Cast Error thrown from DraggableScrollableSheet #112020
Description
b/247858428
Customer reporting error being thrown when providing a DraggableScrollableController to DraggableScrollableSheet.
I have not been able to reproduce this crash yet.
There is a notification listener that is swapping out the DraggableScrollableSheet when it reaches the fully expanded state, and it is in _onExtentReplaced where the _attachedController! is throwing.
This is the redacted stack trace from the customer:
══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
The following _CastError was thrown building NotificationListener<DraggableScrollableNotification>:
Null check operator used on a null value
The relevant error-causing widget was:
NotificationListener<DraggableScrollableNotification>
NotificationListener ... **redacted** ...
When the exception was thrown, this was the stack:
#0 DraggableScrollableController._onExtentReplaced (package:[flutter/src/widgets/draggable_scrollable_sheet.dart:195]
#1 _DraggableScrollableSheetState._replaceExtent (package:[flutter/src/widgets/draggable_scrollable_sheet.dart:732]
#2 _DraggableScrollableSheetState.didUpdateWidget (package:[flutter/src/widgets/draggable_scrollable_sheet.dart:675]
#3 StatefulElement.update (package:[flutter/src/widgets/framework.dart:5069]
#4 Element.updateChild (package:[flutter/src/widgets/framework.dart:3590]
#5 RenderObjectElement.updateChildren (package:[flutter/src/widgets/framework.dart:5908]
... **redacted**
Here is the sample code I have been trying (unsuccessfully) to reproduce this crash with:
import 'package:flutter/material.dart';
void main() {
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({super.key});
@override
Widget build(BuildContext context) {
return const MaterialApp(home: MyHomePage());
}
}
class MyHomePage extends StatefulWidget {
const MyHomePage({super.key});
@override
State<MyHomePage> createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
final _controller = DraggableScrollableController();
bool useExpanded = false;
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('DraggableScrollableSheet'),
),
body: NotificationListener<DraggableScrollableNotification>(
onNotification: (scrollNotification) {
if (scrollNotification.extent == scrollNotification.minExtent) {
print('Fully closed');
setState((){ useExpanded = false; });
} else if (scrollNotification.extent == scrollNotification.maxExtent) {
print('Fully expanded');
setState((){ useExpanded = true; });
}
return true;
},
child: !useExpanded
? DraggableScrollableSheet(
initialChildSize: 0.25,
minChildSize: 0.25,
controller: _controller,
snap: true,
snapSizes: const <double>[0.25, 1.0],
builder: (BuildContext context, ScrollController scrollController) {
return Container(
color: Colors.red[100],
child: ListView.builder(
controller: scrollController,
itemCount: 25,
itemBuilder: (BuildContext context, int index) {
return ListTile(title: Text('Item $index'));
},
),
);
},
)
: DraggableScrollableSheet(
initialChildSize: 1,
minChildSize: 0.25,
controller: _controller,
snap: true,
snapSizes: const <double>[0.25, 1.0],
builder: (BuildContext context, ScrollController scrollController) {
return Container(
color: Colors.blue[100],
child: ListView.builder(
controller: scrollController,
itemCount: 25,
itemBuilder: (BuildContext context, int index) {
return Container(height: 50, child: Text('Item $index'));
},
),
);
},
),
),
);
}
}
@xu-baolin does anything jump out at you here?