Request focus for non-text-based on after change to avoid jumping

Removes focus from textfield thus avoiding the the situation where focus goes back to last textfield after field is changed.
Especially problematic for DropdownButton: Source of hack: https://stackoverflow.com/questions/51534205/flutter-android-moving-focus-from-a-dropdownbutton-to-a-textfield?answertab=active#tab-top

Author: danvick

lib/src/fields/form_builder_checkbox.dart

@@ -55,6 +55,7 @@ class _FormBuilderCheckboxState extends State<FormBuilderCheckbox> {
       onChanged: _readonly
           ? null
           : (bool value) {
+              FocusScope.of(context).requestFocus(FocusNode());
               field.didChange(value);
               if (widget.onChanged != null) widget.onChanged(value);
             },
@@ -107,6 +108,7 @@ class _FormBuilderCheckboxState extends State<FormBuilderCheckbox> {
             onTap: _readonly
                 ? null
                 : () {
+                    FocusScope.of(context).requestFocus(FocusNode());
                     bool newValue = !(field.value ?? false);
                     field.didChange(newValue);
                     if (widget.onChanged != null) widget.onChanged(newValue);

lib/src/fields/form_builder_checkbox_list.dart

@@ -56,6 +56,7 @@ class _FormBuilderCheckboxListState extends State<FormBuilderCheckboxList> {
       onChanged: _readonly
           ? null
           : (bool value) {
+              FocusScope.of(context).requestFocus(FocusNode());
               var currValue = field.value;
               if (value)
                 currValue.add(widget.options[i].value);

lib/src/fields/form_builder_chips_input.dart

@@ -89,6 +89,7 @@ class _FormBuilderChipsInputState extends State<FormBuilderChipsInput> {
             ),
             findSuggestions: widget.findSuggestions,
             onChanged: (data) {
+              FocusScope.of(context).requestFocus(FocusNode());
               field.didChange(data);
               if (widget.onChanged != null) widget.onChanged(data);
             },

lib/src/fields/form_builder_dropdown.dart

@@ -100,9 +100,11 @@ class _FormBuilderDropdownState extends State<FormBuilderDropdown> {
             onChanged: _readonly
                 ? null
                 : (value) {
+                    FocusScope.of(context).requestFocus(FocusNode());
                     field.didChange(value);
                     if (widget.onChanged != null) widget.onChanged(value);
                   },
+            //TODO: add icon, enabledColor, disabledColor
           ),
         );
       },

lib/src/fields/form_builder_radio.dart

@@ -56,6 +56,7 @@ class _FormBuilderRadioState extends State<FormBuilderRadio> {
       onChanged: _readonly
           ? null
           : (dynamic value) {
+              FocusScope.of(context).requestFocus(FocusNode());
               field.didChange(value);
               if (widget.onChanged != null) widget.onChanged(value);
             },

lib/src/fields/form_builder_rate.dart

@@ -87,6 +87,7 @@ class _FormBuilderRateState extends State<FormBuilderRate> {
             onTap: _readonly
                 ? null
                 : (value) {
+                    FocusScope.of(context).requestFocus(FocusNode());
                     field.didChange(value);
                     if (widget.onChanged != null) widget.onChanged(value);
                   },

lib/src/fields/form_builder_segmented_control.dart

@@ -100,6 +100,7 @@ class _FormBuilderSegmentedControlState
                     ),
               ),
               onValueChanged: (dynamic value) {
+                FocusScope.of(context).requestFocus(FocusNode());
                 if (_readonly) {
                   field.reset();
                 } else {

lib/src/fields/form_builder_signature_pad.dart

@@ -111,6 +111,7 @@ class _FormBuilderSignaturePadState extends State<FormBuilderSignaturePad> {
                     penColor: widget.penColor,
                     penStrokeWidth: widget.penStrokeWidth,
                     onChanged: (points) async {
+                      FocusScope.of(context).requestFocus(FocusNode());
                       var signature =
                           await _signatureKey.currentState.exportBytes();
                       setState(() {

lib/src/fields/form_builder_slider.dart

@@ -90,6 +90,7 @@ class _FormBuilderSliderState extends State<FormBuilderSlider> {
                   onChanged: _readonly
                       ? null
                       : (num value) {
+                    FocusScope.of(context).requestFocus(FocusNode());
                           field.didChange(value);
                           if (widget.onChanged != null) widget.onChanged(value);
                         },

lib/src/fields/form_builder_stepper.dart

@@ -89,6 +89,7 @@ class _FormBuilderStepperState extends State<FormBuilderStepper> {
             onChange: _readonly
                 ? null
                 : (value) {
+                    FocusScope.of(context).requestFocus(FocusNode());
                     field.didChange(value);
                     if (widget.onChanged != null) widget.onChanged(value);
                   },