sqflite：数据库操作
   • path_provider：目录路径的读取
   • oktoast：实现 Toast 提示
   • event_bus：通信
   • flutter_custom_calendar：日历功能

dependencies:
  flutter:
    sdk: flutter
  sqflite: ^1.1.6+3
  cupertino_icons: ^0.1.2
  path_provider: ^1.1.0
  oktoast: ^2.2.0
  event_bus: ^1.1.0
  flutter_custom_calendar:
    git:
      url: https://github.com/LXD312569496/flutter_custom_calendar.git

2.3 代码实现

2.3.1 引导页的实现

// 首先我们看下引导页的实现
// 引导页我们主要使用PageView来实现

import 'package:flutter/material.dart';
import 'package:oktoast/oktoast.dart';
import 'ui/Home.dart';

void main() {
  runApp(MyApp());
  // 透明状态栏
//  if (Platform.isAndroid) {
//    SystemUiOverlayStyle systemUiOverlayStyle =
//        SystemUiOverlayStyle(statusBarColor: Colors.transparent);
//    SystemChrome.setSystemUIOverlayStyle(systemUiOverlayStyle);
//  }
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
      // Toast三方库包裹最外层
    return OKToast(
        child:
        MaterialApp(
          title: '日记本',
          theme: ThemeData(
            primarySwatch: Colors.grey,
          ),
          home: MyHomePage(),
        ),
        backgroundColor: Colors.black54,
        textPadding:
            const EdgeInsets.symmetric(horizontal: 16.0, vertical: 10.0),
        radius: 20.0,
        position: ToastPosition.bottom);
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  // 默认选中第一项
  int _selectedIndex = 0;
  var _pageController = new PageController(initialPage: 0);

  @override
  void initState() {
    super.initState();
    _pageController.addListener(() {
      print(_pageController.position);
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: _buildBody(),
    );
  }
  // 构建页面主体
  _buildBody() {
    //SafeArea包裹，保证不会在刘海屏等屏幕下出现裁剪、适配
    return SafeArea(
        child: Stack(
      children: <Widget>[
          // PageView实现引导页页面切换
        PageView(
          // 监听控制类
          controller: _pageController,
          onPageChanged: _onSelectChanged,
          children: <Widget>[
              // 引导页第一个页面
            Container(
              color: Color.fromRGBO(232, 229, 222, 1),
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.center,
                mainAxisAlignment: MainAxisAlignment.center,
                children: <Widget>[
                  Text(
                    '每一天都是电影',
                    style: TextStyle(
                        color: Color.fromRGBO(132, 112, 101, 1), fontSize: 22),
                  ),
                  SizedBox(
                    height: 10,
                  ),
                  Text(
                    '记录精彩的生活，让每一天都有所回忆',
                    style: TextStyle(
                        color: Color.fromRGBO(66, 84, 94, 1), fontSize: 20),
                  )
                ],
              ),
            ),
            // 引导页第二个页面
            Container(
              color: Color.fromRGBO(232, 229, 222, 1),
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.center,
                mainAxisAlignment: MainAxisAlignment.center,
                children: <Widget>[
                  Text(
                    '简约至尚',
                    style: TextStyle(
                        color: Color.fromRGBO(72, 186, 249, 1), fontSize: 22),
                  ),
                  SizedBox(
                    height: 10,
                  ),
                  Text(
                    '从内到外力求简约、精美、个性......',
                    style: TextStyle(
                        color: Color.fromRGBO(66, 84, 94, 1), fontSize: 20),
                  )
                ],
              ),
            ),
            // 引导页第三个页面
            Container(
              color: Color.fromRGBO(232, 229, 222, 1),
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.center,
                mainAxisAlignment: MainAxisAlignment.center,
                children: <Widget>[
                  Text(
                    '此刻，回忆独一无二',
                    style: TextStyle(
                        color: Color.fromRGBO(98, 95, 78, 1), fontSize: 22),
                  ),
                  SizedBox(
                    height: 10,
                  ),
                  InkWell(
                    onTap: () {
                      toPage();
                    },
                    child: Text(
                      '开始体验之旅>>',
                      style: TextStyle(
                          color: Color.fromRGBO(66, 84, 94, 1), fontSize: 20),
                    ),
                  )
                ],
              ),
            ),
          ],
        ),
        // 绘制引导页的三个圆点指示器
        Align(
          alignment: FractionalOffset.bottomCenter,
          child: Row(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Container(
                  width: 10,
                  height: 10,
                  margin: EdgeInsets.all(10),
                  decoration: BoxDecoration(
                      shape: BoxShape.circle,
                      color: (_selectedIndex == 0)
                          ? Colors.white70
                          : Colors.black12)),
              Container(
                  width: 10,
                  height: 10,
                  margin: EdgeInsets.all(10),
                  decoration: BoxDecoration(
                      shape: BoxShape.circle,
                      color: (_selectedIndex == 1)
                          ? Colors.white70
                          : Colors.black12)),
              Container(
                  width: 10,
                  height: 10,
                  margin: EdgeInsets.all(10),
                  decoration: BoxDecoration(
                      shape: BoxShape.circle,
                      color: (_selectedIndex == 2)
                          ? Colors.white70
                          : Colors.black12))
            ],
          ),
        )
      ],
    ));
  }

  void _onSelectChanged(int index) {
    setState(() {
      _selectedIndex = index;
    });
  }

  // 切换
  void setPageViewItemSelect(int indexSelect) {
    _pageController.animateToPage(indexSelect,
        duration: const Duration(milliseconds: 300), curve: Curves.ease);
  }

  toPage() {
    //跳转并关闭当前页面
    Navigator.pushAndRemoveUntil(
      context,
      MaterialPageRoute(builder: (context) {
        return HomePage();
      }),
      (route) => route == null,
    );
  }
}

2.3.2 应用首页

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:flutter_note/ui/search.dart';
import 'package:flutter_note/utils/note_db_helper.dart';
import 'package:flutter_note/utils/tost_utils.dart';
import 'package:sqflite/sqflite.dart';

import 'calendar.dart';
import 'center.dart';
import 'list.dart';
import 'write.dart';
import 'package:path/path.dart';

class HomePage extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return HomePageState();
  }
}

class HomePageState extends State<HomePage> {
  // 默认选中第一项
  int _selectedIndex = 0;
  var _pageController = new PageController(initialPage: 0);
  int last = 0;
  int index = 0;

  NoteDbHelper noteDbHelpter;

  @override
  void initState() {
    super.initState();
    noteDbHelpter = NoteDbHelper();
    getDatabasesPath().then((string) {
      String path = join(string, 'notesDb.db');
      noteDbHelpter.open(path);
    });
    _pageController.addListener(() {});
  }

  // 返回键拦截执行方法
  Future<bool> _onWillPop() {
    int now = DateTime.now().millisecondsSinceEpoch;
    print(now - last);
    if (now - last > 1000) {
      last = now;
      Toast.show("再按一次返回键退出");
      return Future.value(false); //不退出
    } else {
      return Future.value(true); //退出
    }
  }

  @override
  Widget build(BuildContext context) {
    // 要用WillPopScope包裹
    return WillPopScope(
        // 编写onWillPop逻辑
        onWillPop: _onWillPop,
        child: Material(
          child: SafeArea(
              child: Scaffold(
            appBar: PreferredSize(
                // Offstage来控制AppBar的显示与隐藏
                child: Offstage(
                  offstage: _selectedIndex == 2 ? true : false,
                  child: AppBar(
                    backgroundColor: Color.fromRGBO(244, 244, 244, 1),
                    title: Text('备忘录'),
                    primary: true,
                    automaticallyImplyLeading: false,
                    actions: <Widget>[
                      IconButton(
                        icon: Icon(Icons.search),
                        tooltip: '搜索',
                        onPressed: () {
                          Navigator.push(context,
                              MaterialPageRoute(builder: (context) {
                            return SearchPage(
                              noteDbHelpter: noteDbHelpter,
                            );
                          }));
                        },
                      ),
                      IconButton(
                        icon: Icon(Icons.add),
                        tooltip: '写日记',
                        onPressed: () {
                          Navigator.push(context,
                              MaterialPageRoute(builder: (context) {
                            return WritePage(
                              noteDbHelpter: noteDbHelpter,
                              id: -1,
                            );
                          }));
                        },
                      ),
                    ],
                  ),
                ),
                preferredSize:
                    Size.fromHeight(MediaQuery.of(context).size.height * 0.07)),
            // 绑定数据
            body: SafeArea(
                child: PageView(
              // 监听控制类
              controller: _pageController,
              onPageChanged: _onItemTapped,
              physics: NeverScrollableScrollPhysics(),
              children: <Widget>[
                // 三个页面已经进行了封装
                ListPage(
                  noteDbHelpter: noteDbHelpter,
                ),
                CalendarPage(noteDbHelpter: noteDbHelpter),
                CenterPage(noteDbHelpter: noteDbHelpter),
              ],
            )),
            // 底部导航栏用CupertinoTabBar
            bottomNavigationBar: CupertinoTabBar(
              // 导航集合
              items: <BottomNavigationBarItem>[
                BottomNavigationBarItem(
                    activeIcon: Icon(
                      Icons.event_note,
                      color: Colors.blue[300],
                    ),
                    icon: Icon(Icons.event_note),
                    title: Text('主页')),
                BottomNavigationBarItem(
                    activeIcon: Icon(
                      Icons.calendar_today,
                      color: Colors.blue[300],
                    ),
                    icon: Icon(Icons.calendar_today),
                    title: Text('日历')),
                BottomNavigationBarItem(
                    activeIcon: Icon(
                      Icons.person,
                      color: Colors.blue[300],
                    ),
                    icon: Icon(Icons.person),
                    title: Text('个人中心')),
              ],
              currentIndex: _selectedIndex,
              onTap: setPageViewItemSelect,
            ),
          )),
        ));
  }

  void _onItemTapped(int index) {
    setState(() {
      _selectedIndex = index;
    });
  }

  // 底部点击切换
  void setPageViewItemSelect(int indexSelect) {
    _pageController.animateToPage(indexSelect,
        duration: const Duration(milliseconds: 300), curve: Curves.ease);
  }
}

2.3.3 第一个页面

import 'dart:async';

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:flutter_note/entity/note.dart';
import 'package:flutter_note/ui/read.dart';
import 'package:flutter_note/utils/event_bus.dart';
import 'package:flutter_note/utils/note_db_helper.dart';
import 'package:flutter_note/utils/time_utils.dart';

class ListPage extends StatefulWidget {
    // 构造方法传入了全局数据库操作类
  const ListPage({
    Key key,
    @required this.noteDbHelpter,
  }) : super(key: key);

  final NoteDbHelper noteDbHelpter;

  @override
  State<StatefulWidget> createState() {
    return ListPageState();
  }
}

// 继承实现了AutomaticKeepAliveClientMixin用来保证切换页面后数据不会丢失销毁
class ListPageState extends State<ListPage> with AutomaticKeepAliveClientMixin {
  ScrollController _scrollController =
      ScrollController(initialScrollOffset: 5, keepScrollOffset: true);
  // 记录列表的数量
  int _size = 0;
  // 记录列表的数据
  List<Note> _noteList = List();
  // EventBus通信类
  StreamSubscription subscription;

  @override
  void initState() {
    super.initState();
    // 注册和监听t发送来的UserEven类型事件、数据
    subscription = eventBus.on<NoteEvent>().listen((NoteEvent event) {
      _onRefresh();
    });
    _scrollController.addListener(() {
      ///滚动监听
    });
    // 刷新加载数据
    _onRefresh();
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      child: RefreshIndicator(
          child: CustomScrollView(
            shrinkWrap: false,
            primary: false,
            // 回弹效果
            physics: BouncingScrollPhysics(),
            scrollDirection: Axis.vertical,
            controller: _scrollController,
            slivers: <Widget>[
              SliverToBoxAdapter(
                child: SizedBox(
                  height: 10,
                ),
              ),
              SliverList(
                delegate: SliverChildBuilderDelegate(
                    (BuildContext context, int index) {
                    // 列表的Item布局和数据绑定
                  return InkWell(
                    child:
                        index % 2 == 0 ? getItem(index) : getImageItem(index),
                    onTap: () {
                      Navigator.push(context,
                          MaterialPageRoute(builder: (context) {
                        return ReadPage(
                          id: _noteList.elementAt(index).id,
                          noteDbHelpter: widget.noteDbHelpter,
                        );
                      }));
                    },
                    onLongPress: () {
                      _showBottomSheet(index, context);
                    },
                  );
                }, childCount: _size),
              ),
            ],
          ),
          onRefresh: _onRefresh),
    );
  }
    // 长按列表弹窗
  _showBottomSheet(int index, BuildContext c) {
    showModalBottomSheet(
        context: context,
        builder: (BuildContext context) {
          return new Column(
            mainAxisSize: MainAxisSize.min,
            children: <Widget>[
              ListTile(
                leading: Icon(Icons.content_copy),
                title: Text("复制"),
                onTap: () async {
                  Clipboard.setData(
                      ClipboardData(text: _noteList.elementAt(index).content));
                  Scaffold.of(c).showSnackBar(SnackBar(
                    content: Text("已经复制到剪贴板"),
                    backgroundColor: Colors.black87,
                    duration: Duration(
                      seconds: 2,
                    ),
                  ));
                  Navigator.pop(context);
                },
              ),
              ListTile(
                leading: Icon(Icons.delete_sweep),
                title: Text("删除"),
                onTap: () async {
                  widget.noteDbHelpter
                      .deleteById(_noteList.elementAt(index).id);
                  setState(() {
                    _noteList.removeAt(index);
                    _size = _noteList.length;
                  });
                  Navigator.pop(context);
                },
              ),
            ],
          );
        });
  }

  // 刷新
  Future<Null> _onRefresh() async {
    await Future.delayed(Duration(seconds: 1), () {
      print('refresh');
      widget.noteDbHelpter.getDatabase().then((database) {
        database
            .query('notes', orderBy: 'time DESC')
            .then((List<Map<String, dynamic>> records) {
          _size = records.length;
          _noteList.clear();
          for (int i = 0; i < records.length; i++) {
            _noteList.add(Note.fromMap(records.elementAt(i)));
          }
          setState(() {
            print(_noteList.length);
          });
        });
      });
    });
  }

  Widget getItem(int index) {
    return Container(
      child: Card(
        margin: EdgeInsets.fromLTRB(10, 8, 10, 8),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: <Widget>[
            Row(
              mainAxisAlignment: MainAxisAlignment.spaceAround,
              children: <Widget>[
                Container(
                  padding: EdgeInsets.fromLTRB(20, 10, 20, 5),
                  child: Row(
                    children: <Widget>[
                      Text(
                        '${DateTime.fromMillisecondsSinceEpoch(_noteList.elementAt(index).time).day}',
                        style: TextStyle(
                            color: Color.fromRGBO(52, 52, 54, 1),
                            fontSize: 50,
                            fontWeight: FontWeight.normal),
                      ),
                      SizedBox(
                        width: 5,
                      ),
                      Column(
                        crossAxisAlignment: CrossAxisAlignment.start,
                        children: <Widget>[
                          Text(
                            '星期${TimeUtils.getWeekday(DateTime.fromMillisecondsSinceEpoch(_noteList.elementAt(index).time).weekday)}',
                            style: TextStyle(
                                color: Color.fromRGBO(149, 149, 148, 1),
                                fontSize: 18),
                          ),
                          Text(
                            TimeUtils.getDate(
                                DateTime.fromMillisecondsSinceEpoch(
                                    _noteList.elementAt(index).time)),
                            style: TextStyle(
                                color: Color.fromRGBO(149, 149, 148, 1),
                                fontSize: 18),
                          ),
                        ],
                      ),
                    ],
                  ),
                ),
                Expanded(
                  child: Container(
                    alignment: Alignment.centerRight,
                    padding: EdgeInsets.fromLTRB(0, 5, 20, 5),
                    child: Icon(
                      Icons.wb_sunny,
                      size: 50,
                      color: Color.fromRGBO(252, 205, 24, 1),
                    ),
                  ),
                ),
              ],
            ),
            Container(
              margin: EdgeInsets.all(10),
              child: Text(
                _noteList.elementAt(index).content,
                maxLines: 3,
                overflow: TextOverflow.ellipsis,
                style: TextStyle(
                  color: Color.fromRGBO(103, 103, 103, 1),
                  fontSize: 18,
                ),
              ),
            ),
          ],
        ),
      ),
    );
  }

  Widget getImageItem(int index) {
    return Container(
      child: Card(
        margin: EdgeInsets.fromLTRB(10, 8, 10, 8),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: <Widget>[
            Row(
              mainAxisAlignment: MainAxisAlignment.spaceAround,
              children: <Widget>[
                Container(
                  padding: EdgeInsets.fromLTRB(20, 10, 20, 5),
                  child: Row(
                    children: <Widget>[
                      Text(
                        _noteList.length == 0
                            ? ''
                            : '${DateTime.fromMillisecondsSinceEpoch(_noteList.elementAt(index).time).day}',
                        style: TextStyle(
                            color: Color.fromRGBO(52, 52, 54, 1),
                            fontSize: 50,
                            fontWeight: FontWeight.normal),
                      ),
                      SizedBox(
                        width: 5,
                      ),
                      Column(
                        crossAxisAlignment: CrossAxisAlignment.start,
                        children: <Widget>[
                          Text(
                            _noteList.length == 0
                                ? ''
                                : '星期${TimeUtils.getWeekday(DateTime.fromMillisecondsSinceEpoch(_noteList.elementAt(index).time).weekday)}',
                            style: TextStyle(
                                color: Color.fromRGBO(149, 149, 148, 1),
                                fontSize: 18),
                          ),
                          Text(
                            _noteList.length == 0
                                ? ''
                                : TimeUtils.getDate(
                                    DateTime.fromMillisecondsSinceEpoch(
                                        _noteList.elementAt(index).time)),
                            style: TextStyle(
                                color: Color.fromRGBO(149, 149, 148, 1),
                                fontSize: 18),
                          ),
                        ],
                      ),
                    ],
                  ),
                ),
                Expanded(
                  child: Container(
                    alignment: Alignment.centerRight,
                    padding: EdgeInsets.fromLTRB(0, 5, 20, 5),
                    child: Icon(
                      Icons.wb_sunny,
                      size: 50,
                      color: Color.fromRGBO(252, 205, 24, 1),
                    ),
                  ),
                ),
              ],
            ),
            Container(
                margin: EdgeInsets.all(10),
                child: Row(
                  crossAxisAlignment: CrossAxisAlignment.start,
                  children: <Widget>[
                    ClipRRect(
                      borderRadius: BorderRadius.circular(5.0),
                      child: Image.network(
                        'https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1564678338847&di=ab19cbea9b5d88a9969ce0825ac5c84d&imgtype=0&src=http%3A%2F%2Fattachments.gfan.net.cn%2Fforum%2F201501%2F13%2F143316yttiiyiuvufcoyjh.jpg',
                        height: 108,
                        width: 108,
                        fit: BoxFit.cover,
                      ),
                    ),
                    Expanded(
                        child: Container(
                      padding: EdgeInsets.fromLTRB(10, 0, 0, 0),
                      child: Text(
                        _noteList.elementAt(index).content,
                        maxLines: 4,
                        overflow: TextOverflow.ellipsis,
                        style: TextStyle(
                          color: Color.fromRGBO(103, 103, 103, 1),
                          fontSize: 18,
                        ),
                      ),
                    )),
                  ],
                )),
          ],
        ),
      ),
    );
  }

  @override
  void dispose() {
    super.dispose();
    subscription.cancel();
  }
    // 保证数据留存
  @override
  bool get wantKeepAlive => true;
}

里面有一个剪贴板复制的操作：

Clipboard.setData(
                      ClipboardData(text: _noteList.elementAt(index).content));

2.3.4 时间工具类

// 主要就是DateTime的一个操作

class TimeUtils {
  static String getWeekday(int day) {
    switch (day) {
      case 1:
        return "一";
      case 2:
        return "二";
      case 3:
        return "三";
      case 4:
        return "四";
      case 5:
        return "五";
      case 6:
        return "六";
      case 7:
        return "日";
    }
  }

  static String getDateTime(DateTime dateTime) {
    return '${dateTime.year}年${dateTime.month}月${dateTime.day}日 ${dateTime.hour}:${dateTime.minute}:${dateTime.second}';
  }

  static String getDate(DateTime dateTime) {
    return '${dateTime.year}年${dateTime.month}月';
  }
}

其他的页面内容大同小异，通知刷新页面使用的是 EventBus，之前的博客有讲解用法，这里就不重复讲解了。

数据库 sqflite 之前也有讲过，这里也不重复讲解了。

2.3.5 个人中心

import 'package:flutter/material.dart';
import 'package:flutter/widgets.dart';
import 'package:flutter_note/utils/note_db_helper.dart';

import 'about.dart';

class CenterPage extends StatefulWidget {
  const CenterPage({
    Key key,
    @required this.noteDbHelpter,
  }) : super(key: key);

  final NoteDbHelper noteDbHelpter;

  @override
  State<StatefulWidget> createState() {
    return CenterPageState();
  }
}

class CenterPageState extends State<CenterPage>
    with AutomaticKeepAliveClientMixin {
  @override
  void initState() {
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      color: Color.fromRGBO(244, 244, 244, 1),
      padding: EdgeInsets.fromLTRB(10, 0, 10, 0),
      child: Column(
        children: <Widget>[
          SizedBox(
            height: 10,
          ),
          Row(
            children: <Widget>[
              SizedBox(
                width: 5,
              ),
              Container(
                decoration:
                    BoxDecoration(shape: BoxShape.circle, color: Colors.white),
                padding: EdgeInsets.all(3),
                child: CircleAvatar(
                  backgroundColor: Colors.white,
                  foregroundColor: Colors.blue,
                  backgroundImage: NetworkImage(
                      "https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1564763468169&di=02627b2a0ff227690f3a89c5214bfd86&imgtype=0&src=h"
                      "ttp%3A%2F%2Fpic49.nipic.com%2Ffile%2F20140922%2F2531170_191654419000_2.jpg"),
                  radius: 30.0,
                ),
              ),
              SizedBox(
                width: 10,
              ),
              Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: <Widget>[
                  Text(
                    "最美的日记",
                    style: TextStyle(color: Colors.black, fontSize: 26),
                  ),
                  Text(
                    "编辑资料",
                    style: TextStyle(
                        color: Color.fromRGBO(162, 162, 162, 1), fontSize: 18),
                  )
                ],
              )
            ],
          ),
          SizedBox(
            height: 20,
          ),
          Expanded(
              child: Container(
            child: Column(
              children: <Widget>[
                Flexible(
                  child: Row(
                    children: <Widget>[
                      _buildItem(0),
                      _buildItem(1),
                    ],
                  ),
                  flex: 1,
                ),
                Flexible(
                  child: Row(
                    children: <Widget>[
                      _buildItem(2),
                      _buildItem(3),
                    ],
                  ),
                  flex: 1,
                ),
                Flexible(
                  child: Row(
                    children: <Widget>[
                      _buildItem(4),
                      _buildItem(5),
                    ],
                  ),
                  flex: 1,
                ),
              ],
            ),
          )),
          SizedBox(
            height: 10,
          ),
        ],
      ),
    );
  }

  _buildItem(int index) {
    return Expanded(
      child: Container(
        padding: EdgeInsets.fromLTRB(5, 5, 5, 5),
        child: GestureDetector(
          child: Card(
            child: Container(
              padding: EdgeInsets.all(26),
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: <Widget>[
                  _icons.elementAt(index),
                  Expanded(child: Text("")),
                  _title.elementAt(index),
                  _des.elementAt(index),
                ],
              ),
            ),
          ),
          onTap:(){
            _click(index);
          },
        ),
      ),
      flex: 1,
    );
  }

  void _click(int index) {
    switch (index) {
      case 0:
        break;
      case 4:
        Navigator.push(context, MaterialPageRoute(builder: (context) {
          return AboutPage();
        }));
        break;
    }
  }

  List<Icon> _icons = [
    Icon(
      Icons.favorite,
      size: 38,
      color: Colors.yellow,
    ),
    Icon(
      Icons.lock,
      size: 38,
      color: Colors.blue,
    ),
    Icon(
      Icons.feedback,
      size: 38,
      color: Colors.blueAccent,
    ),
    Icon(
      Icons.share,
      size: 38,
      color: Colors.deepPurpleAccent,
    ),
    Icon(
      Icons.error_outline,
      size: 38,
      color: Colors.orange,
    ),
    Icon(
      Icons.settings,
      size: 38,
      color: Colors.red,
    )
  ];

  List<Text> _title = [
    Text(
      "我的收藏",
      style: TextStyle(color: Colors.black, fontSize: 20),
    ),
    Text(
      "密码锁",
      style: TextStyle(color: Colors.black, fontSize: 20),
    ),
    Text(
      "吐槽反馈",
      style: TextStyle(color: Colors.black, fontSize: 20),
    ),
    Text(
      "分享",
      style: TextStyle(color: Colors.black, fontSize: 20),
    ),
    Text(
      "关于日记",
      style: TextStyle(color: Colors.black, fontSize: 20),
    ),
    Text(
      "系统设置",
      style: TextStyle(color: Colors.black, fontSize: 20),
    ),
  ];

  List<Text> _des = [
    Text(
      "收藏的重要日记",
      style: TextStyle(color: Color.fromRGBO(162, 162, 162, 1), fontSize: 16),
    ),
    Text(
      "设置密码锁",
      style: TextStyle(color: Color.fromRGBO(162, 162, 162, 1), fontSize: 16),
    ),
    Text(
      "吐槽反馈你的想法",
      style: TextStyle(color: Color.fromRGBO(162, 162, 162, 1), fontSize: 16),
    ),
    Text(
      "分享应用给他人",
      style: TextStyle(color: Color.fromRGBO(162, 162, 162, 1), fontSize: 16),
    ),
    Text(
      "版本信息",
      style: TextStyle(color: Color.fromRGBO(162, 162, 162, 1), fontSize: 16),
    ),
    Text(
      "系统相关设置",
      style: TextStyle(color: Color.fromRGBO(162, 162, 162, 1), fontSize: 16),
    ),
  ];

  @override
  // TODO: implement wantKeepAlive
  bool get wantKeepAlive => true;
}

2.3.6 数据库操作类

import 'package:flutter_note/entity/note.dart';
import 'package:sqflite/sqflite.dart';

// 数据库操作工具类
class NoteDbHelper {
  Database db;

  Future open(String path) async {
    // 打开/创建数据库
    db = await openDatabase(path, version: 1,
        onCreate: (Database db, int version) async {
      await db.execute(
          "create table notes (_id INTEGER primary key autoincrement,title TEXT not null,content TEXT not null,star INTEGER not null,time INTEGER not null,weather INTEGER not null)");
      print("Table is created");
    });
  }

  Future<Database> getDatabase() async {
    Database database = await db;
    return database;
  }

  // 增加一条数据
  Future<Note> insert(Note note) async {
    note.id = await db.insert("notes", note.toMap());
    return note;
  }

  // 通过ID查询一条数据
  Future<Note> getNoteById(int id) async {
    List<Map> maps = await db.query('notes',
        columns: [
          columnId,
          columnTitle,
          columnContent,
          columnTime,
          columnStar,
          columnWeather
        ],
        where: '_id = ?',
        whereArgs: [id]);
    if (maps.length > 0) {
      return Note.fromMap(maps.first);
    }
    return null;
  }

  // 通过关键字查询数据
  Future<List<Note>> getNoteByContent(String text) async {
    List<Note> _noteList = List();
    List<Map> maps = await db.query('notes',
        columns: [
          columnId,
          columnTitle,
          columnContent,
          columnTime,
          columnStar,
          columnWeather
        ],
        where: 'content like ? ORDER BY time ASC',
        whereArgs: ["%" + text + "%"]);
    if (maps.length > 0) {
      for (int i = 0; i < maps.length; i++) {
        _noteList.add(Note.fromMap(maps.elementAt(i)));
      }
      return _noteList;
    }
    return null;
  }

  // 通过ID删除一条数据
  Future<int> deleteById(int id) async {
    return await db.delete('notes', where: '_id = ?', whereArgs: [id]);
  }

  // 更新数据
  Future<int> update(Note note) async {
    return await db
        .update('notes', note.toMap(), where: '_id = ?', whereArgs: [note.id]);
  }

  // 关闭数据库
  Future close() async => db.close();
}

3.完整项目

完整项目可以在 Github 上进行下载编译、查看学习：
flutter_notes