Flutter制作自己的第一个全平台APP学习之实用功能篇

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摘要

这一篇文章主要是学习flutter中各种在App中可能出现的实用功能,比如白天模式与夜间模式自由切换,分享到社交媒体,照相摄像,打分五星好评之类的等等,一起来看看都有什么吧……

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Flutter制作自己的第一个全平台APP学习之实用功能篇

开篇寄语

这一篇文章主要是学习flutter中各种在App中可能出现的实用功能,比如白天模式与夜间模式自由切换,分享到社交媒体,照相摄像,打分五星好评之类的等等,一起来看看都有什么吧。

前情提要

内容详情

以下内容大多是更改lib下的main.dart文件内容,删掉里面的内容,复制粘贴代码,开启调试就可以出现了。

白天与夜间模式切换

  • 夜间模式现在在制作App中很流行,Flutter中也很容易实现,试举例如下:
// main.dart
import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // Using "static" so that we can easily access it later
  static final ValueNotifier<ThemeMode> themeNotifier =
      ValueNotifier(ThemeMode.light);

  @override
  Widget build(BuildContext context) {
    return ValueListenableBuilder<ThemeMode>(
        valueListenable: themeNotifier,
        builder: (_, ThemeMode currentMode, __) {
          return MaterialApp(
            // Remove the debug banner
            debugShowCheckedModeBanner: false,
            title: 'Flutter Demo',
            theme: ThemeData(primarySwatch: Colors.amber),
            darkTheme: ThemeData.dark(),
            themeMode: currentMode,
            home: HomeScreen(),
          );
        });
  }
}

// Home Screen
class HomeScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Flutter Demo'),
        actions: [
          IconButton(
              icon: Icon(MyApp.themeNotifier.value == ThemeMode.light
                  ? Icons.dark_mode
                  : Icons.light_mode),
              onPressed: () {
                MyApp.themeNotifier.value =
                    MyApp.themeNotifier.value == ThemeMode.light
                        ? ThemeMode.dark
                        : ThemeMode.light;
              })
        ],
      ),
      body: Center(
        child: ElevatedButton(
          child: Text('Go to Other Screen'),
          onPressed: () {
            Navigator.push(context,
                MaterialPageRoute(builder: (context) => OtherScreen()));
          },
        ),
      ),
    );
  }
}

// Other Screen
class OtherScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Other Screen'),
      ),
      body: Center(
        child: Text(
          'Hello',
          style: TextStyle(fontSize: 50),
        ),
      ),
    );
  }
}

生成效果如下图所示:

文字添加超链接

  • 就像是html中的<a></a>标签,点击后就会跳转到网页,试举例如下:
import 'package:flutter/material.dart';
import 'package:url_launcher/url_launcher.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      // Remove the debug banner
      debugShowCheckedModeBanner: false,
      title: 'Flutter Demo',
      home: HomePage(),
    );
  }
}

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Flutter Demo'),
      ),
      body: Padding(
        padding: const EdgeInsets.all(30),
        child: DefaultTextStyle(
          style: TextStyle(fontSize: 24, color: Colors.black87),
          child: Wrap(
            children: [
              Text('Welcome to '),
              GestureDetector(
                child: Text(
                  'Flutter Dev',
                  style: TextStyle(
                      color: Colors.blue, decoration: TextDecoration.underline),
                ),
                onTap: () async => await canLaunch('https://www.flutter.dev')
                    ? await launch('https://www.flutter.dev')
                    : throw 'Something bad happend',
              ),
            ],
          ),
        ),
      ),
    );
  }
}

生成效果如下图所示:

复制粘贴到剪切板

  • 这个功能也是十分常见的,所以也需要掌握的,试举例如下:
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Flutter Demo',
      home: HomePage(),
    );
  }
}

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  TextEditingController _textController = TextEditingController();

  // This key will be used to show the snack bar
  final GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey();

  // This function is triggered when the copy icon is pressed
  Future<void> _copyToClipboard() async {
    await Clipboard.setData(ClipboardData(text: _textController.text));
    _scaffoldKey.currentState!.showSnackBar(SnackBar(
      content: Text('Copied to clipboard'),
    ));
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        key: _scaffoldKey,
        appBar: AppBar(
          title: Text('Flutter Demo'),
          backgroundColor: Colors.deepOrange,
        ),
        body: Center(
            child: Padding(
          padding: const EdgeInsets.all(30),
          child: TextField(
            controller: _textController,
            decoration: InputDecoration(
              icon: IconButton(
                icon: Icon(Icons.copy),
                onPressed: _copyToClipboard,
              ),
            ),
          ),
        )));
  }
}

生成效果如下图所示:

Flutter制作自己的第一个全平台APP学习之实用功能篇

分享按钮

  • 各种消息分享到社交媒体的功能,岂能错过,除了有更多乐趣外,还能扩大App的知名度哦,试举一例:
    • 需要添加一个名为share的支撑库,安装和使用方法请参看这个地址:share
import 'package:flutter/material.dart';
import 'package:share/share.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      // Remove the debug banner
      debugShowCheckedModeBanner: false,
      title: 'Flutter Demo',
      home: HomePage(),
    );
  }
}

class HomePage extends StatelessWidget {
  final String _content =
      'Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum diam ipsum, lobortis quis ultricies non, lacinia at justo.';

  void _shareContent() {
    Share.share(_content);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Flutter Demo'),
      ),
      body: Padding(
        padding: const EdgeInsets.all(25),
        child: Center(
          child: Column(children: [
            Text(_content),
            SizedBox(height: 15),
            ElevatedButton.icon(
                onPressed: _shareContent,
                icon: Icon(Icons.share),
                label: Text('Share This Sentence'))
          ]),
        ),
      ),
    );
  }
}

生成效果如下图所示:

Flutter制作自己的第一个全平台APP学习之实用功能篇

五星好评

  • 这个常见于打分环节,自然也要掌握啦,试举一例:
    • 需要安装一个名为flutter rating bar的支撑库,地址是这里:flutter_rating_bar,安装完成后,可以参考下面这个代码案例:
import 'package:flutter/material.dart';
import 'package:flutter_rating_bar/flutter_rating_bar.dart';

void main() => runApp(MyApp());

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  late final _ratingController;
  late double _rating;

  double _userRating = 3.0;
  int _ratingBarMode = 1;
  double _initialRating = 2.0;
  bool _isRTLMode = false;
  bool _isVertical = false;

  IconData? _selectedIcon;

  @override
  void initState() {
    super.initState();
    _ratingController = TextEditingController(text: '3.0');
    _rating = _initialRating;
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.amber,
        appBarTheme: AppBarTheme(
          textTheme: TextTheme(
            headline6: Theme.of(context)
                .textTheme
                .headline6
                ?.copyWith(color: Colors.white),
          ),
        ),
      ),
      home: Builder(
        builder: (context) => Scaffold(
          appBar: AppBar(
            title: Text('Flutter Rating Bar'),
            actions: [
              IconButton(
                icon: Icon(Icons.settings),
                color: Colors.white,
                onPressed: () async {
                  _selectedIcon = await showDialog<IconData>(
                    context: context,
                    builder: (context) => IconAlert(),
                  );
                  _ratingBarMode = 1;
                  setState(() {});
                },
              ),
            ],
          ),
          body: Directionality(
            textDirection: _isRTLMode ? TextDirection.rtl : TextDirection.ltr,
            child: SingleChildScrollView(
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.center,
                mainAxisSize: MainAxisSize.min,
                children: <Widget>[
                  SizedBox(
                    height: 40.0,
                  ),
                  _heading('Rating Bar'),
                  _ratingBar(_ratingBarMode),
                  SizedBox(height: 20.0),
                  Text(
                    'Rating: $_rating',
                    style: TextStyle(fontWeight: FontWeight.bold),
                  ),
                  SizedBox(height: 40.0),
                  _heading('Rating Indicator'),
                  RatingBarIndicator(
                    rating: _userRating,
                    itemBuilder: (context, index) => Icon(
                      _selectedIcon ?? Icons.star,
                      color: Colors.amber,
                    ),
                    itemCount: 5,
                    itemSize: 50.0,
                    unratedColor: Colors.amber.withAlpha(50),
                    direction: _isVertical ? Axis.vertical : Axis.horizontal,
                  ),
                  SizedBox(height: 20.0),
                  Padding(
                    padding: EdgeInsets.symmetric(horizontal: 16.0),
                    child: TextFormField(
                      controller: _ratingController,
                      keyboardType: TextInputType.number,
                      decoration: InputDecoration(
                        border: OutlineInputBorder(),
                        hintText: 'Enter rating',
                        labelText: 'Enter rating',
                        suffixIcon: MaterialButton(
                          onPressed: () {
                            _userRating =
                                double.parse(_ratingController.text ?? '0.0');
                            setState(() {});
                          },
                          child: Text('Rate'),
                        ),
                      ),
                    ),
                  ),
                  SizedBox(height: 40.0),
                  _heading('Scrollable Rating Indicator'),
                  RatingBarIndicator(
                    rating: 8.2,
                    itemCount: 20,
                    itemSize: 30.0,
                    physics: BouncingScrollPhysics(),
                    itemBuilder: (context, _) => Icon(
                      Icons.star,
                      color: Colors.amber,
                    ),
                  ),
                  SizedBox(height: 20.0),
                  Text(
                    'Rating Bar Modes',
                    style: TextStyle(fontWeight: FontWeight.w300),
                  ),
                  Row(
                    children: [
                      _radio(1),
                      _radio(2),
                      _radio(3),
                    ],
                  ),
                  Row(
                    mainAxisAlignment: MainAxisAlignment.center,
                    children: <Widget>[
                      Text(
                        'Switch to Vertical Bar',
                        style: TextStyle(fontWeight: FontWeight.w300),
                      ),
                      Switch(
                        value: _isVertical,
                        onChanged: (value) {
                          setState(() {
                            _isVertical = value;
                          });
                        },
                        activeColor: Colors.amber,
                      ),
                    ],
                  ),
                  Row(
                    mainAxisAlignment: MainAxisAlignment.center,
                    children: <Widget>[
                      Text(
                        'Switch to RTL Mode',
                        style: TextStyle(fontWeight: FontWeight.w300),
                      ),
                      Switch(
                        value: _isRTLMode,
                        onChanged: (value) {
                          setState(() {
                            _isRTLMode = value;
                          });
                        },
                        activeColor: Colors.amber,
                      ),
                    ],
                  ),
                ],
              ),
            ),
          ),
        ),
      ),
    );
  }

  Widget _radio(int value) {
    return Expanded(
      child: RadioListTile<int>(
        value: value,
        groupValue: _ratingBarMode,
        dense: true,
        title: Text(
          'Mode $value',
          style: TextStyle(
            fontWeight: FontWeight.w300,
            fontSize: 12.0,
          ),
        ),
        onChanged: (value) {
          setState(() {
            _ratingBarMode = value!;
          });
        },
      ),
    );
  }

  Widget _ratingBar(int mode) {
    switch (mode) {
      case 1:
        return RatingBar.builder(
          initialRating: _initialRating,
          minRating: 1,
          direction: _isVertical ? Axis.vertical : Axis.horizontal,
          allowHalfRating: true,
          unratedColor: Colors.amber.withAlpha(50),
          itemCount: 5,
          itemSize: 50.0,
          itemPadding: EdgeInsets.symmetric(horizontal: 4.0),
          itemBuilder: (context, _) => Icon(
            _selectedIcon ?? Icons.star,
            color: Colors.amber,
          ),
          onRatingUpdate: (rating) {
            setState(() {
              _rating = rating;
            });
          },
          updateOnDrag: true,
        );
      case 2:
        return RatingBar(
          initialRating: _initialRating,
          direction: _isVertical ? Axis.vertical : Axis.horizontal,
          allowHalfRating: true,
          itemCount: 5,
          ratingWidget: RatingWidget(
            full: _image('assets/heart.png'),
            half: _image('assets/heart_half.png'),
            empty: _image('assets/heart_border.png'),
          ),
          itemPadding: EdgeInsets.symmetric(horizontal: 4.0),
          onRatingUpdate: (rating) {
            setState(() {
              _rating = rating;
            });
          },
          updateOnDrag: true,
        );
      case 3:
        return RatingBar.builder(
          initialRating: _initialRating,
          direction: _isVertical ? Axis.vertical : Axis.horizontal,
          itemCount: 5,
          itemPadding: EdgeInsets.symmetric(horizontal: 4.0),
          itemBuilder: (context, index) {
            switch (index) {
              case 0:
                return Icon(
                  Icons.sentiment_very_dissatisfied,
                  color: Colors.red,
                );
              case 1:
                return Icon(
                  Icons.sentiment_dissatisfied,
                  color: Colors.redAccent,
                );
              case 2:
                return Icon(
                  Icons.sentiment_neutral,
                  color: Colors.amber,
                );
              case 3:
                return Icon(
                  Icons.sentiment_satisfied,
                  color: Colors.lightGreen,
                );
              case 4:
                return Icon(
                  Icons.sentiment_very_satisfied,
                  color: Colors.green,
                );
              default:
                return Container();
            }
          },
          onRatingUpdate: (rating) {
            setState(() {
              _rating = rating;
            });
          },
          updateOnDrag: true,
        );
      default:
        return Container();
    }
  }

  Widget _image(String asset) {
    return Image.asset(
      asset,
      height: 30.0,
      width: 30.0,
      color: Colors.amber,
    );
  }

  Widget _heading(String text) => Column(
        children: [
          Text(
            text,
            style: TextStyle(
              fontWeight: FontWeight.w300,
              fontSize: 24.0,
            ),
          ),
          SizedBox(
            height: 20.0,
          ),
        ],
      );
}

class IconAlert extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return AlertDialog(
      title: Text(
        'Select Icon',
        style: TextStyle(
          fontWeight: FontWeight.w300,
        ),
      ),
      shape: RoundedRectangleBorder(
        borderRadius: BorderRadius.circular(10.0),
      ),
      titlePadding: EdgeInsets.all(12.0),
      contentPadding: EdgeInsets.all(0),
      content: Wrap(
        children: [
          _iconButton(context, Icons.home),
          _iconButton(context, Icons.airplanemode_active),
          _iconButton(context, Icons.euro_symbol),
          _iconButton(context, Icons.beach_access),
          _iconButton(context, Icons.attach_money),
          _iconButton(context, Icons.music_note),
          _iconButton(context, Icons.android),
          _iconButton(context, Icons.toys),
          _iconButton(context, Icons.language),
          _iconButton(context, Icons.landscape),
          _iconButton(context, Icons.ac_unit),
          _iconButton(context, Icons.star),
        ],
      ),
    );
  }

  Widget _iconButton(BuildContext context, IconData icon) => IconButton(
        icon: Icon(icon),
        onPressed: () => Navigator.pop(context, icon),
        splashColor: Colors.amberAccent,
        color: Colors.amber,
      );
}

生成效果如下图所示:

Flutter制作自己的第一个全平台APP学习之实用功能篇

右下角弹出按钮

  • 可以在该按钮中添加各种实用功能,列出很多选项按钮,需要安装支持库,这里涉及到一个名为flutter speed dial的库,这个需要安装,可前往这个网址参看指导:flutter speed dial
  • 试举例如下:
import 'package:flutter/material.dart';
import 'package:flutter_speed_dial/flutter_speed_dial.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      // Remove the debug banner
      debugShowCheckedModeBanner: false,
      title: 'Flutter Demo',
      home: HomePage(),
    );
  }
}

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Flutter Demo'),
      ),
      body: Center(
        child: Text("Hello World"),
      ),
      floatingActionButton: SpeedDial(
          icon: Icons.share,
          backgroundColor: Colors.amber,
          children: [
            SpeedDialChild(
              child: Icon(Icons.face),
              label: 'Social Network',
              backgroundColor: Colors.amberAccent,
              onTap: () {/* Do someting */},
            ),
            SpeedDialChild(
              child: Icon(Icons.email),
              label: 'Email',
              backgroundColor: Colors.amberAccent,
              onTap: () {/* Do something */},
            ),
            SpeedDialChild(
              child: Icon(Icons.chat),
              label: 'Message',
              backgroundColor: Colors.amberAccent,
              onTap: () {/* Do something */},
            ),
          ]),
    );
  }
}

生成效果如下图所示:

Flutter制作自己的第一个全平台APP学习之实用功能篇
ArrayArrayArray
  • 我的微信
  • 微信扫一扫加好友
  • weinxin
  • 我的微信公众号
  • 扫描关注公众号
  • weinxin

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