diff --git a/lib/widgets/highlighted_text.dart b/lib/widgets/highlighted_text.dart
index a2c892b0..1d528901 100644
--- a/lib/widgets/highlighted_text.dart
+++ b/lib/widgets/highlighted_text.dart
@@ -1,5 +1,3 @@
-// @dart=2.9
-
 import 'package:flutter/material.dart';
 
 class HighlightedText extends StatelessWidget {
@@ -8,15 +6,15 @@ class HighlightedText extends StatelessWidget {
   final String highlightTextLowerCase;
 
   final TextStyle style;
-  final TextStyle highlightStyle;
-  final TextOverflow overflow;
-  final int maxLines;
+  final TextStyle? highlightStyle;
+  final TextOverflow? overflow;
+  final int? maxLines;
 
   HighlightedText({
-    @required this.text,
-    @required this.highlightText,
-    @required this.highlightTextLowerCase,
-    @required this.style,
+    required this.text,
+    required this.highlightText,
+    required this.highlightTextLowerCase,
+    required this.style,
     this.highlightStyle,
     this.overflow,
     this.maxLines,
@@ -61,14 +59,14 @@ class HighlightTextSpan {
   final String highlightTextLowerCase;
 
   final TextStyle style;
-  final TextStyle highlightStyle;
+  TextStyle? highlightStyle;
 
   HighlightTextSpan({
-    @required this.text,
-    @required this.highlightText,
-    @required this.highlightTextLowerCase,
-    @required this.style,
-    this.highlightStyle,
+    required this.text,
+    required this.highlightText,
+    required this.highlightTextLowerCase,
+    required this.style,
+    required this.highlightStyle,
   });
 
   List<InlineSpan> build(BuildContext context) {
diff --git a/lib/widgets/icon_dismissable.dart b/lib/widgets/icon_dismissable.dart
index 0b5302a8..01f629d2 100644
--- a/lib/widgets/icon_dismissable.dart
+++ b/lib/widgets/icon_dismissable.dart
@@ -1,5 +1,3 @@
-// @dart=2.9
-
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 
@@ -8,11 +6,11 @@ class IconDismissable extends Dismissible {
   final IconData iconData;
 
   IconDismissable({
-    @required Key key,
-    @required this.backgroundColor,
-    @required this.iconData,
-    @required Function onDismissed,
-    @required Widget child,
+    required Key key,
+    required this.backgroundColor,
+    required this.iconData,
+    required Function(DismissDirection) onDismissed,
+    required Widget child,
   }) : super(
           key: key,
           child: child,
diff --git a/lib/widgets/markdown_toolbar.dart b/lib/widgets/markdown_toolbar.dart
index ad832514..8efc99fa 100644
--- a/lib/widgets/markdown_toolbar.dart
+++ b/lib/widgets/markdown_toolbar.dart
@@ -1,5 +1,3 @@
-// @dart=2.9
-
 import 'package:flutter/material.dart';
 
 import 'package:font_awesome_flutter/font_awesome_flutter.dart';
@@ -15,13 +13,13 @@ class MarkdownToolBar extends StatelessWidget {
   final TextEditingController textController;
 
   MarkdownToolBar({
-    @required this.textController,
+    required this.textController,
   });
 
   @override
   Widget build(BuildContext context) {
     var textTheme = Theme.of(context).textTheme;
-    var style = textTheme.bodyText2.copyWith(fontWeight: FontWeight.bold);
+    var style = textTheme.bodyText2!.copyWith(fontWeight: FontWeight.bold);
 
     return Container(
       child: Row(
@@ -151,7 +149,7 @@ TextEditingValue modifyCurrentLine(
   for (var blockTagRegExp in _allowedBlockRegExps) {
     var match = blockTagRegExp.matchAsPrefix(text, lineStartPos);
     if (match != null) {
-      var blockTag = match.group(0);
+      var blockTag = match.group(0)!;
       var newVal = _removeFromLine(text, cursorPos, lineStartPos, blockTag);
       if (blockTag == char) {
         return newVal;