add the grid view.

Author: nb312

lib/screen/ListScreen.dart

@@ -60,6 +60,7 @@ const USER_EMAILS = [
   "[email protected]",
   "[email protected]",
 ];
+const GRID_VIEW = "Grid View";
 
 class ListScreen extends StatefulWidget {
   ListScreen({Key key, this.group, this.onClick}) : super(key: key);
@@ -131,13 +132,27 @@ class _ListState extends State<ListScreen> {
     );
   }
 
+  Widget _topRight() {
+    return InkWell(
+      child: Container(
+        child: Center(
+          child: Text(
+            GRID_VIEW,
+            style: TextStyle(color: Colors.white),
+          ),
+        ),
+      ),
+    );
+  }
+
   @override
   Widget build(BuildContext context) {
     return Scaffold(
       appBar: TopAppBar(
         group: widget.group,
         itemType: ItemType.list,
         onClick: widget.onClick,
+        right: _topRight(),
         bottomView: PreferredSize(
             child: ListSelector(
               mainColor: Colors.white,

lib/view/app_bar.dart

@@ -11,30 +11,31 @@ const BAR_FONT_SIZE = 21.0;
 const BAR_TITLE_COLOR = Colors.white;
 
 class TopAppBar extends AppBar {
-  TopAppBar({
-    GroupType group,
-    ItemType itemType,
-    PreferredSize bottomView,
-    VoidCallback onClick,
-  }) : super(
-          leading: IconButton(
-            icon: Icon(
-              BAR_ICONS[group.index],
-              color: BAR_TITLE_COLOR,
+  TopAppBar(
+      {GroupType group,
+      ItemType itemType,
+      PreferredSize bottomView,
+      VoidCallback onClick,
+      Widget right})
+      : super(
+            leading: IconButton(
+              icon: Icon(
+                BAR_ICONS[group.index],
+                color: BAR_TITLE_COLOR,
+              ),
+              onPressed: onClick,
             ),
-            onPressed: onClick,
-          ),
-          title: Text(
-            BOTTOM_TITLES[itemType.index],
-            style: TextStyle(
-              color: BAR_TITLE_COLOR,
-              fontSize: BAR_FONT_SIZE,
+            title: Text(
+              BOTTOM_TITLES[itemType.index],
+              style: TextStyle(
+                color: BAR_TITLE_COLOR,
+                fontSize: BAR_FONT_SIZE,
+              ),
             ),
-          ),
-          bottom: bottomView,
-          backgroundColor: BAR_BACK_COLORS[group.index],
-          elevation: 0.0,
-        );
+            bottom: bottomView,
+            backgroundColor: BAR_BACK_COLORS[group.index],
+            elevation: 0.0,
+            actions: right == null ? null : [right]);
 }
 
 class SliverBar extends SliverAppBar {