known_extents_list_view_builder
See the difference
Watch this video taken in release mode.
About
This package is intended to address a performance issue in Flutter. Whereas the internal flutter list only allows you to pass in a fixed itemExtent to optimize for uniform lists, this allows you to pass in a list of itemExtents for when your list items have variable (though knowable) extents. Includes a basic list and a reorderable list.
Examples
Find examples of the basic list and of the reorderable lists side by side as shown in the video in examples/lib.
Using ReorderableDragStartListener
If you want to turn off default drag handles and create your own or wrap your widget in ReorderableDragStartListener or ReorderableDelayedDragStartListener, be sure to import the listener from this library's known_extents_sliver_reorderable_list and not from flutter/widgets. For example, if using ReorderableDragStartListener, your imports might look like this:
import 'package:flutter/material.dart' hide ReorderableDragStartListener;
import 'package:known_extents_list_view_builder/known_extents_reorderable_list_view_builder.dart';
import 'package:known_extents_list_view_builder/known_extents_sliver_reorderable_list.dart' show ReorderableDragStartListener;
Branches
If your use case requires more functionality on top of this, I may have a fix you're welcome to use in a branch. Read this for more info
Disclaimer
This is not official Flutter package, nor is it put out by the Flutter team. Maintainance and edges cases are not guaranteed.
If you don't need your list to be reorderable, and would prefer to scroll to indexes rather than exact pixel values, consider using scrollable_positioned_list.