PdfViewPinch displays blank screen and throws Null check operator used on a null value error

[MichelMelhem]

When trying to use PdfViewPinch within a custom PdfSandBox widget, the screen displays blank, and the following error is thrown:

E/flutter ( 9704): [ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: Null check operator used on a null value
E/flutter ( 9704): #0      _PdfViewPinchState._updatePageState (package:pdfx/src/viewer/pinch/pdf_view_pinch.dart:363:44)
E/flutter ( 9704): <asynchronous suspension>

However, when embedding PdfViewPinch directly in the parent widget, it works as expected and the PDF is displayed correctly.

Steps to Reproduce:

• Define a PdfSandBox widget that uses PdfViewPinch.
• Integrate the PdfSandBox widget in a parent widget using a switch statement to control the displayed tab.
• Run the app and switch to the tab containing the PdfSandBox.

Expected Behavior:
The PdfViewPinch should display the PDF document correctly without any errors.

Actual Behavior:
The screen remains blank, and the error mentioned above is thrown.

Code Samples:

PdfSandBox Widget:

dart

import 'dart:async';
import 'package:best_report/src/models/Observation.model.dart';
import 'package:best_report/src/models/PdfSandboxArgs.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:pdfx/pdfx.dart';

typedef void OnSandboxLoaded(PdfSandBoxController controller);

class PdfSandBox extends StatefulWidget {
  final PdfSandboxArgs args;
  final PdfControllerPinch pdfControllerPinch;
  final OnSandboxLoaded _onSandboxLoaded;

  const PdfSandBox(this.args, this._onSandboxLoaded, this.pdfControllerPinch,
      {Key? key})
      : super(key: key);

  @override
  State<PdfSandBox> createState() => _PdfSandBoxState();
}

class _PdfSandBoxState extends State<PdfSandBox> {
  final Completer<PdfSandBoxController> _controller =
      Completer<PdfSandBoxController>();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text("PDF Viewer")),
      body: Center(
        child: Container(
          width: double.infinity,
          height: double.infinity,
          child: PdfViewPinch(
            controller: widget.pdfControllerPinch,
            onDocumentLoaded: (document) {
              debugPrint('PDF document loaded');
              final PdfSandBoxController controller =
                  PdfSandBoxController(widget);
              _controller.complete(controller);
              widget._onSandboxLoaded(controller);
            },
            onError: (error) {
              debugPrint('Error loading PDF: $error');
            },
          ),
        ),
      ),
    );
  }
}

class PdfSandBoxController {
  PdfSandBox _widget;

  PdfSandBoxController(this._widget);

  Future<void> setObservations(List<Observation> observations) async {
    try {
      // Your implementation
    } catch (error) {
      debugPrint('Error in setObservations: $error');
    }
  }

  Future<void> editObservation(Observation observation) async {
    try {
      // Your implementation
    } catch (error) {
      debugPrint('Error in editObservation: $error');
    }
  }

  Future<void> setDarkMode(Brightness brightness) async {
    try {
      if (defaultTargetPlatform == TargetPlatform.android) {
        // Your implementation
      }
    } catch (error) {
      debugPrint('Error in setDarkMode: $error');
    }
  }

  Future<void> addObservation(Observation observation) async {
    try {
      // Your implementation
    } catch (error) {
      debugPrint('Error in addObservation: $error');
    }
  }

  Future<void> updateObservations(List<Observation> observations) async {
    try {
      // Your implementation
    } catch (error) {
      debugPrint('Error in updateObservations: $error');
    }
  }
}

Parent Widget:

dart

switch (tabItem) {
  case TabItem.drawing:
    String? pdfPath = widget.args.plan?.path;
    if (pdfPath == null || !File(pdfPath).existsSync()) {
      debugPrint('PDF file does not exist at path: $pdfPath');
      return Center(child: Text("PDF file not found"));
    }
    return PdfSandBox(
      widget.args,
      (controller) {
        this._controller = controller;
        debugPrint('PdfSandBoxController initialized');
      },
      PdfControllerPinch(
        document: PdfDocument.openFile(pdfPath),
      ),
    );
  case TabItem.buildingTrade:
    return Container(
      child: MediaQuery.of(context).orientation == Orientation.portrait
        ? Column(
            children: observationList,
          )
        : Row(
            children: observationList,
          ),
    );
  default:
    return Center(
      child: Text("404 page not found"),
    );
}

Additional Context:

• PdfX version : 2.6.0
• OS: Android
• Flutter doctor :
• Doctor summary (to see all details, run flutter doctor -v):
  [✓] Flutter (Channel stable, 3.22.2, on macOS 14.5 23F79 darwin-arm64, locale en-FR)
  [✓] Android toolchain - develop for Android devices (Android SDK version 34.0.0)
  [!] Xcode - develop for iOS and macOS (Xcode 15.4)
  ✗ Unable to get list of installed Simulator runtimes.
  [✓] Chrome - develop for the web
  [✓] Android Studio (version 2024.1)
  [✓] VS Code (version 1.90.1)
  [✓] Connected device (4 available)
  [✓] Network resources

Any help in resolving this issue would be greatly appreciated. Thank you!

[neverCase]

Is there any solution to fix this problem？
openFile or openData doesn't work