Null check operator used on a null value

[gamestap99]

I have a bug when user download app from store and chplay. The error detected by sentry package. I tried to check my code and i think error is started from your side

[gamestap99]

this is device.

[deremakif]

I have a similar crash report. This is from Countly tools.

java.lang.Exception: Null check operator used on a null value

I think, you should fix this class:

class PhotoViewDefaultLoading extends StatelessWidget {
  const PhotoViewDefaultLoading({Key? key, this.event}) : super(key: key);

  final ImageChunkEvent? event;

  @override
  Widget build(BuildContext context) {
    final value = event == null || event?.expectedTotalBytes != null
        ? 0.0
        : event!.cumulativeBytesLoaded / event!.expectedTotalBytes!;
    return Center(
      child: Container(
        width: 20.0,
        height: 20.0,
        child: CircularProgressIndicator(value: value),
      ),
    );
  }
}

https://stackoverflow.com/a/67990442/10659482

[bounty1342]

There is also this one :

I/flutter (30573): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter (30573): The following _CastError was thrown while finalizing the widget tree:
I/flutter (30573): Null check operator used on a null value
I/flutter (30573):
I/flutter (30573): When the exception was thrown, this was the stack:
I/flutter (30573): #0      IgnorableChangeNotifier.removeIgnorableListener
package:photo_view/…/utils/ignorable_change_notifier.dart:39
I/flutter (30573): #1      PhotoViewController.removeIgnorableListener
package:photo_view/…/controller/photo_view_controller.dart:173
I/flutter (30573): #2      PhotoViewControllerDelegate.dispose
package:photo_view/…/controller/photo_view_controller_delegate.dart:216
I/flutter (30573): #3      PhotoViewCoreState.dispose
package:photo_view/…/core/photo_view_core.dart:279
I/flutter (30573): #4      StatefulElement.unmount
package:flutter/…/widgets/framework.dart:4895
I/

[bounty1342]

And this one too :

I/flutter (30573): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter (30573): The following _CastError was thrown building ImageWrapper(state: _ImageWrapperState#db9b3):
I/flutter (30573): Null check operator used on a null value
I/flutter (30573):
I/flutter (30573): The relevant error-causing widget was:
I/flutter (30573):   PhotoView
I/flutter (30573):
lib/…/picture/picture_widget.dart:529
I/flutter (30573):
I/flutter (30573): When the exception was thrown, this was the stack:
I/flutter (30573): #0      IgnorableChangeNotifier.addIgnorableListener
package:photo_view/…/utils/ignorable_change_notifier.dart:34
I/flutter (30573): #1      PhotoViewController.addIgnorableListener
package:photo_view/…/controller/photo_view_controller.dart:168
I/flutter (30573): #2      PhotoViewControllerDelegate.initDelegate
package:photo_view/…/controller/photo_view_controller_delegate.dart:37
I/flutter (30573): #3      PhotoViewCoreState.initState
package:photo_view/…/core/photo_view_core.dart:261
I/flutter (30573): #4      StatefulElement._firstBuild
package:flutter/…/widgets/framework.dart:4805
I/flutter (30573): #5      ComponentElement.mount
package:flutter/…/widgets/framework.dart:4638

[helenkravchenko]

Hi, I am using photo_view: ^0.13.0 from 5 Oct and the issue that @deremakif described is still present. Could you please fix it)

[helenkravchenko]

Thank you!

[bounty1342]

@renancaraujo, the issue in my previous comment happen with routing, or if you dispose the controller and immediately create a new one to get a new initPosition for exemple.

There is a very simple fix, just protect the nullity with ? instead of enforcing int with ! in the dispose method.
Anyway, enforcing '!' on a method call is a bad pattern and should be avoid 😈 (Otherwise, it should not be nullable but late)

  void removeIgnorableListener(listener) {
    assert(_debugAssertNotDisposed());
    _ignorableListeners!.remove(listener);
  }

  void removeIgnorableListener(listener) {
    assert(_debugAssertNotDisposed());
    _ignorableListeners?.remove(listener);
  }

Let me know if you want a PR for it.

Regards

[eliabieri]

Any updates on this?
I'd love to see a PR for this