Too much widget rebuild occurring when using PanelBuilder [BETA]

[rohansohonee]

Hi @akshathjain

Just started playing around with the new PanelBuilder (beta) using this code snippet from your example docs:

// The sliding up panel
SlidingUpPanel(
      panelBuilder: (ScrollController sc) => _scrollingList(sc),
      body: Center(
        child: Text("This is the Widget behind the sliding panel"),
      ),
)
// The scrolling list
Widget _scrollingList(ScrollController sc) {
    print('scrolling list rebuilt');
    return ListView.builder(
      controller: sc,
      itemCount: 50,
      itemBuilder: (BuildContext context, int i) {
        return Container(
          padding: const EdgeInsets.all(12.0),
          child: Text("$i"),
        );
      },
    );
  }

• I added a print statement print('scrolling list rebuilt');.
• PanelBuilder (beta) keeps rebuilding the widget when scrolling the list. This need to be fixed.

Console log output for reference:

I/flutter ( 9831): scrolling list rebuilt
I/flutter ( 9831): scrolling list rebuilt
I/flutter ( 9831): scrolling list rebuilt
I/flutter ( 9831): scrolling list rebuilt
I/flutter ( 9831): scrolling list rebuilt
I/flutter ( 9831): scrolling list rebuilt

NOTE: When adding setState calls inside _scrollingList widget, it causes even more drastic performance issues as the widget gets rebuilt multiple times.

[akshathjain]

@rohansohonee I profiled the sample code and got render times at < 4 ms / frame which is substantially less than the 16 ms / frame that Flutter recommends to maintain 60 FPS.

However, it is unnecessary to rebuild the panelBuilder widget on each animation tick as the panel slides up and down (which is currently occurring). This will be resolved in the next update.

[ozburo]

@akshathjain just wanted to say that this update saved me! Got my Sliding Panel > PanelBuilder > CustomScrollView working like a charm!

Thanks 🥇

[biklas7]

Hi, @akshathjain I'm having heavy performance problems with this. Glad to know you're working on it! Thanks for the awesome package :+1:

[surveshoeb]

@akshathjain have fixed this issue?

[s0nerik]

Looks like I've fixed it in https://github.com/akshathjain/sliding_up_panel/pull/112

[akshathjain]

Thanks to @s0nerik's PR, I'm closing this issue. This fix will be pushed to prod within the next 24 hours.

[bananagag]

Hi @akshathjain, I started to use this package recently and I found that the rebuilding issue is still there when using PanelBuilder with the scrollcontroller sc used as the child widget's controller (just like the sample code in this issue) and maybe you would like to consider reopening the issue. Thank you very much.

[LarYoungruu]

Hi @akshathjain Has this been fixed or not? I tried and found the problem is still there (2.0.0+1)

[mqhamdam]

come here with the same problem. Cannot use panelbuilder with gridview. It rebuilds children on scroll max/min height

[CagriYonca]

Hi everyone,

I don't know why but the problem is still going on. I've used this solution as workaround and it worked, take a look: https://github.com/akshathjain/sliding_up_panel/issues/188#issuecomment-835254625