flutter中的网络请求和下拉刷新上拉加载，toast的案例

添加依赖

  pull_to_refresh: ^1.5.6
  dio: ^2.1.0
  fluttertoast: ^3.0.1

DioUtil

import 'package:dio/dio.dart';

class DioUtil {

  static DioUtil _instance;
  final Dio _mDio =
      Dio(BaseOptions(baseUrl: "http://192.168.0.60:8080"));
  Dio get mDio => _mDio;
  DioUtil._();
  static DioUtil getInstance() {
    if (_instance == null) {
      _instance = DioUtil._();
      _instance._init();
    }
    return _instance;
  }

  _init() {}
}

Urls

  class Urls {
      static const String getUserUrl = '/user/getAllUserByPage';
  }

LogUtils

class LogUtils {
  static const bool isRelease = const bool.fromEnvironment("dart.vm.product");

  static void d(String tag, Object message) {
    if (!isRelease) _printLog(tag, 'D -> ', message);
  }

  static void i(String tag, Object message) {
    _printLog(tag, 'I -> ', message);
  }

  static void e(String tag, Object message, {Exception e}) {
    _printLog(tag, 'E -> ', message);
  }

  static void _printLog(String tag, String level, Object message) {
    StringBuffer sb = new StringBuffer();
    sb..write(level)..write(tag ?? '')..write(': ')..write(message);
    print(sb.toString());
  }
}

BaseNetResponseModel

class BaseNetResponseModel<T> {
  final int code;

  final String msg;

  final T data;

  const BaseNetResponseModel(
      {this.code,
      this.msg,
      this.data,
  });
}

DataBean

class DataBean {
  String userid;
  String job;

DataBean.fromJson(Map<String, dynamic> json) {
    userid = json['userid'];

    job = json['job'];
  }
}

DataRepository

import './databean.dart';
import 'BaseNetResponseModel.dart';

abstract class DataRepository {
  Future< BaseNetResponseModel<List<DataBean>>> getUserAll(
      String pageIndex,String pageSize
      );
}

NetDataRepository

import 'package:dio/dio.dart';
import 'package:futuredemo/BaseNetResponseModel.dart';
import 'package:futuredemo/DataRepository.dart';
import 'package:futuredemo/DioUtil.dart';
import 'package:futuredemo/databean.dart';
import 'Apis.dart';

class NetDataRepository extends DataRepository {
  Dio _dio = DioUtil.getInstance().mDio;
  List<DataBean> companyCustomerList;
  int code;
  String msg;
  Map<String, dynamic> data;
  @override
  Future<BaseNetResponseModel<List<DataBean>>> getUserAll(
      String pageIndex, String pageSize) async {
    Response response = await _dio.get(
        Urls.getUserUrl + "?pageIndex=" + pageIndex + "&pageSize=" + pageSize);
    print(response.data);
    print(response.data['data']);
    List userslist = response.data['data']["users"] as List;
    code = response.data['code'];
    msg = response.data['msg'];
    companyCustomerList = userslist.map((customer) {
      return DataBean.fromJson(customer);
    }).toList();

    return BaseNetResponseModel<List<DataBean>>(
        code: code, msg: msg, data: companyCustomerList);
  }
}

ToastUtils

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

class ToastUtils {
  static ToastUtils _instance;

  ToastUtils._();

  static ToastUtils getInstance() {
    if (_instance == null) {
      _instance = ToastUtils._();
    }
    return _instance;
  }

  Future _cancelPreToast() async {
    await Fluttertoast.cancel();
  }

  static void toastShort(String message) {
    getInstance()._cancelPreToast();
    Fluttertoast.showToast(
        msg: message,
        toastLength: Toast.LENGTH_SHORT,
        gravity: ToastGravity.CENTER,
        timeInSecForIos: 1,
        backgroundColor: Colors.grey,
        textColor: Colors.white,
        fontSize: 14.0);
  }

  static void toastLong(String message) {
    getInstance()._cancelPreToast();
    Fluttertoast.showToast(
        msg: message,
        toastLength: Toast.LENGTH_LONG,
        gravity: ToastGravity.CENTER,
        timeInSecForIos: 1,
        backgroundColor: Colors.blue[300],
        textColor: Colors.white,
        fontSize: 14.0);
  }
}

PageError

import 'package:flutter/material.dart';

class PageError extends StatelessWidget {
  final VoidCallback callback;

  const PageError({Key key, this.callback}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Center(
      child: MaterialButton(
          child: Text('重新加载', style: TextStyle(color: Theme.of(context).primaryColor),),
          onPressed: () {
            if (callback != null) callback();
          }),
    );
  }
}

PageLoading

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

class PageLoading extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Center(
      child: Row(
        mainAxisAlignment: MainAxisAlignment.center,
        crossAxisAlignment: CrossAxisAlignment.center,
        children: <Widget>[
          CupertinoActivityIndicator(),
        ],
      ),
    );
  }
}

JobPage

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:futuredemo/log_utils.dart';
import 'package:futuredemo/toast_utils.dart';
import './page_error.dart';
import './page_loading.dart';
import 'package:pull_to_refresh/pull_to_refresh.dart';
import 'BaseNetResponseModel.dart';
import 'NetDataRepository.dart';
import 'databean.dart';

class JobPage extends StatefulWidget {
  @override
  _JobPageState createState() => _JobPageState();
}

class _JobPageState extends State<JobPage> {
  NetDataRepository _netDataRepository = NetDataRepository();

  Future<Map<String, dynamic>> _futureBuilderFuture;
  List<DataBean> dataList = List();

  RefreshController _refreshController =
      RefreshController(initialRefresh: false);

  void initState() {
    super.initState();

    _futureBuilderFuture = _loadData();
  }

  void _onRefresh() async {
    BaseNetResponseModel<List<DataBean>> model =
        await _netDataRepository.getUserAll("1", "10");
    dataList.clear();
    dataList.addAll(model.data);
    // 日志打印
    LogUtils.d("tag", model.code);
    _refreshController.refreshCompleted();
    _refreshController.loadComplete();
    if (mounted) setState(() {});
  }

  void _onLoading() async {
    await Future.delayed(Duration(milliseconds: 1000));
    if (dataList.length < 30) {
      dataList.add(dataList[0]);
    } else {
      _refreshController.loadNoData();
      return;
    }

    if (mounted) setState(() {});

    _refreshController.loadComplete();
  }

  Future<Map<String, dynamic>> _loadData() async {
    BaseNetResponseModel<List<DataBean>> model =
        await _netDataRepository.getUserAll("1", "10");
    dataList.clear();
    dataList.addAll(model.data);
    return {"data": 0};
  }

  _refresh() async {
    setState(() {
      _futureBuilderFuture = _loadData();
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(

      appBar: AppBar(
        elevation: 0.0,
        title: Text('职业'),
        centerTitle: true,
      ),
      floatingActionButton: FloatingActionButton(
          backgroundColor: Theme.of(context).primaryColor,
          child: Icon(
            Icons.add,
            size: 28,
            color: Colors.white,
          ),
          elevation: 4,
          onPressed: () {
            //吐司提示
            ToastUtils.toastShort("点击了");
          }),
      body: FutureBuilder(
        builder: (BuildContext context,
            AsyncSnapshot<Map<String, dynamic>> snapshot) {
          Widget widget;
          switch (snapshot.connectionState) {
            case ConnectionState.none:
              widget = Container();
              break;
            case ConnectionState.active:
            case ConnectionState.waiting:
              widget = PageLoading();
              break;
            case ConnectionState.done:
              if (snapshot.hasError) {
                widget = PageError(
                  callback: _refresh,
                );
              } else if (snapshot.hasData) {
                widget = _buildBody(context);
              }
              break;
          }
          return widget;
        },
        future: _futureBuilderFuture,
      ),
    );
  }

  Column _buildBody(BuildContext context) {
    return Column(
      children: <Widget>[
        Expanded(
          child: SmartRefresher(
            enablePullDown: true,
            enablePullUp: true,
            header: WaterDropMaterialHeader(
                // backgroundColor:Color(OxFF00),
                ),
            footer: CustomFooter(
              builder: (BuildContext context, LoadStatus mode) {
                Widget body;
                if (mode == LoadStatus.idle) {
                  body = Row(children: <Widget>[
                    Expanded(
                      flex: 3,
                      child: Divider(
                        indent: 40,
                        height: 1,
                      ),
                    ),
                    Expanded(
                      flex: 2,
                      child: Container(
                        height: 40.0,
                        child: Center(
                            child: Text("上拉加载更多",
                                style: TextStyle(
                                    color: Colors.grey, fontSize: 13))),
                      ),
                    ),
                    Expanded(
                      flex: 3,
                      child: Divider(
                        height: 1,
                        endIndent: 40,
                      ),
                    )
                  ]);
                } else if (mode == LoadStatus.loading) {
                  body = CupertinoActivityIndicator();
                } else if (mode == LoadStatus.failed) {
                  body = Text("加载失败！",
                      style: TextStyle(color: Colors.grey, fontSize: 13));
                } else {
                  body = Row(children: <Widget>[
                    Expanded(
                      flex: 3,
                      child: Divider(
                        indent: 40,
                        height: 1,
                      ),
                    ),
                    Expanded(
                      flex: 2,
                      child: Container(
                        height: 40.0,
                        child: Center(
                            child: Text("已经到底啦",
                                style: TextStyle(
                                    color: Colors.grey, fontSize: 13))),
                      ),
                    ),
                    Expanded(
                      flex: 3,
                      child: Divider(
                        height: 1,
                        endIndent: 40,
                      ),
                    )
                  ]);
                }
                return Container(
                  height: 50.0,
                  child: Center(child: body),
                );
              },
            ),
            controller: _refreshController,
            onRefresh: _onRefresh,
            onLoading: _onLoading,
            child: GridView.builder(
                padding: EdgeInsets.all(10.0),
                shrinkWrap: true,
                itemCount: dataList.length,
                gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
                    crossAxisCount: 2,
                    //纵轴间距
                    mainAxisSpacing: 10.0,
                    //横轴间距
                    crossAxisSpacing: 10.0,
                    //子组件宽高长度比例
                    childAspectRatio: 1.5),
                itemBuilder: (context, index) {
                  // Map<String, dynamic> entry = dataList[index];
                  return UserItemWidget(
                    title: '${dataList[index].job}',
                    onTap: () {},
                  );
                }),
          ),
        ),
      ],
    );
  }
}

class UserItemWidget extends StatefulWidget {
  String title = "";

  int type = 1;
  VoidCallback onTap;

  UserItemWidget({
    Key key,
    this.title,
    this.onTap,
  }) : super(key: key);

  @override
  _UserItemWidgetState createState() => _UserItemWidgetState();
}

class _UserItemWidgetState extends State<UserItemWidget> {
  VoidCallback _onTap;

  @override
  void initState() {
    super.initState();
    _onTap = widget.onTap;
  }

  @override
  Widget build(BuildContext context) {
    return InkWell(
      onTap: _onTap,
      child: Stack(
        children: <Widget>[
          Container(
            padding: EdgeInsets.all(8),
            decoration: new BoxDecoration(
              color: Colors.white,
              border: new Border.all(width: 1.0, color: Colors.grey[300]),
              borderRadius: new BorderRadius.all(new Radius.circular(2)),
            ),
            child: Column(
              mainAxisSize: MainAxisSize.max,
              children: <Widget>[
                Container(
                  margin: EdgeInsets.only(top: 15, bottom: 10, left: 10),
                  alignment: Alignment.centerLeft,
                  child: Text(widget.title == "" ? "未知" : widget.title,
                      style: TextStyle(fontSize: 18)),
                ),
              ],
            ),
          ),
          Positioned(
              top: 0,
              right: 0,
              child: Container(
                color: getTypeColor(widget.type),
                padding: EdgeInsets.all(5),
                child: Center(
                  child: Text(getTypeText(widget.type),
                      style: TextStyle(
                        color: Colors.white,
                        fontSize: 13.0,
                      )),
                ),
              ))
        ],
      ),
    );
  }

  String getTypeText(int type) {
    switch (type) {
      case 1:
        return "黄金职业";
      case 2:
        return "夕阳职业";
      case 3:
        return "朝阳职业";
    }
  }

  Color getTypeColor(int type) {
    switch (type) {
      case 1:
        return Color(0xFFFF00FF);
      case 2:
        return Color(0xFFC6C6C6);
      case 3:
        return Color(0xFF7FC3FD);
    }
  }
}

效果：