Navigator.of(context).pop() Give me black screen - flutter

Question

Noob here.
I've made a update checker with flutter, but if I choose any button, it give me black screen.
How can I fix this? Any ideas?
Code
Full Source : https://github.com/aroxu/LiteCalculator
Dialog Part Source :
import 'package:LiteCalculator/updater/bean/UpdaterBean.dart';
import 'package:flutter/material.dart';
class UpdateHolder extends StatelessWidget {
final List<Version> version;
UpdateHolder({Key key, this.version}) : super(key: key);
#override
Widget build(BuildContext context) {
return calculateResult(
version[0].latestVersion, version[1].currentVersion, context);
}
Widget calculateResult(latestVersion, currentVersion, context) {
print('Latest Version : ${int.parse(latestVersion)}');
print('Current Version : ${int.parse(currentVersion)}');
Widget data;
if ((int.parse(currentVersion) <= int.parse(latestVersion))) {
data = Center(
child: createAlert('Update Required', actions: <Widget>[
FlatButton(
child: Text('OK'),
onPressed: () {
print('OK Button Pressed.');
Navigator.of(context).pop();
},
),
FlatButton(
child: Text('Later'),
onPressed: () {
print('Later Button Pressed.');
Navigator.of(context).pop();
},
),
]),
);
} else
data = Center();
return data;
}
Widget createAlert(content, {List<Widget> actions, title}) {
AlertDialog snackBar;
snackBar = AlertDialog(
content: Text(content),
actions: actions,
);
return snackBar;
}
}

Answer 1

call this for your popup,
void showDialogPopup(){
showDialog(
context: context,
builder: (_)=>AlertDialog(
backgroundColor: Colors.transparent,
content: Container(
child: Center(
child: FlatButton(
onPressed: (){
Navigator.of(context).pop(null);
},
child: Center(
child: Text("close")
)
)
)
)
)
);
}

Answer 2

A black screen or a blank screen? If its a black screen, your are not wrapping your main widget (which goes in the runApp) with a MaterialApp.

Answer 3

You can refer this.
I used url_launcher 5.4.1 to open PlayStore web.
import "package:flutter/material.dart";
import 'package:url_launcher/url_launcher.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
Widget build(BuildContext context) {
return MaterialApp(
home: FirstPage(),
debugShowCheckedModeBanner: false,
);
}
}
class FirstPage extends StatefulWidget {
#override
_FirstPageState createState() => _FirstPageState();
}
class _FirstPageState extends State<FirstPage> {
#override
void initState() {
_checkUpdate();
super.initState();
}
Future<void> _checkUpdate() async {
await Future.delayed(Duration.zero);
await showDialog(
context: context,
builder: (context) => UpdateDialog(),
);
}
#override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: Text("First Page"),
),
);
}
}
class UpdateDialog extends StatefulWidget {
#override
_UpdateDialogState createState() => _UpdateDialogState();
}
class _UpdateDialogState extends State<UpdateDialog> {
Future<void> _updateFound;
#override
void initState() {
_updateFound = _checkForUpdate();
super.initState();
}
Future<bool> _checkForUpdate() async {
await Future.delayed(Duration.zero);
bool updateFound = false;
await Future.delayed(Duration(seconds: 3)); // Do Get call to server
updateFound = true;
if (!updateFound) Navigator.pop(context);
return updateFound;
}
Future<void> _openWebPage() async {
Navigator.pop(context);
launch("https://play.google.com"); //Your link `url_launcher` package
}
void _laterClicked(){
Navigator.pop(context);
}
#override
Widget build(BuildContext context) {
return FutureBuilder(
future: _updateFound,
builder: (context, snapshot) {
if (snapshot.connectionState == ConnectionState.waiting)
return AlertDialog(
content: Column(
mainAxisSize: MainAxisSize.min,
children: <Widget>[
CircularProgressIndicator(),
const SizedBox(height: 12.0),
Text("Checking for Update"),
],
),
);
else if (snapshot.hasError)
return AlertDialog(
title: Text("Error Occured"),
content: Text("ERROR: ${snapshot.error}"),
);
else if(snapshot.data)
return AlertDialog(
title: Text("Update Required"),
content: Text(
"Latest version found. Need an update. bla bla bla bla bla bla"),
actions: <Widget>[
FlatButton(
child: Text("OK"),
onPressed: _openWebPage,
),
FlatButton(
child: Text("LATER"),
onPressed: _laterClicked,
),
],
);
else
return const SizedBox();
},
);
}
}

Answer 4

This happens whenever you try to pop using the Widget's context.
In the following code:
FlatButton(
child: Text('OK'),
onPressed: () {
print('OK Button Pressed.');
Navigator.of(context).pop();
},
)
context represents the context of the widget, itself (provided in the build method).
To resolve this issue instead of creating a Dialog widget and returning it as the main widget, just use showDialog and return a simple Container().
Use dialogContext to pop the dialog and not the widget itself.
for example:
if ((int.parse(currentVersion) <= int.parse(latestVersion))) {
showDialog(
builder: (dialogContext) => AlertDialog(
content: Text('Update Required'),
actions: <Widget>[
FlatButton(
child: Text('OK'),
onPressed: () {
print('OK Button Pressed.');
Navigator.of(dialogContext).pop();
},
),
FlatButton(
child: Text('Later'),
onPressed: () {
print('Later Button Pressed.');
Navigator.of(dialogContext).pop();
},
),
],
),
);
}
return Container();

Answer 5

I had a similar problem and my solution was something like that:
bool hasBeenShown = false;
if(!hasBeenShown) {
Navigator.pop(context);
}
hasBeenShown = true;
The problem for me was that for some reason Navigator.pop been invoked multiple times when it's supposed to be invoked only once.