ScrollablePositionedList can not jump to end without animation

[asjqkkkk]

Problem description

Enviroment

Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, v1.17.5, on Mac OS X 10.15.5 19F101, locale zh-Hans-CN)
 
[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.0)
[✓] Xcode - develop for iOS and macOS (Xcode 11.5)
[✓] Android Studio (version 4.0)
[✓] Connected device (1 available)

scrollable_positioned_list: ^0.1.6

Expected behavior

use itemScrollController.jumpTo(...) should not trigger animation

Sample code

import 'dart:math';
import 'package:flutter/material.dart';
import 'package:scrollable_positioned_list/scrollable_positioned_list.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {

  final List<String> curList = [];
  final ItemScrollController itemScrollController = ItemScrollController();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        actions: <Widget>[
          IconButton(icon: Icon(Icons.refresh), onPressed: (){
            buildTextList();
            setState(() { });
            Future.delayed(Duration(milliseconds: 100,), (){
              itemScrollController.jumpTo(index: curList.length);
            });
          })
        ],
      ),
      body: ScrollablePositionedList.builder(
        itemScrollController: itemScrollController,
        itemCount: curList.length,
        itemBuilder: (ctx, index){
          final cur = curList[index];
          return ListTile(title: Text(cur),onTap: (){},);
        },
      ),
    );
  }

  void buildTextList() => curList.add(Random().nextInt(1000).toString());
}

[jamesderlin]

This is observable with the example app: tapping "Jump to 0" with an alignment > 0 when already scrolled to the top triggers a bounce animation, as does "Jump to 5000" (the end) with an alignment < 1 when already scrolled to the end.

[DamirDautov]

If what you want to do is only jump to one particular item, so maybe this workaround I made can help. There's a restriction of Viewport, so no overscroll is allowed, that's the disadvantage.
Also when you change the target item some strange (for me) thing happens: at first frame heights of leadingNegativeChild and trailingPositiveChild are not correct, like some list items are not being calculated. So it looks buggy, but without this workaround list would just have another animation.
So maybe anyone can look closely to that code, maybe you will go through it and find some final fix, I dunno.
Also this discussion should really be considered

[ModWU]

Can you calculate the items below the center item or above according viewport height before the animation?

[ma125125t]

@DamirDautov Thank you for your workaround solution.This solved my problem.Otherwise,I need to calculate each dynamic list item to scroll to correct offset.You saved my time.

[felipecastrosales]

Any news about this?