Null-safety fixes

@@ -2,18 +2,19 @@ name: Dart CI
 
 on:
   push:
-    branches: [ master ]
+    branches: [master]
   pull_request:
-    branches: [ master ]
+    branches: [master]
 
 jobs:
   build:
-
     runs-on: ubuntu-latest
 
     steps:
       - uses: actions/checkout@v2
       - uses: subosito/flutter-action@v1
+        with:
+          channel: dev
       - name: Install utils
         run: sudo apt install poppler-utils imagemagick
       - name: Run analysis

@@ -121,7 +121,7 @@ test-demo: $(FONTS) demo/pubspec.lock .coverage
 
 test-readme: $(FONTS) test/pubspec.lock
 	cd test; $(DART_BIN) extract_readme.dart
-	cd test; dartanalyzer readme-*.dart
+	cd test; $(DART_BIN) analyze
 
 test: test-pdf test-printing test-demo node_modules
 	cat pdf/lcov.info printing/lcov.info demo/lcov.info | node_modules/.bin/lcov-summary

@@ -38,7 +38,8 @@ Future<Uint8List> generateDocument(PdfPageFormat format) async {
                 border: pw.Border(
                     bottom: pw.BorderSide(width: 0.5, color: PdfColors.grey))),
             child: pw.Text('Portable Document Format',
-                style: pw.Theme.of(context).defaultTextStyle
+                style: pw.Theme.of(context)
+                    .defaultTextStyle
                     .copyWith(color: PdfColors.grey)));
       },
       footer: (pw.Context context) {
@@ -47,7 +48,8 @@ Future<Uint8List> generateDocument(PdfPageFormat format) async {
             margin: const pw.EdgeInsets.only(top: 1.0 * PdfPageFormat.cm),
             child: pw.Text(
                 'Page ${context.pageNumber} of ${context.pagesCount}',
-                style: pw.Theme.of(context).defaultTextStyle
+                style: pw.Theme.of(context)
+                    .defaultTextStyle
                     .copyWith(color: PdfColors.grey)));
       },
       build: (pw.Context context) => <pw.Widget>[

@@ -4,8 +4,8 @@ description: Pdf Printing Demo
 version: 1.0.0+1
 
 environment:
-  sdk: '>=2.12.0-224.0.dev <3.0.0'
-  flutter: ">=1.26.0-17.1.pre <2.0.0"
+  sdk: ">=2.12.0-0 <3.0.0"
+  flutter: ">=1.16.0"
 
 dependencies:
   flutter:

@@ -7,7 +7,7 @@ Future<void> main() async {
 
   pdf.addPage(
     pw.Page(
-      build: (pw.Context? context) => pw.Center(
+      build: (pw.Context context) => pw.Center(
         child: pw.Text('Hello World!'),
       ),
     ),

@@ -94,7 +94,7 @@ class BarDataSet extends Dataset {
       return;
     }
 
-    final grid = Chart.of(context)!.grid;
+    final grid = Chart.of(context).grid;
 
     if (drawSurface) {
       for (final value in data) {

@@ -60,7 +60,7 @@ class Chart extends Widget implements Inherited {
   late Widget _child;
 
   // ignore: avoid_as
-  static Chart? of(Context context) => context.dependsOn<Chart>();
+  static Chart of(Context context) => context.dependsOn<Chart>()!;
 
   PdfPoint _computeSize(BoxConstraints constraints) {
     if (constraints.isTight) {

@@ -244,9 +244,6 @@ class FixedAxis<T extends num> extends GridAxis {
   @override
   void layout(Context context, BoxConstraints constraints,
       {bool parentUsesSize = false}) {
-    assert(Chart.of(context) != null,
-        '$runtimeType cannot be used without a Chart widget');
-
     final size = constraints.biggest;
 
     var maxWidth = 0.0;
@@ -379,7 +376,7 @@ class FixedAxis<T extends num> extends GridAxis {
     }
 
     // ignore: avoid_as
-    final grid = Chart.of(context)!.grid as CartesianGrid;
+    final grid = Chart.of(context).grid as CartesianGrid;
 
     switch (direction) {
       case Axis.horizontal:

@@ -39,11 +39,9 @@ class CartesianGrid extends ChartGrid {
   @override
   void layout(Context context, BoxConstraints constraints,
       {bool parentUsesSize = false}) {
-    assert(Chart.of(context) != null,
-        '$runtimeType cannot be used without a Chart widget');
     super.layout(context, constraints, parentUsesSize: parentUsesSize);
 
-    final datasets = Chart.of(context)!.datasets;
+    final datasets = Chart.of(context).datasets;
     final size = constraints.biggest;
 
     // In simple conditions, this loop will run only 2 times.
@@ -104,7 +102,7 @@ class CartesianGrid extends ChartGrid {
   void paint(Context context) {
     super.paint(context);
 
-    final datasets = Chart.of(context)!.datasets;
+    final datasets = Chart.of(context).datasets;
 
     clip(context, box!.size);
     for (var dataSet in datasets) {

@@ -69,10 +69,7 @@ class ChartLegend extends StatelessWidget {
 
   @override
   Widget build(Context context) {
-    assert(Chart.of(context) != null,
-        '$runtimeType cannot be used without a Chart widget');
-
-    final datasets = Chart.of(context)!.datasets;
+    final datasets = Chart.of(context).datasets;
 
     final Widget wrap = Wrap(
       direction: direction,

@@ -136,7 +136,7 @@ class LineDataSet extends Dataset {
       return;
     }
 
-    final grid = Chart.of(context)!.grid;
+    final grid = Chart.of(context).grid;
 
     if (drawSurface) {
       _drawSurface(context, grid);
@@ -167,7 +167,7 @@ class LineDataSet extends Dataset {
       return;
     }
 
-    final grid = Chart.of(context)!.grid;
+    final grid = Chart.of(context).grid;
 
     if (drawLine) {
       _drawLine(context, grid, true);

@@ -20,6 +20,7 @@ import 'package:meta/meta.dart';
 import 'package:pdf/pdf.dart';
 import 'package:vector_math/vector_math_64.dart';
 
+import 'basic.dart';
 import 'document.dart';
 import 'flex.dart';
 import 'geometry.dart';
@@ -91,7 +92,7 @@ class MultiPage extends Page {
   MultiPage({
     PageTheme? pageTheme,
     PdfPageFormat? pageFormat,
-    BuildListCallback? build,
+    required BuildListCallback build,
     this.mainAxisAlignment = MainAxisAlignment.start,
     this.crossAxisAlignment = CrossAxisAlignment.start,
     this.header,
@@ -106,13 +107,14 @@ class MultiPage extends Page {
         super(
           pageTheme: pageTheme,
           pageFormat: pageFormat,
+          build: (_) => SizedBox(),
           margin: margin,
           theme: theme,
           orientation: orientation,
           textDirection: textDirection,
         );
 
-  final BuildListCallback? _buildList;
+  final BuildListCallback _buildList;
 
   final CrossAxisAlignment crossAxisAlignment;
 
@@ -149,10 +151,6 @@ class MultiPage extends Page {
 
   @override
   void generate(Document document, {bool insert = true, int? index}) {
-    if (_buildList == null) {
-      return;
-    }
-
     assert(pageFormat.width > 0 && pageFormat.width < double.infinity);
     assert(pageFormat.height > 0 && pageFormat.height < double.infinity);
 
@@ -184,7 +182,7 @@ class MultiPage extends Page {
       if (pageTheme.textDirection != null)
         InheritedDirectionality(pageTheme.textDirection),
     ]);
-    final children = _buildList!(baseContext);
+    final children = _buildList(baseContext);
     WidgetContext? widgetContext;
 
     while (_index < children.length) {

@@ -37,7 +37,7 @@ class Page {
   Page({
     PageTheme? pageTheme,
     PdfPageFormat? pageFormat,
-    BuildCallback? build,
+    required BuildCallback build,
     ThemeData? theme,
     PageOrientation? orientation,
     EdgeInsets? margin,
@@ -69,7 +69,7 @@ class Page {
 
   PageOrientation get orientation => pageTheme.orientation;
 
-  final BuildCallback? _build;
+  final BuildCallback _build;
 
   ThemeData? get theme => pageTheme.theme;
 
@@ -136,8 +136,7 @@ class Page {
     Widget? content;
     Widget? foreground;
 
-    if (_build != null) {
-      content = _build!(context);
+    content = _build(context);
 
     final size = layout(content, context, constraints);
 
@@ -152,7 +151,6 @@ class Page {
               maxWidth: _pdfPage!.pageFormat.width - _margin.horizontal,
               maxHeight: _pdfPage!.pageFormat.height - _margin.vertical);
     }
-    }
 
     if (pageTheme.buildBackground != null) {
       background = pageTheme.buildBackground!(context);
@@ -175,9 +173,7 @@ class Page {
       paint(background, context);
     }
 
-    if (content != null) {
     paint(content, context);
-    }
 
     if (foreground != null) {
       paint(foreground, context);

@@ -7,7 +7,7 @@ issue_tracker: https://github.com/DavBfr/dart_pdf/issues
 version: 3.0.0-nullsafety.0
 
 environment:
-  sdk: '>=2.12.0-224.0.dev <3.0.0'
+  sdk: ">=2.12.0-0 <3.0.0"
 
 dependencies:
   archive: ^3.0.0-nullsafety

@@ -464,7 +464,7 @@ void main() {
 
   test('Text Widgets Arabic', () {
     pdf.addPage(Page(
-      build: (Context? context) => RichText(
+      build: (Context context) => RichText(
         textDirection: TextDirection.rtl,
         text: TextSpan(
           text: 'قهوة\n',

@@ -28,8 +28,8 @@ class Color extends StatelessWidget {
   final String? varient;
 
   @override
-  Widget build(Context? context) {
-    final style = Theme.of(context!).defaultTextStyle.copyWith(
+  Widget build(Context context) {
+    final style = Theme.of(context).defaultTextStyle.copyWith(
         color: color.luminance < 0.2 ? PdfColors.white : PdfColors.black,
         fontSize: 14);
     final hexStyle = style.copyWith(font: Font.courier(), fontSize: 10);
@@ -73,7 +73,7 @@ class ColorWheel extends Widget {
   final ColorSpace colorSpace;
 
   @override
-  void layout(Context? context, BoxConstraints? constraints,
+  void layout(Context context, BoxConstraints? constraints,
       {bool parentUsesSize = false}) {
     box = PdfRect.fromPoints(PdfPoint.zero, constraints!.biggest);
   }
@@ -672,11 +672,11 @@ void main() {
 
     wheels.forEach((ColorSpace colorSpace, String name) {
       pdf.addPage(Page(
-          build: (Context? context) => Column(
+          build: (Context context) => Column(
                 children: <Widget>[
                   Header(text: name, outlineStyle: PdfOutlineStyle.italic),
                   SizedBox(
-                    height: context!.page.pageFormat.availableWidth,
+                    height: context.page.pageFormat.availableWidth,
                     child: ColorWheel(
                       colorSpace: colorSpace,
                     ),

@@ -38,7 +38,7 @@ void compute(Message message) {
     message.image,
   );
 
-  pdf.addPage(Page(build: (Context? context) => Center(child: Image(image))));
+  pdf.addPage(Page(build: (Context context) => Center(child: Image(image))));
 
   message.sendPort.send(pdf.save());
 }

@@ -38,14 +38,14 @@ void main() {
 
   test('Pdf Jpeg Download', () async {
     pdf.addPage(Page(
-      build: (Context? context) => Center(child: Image(image)),
+      build: (Context context) => Center(child: Image(image)),
     ));
   });
 
   test('Pdf Jpeg Orientations', () {
     pdf.addPage(
       Page(
-        build: (Context? context) => GridView(
+        build: (Context context) => GridView(
           crossAxisCount: 4,
           crossAxisSpacing: 10,
           children: List<Widget>.generate(
@@ -95,7 +95,7 @@ void main() {
 
     pdf.addPage(
       Page(
-        build: (Context? context) => Center(
+        build: (Context context) => Center(
           child: Wrap(
             spacing: 20,
             runSpacing: 20,

@@ -113,7 +113,7 @@ void main() {
             .codeUnits) {
       pdf.addPage(Page(
           pageFormat: const PdfPageFormat(500, 500, marginAll: 20),
-          build: (Context? context) {
+          build: (Context context) {
             return ConstrainedBox(
                 constraints: const BoxConstraints.expand(),
                 child: FittedBox(

@@ -22,7 +22,7 @@ import 'package:pdf/widgets.dart';
 
 late Document pdf;
 
-Widget content(Context? context) {
+Widget content(Context context) {
   return ListView(children: contentMultiPage(context));
 }
 
@@ -38,7 +38,7 @@ Widget header(Context context) {
   );
 }
 
-List<Widget> contentMultiPage(Context? context) {
+List<Widget> contentMultiPage(Context context) {
   return List<Widget>.generate(
     150,
     (int n) => Container(

@@ -31,7 +31,7 @@ void main() {
   test('Pdf Roll Paper', () async {
     pdf.addPage(Page(
       pageFormat: PdfPageFormat.roll80,
-      build: (Context? context) => Padding(
+      build: (Context context) => Padding(
         padding: const EdgeInsets.all(30),
         child: Center(
           child: Text('Hello World!'),
@@ -43,7 +43,7 @@ void main() {
   test('Pdf Automatic Paper', () async {
     pdf.addPage(Page(
         pageFormat: PdfPageFormat.undefined,
-        build: (Context? context) => Text('Hello World!')));
+        build: (Context context) => Text('Hello World!')));
   });
 
   tearDownAll(() async {

@@ -30,7 +30,7 @@ void main() {
 
   test('Basic Widgets Align 1', () {
     pdf.addPage(Page(
-        build: (Context? context) => Align(
+        build: (Context context) => Align(
               alignment: Alignment.bottomRight,
               child: SizedBox(width: 100, height: 100, child: PdfLogo()),
             )));
@@ -38,7 +38,7 @@ void main() {
 
   test('Basic Widgets Align 2', () {
     pdf.addPage(Page(
-        build: (Context? context) => Align(
+        build: (Context context) => Align(
               alignment: const Alignment(0.8, 0.2),
               child: SizedBox(width: 100, height: 100, child: PdfLogo()),
             )));
@@ -46,7 +46,7 @@ void main() {
 
   test('Basic Widgets AspectRatio', () {
     pdf.addPage(Page(
-        build: (Context? context) => AspectRatio(
+        build: (Context context) => AspectRatio(
               aspectRatio: 1.618,
               child: Placeholder(),
             )));
@@ -54,14 +54,14 @@ void main() {
 
   test('Basic Widgets Center', () {
     pdf.addPage(Page(
-        build: (Context? context) => Center(
+        build: (Context context) => Center(
               child: SizedBox(width: 100, height: 100, child: PdfLogo()),
             )));
   });
 
   test('Basic Widgets ConstrainedBox', () {
     pdf.addPage(Page(
-      build: (Context? context) => ConstrainedBox(
+      build: (Context context) => ConstrainedBox(
           constraints: const BoxConstraints.tightFor(height: 300),
           child: Placeholder()),
     ));
@@ -69,7 +69,7 @@ void main() {
 
   test('Basic Widgets CustomPaint', () {
     pdf.addPage(Page(
-        build: (Context? context) => CustomPaint(
+        build: (Context context) => CustomPaint(
               size: const PdfPoint(200, 200),
               painter: (PdfGraphics canvas, PdfPoint size) {
                 canvas
@@ -79,7 +79,7 @@ void main() {
               },
             )));
     pdf.addPage(Page(
-        build: (Context? context) => CustomPaint(
+        build: (Context context) => CustomPaint(
               size: const PdfPoint(200, 200),
               painter: (PdfGraphics canvas, PdfPoint size) {
                 canvas
@@ -93,7 +93,7 @@ void main() {
 
   test('Basic Widgets FittedBox', () {
     pdf.addPage(Page(
-        build: (Context? context) => Column(
+        build: (Context context) => Column(
                 mainAxisAlignment: MainAxisAlignment.spaceBetween,
                 mainAxisSize: MainAxisSize.max,
                 children: <Widget>[
@@ -151,7 +151,7 @@ void main() {
 
   test('Basic Widgets LimitedBox', () {
     pdf.addPage(Page(
-        build: (Context? context) => ListView(
+        build: (Context context) => ListView(
               children: <Widget>[
                 LimitedBox(
                   maxHeight: 40,
@@ -163,7 +163,7 @@ void main() {
 
   test('Basic Widgets Padding', () {
     pdf.addPage(Page(
-        build: (Context? context) => Center(
+        build: (Context context) => Center(
               child: Padding(
                 padding: const EdgeInsets.all(20),
                 child: PdfLogo(),
@@ -173,7 +173,7 @@ void main() {
 
   test('Basic Widgets SizedBox', () {
     pdf.addPage(Page(
-        build: (Context? context) => SizedBox(
+        build: (Context context) => SizedBox(
               width: 200,
               height: 100,
               child: Placeholder(),
@@ -182,7 +182,7 @@ void main() {
 
   test('Basic Widgets Transform', () {
     pdf.addPage(Page(
-        build: (Context? context) => Transform.scale(
+        build: (Context context) => Transform.scale(
               scale: 0.5,
               child: Transform.rotate(
                 angle: 0.1,
@@ -193,7 +193,7 @@ void main() {
 
   test('Basic Widgets Transform rotateBox', () {
     pdf.addPage(Page(
-        build: (Context? context) => Center(
+        build: (Context context) => Center(
               child: Transform.rotateBox(
                 angle: 3.1416 / 2,
                 child: Text('Hello'),

@@ -32,7 +32,7 @@ void main() {
     test('Default LineChart', () {
       pdf.addPage(Page(
         pageFormat: PdfPageFormat.standard.landscape,
-        build: (Context? context) => Chart(
+        build: (Context context) => Chart(
           grid: CartesianGrid(
             xAxis: FixedAxis<int>(<int>[0, 1, 2, 3, 4, 5, 6]),
             yAxis: FixedAxis<int>(<int>[0, 3, 6, 9], divisions: true),
@@ -53,7 +53,7 @@ void main() {
     test('Default LineChart without lines connecting points', () {
       pdf.addPage(Page(
         pageFormat: PdfPageFormat.standard.landscape,
-        build: (Context? context) => Chart(
+        build: (Context context) => Chart(
           grid: CartesianGrid(
             xAxis: FixedAxis<int>(<int>[0, 1, 2, 3, 4, 5, 6]),
             yAxis: FixedAxis<int>(<int>[0, 3, 6, 9], divisions: true),
@@ -74,7 +74,7 @@ void main() {
 
     test('Default ScatterChart without dots', () {
       pdf.addPage(Page(
-        build: (Context? context) => Chart(
+        build: (Context context) => Chart(
           grid: CartesianGrid(
             xAxis: FixedAxis<int>(<int>[0, 1, 2, 3, 4, 5, 6]),
             yAxis: FixedAxis<int>(<int>[0, 3, 6, 9], divisions: true),
@@ -96,7 +96,7 @@ void main() {
     test('ScatterChart with custom points and lines', () {
       pdf.addPage(Page(
         pageFormat: PdfPageFormat.standard.landscape,
-        build: (Context? context) => Chart(
+        build: (Context context) => Chart(
           grid: CartesianGrid(
             xAxis: FixedAxis<int>(<int>[0, 1, 2, 3, 4, 5, 6]),
             yAxis: FixedAxis<int>(<int>[0, 3, 6, 9], divisions: true),
@@ -122,7 +122,7 @@ void main() {
     test('ScatterChart with custom size', () {
       pdf.addPage(Page(
         pageFormat: PdfPageFormat.standard.landscape,
-        build: (Context? context) => SizedBox(
+        build: (Context context) => SizedBox(
           width: 200,
           height: 100,
           child: Chart(
@@ -147,7 +147,7 @@ void main() {
     test('LineChart with curved lines', () {
       pdf.addPage(Page(
         pageFormat: PdfPageFormat.standard.landscape,
-        build: (Context? context) => Chart(
+        build: (Context context) => Chart(
           grid: CartesianGrid(
             xAxis: FixedAxis<int>(<int>[0, 1, 2, 3, 4, 5, 6]),
             yAxis: FixedAxis<int>(<int>[0, 3, 6, 9], divisions: true),
@@ -172,7 +172,7 @@ void main() {
     test('Default BarChart', () {
       pdf.addPage(Page(
         pageFormat: PdfPageFormat.standard.landscape,
-        build: (Context? context) => Chart(
+        build: (Context context) => Chart(
           grid: CartesianGrid(
             xAxis: FixedAxis<int>(<int>[0, 1, 2, 3, 4, 5, 6]),
             yAxis: FixedAxis<int>(<int>[0, 3, 6, 9], divisions: true),
@@ -193,7 +193,7 @@ void main() {
     test('Vertical BarChart', () {
       pdf.addPage(Page(
         pageFormat: PdfPageFormat.standard.landscape,
-        build: (Context? context) => Chart(
+        build: (Context context) => Chart(
           grid: CartesianGrid(
             xAxis: FixedAxis<int>(<int>[0, 1, 2, 3, 4, 5, 6]),
             yAxis: FixedAxis<int>(<int>[0, 3, 6, 9], divisions: true),

@@ -30,7 +30,7 @@ void main() {
 
   test('Clip Widgets ClipRect', () {
     pdf.addPage(Page(
-      build: (Context? context) => ClipRect(
+      build: (Context context) => ClipRect(
         child: Transform.rotate(
           angle: 0.1,
           child: Container(
@@ -45,7 +45,7 @@ void main() {
 
   test('Clip Widgets ClipRRect', () {
     pdf.addPage(Page(
-      build: (Context? context) => ClipRRect(
+      build: (Context context) => ClipRRect(
         horizontalRadius: 30,
         verticalRadius: 30,
         child: Container(
@@ -59,7 +59,7 @@ void main() {
 
   test('Clip Widgets ClipOval', () {
     pdf.addPage(Page(
-      build: (Context? context) => ClipOval(
+      build: (Context context) => ClipOval(
         child: Container(
           decoration: const BoxDecoration(
             color: PdfColors.blue,

@@ -32,7 +32,7 @@ void main() {
 
   test('Container Widgets Flat', () {
     pdf.addPage(Page(
-      build: (Context? context) => Container(
+      build: (Context context) => Container(
         alignment: Alignment.center,
         margin: const EdgeInsets.all(30),
         padding: const EdgeInsets.all(20),
@@ -92,7 +92,7 @@ void main() {
 
   test('Container Widgets BoxShape Border', () {
     pdf.addPage(Page(
-      build: (Context? context) => Center(
+      build: (Context context) => Center(
         child: Column(
           mainAxisAlignment: MainAxisAlignment.spaceEvenly,
           children: <Widget>[
@@ -121,7 +121,7 @@ void main() {
 
   test('Container Widgets LinearGradient', () {
     pdf.addPage(Page(
-      build: (Context? context) => Container(
+      build: (Context context) => Container(
         alignment: Alignment.center,
         margin: const EdgeInsets.all(30),
         padding: const EdgeInsets.all(20),
@@ -150,7 +150,7 @@ void main() {
 
   test('Container Widgets RadialGradient', () {
     pdf.addPage(Page(
-      build: (Context? context) => Container(
+      build: (Context context) => Container(
         alignment: Alignment.center,
         margin: const EdgeInsets.all(30),
         padding: const EdgeInsets.all(20),
@@ -180,7 +180,7 @@ void main() {
 
   test('Container Widgets BoxShadow', () {
     pdf.addPage(Page(
-      build: (Context? context) => Container(
+      build: (Context context) => Container(
         margin: const EdgeInsets.all(30),
         padding: const EdgeInsets.all(20),
         decoration: const BoxDecoration(

@@ -31,7 +31,7 @@ void main() {
   test('Flex Widgets ListView', () {
     pdf.addPage(
       Page(
-        build: (Context? context) => ListView(
+        build: (Context context) => ListView(
           spacing: 20,
           padding: const EdgeInsets.all(10),
           children: <Widget>[
@@ -47,7 +47,7 @@ void main() {
   test('Flex Widgets ListView.builder', () {
     pdf.addPage(
       Page(
-        build: (Context? context) => ListView.builder(
+        build: (Context context) => ListView.builder(
           itemBuilder: (Context context, int index) => Text('Line $index'),
           itemCount: 30,
           spacing: 2,
@@ -60,7 +60,7 @@ void main() {
   test('Flex Widgets ListView.separated', () {
     pdf.addPage(
       Page(
-        build: (Context? context) => ListView.separated(
+        build: (Context context) => ListView.separated(
           separatorBuilder: (Context context, int index) => Container(
             color: PdfColors.grey,
             height: 0.5,
@@ -76,7 +76,7 @@ void main() {
   test('Flex Widgets Spacer', () {
     pdf.addPage(
       Page(
-        build: (Context? context) => Column(
+        build: (Context context) => Column(
           children: <Widget>[
             Text('Begin'),
             Spacer(), // Defaults to a flex of one.

@@ -74,7 +74,7 @@ void main() {
     () {
       pdf.addPage(
         Page(
-          build: (Context? context) => Wrap(
+          build: (Context context) => Wrap(
             crossAxisAlignment: WrapCrossAlignment.center,
             children: <Widget>[
               Label(label: 'Given Name:', width: 100),

@@ -51,7 +51,7 @@ void main() {
 
   test('Pdf Widgets GridView Horizontal', () {
     pdf.addPage(Page(
-      build: (Context? context) => GridView(
+      build: (Context context) => GridView(
           crossAxisCount: 5,
           direction: Axis.horizontal,
           childAspectRatio: 1,

@@ -47,7 +47,7 @@ void main() {
 
     final pdf = Document();
 
-    pdf.addPage(Page(build: (Context? context) => Column(children: lines)));
+    pdf.addPage(Page(build: (Context context) => Column(children: lines)));
 
     final file = File('widgets-monopage.pdf');
     await file.writeAsBytes(await pdf.save());

@@ -30,7 +30,7 @@ void main() {
   test('Opacity Widgets', () {
     pdf.addPage(
       Page(
-        build: (Context? context) => Stack(
+        build: (Context context) => Stack(
           alignment: Alignment.center,
           children: <Widget>[
             Text('Background', textScaleFactor: 5),

@@ -71,13 +71,13 @@ void main() {
 
   test('Table Widget empty', () {
     pdf.addPage(Page(
-      build: (Context? context) => Table(),
+      build: (Context context) => Table(),
     ));
   });
 
   test('Table Widget filled', () {
     pdf.addPage(Page(
-      build: (Context? context) => Table(
+      build: (Context context) => Table(
         children: buildTable(context: context, count: 20),
         border: TableBorder.all(),
         tableWidth: TableWidth.max,
@@ -135,7 +135,7 @@ void main() {
 
   test('Table Widget Widths', () {
     pdf.addPage(Page(
-      build: (Context? context) => Table(
+      build: (Context context) => Table(
         children: buildTable(context: context, count: 20),
         border: TableBorder.all(),
         columnWidths: <int, TableColumnWidth>{
@@ -189,7 +189,7 @@ void main() {
 
   test('Table fromTextArray', () {
     pdf.addPage(Page(
-      build: (Context? context) => Table.fromTextArray(
+      build: (Context context) => Table.fromTextArray(
         context: context,
         tableWidth: TableWidth.min,
         data: <List<dynamic>>[
@@ -203,7 +203,7 @@ void main() {
 
   test('Table fromTextArray with formatting', () {
     pdf.addPage(Page(
-      build: (Context? context) => Table.fromTextArray(
+      build: (Context context) => Table.fromTextArray(
         border: null,
         cellAlignment: Alignment.center,
         headerDecoration: const BoxDecoration(
@@ -239,7 +239,7 @@ void main() {
       theme: ThemeData.withFont(
         base: loadFont('hacen-tunisia.ttf'),
       ),
-      build: (Context? context) => Directionality(
+      build: (Context context) => Directionality(
         textDirection: TextDirection.rtl,
         child: Table.fromTextArray(
           headers: <dynamic>['ثلاثة', 'اثنان', 'واحد'],
@@ -256,7 +256,7 @@ void main() {
   test('Table fromTextArray with alignment', () {
     pdf.addPage(
       Page(
-        build: (Context? context) => Table.fromTextArray(
+        build: (Context context) => Table.fromTextArray(
           cellAlignment: Alignment.center,
           data: <List<String>>[
             <String>['line 1', 'Text\n\n\ntext'],

@@ -51,7 +51,7 @@ void main() {
     pdf.addPage(Page(
         pageFormat: const PdfPageFormat(400, 400),
         margin: const EdgeInsets.all(10),
-        build: (Context? context) => Column(children: <Widget>[
+        build: (Context context) => Column(children: <Widget>[
               Container(
                 padding: const EdgeInsets.all(5),
                 margin: const EdgeInsets.only(bottom: 10),
@@ -114,7 +114,7 @@ void main() {
                   "That's all Folks!",
                   tightBounds: true,
                   textAlign: TextAlign.center,
-                  style: Theme.of(context!).defaultTextStyle.copyWith(
+                  style: Theme.of(context).defaultTextStyle.copyWith(
                         font: Font.timesBoldItalic(),
                       ),
                   textScaleFactor: 3,
@@ -128,7 +128,7 @@ void main() {
       Page(
         pageFormat: const PdfPageFormat(400, 400),
         margin: const EdgeInsets.all(10),
-        build: (Context? context) => Center(
+        build: (Context context) => Center(
           child: GridView(
             crossAxisCount: 3,
             direction: Axis.vertical,
@@ -205,7 +205,7 @@ void main() {
         Page(
           pageFormat: const PdfPageFormat(400, 200),
           margin: const EdgeInsets.all(10),
-          build: (Context? context) => Stack(
+          build: (Context context) => Stack(
             overflow: Overflow.visible,
             // fit: StackFit.expand,
             // alignment: Alignment.bottomRight,
@@ -227,7 +227,7 @@ void main() {
                   child: RichText(
                     text: TextSpan(
                       text: 'Hello ',
-                      style: Theme.of(context!).defaultTextStyle,
+                      style: Theme.of(context).defaultTextStyle,
                       children: <TextSpan>[
                         TextSpan(
                             text: 'bold',

@@ -53,12 +53,12 @@ void main() {
 
   test('Text Widgets Quotes', () {
     pdf.addPage(Page(
-        build: (Context? context) => Text('Text containing \' or " works!')));
+        build: (Context context) => Text('Text containing \' or " works!')));
   });
 
   test('Text Widgets Unicode Quotes', () {
     pdf.addPage(Page(
-        build: (Context? context) => Text('Text containing ’ and ” works!',
+        build: (Context context) => Text('Text containing ’ and ” works!',
             style: TextStyle(font: ttf))));
   });
 
@@ -249,7 +249,7 @@ void main() {
 
   test('Text Widgets RichText Multiple lang', () {
     pdf.addPage(Page(
-      build: (Context? context) => RichText(
+      build: (Context context) => RichText(
         text: TextSpan(
           text: 'Hello ',
           style: TextStyle(
@@ -276,7 +276,7 @@ void main() {
 
     pdf.addPage(
       Page(
-        build: (Context? context) => RichText(
+        build: (Context context) => RichText(
           maxLines: 3,
           text: TextSpan(
             text: para,

@@ -55,7 +55,7 @@ void main() {
         color: PdfColors.blue);
 
     pdf.addPage(Page(
-      build: (Context? context) => ListView(
+      build: (Context context) => ListView(
         children: <Widget>[
           Text(
             style.font!.fontName!,
@@ -71,7 +71,7 @@ void main() {
 
     pdf.addPage(Page(
       theme: theme,
-      build: (Context? context) => Center(
+      build: (Context context) => Center(
         child: Text('Hello'),
       ),
     ));
@@ -85,7 +85,7 @@ void main() {
 
     pdf.addPage(Page(
       theme: theme,
-      build: (Context? context) => Center(
+      build: (Context context) => Center(
         child: Table.fromTextArray(context: context, data: <List<String>>[
           <String>['Header', '123'],
           <String>['Cell', '456']
@@ -96,7 +96,7 @@ void main() {
 
   test('Theme Page 3', () {
     pdf.addPage(Page(
-      build: (Context? context) => Center(
+      build: (Context context) => Center(
         child: Column(
           mainAxisAlignment: MainAxisAlignment.spaceEvenly,
           children: <Widget>[
@@ -121,7 +121,7 @@ void main() {
         theme: ThemeData(
           defaultTextStyle: TextStyle(font: Font.courier(), fontSize: 10.0),
         ),
-        build: (Context? context) {
+        build: (Context context) {
           return Center(child: Text('Text'));
         }));
   });

@@ -48,7 +48,7 @@ void main() {
     pdf.addPage(
       Page(
         pageTheme: pageTheme,
-        build: (Context? context) => Center(
+        build: (Context context) => Center(
           child: Text(
             'Hello World',
           ),

@@ -53,7 +53,7 @@ void main() {
       Page(
         pageFormat: const PdfPageFormat(400, 800),
         margin: const EdgeInsets.all(10),
-        build: (Context? context) => Column(
+        build: (Context context) => Column(
           mainAxisAlignment: MainAxisAlignment.spaceEvenly,
           children: wraps,
         ),
@@ -85,7 +85,7 @@ void main() {
       Page(
         pageFormat: const PdfPageFormat(800, 400),
         margin: const EdgeInsets.all(10),
-        build: (Context? context) => Row(
+        build: (Context context) => Row(
           mainAxisAlignment: MainAxisAlignment.spaceEvenly,
           children: wraps,
         ),
@@ -119,7 +119,7 @@ void main() {
       Page(
         pageFormat: const PdfPageFormat(400, 800),
         margin: const EdgeInsets.all(10),
-        build: (Context? context) => Column(
+        build: (Context context) => Column(
           mainAxisAlignment: MainAxisAlignment.spaceEvenly,
           children: wraps,
         ),
@@ -153,7 +153,7 @@ void main() {
       Page(
         pageFormat: const PdfPageFormat(800, 400),
         margin: const EdgeInsets.all(10),
-        build: (Context? context) => Row(
+        build: (Context context) => Row(
           mainAxisAlignment: MainAxisAlignment.spaceEvenly,
           children: wraps,
         ),
@@ -189,7 +189,7 @@ void main() {
       Page(
         pageFormat: const PdfPageFormat(400, 800),
         margin: const EdgeInsets.all(10),
-        build: (Context? context) => Column(
+        build: (Context context) => Column(
           mainAxisAlignment: MainAxisAlignment.spaceEvenly,
           children: wraps,
         ),
@@ -225,7 +225,7 @@ void main() {
       Page(
         pageFormat: const PdfPageFormat(800, 400),
         margin: const EdgeInsets.all(10),
-        build: (Context? context) => Row(
+        build: (Context context) => Row(
           mainAxisAlignment: MainAxisAlignment.spaceEvenly,
           children: wraps,
         ),
@@ -239,7 +239,7 @@ void main() {
       Page(
         pageFormat: const PdfPageFormat(200, 200),
         margin: const EdgeInsets.all(10),
-        build: (Context? context) => Wrap(
+        build: (Context context) => Wrap(
           spacing: 10,
           runSpacing: 10,
           children: List<Widget>.generate(
@@ -285,7 +285,7 @@ void main() {
   });
 
   test('Wrap Widget Empty', () {
-    pdf.addPage(Page(build: (Context? context) => Wrap()));
+    pdf.addPage(Page(build: (Context context) => Wrap()));
   });
 
   test('Wrap Widget Columns', () {

@@ -4,7 +4,7 @@ description: Pdf Printing Example
 version: 1.0.0+1
 
 environment:
-  sdk: '>=2.12.0-224.0.dev <3.0.0'
+  sdk: ">=2.12.0-0 <3.0.0"
 
 dependencies:
   flutter:

@@ -7,8 +7,8 @@ issue_tracker: https://github.com/DavBfr/dart_pdf/issues
 version: 5.0.0-nullsafety.0
 
 environment:
-  sdk: '>=2.12.0-224.0.dev <3.0.0'
-  flutter: ">=1.12.13+hotfix.5 <2.0.0"
+  sdk: ">=2.12.0-0 <3.0.0"
+  flutter: ">=1.16.0"
 
 dependencies:
   flutter:

@@ -7,8 +7,8 @@ issue_tracker: https://github.com/DavBfr/dart_pdf/issues
 version: 1.0.0
 
 environment:
-  sdk: '>=2.12.0-224.0.dev <3.0.0'
-  flutter: ">=1.12.13+hotfix.5 <2.0.0"
+  sdk: ">=2.12.0-0 <3.0.0"
+  flutter: ">=1.16.0"
 
 dependencies:
   flutter: