PageStorageKeys might benefit from a way to identify their primary client

Internal: b/292548528

Customer Leafy ran into a confusing problem: ExpansionTiles were asserting in initState():

Error: type 'double' is not a subtype of type 'bool' of 'value'
...

#0 _ExpansionTileState._isExpanded= (package:flutter/src/material/expansion_tile.dart:81)
#1 _ExpansionTileState.initState (package:flutter/src/material/expansion_tile.dart:95)
#2 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3502)
...

The problem was that the ExpansionTile's were looking up their expanded/collapsed boolean with PageStorage, but only the enclosing PageView specified a PageStorageKey. PageView uses PageStorage to save its double scroll offset.

In this case it would have been preferable for the expansion tiles to not save their state.

Some possible ways to improve things:

ExpansionTiles don't save their state by default. The dartdoc for a default false keepExpansionState could cover the need for a PageStorageKey.
Scrollables include an inherited widget that only exists to stop the page storage key tree traversal. If a key wasn't found by the time this widget was reached, the traversal would short-circuit.

The second approach seems like it would result in most apps quietly getting the behavior they'd expect. It would complicate explaining how PageStorageKeys work a little.

I guess another option is that we add the type back in to the key somehow, though then you'd have all the panels stomping on each other which is no good.

I know this is old but just ran into same problem myself. For a flutter beginner it's difficult to know what the problem is from the reported error. The simple fix is to specify a PageStorageKey as the ExpansionTile key. Hope this save someone some time!

new ExpansionTile(key: new PageStorageKey("any string"),  ...

Hey I actually just ran into this problem in a slightly different way. I'm using ExpansionTiles in a TabBarView and each ExpansionTile has a number of SwitchListTiles. I added a PageStorageKey to my ExpansionTiles so the expanded state would be saved but started getting this error. The fix for me was to add a PageStorageKey to each SwitchListTile as well since they have their own boolean selected values which were probably confusing the scroll offset lookup. Just throwing this out there in case this happens to anyone else!

I know this is old but just ran into same problem myself. For a flutter beginner it's difficult to know what the problem is from the reported error. The simple fix is to specify a PageStorageKey as the ExpansionTile key. Hope this save someone some time!
new ExpansionTile(key: new PageStorageKey("any string"),  ...

You are right that the error is rather unhelpful, but there seem to be similar errors whenever widgets expect cached properties but can't find them. If you have more than one ExpansionTile, however, I believe they will each need a unique key to avoid stepping on each other.

I know this is old but just ran into same problem myself. For a flutter beginner it's difficult to know what the problem is from the reported error. The simple fix is to specify a PageStorageKey as the ExpansionTile key. Hope this save someone some time!
new ExpansionTile(key: new PageStorageKey("any string"),  ...

I used "Key" It didnt work in my project. Thank you for your answer

Hi. I have the opposite behavior. I am using ExpansionTile in a ListView. The doc say to use PageStorageKey

/// This widget is typically used with [ListView] to create an
/// "expand / collapse" list entry. When used with scrolling widgets like
/// [ListView], a unique [PageStorageKey] must be specified to enable the
/// [ExpansionTile] to save and restore its expanded state when it is scrolled
/// in and out of view.

when I add PageStorageKey like,

  Material(
          child: ExpansionTile(
            key: PageStorageKey<String>(event.id),
            title: Text(event.text),
            initiallyExpanded: false,
            children: <Widget>[
            .....

I get error when expand. Even with one item. Is it safe to use without PageStorageKey if there are multiple items and list is scrolled? Thanks.

Edit: Looks like the error is from a child TextEdit widget. For example,

class MsgInput extends StatefulWidget {
  @override
  _MsgInputState createState() => _MsgInputState();
}

class _MsgInputState extends State<MsgInput> {
  final _formKey = GlobalKey<FormState>();
  var _passKey = GlobalKey<FormFieldState>();

  @override
  Widget build(BuildContext context) {
    return Form(
      key: _formKey,
      child: TextFormField(
        key: _passKey,
        decoration: InputDecoration(labelText: 'Enter Name', hintText: 'Name'),
        validator: (value) {
          if (value.isEmpty) {
            return 'Please enter a name';
          }
          return null;
        },
        onSaved: (value) {
          setState(() {
            // _name = value;
          });
        },
      ),
    );
  }
}

flutter: ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
flutter: The following assertion was thrown building
flutter: EditableText-[LabeledGlobalKey<EditableTextState>#33601](controller:
flutter: TextEditingController#8c7bb(TextEditingValue(text: ┤├, selection: TextSelection(baseOffset: -1,
flutter: extentOffset: -1, affinity: TextAffinity.downstream, isDirectional: false), composing:
flutter: TextRange(start: -1, end: -1))), focusNode: FocusNode#1c794, debugLabel: (englishLike subhead
flutter: 2014).merge(blackCupertino subhead), inherit: false, color: Color(0xdd000000), family: .SF UI Text,
flutter: size: 16.0, weight: 400, baseline: alphabetic, decoration: TextDecoration.none, textAlign: start,
flutter: keyboardType: TextInputType(name: TextInputType.text, signed: null, decimal: null), dependencies:
flutter: [_FocusMarker], state: EditableTextState#fd565(tickers: tracking 2 tickers)):
flutter: type 'bool' is not a subtype of type 'double'
flutter:
flutter: Either the assertion indicates an error in the framework itself, or we should provide substantially
flutter: more information in this error message to help you determine and fix the underlying cause.
flutter: In either case, please report this assertion by filing a bug on GitHub:
flutter:   https://github.com/flutter/flutter/issues/new?template=BUG.md
flutter:
flutter: When the exception was thrown, this was the stack:
flutter: #0      ScrollPosition.restoreScrollOffset 
package:flutter/…/widgets/scroll_position.dart:356
flutter: #1      new ScrollPosition 
package:flutter/…/widgets/scroll_position.dart:82
flutter: #2      new ScrollPositionWithSingleContext 
package:flutter/…/widgets/scroll_position_with_single_context.dart:57
flutter: #3      ScrollController.createScrollPosition 
package:flutter/…/widgets/scroll_controller.dart:233
flutter: #4      ScrollableState._updatePosition 
package:flutter/…/widgets/scrollable.dart:328
flutter: #5      ScrollableState.didChangeDependencies 
package:flutter/…/widgets/scrollable.dart:337
flutter: #6      StatefulElement._firstBuild 
package:flutter/…/widgets/framework.dart:4051
flutter: #7      ComponentElement.mount 
package:flutter/…/widgets/framework.dart:3902
flutter: #8      Element.inflateWidget 
package:flutter/…/widgets/framework.dart:3084
flutter: #9      Element.updateChild 
package:flutter/…/widgets/framework.dart:2887
flutter: #10     ComponentElement.performRebuild 
package:flutter/…/widgets/framework.dart:3935
flutter: #11     Element.rebuild 
package:flutter/…/widgets/framework.dart:3721
flutter: #12     ComponentElement._firstBuild 
package:flutter/…/widgets/framework.dart:3907
flutter: #13     StatefulElement._firstBuild 
package:flutter/…/widgets/framework.dart:4053
flutter: #14     ComponentElement.mount 
package:flutter/…/widgets/framework.dart:3902
flutter: #15     Element.inflateWidget 
package:flutter/…/widgets/framework.dart:3084
flutter: #16     Element.updateChild 
package:flutter/…/widgets/framework.dart:2887
flutter: #17     SingleChildRenderObjectElement.mount 
package:flutter/…/widgets/framework.dart:5092
flutter: #18     Element.inflateWidget 
package:flutter/…/widgets/framework.dart:3084
flutter: #19     Element.updateChild 
package:flutter/…/widgets/framework.dart:2887
flutter: #20     _RenderDecorationElement._mountChild 
package:flutter/…/material/input_decorator.dart:1481
flutter: #21     _RenderDecorationElement.mount 
package:flutter/…/material/input_decorator.dart:1496
flutter: #22     Element.inflateWidget 
package:flutter/…/widgets/framework.dart:3084
flutter: #23     Element.updateChild 
package:flutter/…/widgets/framework.dart:2887
flutter: #24     ComponentElement.performRebuild 
package:flutter/…/widgets/framework.dart:3935
flutter: #25     Element.rebuild 
package:flutter/…/widgets/framework.dart:3721
flutter: #26     ComponentElement._firstBuild 
package:flutter/…/widgets/framework.dart:3907
flutter: #27     StatefulElement._firstBuild 
package:flutter/…/widgets/framework.dart:4053
flutter: #28     ComponentElement.mount 
package:flutter/…/widgets/framework.dart:3902
flutter: #29     Element.inflateWidget 
package:flutter/…/widgets/framework.dart:3084
flutter: #30     Element.updateChild 
package:flutter/…/widgets/framework.dart:2887
flutter: #31     ComponentElement.performRebuild 
package:flutter/…/widgets/framework.dart:3935
flutter: #32     Element.rebuild 
package:flutter/…/widgets/framework.dart:3721
flutter: #33     ComponentElement._firstBuild 
package:flutter/…/widgets/framework.dart:3907
flutter: #34     StatefulElement._firstBuild 
package:flutter/…/widgets/framework.dart:4053
flutter: #35     ComponentElement.mount 
package:flutter/…/widgets/framework.dart:3902
flutter: #36     Element.inflateWidget 
package:flutter/…/widgets/framework.dart:3084
flutter: #37     Element.updateChild 
package:flutter/…/widgets/framework.dart:2887
flutter: #38     SingleChildRenderObjectElement.mount 
package:flutter/…/widgets/framework.dart:5092

I used PageStorageKey("any string") to handle isuues with expantion tile throwing error when expanded in a listview or a drawer, and it worked perfectly for me. I know the implementation is different but thanks for the idea.

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PageStorageKeys might benefit from a way to identify their primary client #10868

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PageStorageKeys might benefit from a way to identify their primary client #10868

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Hixie commented on Jun 21, 2017

devantic commented on Apr 26, 2018

kgain21 commented on Nov 8, 2018

psine commented on Nov 21, 2018

volkangurol commented on Jun 8, 2019

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