单击DataTable内的颤振应用程序状态未加载(setState)

Question

每当我在DataRow中单击并尝试setState()时，显然主应用程序状态未挂载。如果有人能给我指出正确的方向，为什么会发生这种情况，我会非常感激。我真的需要能够更新应用程序(setState)后点击一个DataTable。

示例代码:

import 'package:flutter/material.dart';
void main() {
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({super.key});
@override
Widget build(BuildContext context) {
return const MaterialApp(
title: 'Flutter Demo',
home: MyHomePage(),
);
}
}
class MyHomePage extends StatefulWidget {
const MyHomePage({super.key});
@override
State<MyHomePage> createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
@override
setState(fn){
if (mounted) {
super.setState(fn);
} else {
debugPrint('Not mounted');
}
}
update() => setState((){});
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Flutter Demo'),
),
body: PaginatedDataTable(
showCheckboxColumn: true,
columns: const <DataColumn>[
DataColumn(
label: Expanded(
child: Text(
'Name',
style: TextStyle(fontStyle: FontStyle.italic),
),
),
),
DataColumn(
label: Expanded(
child: Text(
'Age',
style: TextStyle(fontStyle: FontStyle.italic),
),
),
),
DataColumn(
label: Expanded(
child: Text(
'Role',
style: TextStyle(fontStyle: FontStyle.italic),
),
),
),
],
source: MyDataTableSource(),
),
);
}
}
class MyDataTableSource extends DataTableSource {
@override
DataRow getRow(int index) {
return DataRow.byIndex(
index: index,
cells: <DataCell>[
DataCell(GestureDetector(
onTap: () => _MyHomePageState().update(),
child: const Text('Sarah'),
)),
DataCell(GestureDetector(
onTap: () => _MyHomePageState().update(),
child: const Text('19'),
)),
DataCell(GestureDetector(
onTap: () => _MyHomePageState().update(),
child: const Text('Student'),
)),
],
);
}
@override
bool get isRowCountApproximate => false;
@override
int get rowCount => 3;
@override
int get selectedRowCount => 0;
}

Answer 1

您正在对一个新的状态引用触发.update()。使用适当的状态管理，否则你将被迫使用setState Use "Key"这样的

import 'package:flutter/material.dart';
GlobalKey<MyHomePageState> myHomePageKey = GlobalKey<MyHomePageState>();
void main() {
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({super.key});
@override
Widget build(BuildContext context) {
return  MaterialApp(
title: 'Flutter Demo',
home: MyHomePage(key:myHomePageKey),
);
}
}
class MyHomePage extends StatefulWidget {
const MyHomePage({super.key});
@override
State<MyHomePage> createState() => MyHomePageState();
}
class MyHomePageState extends State<MyHomePage> {
@override
setState(fn){
if (mounted) {
super.setState(fn);
} else {
debugPrint('Not mounted');
}
}
update() => setState((){});
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Flutter Demo'),
),
body: PaginatedDataTable(
showCheckboxColumn: true,
columns: const <DataColumn>[
DataColumn(
label: Expanded(
child: Text(
'Name',
style: TextStyle(fontStyle: FontStyle.italic),
),
),
),
DataColumn(
label: Expanded(
child: Text(
'Age',
style: TextStyle(fontStyle: FontStyle.italic),
),
),
),
DataColumn(
label: Expanded(
child: Text(
'Role',
style: TextStyle(fontStyle: FontStyle.italic),
),
),
),
],
source: MyDataTableSource(),
),
);
}
}
class MyDataTableSource extends DataTableSource {

@override
DataRow getRow(int index) {
return DataRow.byIndex(
index: index,
cells: <DataCell>[
DataCell(GestureDetector(
onTap: () => myHomePageKey.currentState!.update(),
child: const Text('Sarah'),
)),
DataCell(GestureDetector(
onTap: () => myHomePageKey.currentState!.update(),
child: const Text('19'),
)),
DataCell(GestureDetector(
onTap: () => myHomePageKey.currentState!.update(),
child: const Text('Student'),
)),
],
);
}
@override
bool get isRowCountApproximate => false;
@override
int get rowCount => 3;
@override
int get selectedRowCount => 0;
}