I have one StatefulWidget in Flutter with button, which navigates me to another StatefulWidget using Navigator.push(). On second widget I'm changing global state (some user preferences). When I get back from second widget to first, using Navigator.pop() the first widget is in old state, but I want to force it's reload. Any idea how to do this? I have one idea but it looks ugly:
- pop to remove second widget (current one)
- pop again to remove first widget (previous one)
- push first widget (it should force redraw)
There's a couple of things you could do here. @Mahi's answer while correct could be a little more succinct and actually use push rather than showDialog as the OP was asking about. This is an example that uses Navigator.push:
import 'package:flutter/material.dart';
class SecondPage extends StatelessWidget {
@override
Widget build(BuildContext context) {
return new Container(
color: Colors.green,
child: new Column(
children: <Widget>[
new RaisedButton(
onPressed: () => Navigator.pop(context),
child: new Text("back"),
),
],
),
);
}
}
class FirstPage extends StatefulWidget {
@override
State<StatefulWidget> createState() => new FirstPageState();
}
class FirstPageState extends State<FirstPage> {
Color color = Colors.white;
@override
Widget build(BuildContext context) {
return new Container(
color: color,
child: new Column(
children: <Widget>[
new RaisedButton(
child: new Text("next"),
onPressed: () {
Navigator
.push(
context,
new MaterialPageRoute(builder: (context) => new SecondPage()),
)
.then((value) {
setState(() {
color = color == Colors.white ? Colors.grey : Colors.white;
});
});
}),
],
),
);
}
}
void main() => runApp(
new MaterialApp(
builder: (context, child) => new SafeArea(child: child),
home: new FirstPage(),
),
);
However, there's another way to do this that might fit your use-case well. If you're using the global as something that affects the build of your first page, you could use an InheritedWidget to define your global user preferences, and each time they are changed your FirstPage will rebuild. This even works within a stateless widget as shown below (but should work in a stateful widget as well).
An example of inheritedWidget in flutter is the app's Theme, although they define it within a widget instead of having it directly building as I have here.
import 'package:flutter/material.dart';
import 'package:meta/meta.dart';
class SecondPage extends StatelessWidget {
@override
Widget build(BuildContext context) {
return new Container(
color: Colors.green,
child: new Column(
children: <Widget>[
new RaisedButton(
onPressed: () {
ColorDefinition.of(context).toggleColor();
Navigator.pop(context);
},
child: new Text("back"),
),
],
),
);
}
}
class ColorDefinition extends InheritedWidget {
ColorDefinition({
Key key,
@required Widget child,
}): super(key: key, child: child);
Color color = Colors.white;
static ColorDefinition of(BuildContext context) {
return context.inheritFromWidgetOfExactType(ColorDefinition);
}
void toggleColor() {
color = color == Colors.white ? Colors.grey : Colors.white;
print("color set to $color");
}
@override
bool updateShouldNotify(ColorDefinition oldWidget) =>
color != oldWidget.color;
}
class FirstPage extends StatelessWidget {
@override
Widget build(BuildContext context) {
var color = ColorDefinition.of(context).color;
return new Container(
color: color,
child: new Column(
children: <Widget>[
new RaisedButton(
child: new Text("next"),
onPressed: () {
Navigator.push(
context,
new MaterialPageRoute(builder: (context) => new SecondPage()),
);
}),
],
),
);
}
}
void main() => runApp(
new MaterialApp(
builder: (context, child) => new SafeArea(
child: new ColorDefinition(child: child),
),
home: new FirstPage(),
),
);
If you use inherited widget you don't have to worry about watching for the pop of the page you pushed, which will work for basic use-cases but may end up having problems in a more complex scenario.
There are 2 things, passing data from
1st Page to 2nd
Use this in 1st page
// sending "Foo" from 1st
Navigator.push(context, MaterialPageRoute(builder: (_) => Page2("Foo")));
Use this in 2nd page.
class Page2 extends StatelessWidget {
final String string;
Page2(this.string); // receiving "Foo" in 2nd
...
}
2nd Page to 1st
Use this in 2nd page
// sending "Bar" from 2nd
Navigator.pop(context, "Bar");
Use this in 1st page, it is the same which was used earlier but with little modification.
// receiving "Bar" in 1st
String received = await Navigator.push(context, MaterialPageRoute(builder: (_) => Page2("Foo")));
You can use pushReplacement and specify the new Route
//put this where youre pushing to second screen(inside an async function)
Function f;
f = await Navigator.pushNamed(context, 'Screenname');
f();
//put this where you are popping
Navigator.pop(context, () {
setState(() {});
});
//what this does is it pass setState function as an argument to the screen after popping
You can pass back a dynamic result when you are popping the context and then call the setState((){}) when the value is true otherwise just leave the state as it is.
I have pasted some code snippets for your reference.
handleClear() async {
try {
var delete = await deleteLoanWarning(
context,
'Clear Notifications?',
'Are you sure you want to clear notifications. This action cannot be undone',
);
if (delete.toString() == 'true') {
//call setState here to rebuild your state.
}
} catch (error) {
print('error clearing notifications' + error.toString());
}
}
Future<bool> deleteLoanWarning(BuildContext context, String title, String msg) async {
return await showDialog<bool>(
context: context,
child: new AlertDialog(
title: new Text(
title,
style: new TextStyle(fontWeight: fontWeight, color: CustomColors.continueButton),
textAlign: TextAlign.center,
),
content: new Text(
msg,
textAlign: TextAlign.justify,
),
actions: <Widget>[
new Container(
decoration: boxDecoration(),
child: new MaterialButton(
child: new Text('NO',),
onPressed: () {
Navigator.of(context).pop(false);
},
),
),
new Container(
decoration: boxDecoration(),
child: new MaterialButton(
child: new Text('YES', ),
onPressed: () {
Navigator.of(context).pop(true);
},
),
),
],
),
) ??
false;
}
Regards,
Mahi
Today I faced the same situation but I managed to solve it in much easier way, I just defined a global variable which was used in the first stateful class , and when I navigate to a second stateful widget I let it update the value of the global variable which automatically forces the first widget to update. Here is an example (I wrote it in hurry so I didn't put a scaffold or a material app, I just wanted to Illustrate my point):
import 'package:flutter/material.dart';
int count = 0 ;
class FirstPage extends StatefulWidget {
FirstPage({Key key}) : super(key: key);
@override
_FirstPageState createState() => _FirstPageState();
}
class _FirstPageState extends State<FirstPage> {
@override
Widget build(BuildContext context) {
return InkWell(
onTap(){
Navigator.of(context).push(MaterialPageRoute(builder: (context) =>
new SecondPage());
},
child: Text('First', style : TextStyle(fontSize: count == 0 ? 20.0 : 12.0)),
),
}
class SecondPage extends StatefulWidget {
SecondPage({Key key}) : super(key: key);
@override
_SecondPageState createState() => _SecondPageState();
}
class _SecondPageState extends State<SecondPage> {
@override
Widget build(BuildContext context) {
return IconButton(
icon: new Icon(Icons.add),
color: Colors.amber,
iconSize: 15.0,
onPressed: (){
count++ ;
},
),
}
Needed to force rebuild of one of my stateless widgets. Did't want to use stateful. Came up with this solution:
await Navigator.of(context).pushNamed(...);
ModalRoute.of(enclosingWidgetContext);
Note that context and enclosingWidgetContext could be the same or different contexts. If, for example, you push from inside StreamBuilder, they would be different.
We don't do anything here with ModalRoute. The act of subscribing alone is enough to force rebuild.
