class GStyle {
    // __ 自定义图标
    static iconfont(int codePoint, {double size = 16.0, Color color}) {
        return Icon(
            IconData(codePoint, fontFamily: ‘iconfont‘, matchTextDirection: true),
            size: size,
            color: color,
        );
    }
}

◆ flutter中红点/圆点提示

在flutter中没有上图这个红点提示组件，如是简单封装个badge组件

GStyle.badge(0, isdot: true)

GStyle.badge(13, color: Colors.green, height: 12.0, width: 12.0)

class GStyle {
    // 消息红点
    static badge(int count, {Color color = Colors.red, bool isdot = false, double height = 18.0, double width = 18.0}) {
        final _num = count > 99 ? ‘···‘ : count;
        return Container(
            alignment: Alignment.center, height: !isdot ? height : height/2, width: !isdot ? width : width/2,
            decoration: BoxDecoration(color: color, borderRadius: BorderRadius.circular(100.0)),
            child: !isdot ? Text(‘$_num‘, style: TextStyle(color: Colors.white, fontSize: 12.0)) : null
        );
    }
}

◆ flutter主入口页面main.dart

/**
 * @tpl Flutter入口页面 | Q：282310962
 */

import ‘package:flutter/material.dart‘;

// 引入公共样式
import ‘styles/common.dart‘;

// 引入底部Tabbar页面导航
import ‘components/tabbar.dart‘;

// 引入地址路由
import ‘router/routes.dart‘;

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: ‘Flutter App‘,
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primaryColor: GStyle.appbarColor,
      ),
      home: TabBarPage(),
      onGenerateRoute: onGenerateRoute,
    );
  }
}

◆ flutter自定义弹窗实现

长按获取点坐标，通过Positioned组件left top属性实现定位，width控制弹窗宽度

InkWell(
    splashColor: Colors.grey[200],
    child: Container(...),
    onTapDown: (TapDownDetails details) {
        _globalPositionX = details.globalPosition.dx;
        _globalPositionY = details.globalPosition.dy;
    },
    onLongPress: () {
        _showPopupMenu(context);
    },
),

// 长按弹窗
double _globalPositionX = 0.0; //长按位置的横坐标
double _globalPositionY = 0.0; //长按位置的纵坐标
void _showPopupMenu(BuildContext context) {
    // 确定点击位置在左侧还是右侧
    bool isLeft = _globalPositionX > MediaQuery.of(context).size.width/2 ? false : true;
    // 确定点击位置在上半屏幕还是下半屏幕
    bool isTop = _globalPositionY > MediaQuery.of(context).size.height/2 ? false : true;

    showDialog(
      context: context,
      builder: (context) {
        return Stack(
          children: <Widget>[
            Positioned(
              top: isTop ? _globalPositionY : _globalPositionY - 200.0,
              left: isLeft ? _globalPositionX : _globalPositionX - 120.0,
              width: 120.0,
              child: Material(
                ...
              ),
            )
          ],
        );
      }
    );
}

flutter中可否去掉弹窗宽高限制？通过SizedBox组件设置宽度，外层包裹布局无限制容器UnconstrainedBox组件

void _showCardPopup(BuildContext context) {
    showDialog(
      context: context,
      builder: (context) {
        return UnconstrainedBox(
          constrainedAxis: Axis.vertical,
          child: SizedBox(
            width: 260,
            child: AlertDialog(
              content: Container(
                ...
              ),
              elevation: 0,
              contentPadding: EdgeInsets.symmetric(horizontal: 10.0, vertical: 20.0),
            ),
          ),
        );
      }
    );
}

◆ flutter/dart登录、注册表单验证

TextField文本框，右侧清空文本框按钮通过Visibility组件控制

TextField(
  keyboardType: TextInputType.phone,
  controller: TextEditingController.fromValue(TextEditingValue(
    text: formObj[‘tel‘],
    selection: new TextSelection.fromPosition(TextPosition(affinity: TextAffinity.downstream, offset: formObj[‘tel‘].length))
  )),
  decoration: InputDecoration(
    hintText: "请输入手机号",
    isDense: true,
    hintStyle: TextStyle(fontSize: 14.0),
    suffixIcon: Visibility(
      visible: formObj[‘tel‘].isNotEmpty,
      child: InkWell(
        child: GStyle.iconfont(0xe69f, color: Colors.grey, size: 14.0), onTap: () {
          setState(() { formObj[‘tel‘] = ‘‘; });
        }
      ),
    ),
    border: OutlineInputBorder(borderSide: BorderSide.none)
  ),
  onChanged: (val) {
    setState(() { formObj[‘tel‘] = val; });
  },
)

// SnackBar提示
final _scaffoldkey = new GlobalKey<ScaffoldState>();
void _snackbar(String title, {Color color}) {
    _scaffoldkey.currentState.showSnackBar(SnackBar(
      backgroundColor: color ?? Colors.redAccent,
      content: Text(title),
      duration: Duration(seconds: 1),
    ));
}

本地存储使用的是 shared_preferences

https://pub.flutter-io.cn/packages/shared_preferences

void handleSubmit() async {
    if(formObj[‘tel‘] == ‘‘) {
      _snackbar(‘手机号不能为空‘);
    }else if(!Util.checkTel(formObj[‘tel‘])) {
      _snackbar(‘手机号格式有误‘);
    }else if(formObj[‘pwd‘] == ‘‘) {
      _snackbar(‘密码不能为空‘);
    }else {
      // ...接口数据

      // 设置存储信息
      final prefs = await SharedPreferences.getInstance();
      prefs.setBool(‘hasLogin‘, true);
      prefs.setInt(‘user‘, int.parse(formObj[‘tel‘]));
      prefs.setString(‘token‘, Util.setToken());

      _snackbar(‘恭喜你，登录成功‘, color: Colors.greenAccent[400]);
      Timer(Duration(seconds: 2), (){
        Navigator.pushNamedAndRemoveUntil(context, ‘/tabbarpage‘, (route) => route == null);
      });
    }
}

flutter中获取验证码60s倒计时，使用Timer.periodic实现

// 60s倒计时
void handleVcode() {
    if(formObj[‘tel‘] == ‘‘) {
      _snackbar(‘手机号不能为空‘);
    }else if(!Util.checkTel(formObj[‘tel‘])) {
      _snackbar(‘手机号格式有误‘);
    }else {
      _countDown();
    }
}
_countDown() {
    if(_validTimer != null) return;
    
    _validTimer = Timer.periodic(Duration(seconds: 1), (t) {
      setState(() {
        if(formObj[‘time‘] > 0) {
          formObj[‘disabled‘] = true;
          formObj[‘vcodeText‘] = ‘获取验证码(${formObj["time"]--})‘;
        }else {
          formObj[‘time‘] = 60;
          formObj[‘vcodeText‘] = ‘获取验证码‘;
          formObj[‘disabled‘] = false;
          
          _validTimer.cancel();
          _validTimer = null;
        }
      });
    });
}

◆ flutter聊天页面解析

flutter中如何实现TextField换行文本框(类似微信聊天编辑框)，设置 maxLines 属性就能实现多行文本。

不过设置maxLines，文本框有一定高度，这时只需设置maxLines: null及keyboardType并在外层加个容器限制最小高度即可。

Container(
    margin: GStyle.margin(10.0),
    decoration: BoxDecoration(color: Colors.white, borderRadius: BorderRadius.circular(3.0)),
    constraints: BoxConstraints(minHeight: 30.0, maxHeight: 150.0),
    child: TextField(
        maxLines: null,
        keyboardType: TextInputType.multiline,
        decoration: InputDecoration(
          hintStyle: TextStyle(fontSize: 14.0),
          isDense: true,
          contentPadding: EdgeInsets.all(5.0),
          border: OutlineInputBorder(borderSide: BorderSide.none)
        ),
        controller: _textEditingController,
        focusNode: _focusNode,
        onChanged: (val) {
          setState(() {
            editorLastCursor = _textEditingController.selection.baseOffset;
          });
        },
        onTap: () {handleEditorTaped();},
    ),
),

另外通过文本框focusNode属性可以实现隐藏键盘

FocusNode _focusNode = FocusNode();
...
void clickMsgPanel() {
    // 隐藏键盘
    _focusNode.unfocus();
    setState(() { showFootToolbar = false; });
}

flutter中如何实现滚动聊天信息至底部？

通过ListView里controller的获取最大滚动距离，并通过jumpTo方法滚动。

ScrollController _msgController = new ScrollController();
...
ListView(
    controller: _msgController,
    padding: EdgeInsets.all(10.0),
    children: renderMsgTpl(),
)

// 滚动消息至聊天底部
void scrollMsgBottom() {
    timer = Timer(Duration(milliseconds: 100), () => _msgController.jumpTo(_msgController.position.maxScrollExtent));
}

ok，基于flutter+dart跨平台开发仿微信聊天实例项目就分享到这里，希望大家能喜欢！????

最后附上基于electron+vue桌面端IM实例

https://www.cnblogs.com/xiaoyan2017/p/12169391.html

Flutter聊天室|dart+flutter仿微信App界面|flutter聊天实例

码农公寓

一、项目概述

二、技术框架

◆ flutter沉浸式状态栏/底部tabbar导航

◆ flutter中使用字体图标 (阿里iconfont图标)

◆ flutter中红点/圆点提示

◆ flutter主入口页面main.dart

◆ flutter自定义弹窗实现

◆ flutter/dart登录、注册表单验证

◆ flutter聊天页面解析

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