[Gallery] Hide snackbar before showing one (#258)

* Hide snackbar before showing one

* Update code_segments.dart

* Update grind error message with command

gallery/gallery/lib/codeviewer/code_segments.dart

@@ -16737,6 +16737,12 @@ class CodeSegments {
       TextSpan(style: codeStyle.punctuationStyle, text: '.'),
       TextSpan(style: codeStyle.baseStyle, text: 'currentState'),
       TextSpan(style: codeStyle.punctuationStyle, text: '.'),
+      TextSpan(style: codeStyle.baseStyle, text: 'hideCurrentSnackBar'),
+      TextSpan(style: codeStyle.punctuationStyle, text: '();'),
+      TextSpan(style: codeStyle.baseStyle, text: '\u000a      _scaffoldKey'),
+      TextSpan(style: codeStyle.punctuationStyle, text: '.'),
+      TextSpan(style: codeStyle.baseStyle, text: 'currentState'),
+      TextSpan(style: codeStyle.punctuationStyle, text: '.'),
       TextSpan(style: codeStyle.baseStyle, text: 'showSnackBar'),
       TextSpan(style: codeStyle.punctuationStyle, text: '('),
       TextSpan(style: codeStyle.classStyle, text: 'SnackBar'),
@@ -23656,6 +23662,15 @@ class CodeSegments {
       TextSpan(style: codeStyle.punctuationStyle, text: '('),
       TextSpan(style: codeStyle.baseStyle, text: 'context'),
       TextSpan(style: codeStyle.punctuationStyle, text: ').'),
+      TextSpan(style: codeStyle.baseStyle, text: 'hideCurrentSnackBar'),
+      TextSpan(style: codeStyle.punctuationStyle, text: '();'),
+      TextSpan(style: codeStyle.baseStyle, text: '\u000a                '),
+      TextSpan(style: codeStyle.classStyle, text: 'Scaffold'),
+      TextSpan(style: codeStyle.punctuationStyle, text: '.'),
+      TextSpan(style: codeStyle.baseStyle, text: 'of'),
+      TextSpan(style: codeStyle.punctuationStyle, text: '('),
+      TextSpan(style: codeStyle.baseStyle, text: 'context'),
+      TextSpan(style: codeStyle.punctuationStyle, text: ').'),
       TextSpan(style: codeStyle.baseStyle, text: 'showSnackBar'),
       TextSpan(style: codeStyle.punctuationStyle, text: '('),
       TextSpan(style: codeStyle.classStyle, text: 'SnackBar'),
@@ -23715,6 +23730,16 @@ class CodeSegments {
       TextSpan(style: codeStyle.punctuationStyle, text: '('),
       TextSpan(style: codeStyle.baseStyle, text: 'context'),
       TextSpan(style: codeStyle.punctuationStyle, text: ').'),
+      TextSpan(style: codeStyle.baseStyle, text: 'hideCurrentSnackBar'),
+      TextSpan(style: codeStyle.punctuationStyle, text: '();'),
+      TextSpan(
+          style: codeStyle.baseStyle, text: '\u000a                      '),
+      TextSpan(style: codeStyle.classStyle, text: 'Scaffold'),
+      TextSpan(style: codeStyle.punctuationStyle, text: '.'),
+      TextSpan(style: codeStyle.baseStyle, text: 'of'),
+      TextSpan(style: codeStyle.punctuationStyle, text: '('),
+      TextSpan(style: codeStyle.baseStyle, text: 'context'),
+      TextSpan(style: codeStyle.punctuationStyle, text: ').'),
       TextSpan(style: codeStyle.baseStyle, text: 'showSnackBar'),
       TextSpan(style: codeStyle.punctuationStyle, text: '('),
       TextSpan(style: codeStyle.classStyle, text: 'SnackBar'),
@@ -24560,6 +24585,12 @@ class CodeSegments {
       TextSpan(style: codeStyle.punctuationStyle, text: '.'),
       TextSpan(style: codeStyle.baseStyle, text: 'currentState'),
       TextSpan(style: codeStyle.punctuationStyle, text: '.'),
+      TextSpan(style: codeStyle.baseStyle, text: 'hideCurrentSnackBar'),
+      TextSpan(style: codeStyle.punctuationStyle, text: '();'),
+      TextSpan(style: codeStyle.baseStyle, text: '\u000a    _scaffoldKey'),
+      TextSpan(style: codeStyle.punctuationStyle, text: '.'),
+      TextSpan(style: codeStyle.baseStyle, text: 'currentState'),
+      TextSpan(style: codeStyle.punctuationStyle, text: '.'),
       TextSpan(style: codeStyle.baseStyle, text: 'showSnackBar'),
       TextSpan(style: codeStyle.punctuationStyle, text: '('),
       TextSpan(style: codeStyle.classStyle, text: 'SnackBar'),

gallery/gallery/lib/demos/material/dialog_demo.dart

@@ -49,6 +49,7 @@ 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(
         content:
             Text(GalleryLocalizations.of(context).dialogSelectedOption(value)),

gallery/gallery/lib/demos/material/menu_demo.dart

@@ -39,6 +39,7 @@ class _MenuDemoState extends State<MenuDemo> {
   final GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey<ScaffoldState>();
 
   void showInSnackBar(String value) {
+    _scaffoldKey.currentState.hideCurrentSnackBar();
     _scaffoldKey.currentState.showSnackBar(SnackBar(
       content: Text(value),
     ));

gallery/gallery/lib/demos/material/snackbar_demo.dart

@@ -24,6 +24,7 @@ class SnackbarsDemo extends StatelessWidget {
               child: Text(
                   GalleryLocalizations.of(context).demoSnackbarsButtonLabel),
               onPressed: () {
+                Scaffold.of(context).hideCurrentSnackBar();
                 Scaffold.of(context).showSnackBar(SnackBar(
                   content: Text(
                     GalleryLocalizations.of(context).demoSnackbarsText,
@@ -32,6 +33,7 @@ class SnackbarsDemo extends StatelessWidget {
                     label: GalleryLocalizations.of(context)
                         .demoSnackbarsActionButtonLabel,
                     onPressed: () {
+                      Scaffold.of(context).hideCurrentSnackBar();
                       Scaffold.of(context).showSnackBar(SnackBar(
                         content: Text(
                           GalleryLocalizations.of(context).demoSnackbarsAction,

gallery/gallery/lib/demos/material/text_field_demo.dart

@@ -106,6 +106,7 @@ class TextFormFieldDemoState extends State<TextFormFieldDemo> {
   PersonData person = PersonData();
 
   void showInSnackBar(String value) {
+    _scaffoldKey.currentState.hideCurrentSnackBar();
     _scaffoldKey.currentState.showSnackBar(SnackBar(
       content: Text(value),
     ));

gallery/gallery/tool/grind.dart

@@ -86,8 +86,8 @@ Future<void> verifyCodeSegments() async {
   if (codeSegmentsFormatted.trim() != expectedCodeSegmentsOutput.trim()) {
     stderr.writeln(
       'The contents of $codeSegmentsPath are different from that produced by '
-      'codeviewer_cli. Did you forget to run update-code-segments after '
+      'codeviewer_cli. Did you forget to run `flutter pub run grinder '
-      'updating a demo?',
+      'update-code-segments` after updating a demo?',
     );
     exit(1);
   }