[scrollable_positioned_list] _scrollableListState == null using PageView

[oseiasmribeiro]

A state problem occurs when using the ScrollablePositionedList inside a PageView. The problem can be reproduced through the sample repository: https://github.com/oseiasmribeiro/scrollablepositionedlistpageview

Actual behavior

════════ Exception caught by widgets library ═══════════════════════════════════
The following assertion was thrown building Expanded(flex: 1):
'package:scrollable_positioned_list/src/scrollable_positioned_list.dart': Failed assertion: line 222 pos 12: '_scrollableListState == null': is not true.

The relevant error-causing widget was
Expanded
lib/bible.dart:156
When the exception was thrown, this was the stack
#2 ItemScrollController._attach
package:scrollable_positioned_list/src/scrollable_positioned_list.dart:222
#3 _ScrollablePositionedListState.initState
package:scrollable_positioned_list/src/scrollable_positioned_list.dart:271
#4 StatefulElement._firstBuild
package:flutter/…/widgets/framework.dart:4765
#5 ComponentElement.mount
package:flutter/…/widgets/framework.dart:4601
... Normal element mounting (7 frames)
...
════════════════════════════════════════════════════════════════════════════════

════════ Exception caught by widgets library ═══════════════════════════════════
'package:scrollable_positioned_list/src/scrollable_positioned_list.dart': Failed assertion: line 222 pos 12: '_scrollableListState == null': is not true.
The relevant error-causing widget was
Expanded
lib/bible.dart:152
════════════════════════════════════════════════════════════════════════════════

Environment

scrollable_positioned_list: 1.9.0
MacBook Pro 16,2 / macOS 10.15.7 (19H15)
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 1.22.6, on Mac OS X 10.15.7 19H15 darwin-x64, locale pt-BR)

[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.2)
[✓] Xcode - develop for iOS and macOS (Xcode 12.4)
[✓] Android Studio (version 4.1)
[✓] VS Code (version 1.53.2)
[✓] Connected device (1 available)

[oseiasmribeiro]

Please, someone help me. It could be that I'm doing something wrong.

[oseiasmribeiro]

This seems to be the same problem I had a few years ago: #39

[oseiasmribeiro]

Please, help me.

[oseiasmribeiro]

Please, help me.

[saviourdog]

i need help too,5555

[tarobins]

The problem is that the ItemScrollController can only be attached to one ScrollablePositionedList at a time. However, when you switch pages in the PageView, there are two ScrollablePositionedList visible for a moment and you're trying to have the ItemScrollController attached to both.

You'll need to come up with a way to have a different ItemScrollController for each page.

[oseiasmribeiro]

Okay, Tarobins, I'll try. Thanks for your help!

[oseiasmribeiro]

I put the ItemScrollController and the ItemPositionListener inside the PageView.builder's itemBuilder, solved the problem. Thanks @tarobins for the tip.

[ghost]

@oseiasmribeiro can you share the code here, because I'm having the same issue with Page view builder