More type safety tweaks.

Author: awhitford

lib/src/fields/form_builder_checkbox_group.dart

@@ -4,7 +4,7 @@ import 'package:flutter_form_builder/flutter_form_builder.dart';
 import 'package:flutter_form_builder/src/widgets/grouped_checkbox.dart';
 
 class FormBuilderCheckboxGroup<T> extends FormBuilderField<List<T>> {
-  final List<FormBuilderFieldOption> options;
+  final List<FormBuilderFieldOption<T>> options;
   final Color activeColor;
   final Color checkColor;
   final Color focusColor;
@@ -80,7 +80,7 @@ class FormBuilderCheckboxGroup<T> extends FormBuilderField<List<T>> {
                 enabled: !state.readOnly,
                 errorText: decoration?.errorText ?? state.errorText,
               ),
-              child: GroupedCheckbox(
+              child: GroupedCheckbox<T>(
                 orientation: orientation,
                 value: state.value,
                 options: options,

lib/src/fields/form_builder_chips_input.dart

@@ -71,7 +71,7 @@ class FormBuilderChipsInput<T> extends FormBuilderField<List<T>> {
           builder: (FormFieldState<List<T>> field) {
             final _FormBuilderChipsInputState<T> state = field;
 
-            return ChipsInput(
+            return ChipsInput<T>(
               key: ObjectKey(state.value),
               initialValue: field.value,
               enabled: !state.readOnly,

lib/src/fields/form_builder_choice_chips.dart

@@ -4,7 +4,7 @@ import 'package:flutter_form_builder/flutter_form_builder.dart';
 
 class FormBuilderChoiceChip<T> extends FormBuilderField<T> {
   /// The list of items the user can select.
-  final List<FormBuilderFieldOption> options;
+  final List<FormBuilderFieldOption<T>> options;
 
   // FilterChip Settings
   /// Elevation to be applied on the chip relative to its parent.

lib/src/fields/form_builder_dropdown.dart

@@ -294,7 +294,7 @@ class FormBuilderDropdown<T> extends FormBuilderField<T> {
           },
         );
 
-  static void _changeValue<T>(_FormBuilderDropdownState<T> state, value) {
+  static void _changeValue<T>(_FormBuilderDropdownState<T> state, T value) {
     state.requestFocus();
     state.didChange(value);
   }

lib/src/fields/form_builder_image_picker.dart

@@ -176,10 +176,7 @@ class FormBuilderImagePicker extends FormBuilderField<List<dynamic>> {
                                 galleryLabel: galleryLabel,
                                 onImageSelected: (image) {
                                   state.requestFocus();
-                                  field.didChange([
-                                    ...field.value ?? [],
-                                    image,
-                                  ]);
+                                  field.didChange([...field.value, image]);
                                   Navigator.pop(state.context);
                                 },
                                 onImage: (image) {
@@ -205,11 +202,8 @@ class FormBuilderImagePicker extends FormBuilderField<List<dynamic>> {
 
 class _FormBuilderImagePickerState
     extends FormBuilderFieldState<FormBuilderImagePicker, List<dynamic>> {
-  bool get hasMaxImages {
-    if (widget.maxImages == null || value == null) {
-      return false;
-    } else {
-      return value.length >= widget.maxImages;
-    }
-  }
+  bool get hasMaxImages =>
+      widget.maxImages != null &&
+      value != null &&
+      value.length >= widget.maxImages;
 }

lib/src/fields/form_builder_radio_group.dart

@@ -77,7 +77,7 @@ class FormBuilderRadioGroup<T> extends FormBuilderField<T> {
                 enabled: !state.readOnly,
                 errorText: decoration?.errorText ?? state.errorText,
               ),
-              child: GroupedRadio(
+              child: GroupedRadio<T>(
                 orientation: orientation,
                 value: state.value,
                 options: options,

lib/src/fields/form_builder_segmented_control.dart

@@ -100,7 +100,7 @@ class FormBuilderSegmentedControl<T> extends FormBuilderField<T> {
                   },
                   padding: padding,
                   unselectedColor: unselectedColor,
-                  onValueChanged: (T value) {
+                  onValueChanged: (value) {
                     state.requestFocus();
                     if (state.readOnly) {
                       field.reset();