Adds null safety support (#510)

example/lib/src/file_picker_demo.dart

@@ -50,7 +50,7 @@ class _FilePickerDemoState extends State<FilePickerDemo> {
 
   void _clearCachedFiles() {
     FilePicker.platform.clearTemporaryFiles().then((result) {
-      _scaffoldKey.currentState.showSnackBar(
+      ScaffoldMessenger.of(context).showSnackBar(
         SnackBar(
           backgroundColor: result ? Colors.green : Colors.red,
           content: Text((result

example/pubspec.yaml

@@ -2,6 +2,9 @@ name: file_picker_example
 description: An example of how to use the file_picker plugin.
 version: 1.0.0+1
 
+environment:
+  sdk: ">=2.8.1 <3.0.0"
+
 dependencies:
   flutter:
     sdk: flutter

lib/src/file_picker.dart

@@ -60,14 +60,14 @@ abstract class FilePicker extends PlatformInterface {
   /// with useful information regarding the picked [List<PlatformFile>].
   ///
   /// Returns [null] if aborted.
-  Future<FilePickerResult> pickFiles({
+  Future<FilePickerResult?> pickFiles({
     FileType type = FileType.any,
-    List<String> allowedExtensions,
-    Function(FilePickerStatus) onFileLoading,
-    bool allowCompression,
+    List<String>? allowedExtensions,
+    Function(FilePickerStatus)? onFileLoading,
+    bool? allowCompression,
     bool allowMultiple = false,
-    bool withData,
-    bool withReadStream,
+    bool? withData,
+    bool? withReadStream,
   }) async =>
       throw UnimplementedError('pickFiles() has not been implemented.');
 
@@ -78,13 +78,13 @@ abstract class FilePicker extends PlatformInterface {
   /// of it whenever needed. However, this will force the cleanup if you want to manage those on your own.
   ///
   /// Returns [true] if the files were removed with success, [false] otherwise.
-  Future<bool> clearTemporaryFiles() async => throw UnimplementedError(
+  Future<bool?> clearTemporaryFiles() async => throw UnimplementedError(
       'clearTemporaryFiles() has not been implemented.');
 
   /// Selects a directory and returns its absolute path.
   ///
   /// On Android, this requires to be running on SDK 21 or above, else won't work.
   /// Returns [null] if folder path couldn't be resolved.
-  Future<String> getDirectoryPath() async =>
+  Future<String?> getDirectoryPath() async =>
       throw UnimplementedError('getDirectoryPath() has not been implemented.');
 }

lib/src/file_picker_io.dart

@@ -21,17 +21,17 @@ const EventChannel _eventChannel =
 /// An implementation of [FilePicker] that uses method channels.
 class FilePickerIO extends FilePicker {
   static const String _tag = 'MethodChannelFilePicker';
-  static StreamSubscription _eventSubscription;
+  static StreamSubscription? _eventSubscription;
 
   @override
-  Future<FilePickerResult> pickFiles({
+  Future<FilePickerResult?> pickFiles({
     FileType type = FileType.any,
-    List<String> allowedExtensions,
-    Function(FilePickerStatus) onFileLoading,
-    bool allowCompression = true,
+    List<String>? allowedExtensions,
+    Function(FilePickerStatus)? onFileLoading,
+    bool? allowCompression = true,
     bool allowMultiple = false,
-    bool withData = false,
-    bool withReadStream = false,
+    bool? withData = false,
+    bool? withReadStream = false,
   }) =>
       _getPath(
         type,
@@ -44,11 +44,11 @@ class FilePickerIO extends FilePicker {
       );
 
   @override
-  Future<bool> clearTemporaryFiles() async =>
+  Future<bool?> clearTemporaryFiles() async =>
       _channel.invokeMethod<bool>('clear');
 
   @override
-  Future<String> getDirectoryPath() async {
+  Future<String?> getDirectoryPath() async {
     try {
       return await _channel.invokeMethod('dir', {});
     } on PlatformException catch (ex) {
@@ -60,14 +60,14 @@ class FilePickerIO extends FilePicker {
     return null;
   }
 
-  Future<FilePickerResult> _getPath(
+  Future<FilePickerResult?> _getPath(
     FileType fileType,
     bool allowMultipleSelection,
-    bool allowCompression,
-    List<String> allowedExtensions,
-    Function(FilePickerStatus) onFileLoading,
-    bool withData,
-    bool withReadStream,
+    bool? allowCompression,
+    List<String>? allowedExtensions,
+    Function(FilePickerStatus)? onFileLoading,
+    bool? withData,
+    bool? withReadStream,
   ) async {
     final String type = describeEnum(fileType);
     if (type != 'custom' && (allowedExtensions?.isNotEmpty ?? false)) {
@@ -85,7 +85,7 @@ class FilePickerIO extends FilePicker {
             );
       }
 
-      final List<Map> result = await _channel.invokeListMethod(type, {
+      final List<Map>? result = await _channel.invokeListMethod(type, {
         'allowMultipleSelection': allowMultipleSelection,
         'allowedExtensions': allowedExtensions,
         'allowCompression': allowCompression,
@@ -102,7 +102,7 @@ class FilePickerIO extends FilePicker {
         platformFiles.add(
           PlatformFile.fromMap(
             platformFileMap,
-            readStream: withReadStream
+            readStream: withReadStream!
                 ? File(platformFileMap['path']).openRead()
                 : null,
           ),

lib/src/file_picker_result.dart

@@ -27,5 +27,5 @@ class FilePickerResult {
       .toList();
 
   /// A `List<String>` containing all names from picked files with its extensions.
-  List<String> get names => files.map((file) => file.name).toList();
+  List<String?> get names => files.map((file) => file.name).toList();
 }

lib/src/file_picker_web.dart

@@ -9,7 +9,7 @@ import 'file_picker_result.dart';
 import 'platform_file.dart';
 
 class FilePickerWeb extends FilePicker {
-  Element _target;
+  late Element _target;
   final String _kFilePickerInputsDomId = '__file_picker_web-file-input';
 
   final int _readStreamChunkSize = 1000 * 1000; // 1 MB
@@ -26,12 +26,12 @@ class FilePickerWeb extends FilePicker {
 
   /// Initializes a DOM container where we can host input elements.
   Element _ensureInitialized(String id) {
-    Element target = querySelector('#$id');
+    Element? target = querySelector('#$id');
     if (target == null) {
       final Element targetElement = Element.tag('flt-file-picker-inputs')
         ..id = id;
 
-      querySelector('body').children.add(targetElement);
+      querySelector('body')!.children.add(targetElement);
       target = targetElement;
     }
     return target;
@@ -40,18 +40,18 @@ class FilePickerWeb extends FilePicker {
   @override
   Future<FilePickerResult> pickFiles({
     FileType type = FileType.any,
-    List<String> allowedExtensions,
+    List<String>? allowedExtensions,
     bool allowMultiple = false,
-    Function(FilePickerStatus) onFileLoading,
-    bool allowCompression,
-    bool withData = true,
-    bool withReadStream = false,
+    Function(FilePickerStatus)? onFileLoading,
+    bool? allowCompression,
+    bool? withData = true,
+    bool? withReadStream = false,
   }) async {
     final Completer<List<PlatformFile>> filesCompleter =
         Completer<List<PlatformFile>>();
 
     String accept = _fileType(type, allowedExtensions);
-    InputElement uploadInput = FileUploadInputElement();
+    InputElement uploadInput = FileUploadInputElement() as InputElement;
     uploadInput.draggable = true;
     uploadInput.multiple = allowMultiple;
     uploadInput.accept = accept;
@@ -63,14 +63,14 @@ class FilePickerWeb extends FilePicker {
       }
       changeEventTriggered = true;
 
-      final List<File> files = uploadInput.files;
+      final List<File> files = uploadInput.files!;
       final List<PlatformFile> pickedFiles = [];
 
       void addPickedFile(
         File file,
-        Uint8List bytes,
-        String path,
-        Stream<List<int>> readStream,
+        Uint8List? bytes,
+        String? path,
+        Stream<List<int>>? readStream,
       ) {
         pickedFiles.add(PlatformFile(
           name: file.name,
@@ -86,23 +86,23 @@ class FilePickerWeb extends FilePicker {
       }
 
       files.forEach((File file) {
-        if (withReadStream) {
+        if (withReadStream!) {
           addPickedFile(file, null, null, _openFileReadStream(file));
           return;
         }
 
-        if (!withData) {
+        if (!withData!) {
           final FileReader reader = FileReader();
           reader.onLoadEnd.listen((e) {
-            addPickedFile(file, null, reader.result, null);
+            addPickedFile(file, null, reader.result as String?, null);
           });
           reader.readAsDataUrl(file);
           return;
         }
 
         final FileReader reader = FileReader();
         reader.onLoadEnd.listen((e) {
-          addPickedFile(file, reader.result, null, null);
+          addPickedFile(file, reader.result as Uint8List?, null, null);
         });
         reader.readAsArrayBuffer(file);
       });
@@ -119,7 +119,7 @@ class FilePickerWeb extends FilePicker {
     return FilePickerResult(await filesCompleter.future);
   }
 
-  static String _fileType(FileType type, List<String> allowedExtensions) {
+  static String _fileType(FileType type, List<String>? allowedExtensions) {
     switch (type) {
       case FileType.any:
         return '';
@@ -137,11 +137,9 @@ class FilePickerWeb extends FilePicker {
         return 'video/*|image/*';
 
       case FileType.custom:
-        return allowedExtensions.fold(
-            '', (prev, next) => '${prev.isEmpty ? '' : '$prev,'} .$next');
-        break;
+        return allowedExtensions!
+            .fold('', (prev, next) => '${prev.isEmpty ? '' : '$prev,'} .$next');
     }
-    return '';
   }
 
   Stream<List<int>> _openFileReadStream(File file) async* {
@@ -155,7 +153,7 @@ class FilePickerWeb extends FilePicker {
       final blob = file.slice(start, end);
       reader.readAsArrayBuffer(blob);
       await reader.onLoad.first;
-      yield reader.result;
+      yield reader.result as List<int>;
       start += _readStreamChunkSize;
     }
   }

lib/src/platform_file.dart

@@ -21,21 +21,21 @@ class PlatformFile {
   /// ```
   /// final File myFile = File(platformFile.path);
   /// ```
-  final String path;
+  final String? path;
 
   /// File name including its extension.
-  final String name;
+  final String? name;
 
   /// Byte data for this file. Particurlarly useful if you want to manipulate its data
   /// or easily upload to somewhere else.
-  final Uint8List bytes;
+  final Uint8List? bytes;
 
   /// File content as stream
-  final Stream<List<int>> readStream;
+  final Stream<List<int>>? readStream;
 
   /// The file size in bytes.
-  final int size;
+  final int? size;
 
   /// File extension for this file.
-  String get extension => name?.split('.')?.last;
+  String? get extension => name?.split('.').last;
 }