Refactor code

lib/widgets/dialog_import.dart

@@ -0,0 +1,20 @@
+import 'package:flutter/material.dart';
+import 'package:file_selector/file_selector.dart';
+import 'drag_and_drop_area.dart';
+
+showImportDialog(
+  BuildContext context,
+  Function(XFile) onFileDropped,
+) {
+  showDialog(
+    context: context,
+    builder: (context) {
+      return AlertDialog(
+        contentPadding: const EdgeInsets.all(12),
+        content: DragAndDropArea(
+          onFileDropped: onFileDropped,
+        ),
+      );
+    },
+  );
+}