Refactored and null-safe version of the code

example/lib/main.dart

@@ -1,57 +1,69 @@
 import 'package:flutter/material.dart';
 import 'package:screen/screen.dart';
 
-void main() => runApp(new MyApp());
+void main() => runApp(MyApp());
 
 class MyApp extends StatefulWidget {
   @override
-  _MyAppState createState() => new _MyAppState();
+  _MyAppState createState() => _MyAppState();
 }
 
 class _MyAppState extends State<MyApp> {
   bool _isKeptOn = false;
   double _brightness = 1.0;
 
   @override
-  initState() {
+  void initState() {
     super.initState();
     initPlatformState();
   }
 
-  initPlatformState() async {
-    bool keptOn = await Screen.isKeptOn;
-    double brightness = await Screen.brightness;
-    setState((){
-      _isKeptOn = keptOn;
-      _brightness = brightness;
+  Future<void> initPlatformState() async {
+    bool? keptOn = await Screen.isKeptOn;
+    double? brightness = await Screen.brightness;
+    setState(() {
+      _isKeptOn = keptOn ?? false;
+      _brightness = brightness ?? 1.0;
     });
   }
 
   @override
   Widget build(BuildContext context) {
-    return new MaterialApp(
-      home: new Scaffold(
-        appBar: new AppBar(title: new Text('Screen plugin example')),
-        body: new Center(
-            child: new Column(
+    return MaterialApp(
+      home: Scaffold(
+        appBar: AppBar(title: Text('Screen plugin example')),
+        body: Center(
+          child: Column(
+            children: <Widget>[
+              Row(
+                mainAxisAlignment: MainAxisAlignment.center,
                 children: <Widget>[
-                  new Row(
-                    mainAxisAlignment: MainAxisAlignment.center,
-                    children: <Widget>[
-                      new Text("Screen is kept on ? "),
-                      new Checkbox(value: _isKeptOn, onChanged: (bool b){
+                  Text("Screen is kept on ? "),
+                  Checkbox(
+                    value: _isKeptOn,
+                    onChanged: (bool? b) {
+                      if (b != null) {
                         Screen.keepOn(b);
-                        setState((){_isKeptOn = b; });
-                      })
-                    ]
-                  ),
-                  new Text("Brightness :"),
-                  new Slider(value : _brightness, onChanged : (double b){
-                    setState((){_brightness = b;});
-                    Screen.setBrightness(b);
-                  })
-                ]
-            )
+                        setState(() {
+                          _isKeptOn = b;
+                        });
+                      }
+                    },
+                  )
+                ],
+              ),
+              Text("Brightness :"),
+              Slider(
+                value: _brightness,
+                onChanged: (double b) {
+                  setState(() {
+                    _brightness = b;
+                  });
+                  Screen.setBrightness(b);
+                },
+              )
+            ],
+          ),
         ),
       ),
     );

lib/screen.dart

@@ -1,12 +1,18 @@
-import 'dart:async';
-
 import 'package:flutter/services.dart';
 
 class Screen {
-  static const MethodChannel _channel = const MethodChannel('github.com/clovisnicolas/flutter_screen');
+  static const MethodChannel _channel =
+      const MethodChannel('github.com/clovisnicolas/flutter_screen');
+
+  static Future<double?> get brightness async =>
+      (await _channel.invokeMethod('brightness')) as double?;
+
+  static Future<void> setBrightness(double brightness) =>
+      _channel.invokeMethod('setBrightness', {"brightness": brightness});
+
+  static Future<bool?> get isKeptOn async =>
+      (await _channel.invokeMethod('isKeptOn')) as bool?;
 
-  static Future<double> get brightness async => (await _channel.invokeMethod('brightness')) as double;
-  static Future setBrightness(double brightness) =>_channel.invokeMethod('setBrightness',{"brightness" : brightness});
-  static Future<bool> get isKeptOn async => (await _channel.invokeMethod('isKeptOn')) as bool;
-  static Future keepOn(bool on) => _channel.invokeMethod('keepOn', {"on" : on});
-}
+  static Future<void> keepOn(bool on) =>
+      _channel.invokeMethod('keepOn', {"on": on});
+}

pubspec.yaml

@@ -5,7 +5,7 @@ author: Clovis Nicolas <[email protected]>
 homepage: https://github.com/clovisnicolas/flutter_screen
 
 environment:
-  sdk: '>=2.0.0 <3.0.0'
+  sdk: ">=2.12.0 <3.0.0"
 
 dependencies:
   flutter: