我是 Flutter 学习的新手，这是我从一些教程中编写的代码。我尝试这样做。当用户位于数组的第一个或最后一个索引但 AlertDialog 未显示在屏幕上时显示 Run pipeline。
任何人都可以为此指导我，或者可以让我知道我做错了什么。
AlertDialog我在 import 'package:flutter/material.dart';
import './question.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatefulWidget {
@override
State<StatefulWidget> createState() {
return _MyAppState();
}
}
// IF WE DON'T WANT TO ALLOW OTHER CLASS TO ACCESS THIS CLASS THEN WE CAN MAKE IT PRIVATE BY ADDING _ AT THE STARTING OF FUNCTIONS & VARIABLE
class _MyAppState extends State<MyApp> {
var _questionIndex = 0;
//MARK: - NEXT QUESTION TAPPED
void _btnNextQuestionTapped() {
setState(() {
if (_questionIndex < 2) {
_questionIndex = _questionIndex + 1;
print("Index Updated ==> " + _questionIndex.toString());
} else {
_questionIndex = _questionIndex;
print("Index At Last ==> " + _questionIndex.toString());
showAlertDialog("Alert", "You are at the Last Position");
}
});
}
//MARK: - PREVIOUS QUESTION TAPPED
void _btnPreviousQuestionTapped() {
setState(() {
if (_questionIndex == 0) {
_questionIndex = 0;
print("Index At First ==> " + _questionIndex.toString());
showAlertDialog("Alert", "You are at the First Position");
} else {
_questionIndex = _questionIndex - 1;
print("Index Updated ==> " + _questionIndex.toString());
}
});
}
Future<void> showAlertDialog(String title, String message) async {
return showDialog<void>(
context: context,
barrierDismissible: true, // user must tap button!
builder: (BuildContext context) {
return AlertDialog(
title: Text('AlertDialog Title'),
content: SingleChildScrollView(
child: ListBody(
children: <Widget>[
Text(title),
Text(message),
],
),
),
actions: <Widget>[
TextButton(
child: Text('OK'),
onPressed: () {
// Navigator.of(context).pop();
},
),
],
);
},
);
}
@override
Widget build(BuildContext context) {
var arrQuestions = [
"Which Technology is Good?",
"Which development tool is more user friendly?",
"Which language is easy to Learn?"
];
return MaterialApp(
home: Scaffold(
appBar: AppBar(
title: Text("State Management Demo"),
),
body: Column(
children: [
Question(arrQuestions[_questionIndex]),
RaisedButton(
child: Text("Next Question"),
onPressed: () => _btnNextQuestionTapped(),
),
RaisedButton(
child: Text("Previous Question"),
onPressed: () => _btnPreviousQuestionTapped(),
),
],
// mainAxisAlignment: MainAxisAlignment.center,
// verticalDirection: VerticalDirection.up,
),
),
);
}
}
() 和 showAlertDialog();()
_btnNextQuestionTapped
在终端中获取以下日志。
<块引用>VERBOSE-2:ui_dart_state.cc(177)] 未处理的异常：否 找到 MaterialLocalizations。 MyApp 小部件需要 由 Localizations 小部件提供的 MaterialLocalizations 祖先。材料库使用 Localizations 生成 消息、标签和缩写。介绍一个 MaterialLocalizations，或者在你的根目录使用 MaterialApp 应用程序自动包含它们，或添加本地化 带有 MaterialLocalizations 委托的小部件。特定的小部件 找不到 MaterialLocalizations 的祖先是：MyApp 这个小部件的祖先是：[root] #0 debugCheckHasMaterialLocalizations。 （包：flutter/src/material/debug.dart:74:7） #1 debugCheckHasMaterialLocalizations (package:flutter/src/material/debug.dart:94:4) #2 showDialog (package:flutter/src/material/dialog.dart:987:10) #3 _MyAppState.showAlertDialog (package:state_management_demo/main.dart:49:12) #4 _MyAppState._btnNextQuestionTapped。 (pac<…>
答案 0 :(得分：0)
如我所见，这里的上下文存在问题，您能否在 showAlertDialog 中传递上下文作为从调用它的位置传递上下文。 它会解决它 像这样：- Future showAlertDialog(String title, String message,context)