如何获得ScrollController的完整大小 [英] How to get full size of a ScrollController
问题描述
我已将ScrollController附加到[SliverAppBar,SliverList]的CustomScrollView中
I've attached a ScrollController to a CustomScrollView of [SliverAppBar, SliverList]
在默认情况下,我将使用reverse:true和animateTo(0.0)将滚动移动到添加的最后一个元素,但是在这种情况下,使用reverse也将颠倒SliverAppBar/SliverList的顺序!
In a default case I would use reverse:true and animateTo (0.0) to move the scroll to the last element added but in this case using reverse would also reverse the SliverAppBar/SliverList order !
所以我想使用animateTo(sizeOfScrollableAfterElementAdded),但是我找不到这个值.
So I'd like to use animateTo ( sizeOfScrollableAfterElementAdded ) but I can't find this value.
谢谢!
推荐答案
您可以使用_scrollController.position.maxScrollExtent
滚动到末尾.确保在框架后回调中执行此操作,以便它将包括您刚刚添加的新项目.
You can use _scrollController.position.maxScrollExtent
to scroll to the end. Make sure to do this in a post-frame callback so that it will include the new item you just added.
这是一个银条列表的示例,随着添加的更多项目,该列表会滚动到末尾.
Here is an example of a sliver list that scrolls to the end as more items are added.
import 'package:flutter/scheduler.dart';
import 'package:flutter/material.dart';
void main() {
runApp(new MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return new MaterialApp(
title: 'Flutter Demo',
home: new MyHomePage(),
);
}
}
class MyHomePage extends StatefulWidget {
State createState() => new MyHomePageState();
}
class MyHomePageState extends State<MyHomePage> {
ScrollController _scrollController = new ScrollController();
List<Widget> _items = new List.generate(40, (index) {
return new Text("item $index");
});
@override
Widget build(BuildContext context) {
return new Scaffold(
floatingActionButton: new FloatingActionButton(
child: new Icon(Icons.arrow_downward),
onPressed: () {
setState(() {
_items.add(new Text("item ${_items.length}"));
});
SchedulerBinding.instance.addPostFrameCallback((_) {
_scrollController.animateTo(
_scrollController.position.maxScrollExtent,
duration: const Duration(milliseconds: 300),
curve: Curves.easeOut,
);
});
},
),
body: new CustomScrollView(
controller: _scrollController,
slivers: [
new SliverAppBar(
title: new Text('Sliver App Bar'),
),
new SliverList(
delegate: new SliverChildBuilderDelegate(
(context, index) => _items[index],
childCount: _items.length,
),
),
],
),
);
}
}
这篇关于如何获得ScrollController的完整大小的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!