android - 抓住 WorkManager 的答案

Question

我想根据我的后台任务的结果更新我的应用程序的背景颜色。我使用 flutter_bloc 和 WorkManager。我希望我的应用程序在操作期间为蓝色，如果结果良好则为绿色，如果我的函数抛出异常则为红色。或者我可以根据我的 repo.getBattery 调用结果更新我的屏幕颜色吗？在日志中，我可以读取 workmanager.result 错误（错误的 url），但我无法捕捉到它。

主要飞镖：

import 'package:batt/test_cubit.dart';
import 'package:flutter/cupertino.dart';

import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:shared_preferences/shared_preferences.dart';

void main() {
  WidgetsFlutterBinding.ensureInitialized();

  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return BlocProvider(
        create: (context) => TestCubit(),
        child: MaterialApp(
          title: 'Flutter Demo',
          theme: ThemeData(
            primarySwatch: Colors.blue,
          ),
          home: MyHomePage(),
        ));
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key}) : super(key: key);

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

class _MyHomePageState extends State<MyHomePage> {
  bool _sw_value = false;
  TextEditingController _controller = TextEditingController(text: "url");

  Future<Null> tmp() async{
    SharedPreferences prefs = await SharedPreferences.getInstance();
    setState(() {
      _controller = TextEditingController(text: prefs.getString("url"));
    });
  }

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

  @override
  Widget build(BuildContext context) {
    return BlocBuilder<TestCubit, TestState>(builder: (context, state) {
      return Scaffold(
        backgroundColor: state.status,
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            crossAxisAlignment: CrossAxisAlignment.center,
            children: [
              TextField(
                controller: _controller,
                maxLines: null,
                keyboardType: TextInputType.url,
                onChanged: (url) =>
                    context.read<TestCubit>().urlChanged(url),
              ),

              const SizedBox(
                height: 50,
              ),
              CupertinoSwitch(
                  value: _sw_value,
                  onChanged: (value){
                    setState(() {
                      _sw_value = value;
                    });
                    if (value == true){
                      BlocProvider.of<TestCubit>(context).validate();
                    }
                    else {
                      BlocProvider.of<TestCubit>(context).cancel();
                    }
                  }
              ),
            ],
          ),
        ),
      );
    });
  }
}

和我的test_cubit.dart：

import 'dart:async';

import 'package:battery_plus/battery_plus.dart';
import 'package:bloc/bloc.dart';

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

import 'package:workmanager/workmanager.dart';

import 'data/Repository/battery_repo.dart';
import 'data/data_provider/battery_provider.dart';
import 'package:http/http.dart' as http;

part 'test_state.dart';

const fetchBackground = "fetchBackground";

void callbackDispatcher() {
  Workmanager().executeTask((task, inputData) async {
    switch (task) {
      case fetchBackground:
        var battery = Battery();
        var batlevel = await battery.batteryLevel;
        final urlFinal = inputData!["string"] + batlevel.toString();
        try {
          await repo.getBattery(urlFinal);
        } catch (e) {
          return Future.error("bad url");
        }
        break;
    }
    return Future.value(true);
  });
}

final BatteryRepository repo = BatteryRepository(api: ServerAPI(http.Client()));

class TestCubit extends Cubit<TestState> {
  TestCubit() : super(TestState("", Colors.grey));

  urlChanged(String url) {
    state.path = url;
  }

  validate() async {
    if (state.path != "") {
      final SharedPreferences _prefs = await SharedPreferences.getInstance();
      _prefs.setString('url', state.path);
    }

    WidgetsFlutterBinding.ensureInitialized();
    await Workmanager().cancelAll();
    await Workmanager().initialize(
      callbackDispatcher,
      isInDebugMode: false,
    );
    state.status = Colors.blue;
    emit(state);
    try {
      Workmanager().registerPeriodicTask("1", fetchBackground,
          backoffPolicy: BackoffPolicy.exponential,
          inputData: {
            'string': state.path,
          });
    } catch (e) {
      state.status = Colors.red;
      emit(state);
    }

    Workmanager().registerPeriodicTask("2", fetchBackground,
        initialDelay: const Duration(minutes: 5),
        inputData: {
          'string': state.path,
        });
    Workmanager().registerPeriodicTask("3", fetchBackground,
        initialDelay: const Duration(minutes: 10),
        inputData: {
          'string': state.path,
        });
    state.status = Colors.green;
    emit(state);
  }

  cancel() async {
    await Workmanager().cancelAll();
    state.status = Colors.pink;
    emit(state);
  }
}

你能帮帮我吗？:) 我是初学者，所以我认为我的代码也不好：/