Fix Checkbox Widget

 # Changelog
 
+## 3.0.0-nullsafety.2
+
+- Fix Checkbox Widget
+
 ## 3.0.0-nullsafety.1
 
 - Fix Table border

@@ -82,7 +82,7 @@ enum PdfAnnotFlags {
   lockedContent,
 }
 
-enum PdfAnnotApparence {
+enum PdfAnnotAppearance {
   normal,
   rollover,
   down,
@@ -125,6 +125,8 @@ abstract class PdfAnnotBase {
 
   final Map<String?, PdfDataType> _appearances = <String?, PdfDataType>{};
 
+  PdfName? _as;
+
   int get flagValue {
     if (flags == null || flags!.isEmpty) {
       return 0;
@@ -137,21 +139,22 @@ abstract class PdfAnnotBase {
 
   PdfGraphics appearance(
     PdfDocument pdfDocument,
-    PdfAnnotApparence type, {
+    PdfAnnotAppearance type, {
     String? name,
     Matrix4? matrix,
     PdfRect? boundingBox,
+    bool selected = false,
   }) {
     final s = PdfGraphicXObject(pdfDocument, '/Form');
     String? n;
     switch (type) {
-      case PdfAnnotApparence.normal:
+      case PdfAnnotAppearance.normal:
         n = '/N';
         break;
-      case PdfAnnotApparence.rollover:
+      case PdfAnnotAppearance.rollover:
         n = '/R';
         break;
-      case PdfAnnotApparence.down:
+      case PdfAnnotAppearance.down:
         n = '/D';
         break;
     }
@@ -182,6 +185,10 @@ abstract class PdfAnnotBase {
     s.params['/BBox'] =
         PdfArray.fromNum(<double?>[bbox.x, bbox.y, bbox.width, bbox.height]);
     final g = PdfGraphics(s, s.buf);
+
+    if (selected && name != null) {
+      _as = PdfName(name);
+    }
     return g;
   }
 
@@ -223,11 +230,8 @@ abstract class PdfAnnotBase {
 
     if (_appearances.isNotEmpty) {
       params['/AP'] = PdfDict(_appearances);
-      if (_appearances['/N'] is PdfDict) {
-        final n = _appearances['/N'];
-        if (n is PdfDict) {
-          params['/AS'] = PdfName(n.values.keys.first!);
-        }
+      if (_as != null) {
+        params['/AS'] = _as;
       }
     }
   }
@@ -656,7 +660,7 @@ class PdfTextField extends PdfFormField {
 class PdfButtonField extends PdfFormField {
   PdfButtonField({
     required PdfRect rect,
-    String? fieldName,
+    required String fieldName,
     String? alternateName,
     String? mappingName,
     PdfBorder? border,
@@ -683,20 +687,20 @@ class PdfButtonField extends PdfFormField {
           fieldFlags: fieldFlags,
         );
 
-  final bool? value;
+  final String? value;
 
-  final bool? defaultValue;
+  final String? defaultValue;
 
   @override
   void build(PdfPage page, PdfObject object, PdfDict params) {
     super.build(page, object, params);
 
     if (value != null) {
-      params['/V'] = value! ? const PdfName('/Yes') : const PdfName('/Off');
+      params['/V'] = PdfName(value!);
     }
+
     if (defaultValue != null) {
-      params['/DV'] =
-          defaultValue! ? const PdfName('/Yes') : const PdfName('/Off');
+      params['/DV'] = PdfName(defaultValue!);
     }
   }
 }

@@ -290,7 +290,7 @@ class TextField extends Annotation {
     Widget? child,
     double width = 120,
     double height = 13,
-    String? name,
+    required String name,
     PdfBorder? border,
     Set<PdfAnnotFlags>? flags,
     DateTime? date,

@@ -29,7 +29,6 @@ import 'widget.dart';
 class Checkbox extends SingleChildWidget {
   Checkbox({
     required this.value,
-    this.defaultValue,
     this.tristate = false,
     this.activeColor = PdfColors.blue,
     this.checkColor = PdfColors.white,
@@ -51,8 +50,6 @@ class Checkbox extends SingleChildWidget {
 
   final bool value;
 
-  final bool? defaultValue;
-
   final bool tristate;
 
   final PdfColor activeColor;
@@ -69,13 +66,13 @@ class Checkbox extends SingleChildWidget {
     final bf = PdfButtonField(
       rect: context.localToGlobal(box!),
       fieldName: name,
-      value: value,
-      defaultValue: value,
+      value: value ? '/Yes' : null,
+      defaultValue: value ? '/Yes' : null,
       flags: <PdfAnnotFlags>{PdfAnnotFlags.print},
     );
 
-    final g =
-        bf.appearance(context.document, PdfAnnotApparence.normal, name: '/Yes');
+    final g = bf.appearance(context.document, PdfAnnotAppearance.normal,
+        name: '/Yes', selected: value);
     g.drawRect(0, 0, bf.rect.width, bf.rect.height);
     g.setFillColor(activeColor);
     g.fillPath();
@@ -86,7 +83,8 @@ class Checkbox extends SingleChildWidget {
     g.setLineWidth(2);
     g.strokePath();
 
-    bf.appearance(context.document, PdfAnnotApparence.normal, name: '/Off');
+    bf.appearance(context.document, PdfAnnotAppearance.normal,
+        name: '/Off', selected: !value);
 
     PdfAnnot(context.page, bf);
   }
@@ -144,12 +142,6 @@ class FlatButton extends SingleChildWidget {
           ),
         );
 
-  // final PdfColor textColor;
-
-  // final PdfColor color;
-
-  // final EdgeInsets padding;
-
   final String name;
 
   final Widget _childDown;
@@ -177,21 +169,21 @@ class FlatButton extends SingleChildWidget {
       ..translate(box!.x, box!.y);
 
     final cn = context.copyWith(
-        canvas: bf.appearance(context.document, PdfAnnotApparence.normal,
+        canvas: bf.appearance(context.document, PdfAnnotAppearance.normal,
             matrix: mat, boundingBox: box));
     child!.layout(
         cn, BoxConstraints.tightFor(width: box!.width, height: box!.height));
     child!.paint(cn);
 
     final cd = context.copyWith(
-        canvas: bf.appearance(context.document, PdfAnnotApparence.down,
+        canvas: bf.appearance(context.document, PdfAnnotAppearance.down,
             matrix: mat, boundingBox: box));
     _childDown.layout(
         cd, BoxConstraints.tightFor(width: box!.width, height: box!.height));
     _childDown.paint(cd);
 
     final cr = context.copyWith(
-        canvas: bf.appearance(context.document, PdfAnnotApparence.rollover,
+        canvas: bf.appearance(context.document, PdfAnnotAppearance.rollover,
             matrix: mat, boundingBox: box));
     _childRollover.layout(
         cr, BoxConstraints.tightFor(width: box!.width, height: box!.height));

@@ -4,7 +4,7 @@ description: A pdf producer for Dart. It can create pdf files for both web or fl
 homepage: https://github.com/DavBfr/dart_pdf/tree/master/pdf
 repository: https://github.com/DavBfr/dart_pdf
 issue_tracker: https://github.com/DavBfr/dart_pdf/issues
-version: 3.0.0-nullsafety.1
+version: 3.0.0-nullsafety.2
 
 environment:
   sdk: ">=2.12.0-0 <3.0.0"

@@ -118,7 +118,14 @@ void main() {
               Checkbox(
                 name: 'Checkbox',
                 value: true,
-                defaultValue: true,
+              ),
+              //
+              SizedBox(width: 20, height: 10),
+              //
+              Label(label: 'unchecked:', width: 100),
+              Checkbox(
+                name: 'Unchecked',
+                value: false,
               ),
               //
               SizedBox(width: double.infinity, height: 10),