Is there a way to check dropdown attribute selected value on change?

[ckildgypmk]

No description provided.

[danvick]

Not currently.
Could you kindly suggest the possible application/need for this behaviour.

[ckildgypmk]

For example I use dropdown menu to display regions that i get from api, when user selected his region I'm getting available city's in that region.

[danvick]

Hmmm. That would be quite helpful. I'll be willing to start planning for it in near-future releases

[ryanhz]

@danvick Please add formData as parameter in onChanged() callback, so we can check if value change?

instead of:
@OverRide
Widget build(BuildContext context) {
return Form(
key: _formKey,
onChanged: widget.onChanged,

do this:
@OverRide
Widget build(BuildContext context) {
return Form(
key: _formKey,
onChanged: () { widget.onChanged(formData) },

[danvick]

Thanks @huzhiren. You're the best.

Requires _formKey.currentState.save(); first though

[ryanhz]

Awesome, thanks.

[danvick]

@ckildgypmk I'm aware that the current solution may not fully solve the problem but we'll have an onChanged() function attached to each FormInput in the coming releases so that one can react to only the changes one is interested in.

[ryanhz]

Yes, when you try to dynamically update the dropdown options when the other filed changed, I got his error, weird:

Error caught by widgets library, thrown building FormField-[<'followupTask'>](dirty, state: FormFieldState#01d28).
'package:flutter/src/material/dropdown.dart': Failed assertion: line 514 pos 15: 'items == null || value == null || items.where((DropdownMenuItem item) => item.value == value).length == 1': is not true.
#2 new DropdownButton (package:flutter/src/material/dropdown.dart:514:15)
#3 _FormBuilderState.formControlsToForm. (package:flutter_form_builder/src/form_builder.dart:244:24)
#4 FormFieldState.build (package:flutter/src/widgets/form.dart)
#5 StatefulElement.build (package:flutter/src/widgets/framework.dart:3787:27)

[danvick]

As of version 3.0.0, each field has an onChanged callback.