Navigate back and show snack - dart

Question

I am thinking of this pattern for my application, and cannot find a proper way of doing it.
User is in list page, she clicks on an item and goes to edit page. She edits, and hits the save. Now I want the application to
- show spinning wheel, while saving the item
- after save pop the route to go back to list page, AND show a snackbar on the list page.
I don't seem to find a way to pass a parameter to the previous route to tell it about the state, which is to show the snackbar.

Answer 1

For showing progress on click of save button you can use something like this.
Firstly initialize a variable static bool isSaving = false; then in your scaffold use it like this.
child:Stack(
children: <Widget>[
isSaving
? new Container(
child: new CircularProgressIndicator(
value: null,
strokeWidth: 2.0,
),
alignment: Alignment.center,
)
: new Container(
child: new RaisedButton(
onPressed: () {
setState(() {
isSaving = true;
//Other Implementations here
});
},
child: new Text("Save"),
),
),
],
),
When the operation is complete again set state and make variable false.
Now when you get notified that operation has been done use Navigator to go back.
Navigator.pop(context);
For showing snackbar in your previous screen use a Global Key.
GlobalKey<ScaffoldState> scaffoldKey = new GlobalKey<ScaffoldState>();
Assign this key to your scaffold.
new Scaffold(
key: scaffoldKey,
...
)
As answered here show snackbar just after pop operation like this.
scaffoldKey.currentState
.showSnackBar(new SnackBar(content: new Text("Saved Successfully")));
Or can try a different approach as explained in this sample.
Hope it helps.

Answer 2

You can send data back through pop method. You can do something like that.
In your edit page:
bool saved = item.save();
Navigator.pop(context, saved);
In your list page:
var saved = await Navigator.push(
context,
MaterialPageRoute(builder: (context) => EditRoute(item)),
);
if (saved) {
// Show success snackbar
} else {
// Show error snackbar
}