错误:[error:flutter/lib/ui/ui_dart_state.cc(186)]未处理的异常：查找停用小部件的祖先是不安全的。E/Flutter(6342):此时，小部件的元素树的状态不再稳定。E/Flutter（6342）：为了在小部件的dispose（）方法中安全地引用其祖先，可以通过在小部件的didChangeDependencies（）方法中调用dependOnInheritedWidgetOfExactType（）来保存对祖先的引用。E/Flutter(6342):#0 element._DebugCheckStateIsActiveForExcestorLookup。（包:flutter/src/widgets/framework.dart:3864:9)e/flutter(6342):#1 element._debugcheckstateisactiveforcestorlookup（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):#3navigator.of（包ART:2592:15)E/Flutter(6342):#5 NotificationDialog.CheckAvailabilityOfride（包:drivers_app/Notifications/NotificationDialog.Dart:240:20)E/Flutter(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...*/