Looking up a deactivated widget's ancestor is unsafe - flutter

Question

I am new in Flutter and I am trying receive data with a Dialog.
When a click in textField the error of image2 appear...
show(BuildContext context){
var dialog = Dialog(
child: Container(
margin: EdgeInsets.all(8.0),
child: Form(
child: Column(
mainAxisSize: MainAxisSize.min,
children: <Widget>[
TextFormField(
decoration: InputDecoration(
labelText: "Insira o número de telefone",
border: OutlineInputBorder(
borderRadius: BorderRadius.all(Radius.circular(2.0)))),
),
Row(
mainAxisAlignment: MainAxisAlignment.end,
children: <Widget>[
FlatButton(
onPressed: () {
Navigator.of(context).pop();
},
child: Text("Cancelar")),
FlatButton(
onPressed: () {
Navigator.of(context).pop();
},
child: Text("Aceitar"))
],
)
],
),
),
),
);
showDialog(context: context,builder: (context){
return dialog;
});
}
This is my code.
I/flutter (31032): Looking up a deactivated widget's ancestor is unsafe.
I/flutter (31032): At this point the state of the widget's element tree is no longer stable. To safely refer to a
I/flutter (31032): widget's ancestor in its dispose() method, save a reference to the ancestor by calling
I/flutter (31032): inheritFromWidgetOfExactType() in the widget's didChangeDependencies() method.
I/flutter (31032):

Answer 1

Declare a global variable
final GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey<ScaffoldState>();
then register the key on your widget build's scaffold eg
#override
Widget build(BuildContext context) {
return Scaffold(
key: _scaffoldKey,
...
then on the dialog
show(BuildContext context){
var dialog = Dialog(
child: Container(
margin: EdgeInsets.all(8.0),
child: Form(
child: Column(
mainAxisSize: MainAxisSize.min,
children: <Widget>[
TextFormField(
decoration: InputDecoration(
labelText: "Insira o número de telefone",
border: OutlineInputBorder(
borderRadius: BorderRadius.all(Radius.circular(2.0)))),
),
Row(
mainAxisAlignment: MainAxisAlignment.end,
children: <Widget>[
FlatButton(
onPressed: () {
Navigator.of(context).pop();
},
child: Text("Cancelar")),
FlatButton(
onPressed: () {
Navigator.of(context).pop();
},
child: Text("Aceitar"))
],
)
],
),
),
),
);
Pass that scaffold context to the showDialog method
showDialog(context: _scaffoldKey.currentContext ,builder: (context){
return dialog;
});
}

Answer 2

Try This
Give different context name for dialog
showDialog(context: context,builder: (dialogContex){
return Dialog(
child: Container(
margin: EdgeInsets.all(8.0),
child: Form(
child: Column(
mainAxisSize: MainAxisSize.min,
children: <Widget>[
TextFormField(
decoration: InputDecoration(
labelText: "Insira o número de telefone",
border: OutlineInputBorder(
borderRadius: BorderRadius.all(Radius.circular(2.0)))),
),
Row(
mainAxisAlignment: MainAxisAlignment.end,
children: <Widget>[
FlatButton(
onPressed: () {
Navigator.of(dialogContex).pop();
},
child: Text("Cancelar")),
FlatButton(
onPressed: () {
Navigator.of(context).pop();
},
child: Text("Aceitar"))
],
)
],
),
),
),
);
});

Answer 3

I got the same error when attempting to open a dialog and I found a solution here: github flutter issues. Specifically, I followed the poster's recommendation, which was to create a GlobalKey and associate it with the Scaffold widget, and use the context from that key when creating the dialog. In my case, I have a globally accessible object which holds the GlobalKey:
MyGlobals myGlobals = MyGlobals();
class MyGlobals {
GlobalKey _scaffoldKey;
MyGlobals() {
_scaffoldKey = GlobalKey();
}
GlobalKey get scaffoldKey => _scaffoldKey;
}
In the Scaffold widget constructor call:
Scaffold(
appBar: ...,
body: ...,
drawer: ...,
key: myGlobals.scaffoldKey,
)
And in the showDialog call:
showDialog<String>(
barrierDismissible: ...,
builder: ...,
context: myGlobals.scaffoldKey.currentContext,
);

Answer 4

You’re trying to access a context that isn’t probably available. That happens because you’ve assigned your Dialog to a var and afterwards use a different context (the one from your dialog builder).
Either create your dialog directly after your return in the builder or make it a method instead that returns a Dialog and pass it a BuildContext parameter.
Widget myDialog(BuildContext context) => Dialog(/*your dialog here*/);
This is also a more convenient Flutter practice. You should use methods that return widgets instead of assigning it to variables.

Answer 5

use this:
Navigator.of(context,rootNavigator: true).pop();
instead of
Navigator.of(context).pop();

Answer 6

This might happen while you are popping from the context and trying to open new content on the context you are popping.
()async{
Navigator.of(context).pop();
_alertPopUp(); // shows a dialog
// might do some work after
}
if alert dialog is created on current context then it throws an error because context doesn't exist anymore

Answer 7

My problem was that I was using hot reload for pretty long time, I think at some point everything got messed up, doing a normal run of the app fixed the problem.

Answer 8

removing application from emulator and run below commands
flutter clean
flutter pub get
works for me

Answer 9

Though you got desired answer, just for better clarification for others I put my opinion here.
Reason :
It is happend due to context mismatch issue. Your passing context to Navigator.of(context).pop() is not matching with your MainApp BuildContext.
Solution : There has 2 way
U can use Global key
pass actual context to your Navigator
Below link I already mentioned how to solve this by passing actual context
https://stackoverflow.com/a/73543251/6109034

Answer 10

Try this:
Future<AlertDialog> myDialog(BuildContext context) {
return showDialog<AlertDialog>(
context: context,
builder: (BuildContext context) {
return AlertDialog(
content: Container(
margin: EdgeInsets.all(8.0),
child: Form(
child: Column(
mainAxisSize: MainAxisSize.min,
children: <Widget>[
TextFormField(
decoration: InputDecoration(
labelText: "Insira o número de telefone",
border: OutlineInputBorder(
borderRadius:
BorderRadius.all(Radius.circular(2.0)))),
),
],
),
),
),
actions: <Widget>[
FlatButton(
onPressed: () {
Navigator.of(context).pop();
},
child: Text("Cancelar")),
FlatButton(
onPressed: () {
Navigator.of(context).pop();
},
child: Text("Aceitar"))
],
);
},
);
}

Answer 11

declare dialog and set in initState
late Dialog dialog;
#override
void initState() {
super.initState();
dialog = Dialog(
...
);
}

Answer 12

before calling a dialog when a page is just loading, call it by adding SchedulerBinding to it, call it like this
SchedulerBinding.instance?.addPostFrameCallback((_) => showDialog( context: context, barrierDismissible: false, builder: (context) { return dialogBox(context, "Fetching account data", 'Profile page', DialogType.processing, function: () {}, dismissText: "", ); }));

Answer 13

In my case I was using a provider where I used a context as an argument to a function, the thing was that when I passed that page I did it with pushnamedAndRemove Until then on the next page I was trying to use a function where I required the above context, so the error was mine because it was trying to get a parameter that I destroyed earlier, for that reason it didn't work. So be careful if you are deleting old pages.

Answer 14

Use this if You are using Stack in AlertDialog Not Closing on Navigator.of(context).pop();
late NavigatorState _navigator;
#override
void didChangeDependencies() {
_navigator = Navigator.of(context);
super.didChangeDependencies();
}
Use This
Positioned(right: 10.0,child: GestureDetector(
// behavior: HitTestBehavior.translucent,
onTap: () {
_navigator.pop(context);
},
child: Align(
alignment: Alignment.topRight,
child: CircleAvatar(
radius: 14.0,
backgroundColor: Colors.white,
child: Icon(Icons.close, color: black),
),
),
),
),

Answer 15

I simply solved this by wrapping the showDialog with a Builder widget, though for me the error came from a stream builder I simply wrap the stream builder with a builder widget and the remove the notify listeners from the a stream am calling in the stream builder, but in your case wrap the showDialog with a Builder widget and it will use the context from the builder, problem solved

Answer 16

first : declare a FormKey.
GlobalKey<FormState>myFormKey=GlobalKey<FormState>();
second : add the FormKey to your Form widget.
Form(
key:myFormKey,
child:child
)

Answer 17

In my case i was calling
setState(() {
Navigator.pop(context);
});