pdf reader

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/material.dart';
import 'package:syncfusion_flutter_pdfviewer/pdfviewer.dart';


/// Represents Homepage for Navigation
class ViewPdf extends StatefulWidget {
   const ViewPdf({super.key});

  @override
  State<ViewPdf> createState() => _ViewPdfState();
}

class _ViewPdfState extends State<ViewPdf> {
  final GlobalKey<SfPdfViewerState> _pdfViewerKey = GlobalKey();

  //getting pdf link from database
  Future<String?> getlessonpdf() async {
    try {
      final DocumentSnapshot docRef = await FirebaseFirestore.instance
          .collection("Lessonpdf")
          .doc("adultquarterlesson")
          .get();

      if (docRef.exists) {
        final map = docRef.data() as Map<String, dynamic>;
        String pdf = map['pdflink'];
        //String profilepic=map['profilephoto'];

        return pdf;
      } else {
        print("document with id : \"adult lesson\" does not exists");

        return null;
      }
    } catch (e) {
      print(e.toString());
      rethrow;
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('ADULT LESSON' ,style:TextStyle(color: Colors.white,fontWeight: FontWeight.bold)),
        backgroundColor: Colors.purple,
        actions: <Widget>[
          IconButton(
            icon: const Icon(
              Icons.bookmark,
              color: Colors.white,
              semanticLabel: 'Bookmark',
            ),
            onPressed: () {
              _pdfViewerKey.currentState?.openBookmarkView();
            },
          ),
        ],
      ),
      body: SfPdfViewer.network(
            await getlessonpdf(),
        //'https://www.adultbiblestudyguide.org/assets/public/files/lessons/2024/3Q/SE/PDFs/EAQ324_13.pdf',
        key: _pdfViewerKey,
      ),
    );
  }
}
solved
class Example extends StatefulWidget {
  const Example({super.key});

  @override
  State<Example> createState() => _ExampleState();
}
class _ExampleState extends State<Example> {

  Future<String> getPdfURL() async {
    await Future.delayed(const Duration(seconds: 5));

    return "http://example.com/pdf.pdf";
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: FutureBuilder(
        future: getPdfURL(), // add your future method here
        builder: (context, snapshot) {
          if (snapshot.connectionState == ConnectionState.waiting) {
            return const CircularProgressIndicator();
          } else if (snapshot.hasError) {
            return Text('Error: ${snapshot.error}');
          } else {
            String url = snapshot.data!;
            return YourPDFViewerWidget(url: url);
          }
        },
      ),
    );
  }
}