我有一个 Scaffold 和 BottomNavigationBar：
class Home extends StatefulWidget {
@override
_HomeState createState() => _HomeState();
}
class _HomeState extends State<Home> {
int _currentIndex = 0;
final List<Widget> _children = [
const FirstPage(),
const SecondPage(),
const ThirdPage(),
];
void onTabTapped(int index) {
setState(() {
_currentIndex = index;
});
}
@override
Widget build(BuildContext context) {
size = MediaQuery.of(context).size;
topPadding = MediaQuery.of(context).padding.top;
return Scaffold(
body: _children[_currentIndex],
bottomNavigationBar: SizedBox(
height: 60,
child: BottomNavigationBar(
elevation: 0,
selectedItemColor: Colors.orange,
unselectedItemColor: Colors.black,
showSelectedLabels: false,
showUnselectedLabels: false,
onTap: onTabTapped,
currentIndex: _currentIndex, // this will be set when a new tab is tapped
items: const [
BottomNavigationBarItem(
icon: Icon(Icons.home),
label: 'Home',
),
BottomNavigationBarItem(
icon: Icon(Icons.video_call_rounded),
label: "Settings",
),
BottomNavigationBarItem(
icon: Icon(Icons.person),
label: 'Profile',
)
],
),
),
);
}
}
但是当我使用 BottomNavigationBar 在屏幕之间切换时，我有时会收到错误 Unhandled Exception: 'package:flutter/src/painting/text_painter.dart': Failed assertion: line 881 pos 12: '!_needsLayout': is not true.
如何解决这个问题？
编辑
这是带有错误日志的完整代码：
main.dart
import 'package:cook_it/home.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
void main() {
runApp(ProviderScope(child: MyApp()));
}
class MyApp extends StatelessWidget {
// This widget is the root of your application.
@override
Widget build(BuildContext context) {
SystemChrome.setPreferredOrientations([DeviceOrientation.portraitUp]);
return MaterialApp(
debugShowCheckedModeBanner: false,
title: 'Flutter App!',
theme: ThemeData(
primarySwatch: Colors.blue,
splashFactory: InkRipple.splashFactory,
),
home: Home(),
);
}
}
home.dart
import 'package:cook_it/screens/profile_page.dart';
import 'package:flutter/material.dart';
class Home extends StatefulWidget {
@override
_HomeState createState() => _HomeState();
}
class _HomeState extends State<Home> {
int _currentIndex = 0;
final List<Widget> _children = [
const ProfilePage(),
const ProfilePage(),
const ProfilePage(),
];
void onTabTapped(int index) {
setState(() {
_currentIndex = index;
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
body: _children[_currentIndex],
bottomNavigationBar: SizedBox(
height: 60,
child: BottomNavigationBar(
elevation: 0,
selectedItemColor: Colors.orange,
unselectedItemColor: Colors.black,
showSelectedLabels: false,
showUnselectedLabels: false,
onTap: onTabTapped,
currentIndex: _currentIndex, // this will be set when a new tab is tapped
items: const [
BottomNavigationBarItem(
icon: Icon(Icons.home),
label: 'Home',
),
BottomNavigationBarItem(
icon: Icon(Icons.video_call_rounded),
label: "Settings",
),
BottomNavigationBarItem(
icon: Icon(Icons.person),
label: 'Profile',
)
],
),
),
);
}
}
profile_page.dart
import 'package:flutter/material.dart';
class ProfilePage extends StatefulWidget {
const ProfilePage({ Key? key }) : super(key: key);
@override
_ProfilePageState createState() => _ProfilePageState();
}
class _ProfilePageState extends State<ProfilePage> {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(backgroundColor: Colors.red,),
);
}
}
错误
E/flutter (15525): [ERROR:flutter/lib/ui/ui_dart_state.cc(199)] Unhandled Exception: 'package:flutter/src/painting/text_painter.dart': Failed assertion: line 881 pos 12: '!_needsLayout': is not true.
E/flutter (15525): #0 _AssertionError._doThrowNew (dart:core-patch/errors_patch.dart:46:39)
E/flutter (15525): #1 _AssertionError._throwNew (dart:core-patch/errors_patch.dart:36:5)
E/flutter (15525): #2 TextPainter.getPositionForOffset
package:flutter/…/painting/text_painter.dart:881
E/flutter (15525): #3 RenderParagraph.hitTestChildren
package:flutter/…/rendering/paragraph.dart:456
E/flutter (15525): #4 RenderBox.hitTest
package:flutter/…/rendering/box.dart:2414
E/flutter (15525): #5 RenderProxyBoxMixin.hitTestChildren
package:flutter/…/rendering/proxy_box.dart:131
E/flutter (15525): #6 RenderTransform.hitTestChildren.<anonymous closure>
package:flutter/…/rendering/proxy_box.dart:2347
E/flutter (15525): #7 BoxHitTestResult.addWithRawTransform
package:flutter/…/rendering/box.dart:826
E/flutter (15525): #8 BoxHitTestResult.addWithPaintTransform
package:flutter/…/rendering/box.dart:751
E/flutter (15525): #9 RenderTransform.hitTestChildren
package:flutter/…/rendering/proxy_box.dart:2343
E/flutter (15525): #10 RenderTransform.hitTest
package:flutter/…/rendering/proxy_box.dart:2337
E/flutter (15525): #11 RenderProxyBoxMixin.hitTestChildren
package:flutter/…/rendering/proxy_box.dart:131
E/flutter (15525): #12 RenderBox.hitTest
package:flutter/…/rendering/box.dart:2414
E/flutter (15525): #13 RenderShiftedBox.hitTestChildren.<anonymous closure>
package:flutter/…/rendering/shifted_box.dart:92
E/flutter (15525): #14 BoxHitTestResult.addWithPaintOffset
package:flutter/…/rendering/box.dart:787
E/flutter (15525): #15 RenderShiftedBox.hitTestChildren
package:flutter/…/rendering/shifted_box.dart:87
E/flutter (15525): #16 RenderBox.hitTest
package:flutter/…/rendering/box.dart:2414
E/flutter (15525): #17 RenderBoxContainerDefaultsMixin.defaultHitTestChildren.<anonymous closure>
package:flutter/…/rendering/box.dart:2775
E/flutter (15525): #18 BoxHitTestResult.addWithPaintOffset
package:flutter/…/rendering/box.dart:787
E/flutter (15525): #19 RenderBoxContainerDefaultsMixin.defaultHitTestChildren
package:flutter/…/rendering/box.dart:2770
E/flutter (15525): #20 RenderFlex.hitTestChildren
package:flutter/…/rendering/flex.dart:1072
E/flutter (15525): #21 RenderBox.hitTest
package:flutter/…/rendering/box.dart:2414
E/flutter (15525): #22 RenderShiftedBox.hitTestChildren.<anonymous closure>
package:flutter/…/rendering/shifted_box.dart:92
E/flutter (15525): #23 BoxHitTestResult.addWithPaintOffset
package:flutter/…/rendering/box.dart:787
E/flutter (15525): #24 RenderShiftedBox.hitTestChildren
package:flutter/…/rendering/shifted_box.dart:87
E/flutter (15525): #25 RenderBox.hitTest
package:flutter/…/rendering/box.dart:2414
E/flutter (15525): #26 RenderProxyBoxMixin.hitTestChildren
package:flutter/…/rendering/proxy_box.dart:131
E/flutter (15525): #27 RenderProxyBoxWithHitTestBehavior.hitTest
package:flutter/…/rendering/proxy_box.dart:178
E/flutter (15525): #28 RenderProxyBoxMixin.hitTestChildren
package:flutter/…/rendering/proxy_box.dart:131
E/flutter (15525): #29 RenderBox.hitTest
package:flutter/…/rendering/box.dart:2414
E/flutter (15525): #30 RenderProxyBoxMixin.hitTestChildren
package:flutter/…/rendering/proxy_box.dart:131
E/flutter (15525): #31 RenderBox.hitTest
package:flutter/…/rendering/box.dart:2414
E/flutter (15525): #32 RenderMouseRegion.hitTest
package:flutter/…/rendering/proxy_box.dart:2905
E/flutter (15525): #33 RenderProxyBoxMixin.hitTestChildren
package:flutter/…/rendering/proxy_box.dart:131
E/flutter (15525): #34 RenderBox.hitTest
package:flutter/…/rendering/box.dart:2414
E/flutter (15525): #35 RenderProxyBoxMixin.hitTestChildren
package:flutter/…/rendering/proxy_box.dart:131
E/flutter (15525): #36 RenderBox.hitTest
package:flutter/…/rendering/box.dart:2414
E/flutter (15525): #37 RenderProxyBoxMixin.hitTestChildren
package:flutter/…/rendering/proxy_box.dart:131
E/flutter (15525): #38 RenderProxyBoxWithHitTestBehavior.hitTest
package:flutter/…/rendering/proxy_box.dart:178
E/flutter (15525): #39 RenderBoxContainerDefaultsMixin.defaultHitTestChildren.<anonymous closure>
package:flutter/…/rendering/box.dart:2775
E/flutter (15525): #40 BoxHitTestResult.addWithPaintOffset
package:flutter/…/rendering/box.dart:787
E/flutter (15525): #41 RenderBoxContainerDefaultsMixin
E/flutter (15525): [ERROR:flutter/lib/ui/ui_dart_state.cc(199)] Unhandled Exception: 'package:flutter/src/painting/text_painter.dart': Failed assertion: line 881 pos 12: '!_needsLayout': is not true.
E/flutter (15525): #0 _AssertionError._doThrowNew (dart:core-patch/errors_patch.dart:46:39)
E/flutter (15525): #1 _AssertionError._throwNew (dart:core-patch/errors_patch.dart:36:5)
E/flutter (15525): #2 TextPainter.getPositionForOffset
package:flutter/…/painting/text_painter.dart:881
E/flutter (15525): #3 RenderParagraph.hitTestChildren
package:flutter/…/rendering/paragraph.dart:456
我稍微修改了代码以使其更清晰，但我测试了这段代码，有时它仍然会出现相同的错误（日志在上面）。
答案 0 :(得分：1)
这里有效，这里试试
import 'package:flutter/material.dart';
class FirstPage extends StatelessWidget {
const FirstPage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Container(
child: Text("1stPage"),
);
}
}
class SecondPage extends StatelessWidget {
const SecondPage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Container(
child: Text("2nd Page"),
);
}
}
class ThirdPage extends StatelessWidget {
const ThirdPage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return Container(
child: Text("3rd PAge"),
);
}
}
class Home extends StatefulWidget {
@override
_HomeState createState() => _HomeState();
}
class _HomeState extends State<Home> {
int _currentIndex = 0;
final List<Widget> _children = [
const FirstPage(),
const SecondPage(),
const ThirdPage(),
];
void onTabTapped(int index) {
setState(() {
_currentIndex = index;
});
}
@override
Widget build(BuildContext context) {
// size = MediaQuery.of(context).size;
// topPadding = MediaQuery.of(context).padding.top;
return Scaffold(
body: _children[_currentIndex],
bottomNavigationBar: SizedBox(
height: 60,
child: BottomNavigationBar(
elevation: 0,
selectedItemColor: Colors.orange,
unselectedItemColor: Colors.black,
showSelectedLabels: false,
showUnselectedLabels: false,
onTap: onTabTapped,
currentIndex:
_currentIndex, // this will be set when a new tab is tapped
items: const [
BottomNavigationBarItem(
icon: Icon(Icons.home),
label: 'Home',
),
BottomNavigationBarItem(
icon: Icon(Icons.video_call_rounded),
label: "Settings",
),
BottomNavigationBarItem(
icon: Icon(Icons.person),
label: 'Profile',
)
],
),
),
);
}
}