尝试在单击图标时弹出的 AlertDialog 框中流式传输数据时出现错误。我了解该问题涉及在不允许的情况下发生的流构建器构建，但我还没有找到解决此问题的方法。我的目标是能够单击一个图标并出现一个弹出框，显示一些流数据或带有取消按钮和清除数据按钮的最新实例。
enum WarningInfo { CANCEL, CLEAR }
class WarningStatus extends StatefulWidget {
final ROSBridgeClient client;
WarningStatus({Key key, this.client}) : super(key: key);
@override
State<StatefulWidget> createState() => WarningStatusState();
}
class WarningStatusState extends State<WarningStatus> {
static const String _FAULT_TOPIC = '/active_faults';
//color (gray) when icon has not been enabled
Color _iconColor = Color(0xff4e4e4e);
@override
void initState() {
super.initState();
}
Future<WarningInfo> _asyncWarningBox(BuildContext context) async {
return showDialog<WarningInfo>(
context: context,
barrierDismissible:
true, // user must tap button for close dialog if false!
builder: (BuildContext context) {
return AlertDialog(
// content: StatefulBuilder(),
title: Text('Robot Warnings'),
// content: const Text('No warnings'),
content: StatefulBuilder(
builder: (BuildContext context, StateSetter setState) {
return StreamBuilder(
stream: widget.client.getTopicStream(_FAULT_TOPIC),
builder: (context, snapshot) {
if (!snapshot.hasData) {
return Text('None');
}
return _buildFaultOutput(snapshot);
});
}),
actions: <Widget>[
FlatButton(
child: const Text('CANCEL'),
onPressed: () {
Navigator.of(context).pop(WarningInfo.CANCEL);
},
),
FlatButton(
child: const Text(
'CLEAR WARNINGS',
style: TextStyle(color: Colors.red),
),
onPressed: () {
// Navigator.of(context).pop(WarningInfo.CLEAR);
_clearFaults();
},
)
],
);
},
);
}
@override
Widget build(BuildContext context) {
widget.client.subscribe(_FAULT_TOPIC, 'rover_safety/FaultListMsg');
return SizedBox(
child: Column(
mainAxisSize: MainAxisSize.min,
children: <Widget>[
IconButton(
icon: Icon(
CustomIcons.attention,
color: _iconColor,
),
disabledColor: Color(0xff4e4e4e),
iconSize: 80,
tooltip: "Warnings",
onPressed: () async {
final WarningInfo action = await _asyncWarningBox(context);
print("Confirm Action $action");
},
// onPressed: () {
// setState(() {
// _iconColor = Colors.yellow;
// });
// },
),
// Text("Fault Messages:"),
// SizedBox(
// height: 10.0,
// ),
// StreamBuilder(
// stream: widget.client.getTopicStream(_FAULT_TOPIC),
// builder: (context, snapshot) {
// if (!snapshot.hasData) {
// return CircularProgressIndicator();
// }
// return _buildFaultOutput(snapshot);
// },
// ),
// SizedBox(
// height: 10.0,
// ),
// ButtonBar(
// mainAxisSize: MainAxisSize.min,
// children: <Widget>[
// RaisedButton(
// child: const Text("Clear Faults"),
// onPressed: _clearFaults,
// ),
// ],
// )
],
),
);
}
Widget _buildFaultOutput(snapshot) {
setState(() {
_iconColor = Colors.blue;
});
var msg = snapshot.data;
// print(payload);
var faultList = msg["fault_list"];
print("Number of faults: ${faultList.length}");
// if (faultListLength>0){
// var faults = faultList[0];
// var motorCurrent = faults["fault"];
// var severity = faults["severity"];
// print(faults);
// return Text("Number of Faults: $faultListLength\n$motorCurrent\nseverity: $severity");
// }
// else{
// return Text("No faults");
// }
if (faultList.length == 0) {
return Text("No faults");
} else {
for (var i = 0; i < faultList.length; i++) {
var faults = faultList[i];
var motorCurrent = faults["fault"];
var severity = faults["severity"];
print(faults);
print(i);
return Text(
"Number of Faults: ${faultList.length}\n$motorCurrent\nseverity: $severity");
}
}
}
void _clearFaults() {
widget.client.publish('/clear_faults', 'std_msgs/Empty');
}
@override
void dispose() {
super.dispose();
}
}
错误：
I/flutter ( 1382): Another exception was thrown: setState() or markNeedsBuild() called during build.
错误：
I/flutter ( 2967): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter ( 2967): The following assertion was thrown building StreamBuilder<dynamic>(dirty, state:
I/flutter ( 2967): _StreamBuilderBaseState<dynamic, AsyncSnapshot<dynamic>>#dc80d):
I/flutter ( 2967): setState() or markNeedsBuild() called during build.
I/flutter ( 2967): This WarningStatus widget cannot be marked as needing to build because the framework is already in
I/flutter ( 2967): the process of building widgets. A widget can be marked as needing to be built during the build
I/flutter ( 2967): phase only if one of its ancestors is currently building. This exception is allowed because the
I/flutter ( 2967): framework builds parent widgets before children, which means a dirty descendant will always be
I/flutter ( 2967): built. Otherwise, the framework might not visit this widget during this build phase.
I/flutter ( 2967): The widget on which setState() or markNeedsBuild() was called was:
I/flutter ( 2967): WarningStatus
I/flutter ( 2967): The widget which was currently being built when the offending call was made was:
I/flutter ( 2967): StreamBuilder<dynamic>
I/flutter ( 2967):
I/flutter ( 2967): The relevant error-causing widget was:
I/flutter ( 2967): StreamBuilder<dynamic> file:///home/megan/rr_app/lib/widgets/warnings.dart:45:20
I/flutter ( 2967):
I/flutter ( 2967): When the exception was thrown, this was the stack:
I/flutter ( 2967): #0 Element.markNeedsBuild.<anonymous closure> (package:flutter/src/widgets/framework.dart:4167:11)
I/flutter ( 2967): #1 Element.markNeedsBuild (package:flutter/src/widgets/framework.dart:4182:6)
I/flutter ( 2967): #2 State.setState (package:flutter/src/widgets/framework.dart:1253:14)
I/flutter ( 2967): #3 WarningStatusState._buildFaultOutput (package:rrapp/widgets/warnings.dart:135:5)
I/flutter ( 2967): #4 WarningStatusState._asyncWarningBox.<anonymous closure>.<anonymous closure>.<anonymous closure> (package:rrapp/widgets/warnings.dart:51:26)
I/flutter ( 2967): #5 StreamBuilder.build (package:flutter/src/widgets/async.dart:509:81)
I/flutter ( 2967): #6 _StreamBuilderBaseState.build (package:flutter/src/widgets/async.dart:127:48)
I/flutter ( 2967): #7 StatefulElement.build (package:flutter/src/widgets/framework.dart:4619:28)
I/flutter ( 2967): #8 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4502:15)
I/flutter ( 2967): #9 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4675:11)
I/flutter ( 2967): #10 Element.rebuild (package:flutter/src/widgets/framework.dart:4218:5)
I/flutter ( 2967): #11 BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2627:33)
I/flutter ( 2967): #12 WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:883:20)
I/flutter ( 2967): #13 RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:284:5)
I/flutter ( 2967): #14 SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1108:15)
I/flutter ( 2967): #15 SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1047:9)
I/flutter ( 2967): #16 SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:963:5)
I/flutter ( 2967): #20 _invoke (dart:ui/hooks.dart:261:10)
I/flutter ( 2967): #21 _drawFrame (dart:ui/hooks.dart:219:3)
I/flutter ( 2967): (elided 3 frames from dart:async)
I/flutter ( 2967):
I/flutter ( 2967): ════════════════════════════════════════════════════════════════════════════════════════════════════
I/flutter ( 2967): Another exception was thrown: setState() or markNeedsBuild() called during build.