Made elements on component screen stay compact on wider screen, take 2 (#1267)

* Revert "Revert "Made elements on component screen stay compact on wider screen (#1258)" (#1266)"

This reverts commit 53c83adc71.

* ran flutter format for the changed files

* fixed test

Co-authored-by: Qun Cheng <quncheng@google.com>

material_3_demo/lib/component_screen.dart

@@ -11,6 +11,10 @@ class ComponentScreen extends StatelessWidget {
     return Expanded(
       child: Padding(
         padding: const EdgeInsets.symmetric(horizontal: 10),
+        child: Align(
+          alignment: Alignment.topCenter,
+          child: SizedBox(
+            width: _maxWidthConstraint,
             child: ListView(
               shrinkWrap: true,
               children: [
@@ -33,6 +37,8 @@ class ComponentScreen extends StatelessWidget {
               ],
             ),
           ),
+        ),
+      ),
     );
   }
 }
@@ -40,6 +46,7 @@ class ComponentScreen extends StatelessWidget {
 const _rowDivider = SizedBox(width: 10);
 const _colDivider = SizedBox(height: 10);
 const double _cardWidth = 115;
+const double _maxWidthConstraint = 400;
 
 void Function()? handlePressed(
     BuildContext context, bool isDisabled, String buttonName) {
@@ -255,8 +262,7 @@ class Cards extends StatelessWidget {
                       alignment: Alignment.topRight,
                       child: Icon(Icons.more_vert),
                     ),
-                    _colDivider,
+                    SizedBox(height: 35),
-                    _colDivider,
                     Align(
                       alignment: Alignment.bottomLeft,
                       child: Text("Elevated"),
@@ -279,8 +285,7 @@ class Cards extends StatelessWidget {
                       alignment: Alignment.topRight,
                       child: Icon(Icons.more_vert),
                     ),
-                    _colDivider,
+                    SizedBox(height: 35),
-                    _colDivider,
                     Align(
                       alignment: Alignment.bottomLeft,
                       child: Text("Filled"),
@@ -308,8 +313,7 @@ class Cards extends StatelessWidget {
                       alignment: Alignment.topRight,
                       child: Icon(Icons.more_vert),
                     ),
-                    _colDivider,
+                    SizedBox(height: 35),
-                    _colDivider,
                     Align(
                       alignment: Alignment.bottomLeft,
                       child: Text("Outlined"),

material_3_demo/lib/main.dart

@@ -179,7 +179,8 @@ class _Material3DemoState extends State<Material3Demo> {
             body: SafeArea(
               bottom: false,
               top: false,
-              child: Row(children: <Widget>[
+              child: Row(
+                children: <Widget>[
                   Padding(
                       padding: const EdgeInsets.symmetric(horizontal: 5),
                       child: NavigationRailSection(
@@ -187,7 +188,8 @@ class _Material3DemoState extends State<Material3Demo> {
                           selectedIndex: screenIndex)),
                   const VerticalDivider(thickness: 1, width: 1),
                   createScreenFor(screenIndex, true),
-              ]),
+                ],
+              ),
             ),
           );
         }

material_3_demo/test/component_screen_test.dart

@@ -27,6 +27,11 @@ void main() {
     expect(find.text("Icon"), findsNWidgets(5));
 
     // FABs
+    Finder floatingActionButton = find.text("Create");
+    await tester.scrollUntilVisible(
+      floatingActionButton,
+      500.0,
+    );
     expect(
         find.widgetWithIcon(FloatingActionButton, Icons.add), findsNWidgets(4));
     expect(find.widgetWithText(FloatingActionButton, "Create"), findsOneWidget);