Move RenameDialog to its own file

Also make it a bit more generic

lib/screens/folder_listing.dart

@@ -4,6 +4,7 @@ import 'package:provider/provider.dart';
 import 'package:gitjournal/widgets/app_bar_menu_button.dart';
 import 'package:gitjournal/widgets/app_drawer.dart';
 import 'package:gitjournal/widgets/folder_tree_view.dart';
+import 'package:gitjournal/widgets/rename_dialog.dart';
 import 'package:gitjournal/state_container.dart';
 import 'package:gitjournal/core/notes_folder.dart';
 
@@ -68,7 +69,11 @@ class _FolderListingScreenState extends State<FolderListingScreen> {
           if (value == "Rename") {
             var folderName = await showDialog(
               context: context,
-              builder: (_) => RenameFolderDialog(selectedFolder),
+              builder: (_) => RenameDialog(
+                oldName: selectedFolder.name,
+                inputDecoration: 'Folder Name',
+                dialogTitle: "Rename Folder",
+              ),
             );
             if (folderName is String) {
               final container = StateContainer.of(context);
@@ -205,70 +210,6 @@ class _CreateFolderAlertDialogState extends State<CreateFolderAlertDialog> {
   }
 }
 
-class RenameFolderDialog extends StatefulWidget {
-  final NotesFolder folder;
-
-  RenameFolderDialog(this.folder);
-
-  @override
-  _RenameFolderDialogState createState() => _RenameFolderDialogState();
-}
-
-class _RenameFolderDialogState extends State<RenameFolderDialog> {
-  TextEditingController _textController;
-
-  @override
-  void initState() {
-    super.initState();
-    _textController = TextEditingController(text: widget.folder.name);
-  }
-
-  @override
-  Widget build(BuildContext context) {
-    var form = Form(
-      child: Column(
-        mainAxisSize: MainAxisSize.min,
-        children: <Widget>[
-          TextFormField(
-            decoration: const InputDecoration(labelText: 'Folder Name'),
-            validator: (value) {
-              if (value.isEmpty) return 'Please enter a name';
-              return "";
-            },
-            autofocus: true,
-            keyboardType: TextInputType.text,
-            controller: _textController,
-          ),
-        ],
-      ),
-    );
-
-    return AlertDialog(
-      title: const Text("Rename Folder"),
-      actions: <Widget>[
-        FlatButton(
-          onPressed: () => Navigator.of(context).pop(false),
-          child: const Text("Cancel"),
-        ),
-        FlatButton(
-          onPressed: () {
-            var newFolderName = _textController.text;
-            return Navigator.of(context).pop(newFolderName);
-          },
-          child: const Text("Rename"),
-        ),
-      ],
-      content: form,
-    );
-  }
-
-  @override
-  void dispose() {
-    _textController.dispose();
-    super.dispose();
-  }
-}
-
 class FolderErrorDialog extends StatelessWidget {
   @override
   Widget build(BuildContext context) {

lib/widgets/rename_dialog.dart

@@ -0,0 +1,73 @@
+import 'package:flutter/material.dart';
+
+class RenameDialog extends StatefulWidget {
+  final String oldName;
+  final String inputDecoration;
+  final String dialogTitle;
+
+  RenameDialog({
+    @required this.oldName,
+    @required this.inputDecoration,
+    @required this.dialogTitle,
+  });
+
+  @override
+  _RenameDialogState createState() => _RenameDialogState();
+}
+
+// FIXME: Do not allow paths which already exist!
+
+class _RenameDialogState extends State<RenameDialog> {
+  TextEditingController _textController;
+
+  @override
+  void initState() {
+    super.initState();
+    _textController = TextEditingController(text: widget.oldName);
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    var form = Form(
+      child: Column(
+        mainAxisSize: MainAxisSize.min,
+        children: <Widget>[
+          TextFormField(
+            decoration: InputDecoration(labelText: widget.inputDecoration),
+            validator: (value) {
+              if (value.isEmpty) return 'Please enter a name';
+              return "";
+            },
+            autofocus: true,
+            keyboardType: TextInputType.text,
+            controller: _textController,
+          ),
+        ],
+      ),
+    );
+
+    return AlertDialog(
+      title: Text(widget.dialogTitle),
+      actions: <Widget>[
+        FlatButton(
+          onPressed: () => Navigator.of(context).pop(false),
+          child: const Text("Cancel"),
+        ),
+        FlatButton(
+          onPressed: () {
+            var newFolderName = _textController.text;
+            return Navigator.of(context).pop(newFolderName);
+          },
+          child: const Text("Rename"),
+        ),
+      ],
+      content: form,
+    );
+  }
+
+  @override
+  void dispose() {
+    _textController.dispose();
+    super.dispose();
+  }
+}