我试图在异步函数中运行两个wait和一个navigator.push，但我在flutter中遇到了这个错误

Question

错误：[错误：flutter/lib/ui/ui_start_state.cc(186(]未处理的异常：查找停用的小部件的祖先是不安全的。E/flutter(6342(：此时小部件元素树的状态不再稳定。E/flutter(6342(：为了在其dispose((方法中安全地引用小部件的祖先，请通过在小部件的didChangeDependencies((方法调用dependentOnInheritedWidgetOfExactType((来保存对祖先的引用。E/颤振(6342(：#0元件_debugCheckStateIsActiveForAncestorLookup。(包：flutter/src/widgets/framework。dart:3864:9(E/颤振(6342(：#1元件_debugCheckStateIsActiveForAncestorLookup(包：flutter/src/widgets/framework.dart:3878:6(E/flutter(6342(：#2 Element.findAncestorStateOfType(包：flutter/src/widgets/framework。dart:3926:12(E/flutter(6342(：#3 Navigator.of(包：flutter/src/widgets/Navigator.dart:2706:40(E/flutter(6342(：#4 Navigator.pop(包：flutter/src/widgets/Navigator.dart:2592:15(E/flutter(6342(：#5 NotificationDialog.checkAvailabilityOfRide(包：drivers_app/Notifications/NotificationDialog.dart:240:20(E/颤振(6342(：

我的代码片段：

void checkAvailabilityOfRide(context) async {

var rideRequestId = await rideRequestRef.once();
...
var dataSnapShot2 =  await newRequestsRef.child(rideRequestId.value).once();
...
Navigator.push(context, MaterialPageRoute(builder: (context)=> 
NewRideScreen(rideDetails: rideDetails)));
...
}

更新代码：

Widget build(BuildContext context) {
return Dialog(
shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(12.0)),
backgroundColor: Colors.transparent,
elevation: 1.0,
child: Container(
margin: EdgeInsets.all(5.0),
width: double.infinity,
decoration: BoxDecoration(
color: Colors.white,
borderRadius: BorderRadius.circular(5.0),
),
child: Column(
mainAxisSize: MainAxisSize.min,
children: [
SizedBox(height: 30.0),
Image.asset("images/taxi.png", width: 120.0,),
SizedBox(height: 18.0,),
Text("New Ride Request", style: TextStyle(fontFamily: "Brand-Bold", fontSize: 18.0,),),
SizedBox(height: 30.0),
Padding(
padding: EdgeInsets.all(18.0),
child: Column(
children: [
Row(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Image.asset("images/pickicon.png", height: 16.0, width: 16.0,),
SizedBox(width: 20.0,),
Expanded(
child: Container(child: Text(rideDetails.pickup_address, style: TextStyle(fontSize: 18.0),)),
),
],
),
SizedBox(height: 15.0),
Row(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Image.asset("images/desticon.png", height: 16.0, width: 16.0,),
SizedBox(width: 20.0,),
Expanded(
child: Container(child: Text(rideDetails.dropOff_address, style: TextStyle(fontSize: 18.0),)),
)
],
),
SizedBox(height: 15.0),
],
),
),
SizedBox(height: 20.0),
Divider(height: 2.0,color: Colors.black, thickness: 2.0,),
SizedBox(height: 8.0),
Padding(
padding: EdgeInsets.all(20.0),
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
children: [
FlatButton(
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(18.0),
side: BorderSide(color: Colors.red)),
color: Colors.white,
textColor: Colors.red,
padding: EdgeInsets.all(8.0),
onPressed: ()
{
assetsAudioPlayer.stop();
Navigator.pop(context);
},
child: Text(
"Cancel".toUpperCase(),
style: TextStyle(
fontSize: 14.0,
),
),
),
SizedBox(width: 25.0),
RaisedButton(
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(18.0),
side: BorderSide(color: Colors.green)),
onPressed: ()
{
assetsAudioPlayer.stop();
checkAvailabilityOfRide0(context);
checkAvailabilityOfRide(context);
},
color: Colors.green,
textColor: Colors.white,
child: Text("Accept".toUpperCase(),
style: TextStyle(fontSize: 14)),
),
],
),
),
SizedBox(height: 10.0),
],
),
),
);

}

Future<void> checkAvailabilityOfRide(context) async {
var rideRequestId = await rideRequestRef.once();
Navigator.push(context);
String theRideId = "";
var dataSnapShot2 =  await newRequestsRef.child( rideRequestId.value).once();
/*... process...*/
if(theRideId == rideDetails.ride_request_id && r2canShare) {
rideRequestRef.set("accepted");
AssistantMethods.disableHomeTabLiveLocationUpdates();
Navigator.push(context, MaterialPageRoute(builder: (context) => 
NewRideScreen(rideDetails: rideDetails)));
}
else if(theRideId == 'cancelled') {
displayToastMessage("Ride has been Cancelled.", context);
}
else if(theRideId == 'cancelled') {
displayToastMessage("Ride has been time out.", context);
}
else if(r2canShare == false) {
assetsAudioPlayer.stop();
displayToastMessage("Rider 2 cannot shared ride, out of range.", context);
}
else {
displayToastMessage("Ride not exists.", context);
}

}

更改代码：

void checkAvailabilityOfRide(context)async{
var dataSnapShot2 =  await newRequestsRef.child( (await 
rideRequestRef.once()).value).once();
Navigator.pop(context);
String theRideId = "";
/*... process...*/

Answer 1

如海报所示(请参阅问题注释(，错误是由在Navigator.pop和Navigator.push之间执行异步await引起的。我想await给Flutter时间在push之前破坏当前屏幕，这会导致push上的异常。

请注意，Flutter提供了多种同时弹出和推送的方式，从而避免了代码介入的机会：pushReplacement和pushReplacementNamed用新屏幕替换当前屏幕，popAndPushNamed对不同的动画也这样做。

Answer 2

@Nin Yu，过去几天我遇到了同样的错误，我试图用@Patrick答案来修复，但有时也不起作用。当我仔细调试它时，我发现我多次调用包含Navigator的方法。所以有时我会得到上下文，然后安全地转到下一个屏幕，有些屏幕会出现错误。我会建议调试方法并检查它是否发生。