Add Null Safety Support

example/lib/main.dart

@@ -155,35 +155,35 @@ class _MyAppState extends State<MyApp> {
           ),
           body: Column(
             children: <Widget>[
-              RaisedButton(
+              ElevatedButton(
                 child: Text("Platform Version"),
                 onPressed: initPlatformState,
               ),
               Center(
                 child: Text('Running on: $_platformVersion\n'),
               ),
-              RaisedButton(
+              ElevatedButton(
                 child: Text("Set wallpaper from file"),
                 onPressed: setWallpaperFromFile,
               ),
               Center(
                 child: Text('Wallpaper status: $_wallpaperFile\n'),
               ),
-              RaisedButton(
+              ElevatedButton(
                 child: Text("Set wallpaper from file with crop"),
                 onPressed: setWallpaperFromFileWithCrop,
               ),
               Center(
                 child: Text('Wallpaper status: $_wallpaperFileWithCrop\n'),
               ),
-              RaisedButton(
+              ElevatedButton(
                 child: Text("Set wallpaper from asset"),
                 onPressed: setWallpaperFromAsset,
               ),
               Center(
                 child: Text('Wallpaper status: $_wallpaperAsset\n'),
               ),
-              RaisedButton(
+              ElevatedButton(
                 child: Text("Set wallpaper from asset with crop"),
                 onPressed: setWallpaperFromAssetWithCrop,
               ),

example/pubspec.lock

@@ -7,42 +7,42 @@ packages:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.4.1"
+    version: "2.6.1"
   boolean_selector:
     dependency: transitive
     description:
       name: boolean_selector
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.0"
+    version: "2.1.0"
   characters:
     dependency: transitive
     description:
       name: characters
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.0"
+    version: "1.1.0"
   charcode:
     dependency: transitive
     description:
       name: charcode
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.3"
+    version: "1.2.0"
   clock:
     dependency: transitive
     description:
       name: clock
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.1"
+    version: "1.1.0"
   collection:
     dependency: transitive
     description:
       name: collection
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.14.13"
+    version: "1.15.0"
   convert:
     dependency: transitive
     description:
@@ -70,7 +70,7 @@ packages:
       name: fake_async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.0"
+    version: "1.2.0"
   flutter:
     dependency: "direct main"
     description: flutter
@@ -108,21 +108,21 @@ packages:
       name: matcher
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.12.8"
+    version: "0.12.10"
   meta:
     dependency: transitive
     description:
       name: meta
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.8"
+    version: "1.3.0"
   path:
     dependency: transitive
     description:
       name: path
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.7.0"
+    version: "1.8.0"
   path_provider:
     dependency: transitive
     description:
@@ -155,7 +155,7 @@ packages:
       name: source_span
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.7.0"
+    version: "1.8.1"
   sqflite:
     dependency: transitive
     description:
@@ -169,21 +169,21 @@ packages:
       name: stack_trace
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.9.3"
+    version: "1.10.0"
   stream_channel:
     dependency: transitive
     description:
       name: stream_channel
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.0"
+    version: "2.1.0"
   string_scanner:
     dependency: transitive
     description:
       name: string_scanner
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.5"
+    version: "1.1.0"
   synchronized:
     dependency: transitive
     description:
@@ -197,21 +197,21 @@ packages:
       name: term_glyph
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.0"
+    version: "1.2.0"
   test_api:
     dependency: transitive
     description:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.17"
+    version: "0.3.0"
   typed_data:
     dependency: transitive
     description:
       name: typed_data
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.6"
+    version: "1.3.0"
   uuid:
     dependency: transitive
     description:
@@ -225,7 +225,7 @@ packages:
       name: vector_math
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.8"
+    version: "2.1.0"
   wallpaper_manager:
     dependency: "direct dev"
     description:
@@ -234,5 +234,5 @@ packages:
     source: path
     version: "1.0.10"
 sdks:
-  dart: ">=2.9.0-14.0.dev <3.0.0"
-  flutter: ">=1.10.1 <2.0.0"
+  dart: ">=2.12.0 <3.0.0"
+  flutter: ">=1.10.1"

lib/wallpaper_manager.dart

@@ -5,7 +5,7 @@ import 'package:flutter/services.dart';
 class WallpaperManager {
   /// Define channel
   static const MethodChannel _channel =
-      const MethodChannel('wallpaper_manager');
+      MethodChannel('wallpaper_manager');
 
   /// Static code for Home Screen Wallpaper Choice
   static const int HOME_SCREEN = 1;
@@ -17,9 +17,9 @@ class WallpaperManager {
   static const int BOTH_SCREENS = 3;
 
   /// Function to check working/validity of method channels
-  static Future<String> get platformVersion async {
+  static Future<String?> get platformVersion async {
     /// String to store the version number before returning. This is just to test working/validity.
-    final String version = await _channel.invokeMethod('getPlatformVersion');
+    final String? version = await _channel.invokeMethod('getPlatformVersion');
 
     /// Function returns version number
     return version;
@@ -29,18 +29,18 @@ class WallpaperManager {
   static Future<String> setWallpaperFromFile(
       String filePath, int wallpaperLocation) async {
     /// Variable to store operation result
-    final int result = await _channel.invokeMethod('setWallpaperFromFile',
-        {'filePath': filePath, 'wallpaperLocation': wallpaperLocation});
+    final int result = await (_channel.invokeMethod('setWallpaperFromFile',
+        {'filePath': filePath, 'wallpaperLocation': wallpaperLocation}) as FutureOr<int>);
 
     /// Function returns the set String as result, use for debugging
-    return result > 0 ? "Wallpaper set" : "There was an error.";
+    return result > 0 ? 'Wallpaper set' : 'There was an error.';
   }
 
   /// Function takes input file's path & location choice
   static Future<String> setWallpaperFromFileWithCrop(String filePath,
       int wallpaperLocation, int left, int top, int right, int bottom) async {
     /// Variable to store operation result
-    int result;
+    int? result;
     if (left > right || top > bottom) {
       result = 0;
     } else {
@@ -55,25 +55,25 @@ class WallpaperManager {
     }
 
     /// Function returns the set String as result, use for debugging
-    return result > 0 ? "Wallpaper set" : "There was an error.";
+    return result! > 0 ? 'Wallpaper set' : 'There was an error.';
   }
 
   /// Function takes input file's asset (Dart/Flutter; pre-indexed in pubspec.yaml) & location choice
   static Future<String> setWallpaperFromAsset(
       String assetPath, int wallpaperLocation) async {
     /// Variable to store operation result
-    final int result = await _channel.invokeMethod('setWallpaperFromAsset',
-        {'assetPath': assetPath, 'wallpaperLocation': wallpaperLocation});
+    final int result = await (_channel.invokeMethod('setWallpaperFromAsset',
+        {'assetPath': assetPath, 'wallpaperLocation': wallpaperLocation}) as FutureOr<int>);
 
     /// Function returns the set String as result, use for debugging
-    return result > 0 ? "Wallpaper set" : "There was an error.";
+    return result > 0 ? 'Wallpaper set' : 'There was an error.';
   }
 
   /// Function takes input file's asset (Dart/Flutter; pre-indexed in pubspec.yaml) & location choice
   static Future<String> setWallpaperFromAssetWithCrop(String assetPath,
       int wallpaperLocation, int left, int top, int right, int bottom) async {
     /// Variable to store operation result
-    int result;
+    int? result;
     if (left > right || top > bottom || left < 0 || top < 0) {
       result = 0;
     } else {
@@ -88,6 +88,6 @@ class WallpaperManager {
     }
 
     /// Function returns the set String as result, use for debugging
-    return result > 0 ? "Wallpaper set" : "There was an error.";
+    return result! > 0 ? 'Wallpaper set' : 'There was an error.';
   }
 }