Add basic work editor

This also adds a tile to the temporary home screen for debugging
purposes.

lib/editors/work.dart

@@ -0,0 +1,101 @@
+import 'package:flutter/material.dart';
+
+import '../backend.dart';
+import '../database.dart';
+import '../selectors/person.dart';
+
+class WorkEditor extends StatefulWidget {
+  final Work work;
+
+  WorkEditor({
+    this.work,
+  });
+
+  @override
+  _WorkEditorState createState() => _WorkEditorState();
+}
+
+class _WorkEditorState extends State<WorkEditor> {
+  final titleController = TextEditingController();
+
+  Backend backend;
+  Person composer;
+
+  @override
+  void initState() {
+    super.initState();
+
+    if (widget.work != null) {
+      titleController.text = widget.work.title;
+    }
+  }
+
+  @override
+  void didChangeDependencies() {
+    super.didChangeDependencies();
+
+    backend = Backend.of(context);
+
+    if (widget.work != null && widget.work.composer != null) {
+      () async {
+        final person =
+            await backend.db.personById(widget.work.composer).getSingle();
+
+        // We don't want to override a newly selected composer.
+        if (composer != null) {
+          setState(() {
+            composer = person;
+          });
+        }
+      }();
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        title: Text('Work'),
+        actions: <Widget>[
+          FlatButton(
+            child: Text('DONE'),
+            onPressed: () {},
+          ),
+        ],
+      ),
+      body: ListView(
+        children: <Widget>[
+          Padding(
+            padding: const EdgeInsets.all(16.0),
+            child: TextField(
+              controller: titleController,
+              decoration: InputDecoration(
+                labelText: 'Title',
+              ),
+            ),
+          ),
+          ListTile(
+            title: Text('Composer'),
+            subtitle: Text(composer != null
+                ? '${composer.firstName} ${composer.lastName}'
+                : 'Select composer'),
+            onTap: () async {
+              final Person person = await Navigator.push(
+                  context,
+                  MaterialPageRoute(
+                    builder: (context) => PersonsSelector(),
+                    fullscreenDialog: true,
+                  ));
+
+              if (person != null) {
+                setState(() {
+                  composer = person;
+                });
+              }
+            },
+          ),
+        ],
+      ),
+    );
+  }
+}

lib/screens/home.dart

@@ -1,6 +1,7 @@
 import 'package:flutter/material.dart';
 
 import '../backend.dart';
+import '../editors/work.dart';
 import '../selectors/person.dart';
 import '../selectors/instruments.dart';
 
@@ -42,6 +43,15 @@ class HomeScreen extends StatelessWidget {
                   fullscreenDialog: true,
                 )),
           ),
+          ListTile(
+            title: Text('Add work'),
+            onTap: () => Navigator.push(
+                context,
+                MaterialPageRoute(
+                  builder: (context) => WorkEditor(),
+                  fullscreenDialog: true,
+                )),
+          ),
         ],
       ),
     );