Migrate SnackBar methods to ScaffoldMessenger

lib/demos/material/dialog_demo.dart

@@ -19,7 +19,6 @@ enum DialogDemoType {
 class DialogDemo extends StatelessWidget {
   DialogDemo({Key key, @required this.type}) : super(key: key);
 
-  final GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey<ScaffoldState>();
   final DialogDemoType type;
 
   String _title(BuildContext context) {
@@ -49,8 +48,8 @@ class DialogDemo extends StatelessWidget {
     );
     // The value passed to Navigator.pop() or null.
     if (value != null && value is String) {
-      _scaffoldKey.currentState.hideCurrentSnackBar();
-      _scaffoldKey.currentState.showSnackBar(SnackBar(
+      ScaffoldMessenger.of(context).hideCurrentSnackBar();
+      ScaffoldMessenger.of(context).showSnackBar(SnackBar(
         content:
             Text(GalleryLocalizations.of(context).dialogSelectedOption(value)),
       ));
@@ -132,7 +131,6 @@ class DialogDemo extends StatelessWidget {
       onGenerateRoute: (settings) {
         return _NoAnimationMaterialPageRoute<void>(
           builder: (context) => Scaffold(
-            key: _scaffoldKey,
             appBar: AppBar(
               automaticallyImplyLeading: false,
               title: Text(_title(context)),

lib/demos/material/menu_demo.dart

@@ -39,8 +39,8 @@ class _MenuDemoState extends State<MenuDemo> {
   final GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey<ScaffoldState>();
 
   void showInSnackBar(String value) {
-    _scaffoldKey.currentState.hideCurrentSnackBar();
-    _scaffoldKey.currentState.showSnackBar(SnackBar(
+    ScaffoldMessenger.of(context).hideCurrentSnackBar();
+    ScaffoldMessenger.of(context).showSnackBar(SnackBar(
       content: Text(value),
     ));
   }

lib/demos/material/snackbar_demo.dart

@@ -17,37 +17,28 @@ class SnackbarsDemo extends StatelessWidget {
         automaticallyImplyLeading: false,
         title: Text(GalleryLocalizations.of(context).demoSnackbarsTitle),
       ),
-      body: Builder(
-        // Create an inner BuildContext so that the snackBar onPressed methods
-        // can refer to the Scaffold with Scaffold.of().
-        builder: (context) {
-          return Center(
-            child: RaisedButton(
-              child: Text(
-                  GalleryLocalizations.of(context).demoSnackbarsButtonLabel),
-              onPressed: () {
-                Scaffold.of(context).hideCurrentSnackBar();
-                Scaffold.of(context).showSnackBar(SnackBar(
-                  content: Text(
-                    GalleryLocalizations.of(context).demoSnackbarsText,
-                  ),
-                  action: SnackBarAction(
-                    label: GalleryLocalizations.of(context)
-                        .demoSnackbarsActionButtonLabel,
-                    onPressed: () {
-                      Scaffold.of(context).hideCurrentSnackBar();
-                      Scaffold.of(context).showSnackBar(SnackBar(
-                        content: Text(
-                          GalleryLocalizations.of(context).demoSnackbarsAction,
-                        ),
-                      ));
-                    },
-                  ),
-                ));
-              },
-            ),
-          );
-        },
+      body: Center(
+        child: RaisedButton(
+          child:
+              Text(GalleryLocalizations.of(context).demoSnackbarsButtonLabel),
+          onPressed: () {
+            ScaffoldMessenger.of(context).hideCurrentSnackBar();
+            ScaffoldMessenger.of(context).showSnackBar(SnackBar(
+              content: Text(GalleryLocalizations.of(context).demoSnackbarsText),
+              action: SnackBarAction(
+                label: GalleryLocalizations.of(context)
+                    .demoSnackbarsActionButtonLabel,
+                onPressed: () {
+                  ScaffoldMessenger.of(context).hideCurrentSnackBar();
+                  ScaffoldMessenger.of(context).showSnackBar(SnackBar(
+                      content: Text(
+                    GalleryLocalizations.of(context).demoSnackbarsAction,
+                  )));
+                },
+              ),
+            ));
+          },
+        ),
       ),
     );
   }

lib/demos/material/text_field_demo.dart

@@ -107,8 +107,8 @@ class TextFormFieldDemoState extends State<TextFormFieldDemo> {
   PersonData person = PersonData();
 
   void showInSnackBar(String value) {
-    _scaffoldKey.currentState.hideCurrentSnackBar();
-    _scaffoldKey.currentState.showSnackBar(SnackBar(
+    ScaffoldMessenger.of(context).hideCurrentSnackBar();
+    ScaffoldMessenger.of(context).showSnackBar(SnackBar(
       content: Text(value),
     ));
   }

lib/pages/demo.dart

@@ -733,7 +733,7 @@ class CodeDisplayPage extends StatelessWidget {
     final _plainTextCode = _richTextCode.toPlainText();
 
     void _showSnackBarOnCopySuccess(dynamic result) {
-      Scaffold.of(context).showSnackBar(
+      ScaffoldMessenger.of(context).showSnackBar(
         SnackBar(
           content: Text(
             GalleryLocalizations.of(context)
@@ -744,7 +744,7 @@ class CodeDisplayPage extends StatelessWidget {
     }
 
     void _showSnackBarOnCopyFailure(Object exception) {
-      Scaffold.of(context).showSnackBar(
+      ScaffoldMessenger.of(context).showSnackBar(
         SnackBar(
           content: Text(
             GalleryLocalizations.of(context)

pubspec.lock

@@ -317,7 +317,7 @@ packages:
       name: meta
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.3.0-nullsafety.3"
+    version: "1.3.0-nullsafety.4"
   mime:
     dependency: transitive
     description:
@@ -581,7 +581,7 @@ packages:
       name: stack_trace
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.10.0-nullsafety.1"
+    version: "1.10.0-nullsafety.2"
   stream_channel:
     dependency: transitive
     description:
@@ -744,5 +744,5 @@ packages:
     source: hosted
     version: "2.2.1"
 sdks:
-  dart: ">=2.10.0-110 <2.11.0"
+  dart: ">=2.10.0-110 <=2.11.0-207.0.dev"
   flutter: ">=1.17.0 <2.0.0"