fix(example): migrate to null-safety

example/lib/main.dart

@@ -10,14 +10,14 @@ void main() {
 /// Example app widget for the plugin.
 class MyApp extends StatefulWidget {
   /// Constructor of MyApp widget.
-  const MyApp({Key key}) : super(key: key);
+  const MyApp({Key? key}) : super(key: key);
 
   @override
   State<MyApp> createState() => _MyAppState();
 }
 
 class _MyAppState extends State<MyApp> {
-  Intent _initialIntent;
+  Intent? _initialIntent;
 
   @override
   void initState() {
@@ -35,7 +35,7 @@ class _MyAppState extends State<MyApp> {
     });
   }
 
-  Widget _buildFromIntent(String label, Intent intent) {
+  Widget _buildFromIntent(String label, Intent? intent) {
     return Center(
       child: Column(
         children: [
@@ -63,7 +63,7 @@ class _MyAppState extends State<MyApp> {
             mainAxisAlignment: MainAxisAlignment.spaceEvenly,
             children: [
               _buildFromIntent("INITIAL", _initialIntent),
-              StreamBuilder<Intent>(
+              StreamBuilder<Intent?>(
                 stream: ReceiveIntent.receivedIntentStream,
                 builder: (context, snapshot) =>
                     _buildFromIntent("STREAMED", snapshot.data),

example/pubspec.yaml

@@ -6,7 +6,7 @@ description: Demonstrates how to use the receive_intent plugin.
 publish_to: 'none' # Remove this line if you wish to publish to pub.dev
 
 environment:
-  sdk: ">=2.7.0 <3.0.0"
+  sdk: ">=2.12.0 <3.0.0"
 
 dependencies:
   flutter:

example/test/widget_test.dart

@@ -10,17 +10,5 @@ import 'package:flutter_test/flutter_test.dart';
 import 'package:receive_intent_example/main.dart';
 
 void main() {
-  testWidgets('Verify Platform version', (WidgetTester tester) async {
-    // Build our app and trigger a frame.
-    await tester.pumpWidget(const MyApp());
-
-    // Verify that platform version is retrieved.
-    expect(
-      find.byWidgetPredicate(
-        (Widget widget) =>
-            widget is Text && widget.data.startsWith('Running on:'),
-      ),
-      findsOneWidget,
-    );
-  });
+  // TODO
 }