refactor: extract loading widget

lib/main.dart

@@ -19,6 +19,10 @@ class _HomeState extends State<Home> {
         icon: Icon(Icons.rss_feed),
         title: Text('News'),
       ),
+      BottomNavigationBarItem(
+        icon: Icon(Icons.search),
+        title: Text('Search'),
+      ),
       BottomNavigationBarItem(
         icon: StreamBuilder<int>(builder: (context, snapshot) {
           int count = snapshot.data;
@@ -42,10 +46,6 @@ class _HomeState extends State<Home> {
         }),
         title: Text('Notification'),
       ),
-      BottomNavigationBarItem(
-        icon: Icon(Icons.search),
-        title: Text('Search'),
-      ),
       BottomNavigationBarItem(
         icon: Icon(Icons.person),
         title: Text('Me'),
@@ -58,9 +58,9 @@ class _HomeState extends State<Home> {
       case 0:
         return NewsScreen();
       case 1:
-        return NotificationScreen();
-      case 2:
         return SearchScreen();
+      case 2:
+        return NotificationScreen();
       case 3:
         return ProfileScreen();
     }

lib/screens/news.dart

@@ -2,6 +2,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter/cupertino.dart';
 import '../providers/settings.dart';
 import '../widgets/event_item.dart';
+import '../widgets/loading.dart';
 import '../utils/utils.dart';
 
 class NewsScreen extends StatefulWidget {
@@ -53,6 +54,17 @@ class NewsScreenState extends State<NewsScreen> {
     });
   }
 
+  Widget _buildItems(BuildContext context, int index) {
+    // return Loading(more: false);
+    if (_events.length == 0) {
+      return Loading(more: false);
+    } else if (index == _events.length) {
+      return Loading(more: true);
+    } else {
+      return EventItem(_events[index]);
+    }
+  }
+
   @override
   Widget build(context) {
     switch (SettingsProvider.of(context).layout) {
@@ -66,20 +78,13 @@ class NewsScreenState extends State<NewsScreen> {
               SliverSafeArea(
                 top: false,
                 sliver: SliverList(
-                  delegate: SliverChildBuilderDelegate(
+                  delegate: SliverChildBuilderDelegate(_buildItems,
-                    (BuildContext context, int index) {
+                      childCount: _events.length + 1),
-                      if (index == _events.length) {
-                        return Padding(
-                          padding: EdgeInsets.symmetric(vertical: 15),
-                          child: CupertinoActivityIndicator(radius: 12),
-                        );
-                      } else {
-                        return EventItem(_events[index]);
-                      }
-                    },
-                    childCount: _events.length + 1,
-                  ),
                 ),
+                // sliver: SliverList(
+                //   delegate:
+                //       SliverChildBuilderDelegate(_buildItems, childCount: 1),
+                // ),
               ),
             ],
           ),
@@ -100,16 +105,8 @@ class NewsScreenState extends State<NewsScreen> {
             child: ListView.builder(
               controller: _controller,
               itemCount: _events.length + 1,
-              itemBuilder: (context, index) {
+              // itemCount: 1,
-                if (index == _events.length) {
+              itemBuilder: _buildItems,
-                  return Padding(
-                    padding: EdgeInsets.symmetric(vertical: 15),
-                    child: CircularProgressIndicator(),
-                  );
-                } else {
-                  return EventItem(_events[index]);
-                }
-              },
             ),
           ),
         );

lib/screens/notifications.dart

@@ -3,6 +3,7 @@ import 'package:flutter/cupertino.dart' hide Notification;
 import '../providers/settings.dart';
 import '../screens/screens.dart';
 import '../widgets/notification_item.dart';
+import '../widgets/loading.dart';
 import '../utils/utils.dart';
 
 class NotificationGroup {
@@ -116,10 +117,7 @@ class NotificationScreenState extends State<NotificationScreen> {
                   delegate: SliverChildBuilderDelegate(
                     (BuildContext context, int index) {
                       if (index == groups.length) {
-                        return Padding(
+                        return Loading(more: true);
-                          padding: EdgeInsets.symmetric(vertical: 15),
-                          child: CupertinoActivityIndicator(radius: 12),
-                        );
                       } else {
                         return _buildGroupItem(context, index);
                       }

lib/widgets/issue_pull_request.dart

@@ -1,6 +1,7 @@
 import 'package:flutter/material.dart';
 import 'package:flutter/cupertino.dart';
 import '../widgets/widgets.dart';
+import '../widgets/loading.dart';
 
 // Widget of issue screen and pull request screen
 class IssuePullRequestScreen extends StatefulWidget {
@@ -39,7 +40,7 @@ class _IssuePullRequestScreenState extends State<IssuePullRequestScreen> {
 
   Widget _buildBody(BuildContext context) {
     if (payload == null) {
-      return CupertinoActivityIndicator();
+      return Loading();
     }
 
     List items = payload['timeline']['nodes'];

lib/widgets/loading.dart

@@ -0,0 +1,39 @@
+import 'package:flutter/material.dart';
+import 'package:flutter/cupertino.dart';
+import '../providers/settings.dart';
+
+class Loading extends StatelessWidget {
+  final bool more;
+
+  Loading({this.more});
+
+  Widget _buildIndicator(BuildContext context) {
+    switch (SettingsProvider.of(context).layout) {
+      case LayoutMap.cupertino:
+        return CupertinoActivityIndicator(radius: 12);
+      default:
+        return Center(
+          child: SizedBox(
+            width: 24,
+            height: 24,
+            child: CircularProgressIndicator(),
+          ),
+        );
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    if (more) {
+      return Padding(
+        padding: EdgeInsets.symmetric(vertical: 20),
+        child: _buildIndicator(context),
+      );
+    } else {
+      return Padding(
+        padding: EdgeInsets.symmetric(vertical: 40),
+        child: _buildIndicator(context),
+      );
+    }
+  }
+}