Add ExpansionTile.builder ? ExpansionTile Performance Issue

ExpansionTile needs a (.builder constructor) just like listview
if expansion tile have lots of heavy children it causes hard fps drop

[√] Flutter (Channel stable, v1.9.1+hotfix.2, on Microsoft Windows [Version 10.0.17763.678], locale en-US)
 • Flutter version 1.9.1+hotfix.2 at C:\flutter
 • Framework revision 2d2a1ffec9 (11 days ago), 2019-09-06 18:39:49 -0700
 • Engine revision b863200c37
 • Dart version 2.5.0


[√] Android toolchain - develop for Android devices (Android SDK version 29.0.0)
 • Android SDK at C:\Users\Kirolous.nashaat\AppData\Local\Android\Sdk
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 • Platform android-29, build-tools 29.0.0
 • ANDROID_HOME = C:\Users\Kirolous.nashaat\AppData\Local\Android\Sdk
 • Java binary at: D:\Sources\android-studio-ide-181.4987877-windows\android-studio\jre\bin\java
 • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1136-b06)
 • All Android licenses accepted.

[!] Android Studio (version 3.2)
 • Android Studio at D:\Sources\android-studio-ide-181.4987877-windows\android-studio
 X Flutter plugin not installed; this adds Flutter specific functionality.
 X Dart plugin not installed; this adds Dart specific functionality.
 • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1136-b06)

[√] IntelliJ IDEA Community Edition (version 2019.2)
 • IntelliJ at C:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2019.1.1
 • Flutter plugin version 39.0.5
 • Dart plugin version 192.6603.23

[√] Connected device (1 available)
 • Android SDK built for x86 64 • emulator-5554 • android-x64 • Android 9 (API 28) (emulator)

! Doctor found issues in 1 category.

[deisold]

on Flutter Web (Channel master, v1.13.1-pre.76) it stucks completely and the listview stops scrolling while cpu gets up to 100%.

Would be nice to have this fixed.

[liyuqian]

Adding web label as the performance seems to be particularly bad on web. This doesn't seem to be a very complicated change so I'm adding it to "Framework Performance Opportunities" project.

[yjbanov]

We made some improvements in Q2 in scrollable content with lots of children. Is there a repro case we could look at?

[jmagman]

Without additional information, we are unfortunately not sure how to resolve this issue. We are therefore reluctantly going to close this bug for now. Please don't hesitate to comment on the bug if you have any more information for us; we will reopen it right away!

Thanks for your contribution.

[MatrixDev]

I have the same issue. Which exact information do you need?
Just create ListView with ExpansionTile which contains 1000+ heavy items and fps will stuck.
Problem is that ExpansionTile, unlike ListView, is not lazy and loads all the items at once. It must load only visible items to have optimal performance.

 final Widget result = Offstage(
 child: TickerMode(
 child: Padding(
 padding: widget.childrenPadding ?? EdgeInsets.zero,
 child: Column(
 crossAxisAlignment: widget.expandedCrossAxisAlignment ?? CrossAxisAlignment.center,
 children: widget.children, // <<< this is what causes performance problems
 ),
 ),
 enabled: !closed,
 ),
 offstage: closed
 );

In my case I have 3 ExpansionTile collapsed by default with 100+ items in each. First time displaying my screen takes a huge performance hit, same as each collapse/expand.

IMHO to properly fix this issue ExpansionTile must cooperate with ListView very tightly to display only visible children.

[github-actions]

This thread has been automatically locked since there has not been any recent activity after it was closed. If you are still experiencing a similar issue, please open a new bug, including the output of flutter doctor -v and a minimal reproduction of the issue.