setState出现Flutter刷新按钮错误

Question

我试图创建一个刷新按钮，它可以重新加载布局并从网站中提取日期(再次)。我尝试使用setState，但它不起作用，只会给我一个错误。该按钮应触发(选项卡式)布局的重新创建

这是我的主菜：

class MyHomePageState extends State<MyHomePage>  {
final GetWebsites _getWebsites = GetWebsites();
@override
void initState() {
super.initState();
WidgetsBinding.instance.addPostFrameCallback((_) {
refresh();
});
}
@override
Widget build(BuildContext context) {
return MaterialApp(
home: getSites(),
);
}
//Get sites => Document, store them in a Document list
Widget getSites() {
return FutureBuilder<List<html.Document>>(
//gets Dates of each date in other class and puts it in an List -> snapshot
future: _getWebsites.getWebsite(),
builder: (BuildContext context, AsyncSnapshot<List<html.Document>> snapshot) {
//Cases for Connections
switch(snapshot.connectionState) {
case ConnectionState.active:
case ConnectionState.waiting:
return const Center(
//TODO: Make better loading screen
child: RefreshProgressIndicator(),
);
case ConnectionState.none:
return const Center(
child: Text("Keine Verbindung"),
);
case ConnectionState.done:
if (snapshot.hasError) {
return const Center(
child: Text('Fehler'),
);
}
//create tabs
return buildrefresh(snapshot);
}
},
);
}
Widget buildrefresh(AsyncSnapshot<List<html.Document>> snapshot) {
return RefreshIndicator(
onRefresh: () {
return refresh();
},
child: rowortabbedLayout(snapshot),
);
}
Widget rowortabbedLayout(AsyncSnapshot<List<html.Document>> snapshot) {
if(Settings.getValue<bool>("keyrowortabbed", true)){
return TabbedLayout().createTabbedLayout(snapshot, context);
}else{
return RowLayout().createRowLayout(snapshot, context);
}
}
Future<void> refresh() async {
setState((){
FutureBuilder<List<html.Document>>(
//gets Dates of each date in other class and puts it in an List -> snapshot
future: _getWebsites.getWebsite(),
builder: (BuildContext context, AsyncSnapshot<List<html.Document>> snapshot) {
//Cases for Connections
switch(snapshot.connectionState) {
case ConnectionState.active:
case ConnectionState.waiting:
return const Center(
child: RefreshProgressIndicator(),
);
case ConnectionState.none:
return const Center(
child: Text("Keine Verbindung"),
);
case ConnectionState.done:
if (snapshot.hasError) {
return const Center(
child: Text('Fehler'),
);
}
//create tabs
return buildrefresh(snapshot);
}
},
);
});
print("Do something!");
}
Future<void> setstaterefresh() async {
setState((){});
print("Do something!");
}

}

我的第二类Tabbed布局(和按钮)是：

class TabbedLayout{
final SiteParser _getSiteData = SiteParser();
Widget createTabbedLayout(AsyncSnapshot<List<html.Document>> snapshot, BuildContext context){
return buildrevresh(snapshot,context);
}
Widget buildrevresh(AsyncSnapshot<List<html.Document>> snapshot, BuildContext context) {
return RefreshIndicator(
onRefresh: () {
return MyHomePageState().setstaterefresh();
},
child: tabcontroller(snapshot,context),
);
}
Widget tabcontroller(AsyncSnapshot<List<html.Document>> snapshot, BuildContext context) {
return DefaultTabController(length: snapshot.data!.length,
child: Scaffold(
appBar: AppBar(
actions: <Widget> [
IconButton(
onPressed: () {
Navigator.push(context, MaterialPageRoute(builder: (context) => const MySettings()),
);
},
icon: const Icon(Icons.settings),
),
//Refresh Button:
IconButton(
icon: const Icon(Icons.refresh),
onPressed: () {
MyHomePageState().refresh();
},
),
],
bottom: TabBar(
isScrollable: true,
tabs:
//Tab names
tabBarMaker(snapshot),
),
title: const Text("Vertretungsplan")
),
body:
TabBarView(
children:
tabMaker(snapshot),
physics: const BouncingScrollPhysics(),
),
),
);
}
List<Widget> tabBarMaker(AsyncSnapshot<List<html.Document>> snapshot) {
List<Tab> tabs = [];
for(int x = 0; x<snapshot.data!.length; x++) {
tabs.add(Tab(text: snapshot.data![x].querySelector('h1.list-table-caption')!.text
.toString()));
}
return tabs;
}
//Create Tabs with contetnt for each site
List<Widget> tabMaker(AsyncSnapshot<List<html.Document>> snapshot) {
List<Widget> tabwidgets = [];
for(int x = 0; x<snapshot.data!.length; x++) {
tabwidgets.add(_buildDay(snapshot.data![x]));
}
return tabwidgets;
}
//Widget to create Tabs of each day and their contents
//Get Contents of a day
Widget _buildDay(html.Document site) {
List<tage> days = _getSiteData.getData(site);
return ListView.builder(
padding: const EdgeInsets.all(10),
itemCount: days.length,
physics: const BouncingScrollPhysics(),
itemBuilder: (context, index) {
//Build cards for each content
return MyThemes().buildCard(days[index]);
},
);
}
}

这是错误日志：

E/flutter (13792): [ERROR:flutter/lib/ui/ui_dart_state.cc(209)] Unhandled Exception: setState() called in constructor: MyHomePageState#a8b0c(lifecycle state: created, no widget, not mounted)
E/flutter (13792): This happens when you call setState() on a State object for a widget that hasn't been inserted into the widget tree yet. It is not necessary to call setState() in the constructor, since the state is already assumed to be dirty when it is initially created.
E/flutter (13792): #0      State.setState.<anonymous closure> (package:flutter/src/widgets/framework.dart:1076:9)
E/flutter (13792): #1      State.setState (package:flutter/src/widgets/framework.dart:1087:6)
E/flutter (13792): #2      MyHomePageState.refresh (package:khsplan/main.dart:140:5)
E/flutter (13792): #3      TabbedLayout.tabcontroller.<anonymous closure> (package:khsplan/Vplan/tabbedlayout.dart:42:37)
E/flutter (13792): #4      _InkResponseState._handleTap (package:flutter/src/material/ink_well.dart:989:21)
E/flutter (13792): #5      GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:193:24)
E/flutter (13792): #6      TapGestureRecognizer.handleTapUp (package:flutter/src/gestures/tap.dart:608:11)
E/flutter (13792): #7      BaseTapGestureRecognizer._checkUp (package:flutter/src/gestures/tap.dart:296:5)
E/flutter (13792): #8      BaseTapGestureRecognizer.handlePrimaryPointer (package:flutter/src/gestures/tap.dart:230:7)
E/flutter (13792): #9      PrimaryPointerGestureRecognizer.handleEvent (package:flutter/src/gestures/recognizer.dart:558:9)
E/flutter (13792): #10     PointerRouter._dispatch (package:flutter/src/gestures/pointer_router.dart:94:12)
E/flutter (13792): #11     PointerRouter._dispatchEventToRoutes.<anonymous closure> (package:flutter/src/gestures/pointer_router.dart:139:9)
E/flutter (13792): #12     _LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:400:8)
E/flutter (13792): #13     PointerRouter._dispatchEventToRoutes (package:flutter/src/gestures/pointer_router.dart:137:18)
E/flutter (13792): #14     PointerRouter.route (package:flutter/src/gestures/pointer_router.dart:123:7)
E/flutter (13792): #15     GestureBinding.handleEvent (package:flutter/src/gestures/binding.dart:440:19)
E/flutter (13792): #16     GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:420:22)
E/flutter (13792): #17     RendererBinding.dispatchEvent (package:flutter/src/rendering/binding.dart:278:11)
E/flutter (13792): #18     GestureBinding._handlePointerEventImmediately (package:flutter/src/gestures/binding.dart:374:7)
E/flutter (13792): #19     GestureBinding.handlePointerEvent (package:flutter/src/gestures/binding.dart:338:5)
E/flutter (13792): #20     GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:296:7)
E/flutter (13792): #21     GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:279:7)
E/flutter (13792): #22     _rootRunUnary (dart:async/zone.dart:1444:13)
E/flutter (13792): #23     _CustomZone.runUnary (dart:async/zone.dart:1335:19)
E/flutter (13792): #24     _CustomZone.runUnaryGuarded (dart:async/zone.dart:1244:7)
E/flutter (13792): #25     _invoke1 (dart:ui/hooks.dart:185:10)
E/flutter (13792): #26     PlatformDispatcher._dispatchPointerDataPacket (dart:ui/platform_dispatcher.dart:293:7)
E/flutter (13792): #27     _dispatchPointerDataPacket (dart:ui/hooks.dart:98:31)

Answer 1

我认为错误可能是在Switch case选项ConnectionState.active上，它没有停止或其他什么，它继续到ConnectionState.waiting，所以我会尝试添加类似break的语句，同时在那里添加另一个功能：

Future<void> refresh() async {
setState((){
FutureBuilder<List<html.Document>>(
//gets Dates of each date in other class and puts it in an List -> snapshot
future: _getWebsites.getWebsite(),
builder: (BuildContext context, AsyncSnapshot<List<html.Document>> snapshot) {
//Cases for Connections
switch(snapshot.connectionState) {
// ! ADDING CODE HERE
case ConnectionState.active:
// ! ADDING CODE HERE
break;
case ConnectionState.waiting:
return const Center(
child: RefreshProgressIndicator(),
);
case ConnectionState.none:
return const Center(
child: Text("Keine Verbindung"),
);
case ConnectionState.done:
if (snapshot.hasError) {
return const Center(
child: Text('Fehler'),
);
}
//create tabs
return buildrefresh(snapshot);
}
},
);
});
print("Do something!");
}

我希望这会有所帮助。