Fix bug in RadioGroup where reset and didChange doesnt affect UI. Fixes #646, Fixes 647

Author: danvick

example/lib/sources/complete_form.dart

@@ -463,10 +463,11 @@ class CompleteFormState extends State<CompleteForm> {
                 const SizedBox(width: 20),
                 Expanded(
                   child: OutlineButton(
-                    focusNode: FocusNode(),
                     color: Theme.of(context).accentColor,
-                    child: const Text('Reset',
-                        style: TextStyle(color: Colors.white)),
+                    child: Text(
+                      'Reset',
+                      style: TextStyle(color: Theme.of(context).accentColor),
+                    ),
                     onPressed: () {
                       _formKey.currentState.reset();
                     },

lib/src/widgets/grouped_radio.dart

@@ -198,15 +198,6 @@ class GroupedRadio<T> extends StatefulWidget {
 }
 
 class _GroupedRadioState<T> extends State<GroupedRadio<T>> {
-  T selectedValue;
-
-  @override
-  void initState() {
-    super.initState();
-
-    selectedValue = widget.value;
-  }
-
   @override
   Widget build(BuildContext context) {
     final widgetList = <Widget>[];
@@ -254,7 +245,7 @@ class _GroupedRadioState<T> extends State<GroupedRadio<T>> {
     final optionValue = option.value;
     final isOptionDisabled = true == widget.disabled?.contains(optionValue);
     final control = Radio<T>(
-      groupValue: selectedValue,
+      groupValue: widget.value,
       activeColor: widget.activeColor,
       focusColor: widget.focusColor,
       hoverColor: widget.hoverColor,
@@ -263,10 +254,7 @@ class _GroupedRadioState<T> extends State<GroupedRadio<T>> {
       onChanged: isOptionDisabled
           ? null
           : (T selected) {
-              setState(() {
-                selectedValue = selected;
-              });
-              widget.onChanged(selectedValue);
+              widget.onChanged(selected);
             },
     );
 
@@ -275,10 +263,7 @@ class _GroupedRadioState<T> extends State<GroupedRadio<T>> {
       onTap: isOptionDisabled
           ? null
           : () {
-              setState(() {
-                selectedValue = optionValue;
-              });
-              widget.onChanged(selectedValue);
+              widget.onChanged(optionValue);
             },
     );