flutter扩展功能

1. Android中实现消息推送、指定设备推送
    第三方包： jpush_flutter
    实例：
        import 'package:flutter/material.dart';
        import 'package:jpush_flutter/jpush_flutter.dart';

        class ExamplePage extends StatefulWidget {
          Map arguments;

          ExamplePage({Key key, this.arguments}) : super(key: key);

          @override
          _ExamplePageState createState() =>
              _ExamplePageState(arguments: this.arguments);
        }

        class _ExamplePageState extends State<ExamplePage> {
          Map arguments;

          _ExamplePageState({this.arguments});

          @override
          void initState() {
            super.initState();
            this.initJpush();
          }

          // 监听极光推送
          initJpush() {
            JPush jpush = new JPush();
            jpush.setup(
              appKey: '20fa4b7bb897ee829a8f0e18',
              channel: 'theChannel',
              production: false,
              debug: false
            );

            // 设置别名，用于指定设备推送
            jpush.setAlias('wq123').then((map){
              print('设置别名成功$map');
            });

            jpush.addEventHandler(
              // 接受通知回调方法
              onReceiveNotification: (Map<String,dynamic> message) async {
                print("接受通知回调方法 $message");
              },
              // 点击通知回调方法
              onOpenNotification: (Map<String,dynamic> message) async {
                print("点击通知回调方法 $message");
              },
              // 接受自定义消息回调方法
              onReceiveMessage: (Map<String,dynamic> message) async {
                print("接受自定义消息回调方法 $message");
              }
            );
          }

          @override
          Widget build(BuildContext context) {
            return Scaffold(
                appBar: AppBar(
                  title: Text('极光推送'),
                ),
                body: Center(
                  child: Column(),
                ) // This trailing comma makes auto-formatting nicer for build methods.
            );
          }
        }

2. Flutter国际化 、升级Flutter Sdk
    (1)找到 pubspec.yaml 配置 flutter_localizations
        dependencies:
            flutter:
                sdk: flutter
            flutter_localizations:
                sdk: flutter
    (2)main.dart 中导入国际化的包 flutter_localizations
        import 'package:flutter_localizations/flutter_localizations.dart';
    (3)设置国际化
        import 'package:flutter/material.dart';
        import 'package:flutter_localizations/flutter_localizations.dart';
        import './Example.dart';
        void main() => runApp(MyApp());

        class MyApp extends StatelessWidget {
          // This widget is the root of your application.
          @override
          Widget build(BuildContext context) {
            return MaterialApp(
              title: 'Flutter Demo',
              theme: ThemeData(
                primarySwatch: Colors.blue,
              ),
              home: ExamplePage(),
              localizationsDelegates: [
                GlobalMaterialLocalizations.delegate,
                GlobalWidgetsLocalizations.delegate
              ],
              supportedLocales: [
                const Locale('zh', 'CH'),
                const Locale('en', 'US'),
              ]
            );
          }
        }

    链接：https://segmentfault.com/a/1190000018773751

3. 及时通信
    第三方库：  socket_io_client
    import 'package:flutter/material.dart';
    import 'package:socket_io_client/socket_io_client.dart';

    class ExamplePage extends StatefulWidget {
      Map arguments;
      ExamplePage({Key key, this.arguments}) : super(key: key);

      @override
      _ExamplePageState createState() =>
          _ExamplePageState(arguments: this.arguments);
    }

    class _ExamplePageState extends State<ExamplePage> {
      Map arguments;
      Socket socket;
      List messageList = [];
      ScrollController scrollController = new ScrollController();
      _ExamplePageState({this.arguments});

      @override
      void initState() {
        super.initState();
        this.connectServer();
      }

      connectServer() {
        socket = io('http://192.168.124.25:8000', <String, dynamic>{
          'transports': ['websocket'],
          'autoConnect': true,
          'extraHeaders': {'foo': 'bar'} // optional
        });
        socket.on('connect', (_){
          print('connect');
          socket.emit('toServer','已经连接上了....');
        });
        socket.on('toClient', (data){
          setState(() {
            this.messageList.add(data);
            this.scrollController.jumpTo(this.scrollController.position.maxScrollExtent+30);
          });
        });
      }

      @override
      Widget build(BuildContext context) {
        return Scaffold(
            appBar: AppBar(
              title: Text('及时通信'),
            ),
            body: Center(
              child: Column(
                children: <Widget>[
                  Container(
                    height: 400,
                    child: ListView.builder(
                        controller: this.scrollController,
                        itemCount: this.messageList.length,
                        itemBuilder: (context,index){
                          return ListTile(
                            title: Text(this.messageList[index]),
                          );
                        }
                    ),
                  ),
                  RaisedButton(
                    child: Text('发送消息'),
                    onPressed: (){
                      this.socket.emit('toServer','帅不？');
                    },
                  ),
                ],
              ),
            ) // This trailing comma makes auto-formatting nicer for build methods.
        );
      }
    }

4. 流媒体在线直播
   直播主要通过两步实现：1.推流 2.拉流
   推流：指的是把采集阶段封包好的内容传输到服务器的过程。推流的设备可以是计算机也可以是摄像头或者手机
   拉流：指服务器已有直播内容，用指定地址进行拉取播放的过程

   第三方库：flutter_ijkplayer

   示例：
        import 'package:flutter/material.dart';
        import 'package:flutter_ijkplayer/flutter_ijkplayer.dart';

        class ExamplePage extends StatefulWidget {
          Map arguments;
          ExamplePage({Key key, this.arguments}) : super(key: key);

          @override
          _ExamplePageState createState() =>
              _ExamplePageState(arguments: this.arguments);
        }

        class _ExamplePageState extends State<ExamplePage> {
          Map arguments;
          IjkMediaController controller = IjkMediaController();
          _ExamplePageState({this.arguments});

          @override
          void initState() {
            super.initState();
            this.initMedia();
          }

          @override
          void dispose() {
            controller.dispose();
            super.dispose();
          }

          initMedia() async {
            await controller.setNetworkDataSource(
              'https://www.sample-videos.com/video123/mp4/720/big_buck_bunny_720p_20mb.mp4',
              autoPlay: false
            );
          }

          @override
          Widget build(BuildContext context) {
            return Scaffold(
                appBar: AppBar(
                  title: Text('流媒体'),
                ),
                body: ListView(
                  children: <Widget>[
                    Container(
                         height: 200, // 这里随意
                          child: IjkPlayer(
                            mediaController: controller,
                          ),
                    )
                  ],
                ) // This trailing comma makes auto-formatting nicer for build methods.
            );
          }
        }

5. 指纹识别认证
    第三方库： local_auth
    实例：
        import 'package:flutter/material.dart';
        import 'package:local_auth/local_auth.dart';
        import 'package:local_auth/auth_strings.dart';

        class ExamplePage extends StatefulWidget {
          Map arguments;
          ExamplePage({Key key, this.arguments}) : super(key: key);

          @override
          _ExamplePageState createState() =>
              _ExamplePageState(arguments: this.arguments);
        }

        class _ExamplePageState extends State<ExamplePage> {
          Map arguments;
          _ExamplePageState({this.arguments});

          @override
          void initState() {
            super.initState();
          }

          @override
          Widget build(BuildContext context) {
            LocalAuthentication localAuth = LocalAuthentication();

            return Scaffold(
                appBar: AppBar(
                  title: Text('指纹识别'),
                ),
                body: ListView(
                  children: <Widget>[
                    RaisedButton(
                      child: Text('检测是否支持生物识别'),
                      onPressed: () async{
                        bool canCheckBiometrics = await localAuth.canCheckBiometrics;
                        print("canCheckBiometrics $canCheckBiometrics");
                      },
                    ),
                    RaisedButton(
                      child: Text('获取支持的生物识别列表'),
                      onPressed: () async{
                        List<BiometricType> availableBiometrics = await localAuth.getAvailableBiometrics();
                        print("availableBiometrics $availableBiometrics");
                      },
                    ),
                    RaisedButton(
                      child: Text('指纹生物认证'),
                      onPressed: () async{
                        const andStrings = const AndroidAuthMessages(
                          cancelButton: '取消',
                          goToSettingsButton: '去设置',
                          fingerprintNotRecognized: '指纹识别失败',
                          goToSettingsDescription: '请设置指纹.',
                          fingerprintHint: '指纹',
                          fingerprintSuccess: '指纹识别成功',
                          signInTitle: '指纹验证',
                          fingerprintRequiredTitle: '请先录入指纹!',
                        );

                        bool didAuthenticate = await localAuth.authenticateWithBiometrics(
                            localizedReason: '扫描指纹进行验证',
                            useErrorDialogs: false,
                            stickyAuth: true,
                            androidAuthStrings :andStrings
                        );
                        print("didAuthenticate $didAuthenticate");
                      },
                    )
                  ],
                ) // This trailing comma makes auto-formatting nicer for build methods.
            );
          }
        }
6.Flutter 底部 Tab 切换保持页面状态的几种 方法
	(1)IndexedStack用法：
		Container( 
		width: double.infinity, 
		height: double.infinity,
		child: new IndexedStack(
			 index: 0,
			 alignment: Alignment.center, 
			 children: <Widget>[ 			
			 		Image.network("https://www.itying.com/images/flutter/list1.jpg",fit: BoxFit.cover,), 
			 		Image.network("https://www.itying.com/images/flutter/list2.jpg",fit: BoxFit.cover)
			 ])
		)
	(2)AutomaticKeepAliveClientMixin用法
		import 'package:flutter/material.dart';
		import '../../pages/Home/view.dart';
		import '../../pages/Category/view.dart';
		import '../../pages/Cart/view.dart';
		import '../../pages/User/view.dart';
		
		class Tabs extends StatefulWidget {
		  @override
		  _TabsState createState() => _TabsState();
		}
		
		class _TabsState extends State<Tabs> {
		
		
		  List bottomItems = [
		    {
		      "icon": Icon(Icons.home),
		      "title": Text('首页'),
		    },
		    {
		      "icon": Icon(Icons.category),
		      "title": Text('分类'),
		    },
		    {
		      "icon": Icon(Icons.shopping_cart),
		      "title": Text('购物车'),
		    },
		    {
		      "icon": Icon(Icons.people),
		      "title": Text('我的'),
		    },
		  ];
		
		  List<Widget> pageList = [
		    Home(),
		    Category(),
		    Cart(),
		    User()
		  ];
		
		  getBottomItems () {
		    return bottomItems.map((item){
		      return BottomNavigationBarItem(
		          icon: item['icon'],
		          title: item['title']
		      );
		    }).toList();
		  }
		
		  int currentIndex = 1;
		
		  PageController pageController;
		
		  @override
		  void initState() {
		    super.initState();
		    this.pageController = PageController(initialPage: this.currentIndex);
		  }
		
		  @override
		  Widget build(BuildContext context) {
		    return Scaffold(
		      appBar: AppBar(
		        title: Text("京东商城"),
		      ),
		      body: PageView(
		        controller: this.pageController,
		        children: pageList，
		        onPageChanged: (index){
			          this.setState((){
			           	 this.currentIndex = index;
			          });
			     },
		      ),
		      bottomNavigationBar: BottomNavigationBar(
		        type: BottomNavigationBarType.fixed,
		        fixedColor: Colors.red,
		        currentIndex: this.currentIndex,
		        onTap: (index) {
		            this.setState((){
		              this.currentIndex = index;
		              this.pageController.jumpToPage(this.currentIndex);
		            });
		        },
		        // 禁止PageView左右滑动
        		physics: NeverScrollableScrollPhysics(),
		        items: getBottomItems(),
		      ),
		    );
		  }
		}
		// 需要在页面中继承AutomaticKeepAliveClientMixin
		class HomePage extends StatefulWidget { 
				HomePage({Key key}) : super(key: key);
				 _HomePageState createState() => _HomePageState(); 
		}
		class _HomePageState extends State<HomePage> with AutomaticKeepAliveClientMixin{ 
				@override bool get wantKeepAlive => true; 
		}