Using panelBuilder and header in a nested panel has odd behavior

Describe the bug The touch events on the header of a nested panel using a panelBuilder will get passed onto the parent panel.

To Reproduce Steps to reproduce the behavior:

See https://www.dartpad.dev/64c1a56cf9e4af1322c8ea305af3b2a6
Expand the first panel
Expand the second panel
Touch events behave correctly if they're on top of the list view
If the listview is scrolled to the top, closing the second panel via the header will also close the first panel
If the listview is not scrolled to the top, attempting to close the second panel with the header will just close the first panel

Expected behavior Swiping down on the second panel header should always close the second panel, the first panel should not be affected. For context, I'm trying to reproduce something like this: https://youtu.be/0MCwl9CpYtg

Screenshots If applicable, add screenshots to help explain your problem.

Additional context My first thought was to (partially) fix it by using setState to make the first panel undraggable whenever the second one opens, however it seems that running setState will randomly cause the second panel to redraw as closed. https://www.dartpad.dev/0b8a550ced402e421d9f4e778ae95b6a

Smartphone (please complete the following information):

Device: Oneplus 6, dartpad
OS: Android 10, dartpad/web
Flutter Version 1.20.0-7.4.pre, whatever dartpad uses
sliding_up_panel Version: 1.0.2 (my own local project), master (in the dartpad)

Sample main.dart Please provide a sample main.dart that reproduces this issue. The code provided here should be able to be run on its own without any external dependencies.

import 'package:flutter/material.dart';
import 'package:flutter/gestures.dart';
import 'dart:math';
import 'package:flutter/physics.dart';

final Color darkBlue = Color.fromARGB(255, 18, 32, 47);

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.dark().copyWith(scaffoldBackgroundColor: darkBlue),
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: SlidingUpPanel(
          maxHeight: 400,
          body: Center(child: Text("Base View")),
          panel: SlidingUpPanel(
            maxHeight: 350,
            body: Container(
              color: Colors.red,
              child: Text("First Panel")
            ),
            header: Container(
              width: 100.0,
              height: 100.0,
              color: Colors.green,
              child: Text("Second Panel Header"),
            ),
            panelBuilder: (sc) {
              return ListView.builder(
                itemCount: 100,
                controller: sc,
                itemBuilder: (context, idx) {
                  return Container(
                    color: Colors.blue,
                    height: 50.0,
                    child: Text("$idx")
                  );
                }
              );
            }
          )

        )
      ),
    );
  }
}

akshathjain / sliding_up_panel

Using panelBuilder and header in a nested panel has odd behavior #181