added bottom navigation bar to list view

lib/pages/list/list.dart

@@ -23,6 +23,7 @@ class ListPage extends StatefulWidget {
 }
 
 class _ListPageState extends State<ListPage> {
+  int _viewIndex = 0;
   TaskList _list;
   List<Task> _loadingTasks = [];
   int _currentPage = 1;
@@ -103,9 +104,31 @@ class _ListPageState extends State<ListPage> {
         builder: (context) => FloatingActionButton(
             onPressed: () => _addItemDialog(context), child: Icon(Icons.add)),
       ),
+      bottomNavigationBar: BottomNavigationBar(
+        items: const <BottomNavigationBarItem>[
+          BottomNavigationBarItem(
+            icon: Icon(Icons.view_list),
+            label: 'List',
+            tooltip: 'List',
+          ),
+          BottomNavigationBarItem(
+            icon: Icon(Icons.view_kanban),
+            label: 'Kanban',
+            tooltip: 'Kanban',
+          ),
+        ],
+        currentIndex: _viewIndex,
+        onTap: _onViewTapped,
+      ),
     );
   }
 
+  void _onViewTapped(int index) {
+    setState(() {
+      _viewIndex = index;
+    });
+  }
+
   TaskTile _buildTile(Task task) {
     return TaskTile(
       task: task,

lib/theme/theme.dart

@@ -1,3 +1,5 @@
+import 'dart:math';
+
 import 'package:flutter/material.dart';
 import 'package:vikunja_app/theme/constants.dart';
 
@@ -32,5 +34,16 @@ ThemeData _buildVikunjaTheme(ThemeData base) {
             vWhite, // This does not work, looks like a bug in Flutter: https://github.com/flutter/flutter/issues/19623
       ),
     ),
+    bottomNavigationBarTheme: base.bottomNavigationBarTheme.copyWith(
+      // Make bottomNavigationBar backgroundColor darker to provide more separation
+      backgroundColor: () {
+        final _hslColor = HSLColor.fromColor(
+            base.bottomNavigationBarTheme.backgroundColor != null
+            ? base.bottomNavigationBarTheme.backgroundColor
+            : base.scaffoldBackgroundColor
+        );
+        return _hslColor.withLightness(max(_hslColor.lightness - 0.03, 0)).toColor();
+      }(),
+    ),
   );
 }