Migrate Linux example

packages/path_provider/path_provider_linux/example/integration_test/path_provider_test.dart

@@ -2,6 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+// @dart=2.9
+
 import 'dart:io';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:path_provider_linux/path_provider_linux.dart';

packages/path_provider/path_provider_linux/example/lib/main.dart

@@ -15,10 +15,10 @@ class MyApp extends StatefulWidget {
 }
 
 class _MyAppState extends State<MyApp> {
-  String _tempDirectory = 'Unknown';
-  String _downloadsDirectory = 'Unknown';
-  String _appSupportDirectory = 'Unknown';
-  String _documentsDirectory = 'Unknown';
+  String? _tempDirectory = 'Unknown';
+  String? _downloadsDirectory = 'Unknown';
+  String? _appSupportDirectory = 'Unknown';
+  String? _documentsDirectory = 'Unknown';
   final PathProviderLinux _provider = PathProviderLinux();
 
   @override
@@ -29,10 +29,10 @@ class _MyAppState extends State<MyApp> {
 
   // Platform messages are asynchronous, so we initialize in an async method.
   Future<void> initDirectories() async {
-    String tempDirectory;
-    String downloadsDirectory;
-    String appSupportDirectory;
-    String documentsDirectory;
+    String? tempDirectory;
+    String? downloadsDirectory;
+    String? appSupportDirectory;
+    String? documentsDirectory;
     // Platform messages may fail, so we use a try/catch PlatformException.
     try {
       tempDirectory = await _provider.getTemporaryPath();

packages/path_provider/path_provider_linux/example/pubspec.yaml

@@ -3,7 +3,7 @@ description: Demonstrates how to use the path_provider_linux plugin.
 publish_to: "none"
 
 environment:
-  sdk: ">=2.1.0 <3.0.0"
+  sdk: ">=2.12.0-0 <3.0.0"
 
 dependencies:
   flutter:

packages/path_provider/path_provider_linux/example/test/widget_test.dart

@@ -30,7 +30,7 @@ void main() {
           find.byWidgetPredicate(
             (Widget widget) =>
                 widget is Text &&
-                widget.data.startsWith('Temp Directory: /tmp'),
+                widget.data!.startsWith('Temp Directory: /tmp'),
           ),
           findsOneWidget,
         );
@@ -48,7 +48,7 @@ void main() {
           find.byWidgetPredicate(
             (Widget widget) =>
                 widget is Text &&
-                widget.data.startsWith('Documents Directory: /'),
+                widget.data!.startsWith('Documents Directory: /'),
           ),
           findsOneWidget,
         );
@@ -66,7 +66,7 @@ void main() {
           find.byWidgetPredicate(
             (Widget widget) =>
                 widget is Text &&
-                widget.data.startsWith('Downloads Directory: /'),
+                widget.data!.startsWith('Downloads Directory: /'),
           ),
           findsOneWidget,
         );
@@ -85,7 +85,7 @@ void main() {
           find.byWidgetPredicate(
             (Widget widget) =>
                 widget is Text &&
-                widget.data.startsWith('Application Support Directory: /'),
+                widget.data!.startsWith('Application Support Directory: /'),
           ),
           findsOneWidget,
         );