support nullsafety

example/lib/main.dart

@@ -31,7 +31,7 @@ class MyApp extends StatelessWidget {
 }
 
 class MyHomePage extends StatefulWidget {
-  MyHomePage({Key key, this.title}) : super(key: key);
+  MyHomePage({Key? key, this.title = ""}) : super(key: key);
 
   // This widget is the home page of your application. It is stateful, meaning
   // that it has a State object (defined below) that contains fields that affect
@@ -50,7 +50,7 @@ class MyHomePage extends StatefulWidget {
 
 class _MyHomePageState extends State<MyHomePage> {
   int _counter = 0;
-  Uint8List _imageFile;
+  Uint8List? _imageFile;
 
   //Create an instance of ScreenshotController
   ScreenshotController screenshotController = ScreenshotController();
@@ -100,22 +100,24 @@ class _MyHomePageState extends State<MyHomePage> {
           _imageFile = null;
           screenshotController
               .capture(delay: Duration(milliseconds: 10))
-              .then((Uint8List image) async {
+              .then((Uint8List? image) async {
             _imageFile = image;
-            showDialog(
-              context: context,
-              builder: (context) => Scaffold(
-                appBar: AppBar(
-                  title: Text("CAPURED SCREENSHOT"),
+            if (image != null) {
+              showDialog(
+                context: context,
+                builder: (context) => Scaffold(
+                  appBar: AppBar(
+                    title: Text("CAPURED SCREENSHOT"),
+                  ),
+                  body: Center(
+                      child: Column(
+                    children: [
+                      if (image != null) Image.memory(image),
+                    ],
+                  )),
                 ),
-                body: Center(
-                    child: Column(
-                  children: [
-                    _imageFile != null ? Image.memory(_imageFile) : Container(),
-                  ],
-                )),
-              ),
-            );
+              );
+            }
           }).catchError((onError) {
             print(onError);
           });

example/pubspec.yaml

@@ -10,8 +10,8 @@ description: A new Flutter project.
 version: 1.0.0+1
 
 environment:
-  sdk: '>=2.8.0 <3.0.0'
-  # sdk: '>=2.12.0-259.8.beta <3.0.0'
+  # sdk: '>=2.8.0 <3.0.0'
+  sdk: '>=2.12.0-259.8.beta <3.0.0'
 
 dependencies:
   flutter:

lib/screenshot.dart

@@ -16,42 +16,44 @@ import 'dart:ui' as ui;
 ///
 ///
 class ScreenshotController {
-  GlobalKey _containerKey;
+  late GlobalKey _containerKey;
   ScreenshotController() {
     _containerKey = GlobalKey();
   }
 
   /// Captures image and saves to given path
-  Future<String> captureAndSave(
+  Future<String?> captureAndSave(
     String directory, {
-    String fileName,
-    double pixelRatio,
-    Duration delay: const Duration(milliseconds: 20),
+    String? fileName,
+    double? pixelRatio,
+    Duration delay = const Duration(milliseconds: 20),
   }) async {
-    Uint8List content = await capture(
+    Uint8List? content = await capture(
       pixelRatio: pixelRatio,
       delay: delay,
     );
+    if (content != null) {
+      PlatformFileManager fileManager = PlatformFileManager();
 
-    PlatformFileManager fileManager = PlatformFileManager();
-
-    return fileManager.saveFile(content, directory, name: fileName);
+      return fileManager.saveFile(content, directory, name: fileName);
+    }
+    return null;
   }
 
-  Future<Uint8List> capture({
-    double pixelRatio,
-    Duration delay: const Duration(milliseconds: 20),
+  Future<Uint8List?> capture({
+    double? pixelRatio,
+    Duration? delay = const Duration(milliseconds: 20),
   }) {
     //Delay is required. See Issue https://github.com/flutter/flutter/issues/22308
-    return new Future.delayed(delay, () async {
+    return new Future.delayed(delay ?? Duration(milliseconds: 20), () async {
       try {
         ui.Image image = await captureAsUiImage(
           delay: Duration.zero,
           pixelRatio: pixelRatio,
         );
-        ByteData byteData =
+        ByteData? byteData =
             await image.toByteData(format: ui.ImageByteFormat.png);
-        Uint8List pngBytes = byteData.buffer.asUint8List();
+        Uint8List? pngBytes = byteData?.buffer.asUint8List();
 
         return pngBytes;
       } catch (Exception) {
@@ -61,18 +63,20 @@ class ScreenshotController {
   }
 
   Future<ui.Image> captureAsUiImage(
-      {double pixelRatio: 1,
-      Duration delay: const Duration(milliseconds: 20)}) {
+      {double? pixelRatio, Duration delay: const Duration(milliseconds: 20)}) {
     //Delay is required. See Issue https://github.com/flutter/flutter/issues/22308
     return new Future.delayed(delay, () async {
       try {
         RenderRepaintBoundary boundary = this
             ._containerKey
             .currentContext
-            .findRenderObject() as RenderRepaintBoundary;
-        pixelRatio = pixelRatio ??
-            MediaQuery.of(_containerKey.currentContext).devicePixelRatio;
-        ui.Image image = await boundary.toImage(pixelRatio: pixelRatio);
+            ?.findRenderObject() as RenderRepaintBoundary;
+        BuildContext? context = _containerKey.currentContext;
+        if (pixelRatio == null) {
+          if (context != null)
+            pixelRatio = pixelRatio ?? MediaQuery.of(context).devicePixelRatio;
+        }
+        ui.Image image = await boundary.toImage(pixelRatio: pixelRatio??1);
         return image;
       } catch (Exception) {
         throw (Exception);
@@ -85,9 +89,9 @@ class Screenshot<T> extends StatefulWidget {
   final Widget child;
   final ScreenshotController controller;
   const Screenshot({
-    Key key,
-    this.child,
-    this.controller,
+    Key? key,
+   required this.child,
+   required this.controller,
   }) : super(key: key);
 
   @override
@@ -97,14 +101,15 @@ class Screenshot<T> extends StatefulWidget {
 }
 
 class ScreenshotState extends State<Screenshot> with TickerProviderStateMixin {
+  late
   ScreenshotController _controller;
 
   @override
   void initState() {
     super.initState();
-    if (widget.controller == null) {
-      _controller = ScreenshotController();
-    } else
+    // if (widget.controller == null) {
+    //   _controller = ScreenshotController();
+    // } else
       _controller = widget.controller;
   }
 

lib/src/platform_specific/file_manager/file_manager.dart

@@ -7,5 +7,5 @@ import 'file_manager_stub.dart'
 
 abstract class PlatformFileManager {
   factory PlatformFileManager() => getFileManager();
-  Future<String> saveFile(Uint8List fileContent, String path, {String name});
+  Future<String> saveFile(Uint8List fileContent, String path, {String? name});
 }

lib/src/platform_specific/file_manager/file_manager_io.dart

@@ -8,7 +8,7 @@ PlatformFileManager getFileManager() => PlatformFilePickerWindows();
 class PlatformFilePickerWindows implements PlatformFileManager {
   @override
   Future<String> saveFile(Uint8List fileContent, String path,
-      {String name}) async {
+      {String? name}) async {
     name = name ?? "${DateTime.now().microsecondsSinceEpoch}.png";
     File file = await File("$path/$name").create(recursive: true);
     file.writeAsBytesSync(fileContent);

lib/src/platform_specific/file_manager/non_io.dart

@@ -8,7 +8,7 @@ PlatformFileManager getFileManager() => PlatformFileManagerWeb();
 class PlatformFileManagerWeb implements PlatformFileManager {
   @override
   Future<String> saveFile(Uint8List fileContent, String path,
-      {String name}) async {
+      {String? name}) async {
   throw UnsupportedError("File cannot be saved in current platform");
     // name = name ?? "${DateTime.now().microsecondsSinceEpoch}.png";
     // File file = await File("$path/$name").create(recursive: true);

pubspec.lock

@@ -143,4 +143,4 @@ packages:
     source: hosted
     version: "2.1.0-nullsafety.5"
 sdks:
-  dart: ">=2.12.0-0.0 <3.0.0"
+  dart: ">=2.12.0-259.8.beta <3.0.0"

pubspec.yaml

@@ -4,8 +4,8 @@ version: 0.3.0
 homepage: https://github.com/SachinGanesh/screenshot
 
 environment:
-  sdk: '>=2.8.0 <3.0.0'
-  # sdk: '>=2.12.0-259.8.beta <3.0.0'
+  # sdk: '>=2.8.0 <3.0.0'
+  sdk: '>=2.12.0-259.8.beta <3.0.0'
 
 # analyzer:
 #   enable-experiment: