英文:
How to resolve "The method 'read' isn't defined for the type 'BuildContext'" error when using Riverpod for state management?
问题
我正在尝试在我的Flutter应用程序中将Riverpod用作状态管理解决方案。我有一个CountDownController类，它创建了一个动画控制器，以及一个PomodoroIntervals小部件，它使用CountDownController来管理一些倒计时逻辑。然而，当我尝试从BuildContext访问read方法时，我遇到以下错误：
方法'read'未针对类型'BuildContext'定义。尝试更正名称为现有方法的名称，或定义一个名为'read'的方法。dartundefined_method
这个错误发生在PomodoroIntervals小部件的initState方法中，我正在尝试使用Riverpod提供程序的read方法来初始化_countDownController变量：
_countDownController = context.read(countDownControllerProvider);
此外，当我尝试访问CountDownController类的timerString属性时，我也遇到另一个错误：
获取器'timerString'未针对类型'CountDownController'定义。尝试导入定义'timerString'的库，将名称更正为现有获取器的名称，或定义一个名为'timerString'的获取器或字段。
这个错误发生在PomodoroIntervals小部件的notify方法中：
if (_countDownController.timerString == '00:00:00') {
_tabController.animateTo(1, duration: const Duration(milliseconds: 300));
}
以下是完整的代码，为这两个问题提供了上下文：
import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:google_fonts/google_fonts.dart';
final countDownControllerProvider =
Provider<CountDownController>((ref) => CountDownController());
class CountDownController {
late AnimationController controller;
void createAnimationController(TickerProvider tickerProvider) {
controller = AnimationController(
vsync: tickerProvider,
duration: const Duration(seconds: 60),
);
}
}
class PomodoroIntervals extends StatefulWidget {
const PomodoroIntervals({Key? key}) : super(key: key);
@override
State<PomodoroIntervals> createState() => _PomodoroIntervalsState();
}
class _PomodoroIntervalsState extends State<PomodoroIntervals>
with TickerProviderStateMixin {
late TabController _tabController;
late CountDownController _countDownController;
@override
void initState() {
super.initState();
_tabController = TabController(length: 3, vsync: this, initialIndex: 0);
_countDownController = context.read(countDownControllerProvider.notifier);
_countDownController.createAnimationController(this);
}
@override
void dispose() {
_tabController.dispose();
super.dispose();
}
void notify() {
if (_countDownController.timerString == '00:00:00') {
_tabController.animateTo(1, duration: const Duration(milliseconds: 300));
}
}
double progress = 1.0;
bool LongBreak = true;
@override
Widget build(BuildContext context) {
return ProviderScope(
child: SizedBox(
height: MediaQuery.of(context).size.height,
width: double.infinity,
child: AnimatedBuilder(
animation: _countDownController.controller,
builder: (context, child) {
return DefaultTabController(
length: 3,
child: Scaffold(
appBar: AppBar(
elevation: 0,
backgroundColor: Colors.transparent,
bottom: PreferredSize(
preferredSize: const Size.fromHeight(22),
child: Container(
color: Colors.transparent,
child: SafeArea(
child: Column(children: [
TabBar(
controller: _tabController,
indicator: const UnderlineTabIndicator(
borderSide:
BorderSide(color: Color(0xff3B3B3B), width: 2.0),
insets: EdgeInsets.fromLTRB(12.0, 12.0, 12.0, 12.0),
),
indicatorWeight: 5,
indicatorSize: TabBarIndicatorSize.label,
labelColor: const Color(0xff3B3B3B),
labelStyle: GoogleFonts.nunito(
fontSize: 16.0,
fontWeight: FontWeight.w500,
),
unselectedLabelColor: const Color(0xffD7D7D7),
tabs: const [
Tab(
text: "Pomodoro",
icon: Icon(Icons.work_history_outlined, size: 24),
),
Tab(
text: "Short break",
icon: Icon(Icons.ramen_dining_outlined, size: 24),
),
Tab(
text: "Long break",
icon: Icon(Icons.battery_charging_full_outlined, size: 24),
),
],
),
]),
),
),
),
),
body: TabBarView(
controller: _tabController,
children: const <Widget>[
Center(
child: Text('Short break'),
),
Center(
child: Text('Short break'),
),
Center(child: Text('Long break')),
],
),
),
);
},
),
),
);
}
}
我已经检查了导入并确保包含了必要的包。您如何解决这些错误并成功在Flutter应用程序中使用Riverpod进行状态管理？
英文:
I'm trying to use Riverpod as my state management solution in a Flutter app. I have a CountDownController class that creates an animation controller and a PomodoroIntervals widget that uses the CountDownController to manage some countdown logic. However, I'm encountering the following error when trying to access the read method from BuildContext:
> The method 'read' isn't defined for the type 'BuildContext'. Try
> correcting the name to the name of an existing method, or defining a
> method named 'read'.dartundefined_method
This error occurs in the initState method of the PomodoroIntervals widget, where I'm trying to initialize the _countDownController variable using the read method from the Riverpod provider:
_countDownController = context.read(countDownControllerProvider);
Additionally, I'm also facing another error when trying to access the timerString property of the CountDownController class:
> The getter 'timerString' isn't defined for the type
> 'CountDownController'. Try importing the library that defines
> 'timerString', correcting the name to the name of an existing getter,
> or defining a getter or field named 'timerString'.
This error occurs in the notify method of the PomodoroIntervals widget:
if (_countDownController.timerString == '00:00:00') {
_tabController.animateTo(1, duration: const Duration(milliseconds: 300));
}
This is the complete code, which provides context for the two problems:
import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:google_fonts/google_fonts.dart';
final countDownControllerProvider =
Provider<CountDownController>((ref) => CountDownController());
class CountDownController {
late AnimationController controller;
void createAnimationController(TickerProvider tickerProvider) {
controller = AnimationController(
vsync: tickerProvider,
duration: const Duration(seconds: 60),
);
}
}
class PomodoroIntervals extends StatefulWidget {
const PomodoroIntervals({Key? key}) : super(key: key);
@override
State<PomodoroIntervals> createState() => _PomodoroIntervalsState();
}
class _PomodoroIntervalsState extends State<PomodoroIntervals>
with TickerProviderStateMixin {
late TabController _tabController;
late CountDownController _countDownController;
@override
void initState() {
super.initState();
_tabController = TabController(length: 3, vsync: this, initialIndex: 0);
_countDownController = context.read(countDownControllerProvider.notifier);
_countDownController.createAnimationController(this);
}
@override
void dispose() {
_tabController.dispose();
super.dispose();
}
void notify() {
if (_countDownController.timerString == '00:00:00') {
_tabController.animateTo(1, duration: const Duration(milliseconds: 300));
}
}
double progress = 1.0;
bool LongBreak = true;
@override
Widget build(BuildContext context) {
return ProviderScope(
child: SizedBox(
height: MediaQuery.of(context).size.height,
width: double.infinity,
child: AnimatedBuilder(
animation: _countDownController.controller,
builder: (context, child) {
return DefaultTabController(
length: 3,
child: Scaffold(
appBar: AppBar(
elevation: 0,
backgroundColor: Colors.transparent,
bottom: PreferredSize(
preferredSize: const Size.fromHeight(22),
child: Container(
color: Colors.transparent,
child: SafeArea(
child: Column(children: [
TabBar(
controller: _tabController,
indicator: const UnderlineTabIndicator(
borderSide:
BorderSide(color: Color(0xff3B3B3B), width: 2.0),
insets: EdgeInsets.fromLTRB(12.0, 12.0, 12.0, 12.0),
),
indicatorWeight: 5,
indicatorSize: TabBarIndicatorSize.label,
labelColor: const Color(0xff3B3B3B),
labelStyle: GoogleFonts.nunito(
fontSize: 16.0,
fontWeight: FontWeight.w500,
),
unselectedLabelColor: const Color(0xffD7D7D7),
tabs: const [
Tab(
text: "Pomodoro",
icon: Icon(Icons.work_history_outlined, size: 24),
),
Tab(
text: "Short break",
icon: Icon(Icons.ramen_dining_outlined, size: 24),
),
Tab(
text: "Long break",
icon: Icon(Icons.battery_charging_full_outlined, size: 24),
),
],
),
]),
),
),
),
),
body: TabBarView(
controller: _tabController,
children: const <Widget>[
Center(
child: Text('Short break'),
),
Center(
child: Text('Short break'),
),
Center(child: Text('Long break')),
],
),
),
);
},
),
),
);
}
}
I've checked the imports and made sure the necessary packages are included. How can I resolve these errors and successfully use Riverpod for state management in my Flutter app?
答案1
得分: 1
这是翻译好的部分：
"That's right, because context has no such parameter. Here's how to do it (and using ConsumerStatefulWidget):
class PomodoroIntervals extends ConsumerStatefulWidget {
const PomodoroIntervals ({super.key});
@override
ConsumerState createState() => _PomodoroIntervalsState();
}
class _PomodoroIntervalsState extends ConsumerState<PomodoroIntervals> {
@override
void initState() {
...
_countDownController = ref.read(countDownControllerProvider);
}
@override
Widget build(BuildContext context) {
ref.watch(myProvider); // and here...
return Container();
}
}
The ref instance is available as a field of the ConsumerStatefulWidget class"
英文:
That's right, because context has no such parameter. Here's how to do it (and using ConsumerStatefulWidget):
class PomodoroIntervals extends ConsumerStatefulWidget {
const PomodoroIntervals ({super.key});
@override
ConsumerState createState() => _PomodoroIntervalsState();
}
class _PomodoroIntervalsState extends ConsumerState<PomodoroIntervals> {
@override
void initState() {
...
_countDownController = ref.read(countDownControllerProvider);
}
@override
Widget build(BuildContext context) {
ref.watch(myProvider); // and here...
return Container();
}
}
The ref instance is available as a field of the ConsumerStatefulWidget class
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