channel_list: Show a label when no channels are found

Author: Khader-1

assets/l10n/app_en.arb

@@ -491,6 +491,10 @@
   "@channelListPageTitle": {
     "description": "Title for the page of all channels."
   },
+  "noChannelsFound": "There are no channels you can view in this organization.",
+  "@noChannelsFound": {
+    "description": "Message when no channels are found"
+  },
   "notifGroupDmConversationLabel": "{senderFullName} to you and {numOthers, plural, =1{1 other} other{{numOthers} others}}",
   "@notifGroupDmConversationLabel": {
     "description": "Label for a group DM conversation notification.",

lib/widgets/channel_list.dart

@@ -24,12 +24,32 @@ class ChannelListPage extends StatelessWidget {
     return Scaffold(
       appBar: AppBar(title: Text(zulipLocalizations.channelListPageTitle)),
       body: SafeArea(
-        child: ListView.builder(
+        child: streams.isEmpty ? const _NoStreamsItem() : ListView.builder(
           itemCount: streams.length,
           itemBuilder: (context, index) => ChannelItem(stream: streams[index]))));
   }
 }
 
+class _NoStreamsItem extends StatelessWidget {
+  const _NoStreamsItem();
+
+  @override
+  Widget build(BuildContext context) {
+    final zulipLocalizations = ZulipLocalizations.of(context);
+    return Center(
+      child: Padding(
+        padding: const EdgeInsets.all(10),
+        child: Text(zulipLocalizations.noChannelsFound,
+          textAlign: TextAlign.center,
+          style: TextStyle(
+            // TODO(#95) need dark-theme color
+            color: const HSLColor.fromAHSL(1.0, 240, 0.1, 0.5).toColor(),
+            fontSize: 18,
+            height: (20 / 18),
+          ))));
+  }
+}
+
 @visibleForTesting
 class ChannelItem extends StatelessWidget {
   const ChannelItem({super.key, required this.stream});

test/widgets/channel_list_test.dart

@@ -1,6 +1,7 @@
 import 'package:checks/checks.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:zulip/api/model/model.dart';
+import 'package:zulip/model/localizations.dart';
 import 'package:zulip/widgets/channel_list.dart';
 
 import '../model/binding.dart';
@@ -30,8 +31,10 @@ void main() {
   }
 
   testWidgets('smoke', (tester) async {
+    final zulipLocalizations = GlobalLocalizations.zulipLocalizations;
     await setupChannelListPage(tester, streams: [], subscriptions: []);
     check(getItemCount()).equals(0);
+    check(find.text(zulipLocalizations.noChannelsFound).evaluate()).isNotEmpty();
   });
 
   testWidgets('basic list', (tester) async {