import 'package:flutter/material.dart';import 'package:flutter/rendering.dart';void main() { runApp(new MyApp());}class MyApp extends StatelessWidget { // This widget is the root of your application. @override Widget build(BuildContext context) { return new MaterialApp( title: 'Flutter Demo', theme: new ThemeData( primarySwatch: Colors.blue, ), home: new MyHomePage(title: 'Flutter Demo Home Page'), ); } }class MyHomePage extends StatefulWidget { MyHomePage({Key key, this.title}) : super(key: key); final String title; @override _MyHomePageState createState() => new _MyHomePageState(); } class _MyHomePageState extends State<MyHomePage> { int _counter = 0; ScrollController _hideButtonController; void _incrementCounter() { setState(() { _counter++; }); } var _isVisible; @override initState(){ super.initState(); _isVisible = true; _hideButtonController = new ScrollController(); _hideButtonController.addListener((){ if(_hideButtonController.position.userScrollDirection == ScrollDirection.reverse){ if(_isVisible == true) { print("**** ${_isVisible} up"); //Move IO away from setState setState((){ _isVisible = false; }); } } else { if(_hideButtonController.position.userScrollDirection == ScrollDirection.forward){ if(_isVisible == false) { print("**** ${_isVisible} down"); //Move IO away from setState setState((){ _isVisible = true; });} } }}); } @override Widget build(BuildContext context) { return new Scaffold( appBar: new AppBar( title: new Text(widget.title), ), body: new Center( child: new CustomScrollView( controller: _hideButtonController, shrinkWrap: true, slivers: <Widget>[ new SliverPadding( padding: const EdgeInsets.all(20.0), sliver: new SliverList( delegate: new SliverChildListDelegate( <Widget>[ const Text('I'm dedicating every day to you'), const Text('Domestic life was never quite my style'), const Text('When you smile, you knock me out, I fall apart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('And I thought I was so smart'), const Text('I realize I am crazy'), ], ), ), ), ], ) ), floatingActionButton: new Visibility( visible: _isVisible, child: new FloatingActionButton( onPressed: _incrementCounter, tooltip: 'Increment', child: new Icon(Icons.add), ),), ); }}如果我不使用列表视图，我深表歉意，因为我不知道如何使用列表视图滚动。我将回答您问题的其他部分。
首先，你需要创建一个scrollcontroller将侦听scrollPostion事件
如果scrollcontroller设法找到向前或向后的滚动方向。您添加一个状态，将状态设置为可见。
绘制按钮时，将按钮包装在可见性类中。您设置了可见标志，并且小部件应忽略输入命令。
编辑：我似乎无法添加到ScrollController，ScrollerPosition，ScrollDirection和不透明度的链接。我想您可以自己搜索，也可以由其他人在链接中进行编辑
Edit2：使用CopsonRoad或使用可见性小部件，除非您希望在布局树中使用未绘制的小部件
Edit3：鉴于新来者按原样使用代码，因此我将更新代码以鼓励更好的实践。使用可见性而不是不透明度。从setState中删除io。在Flutter
1.5.4-hotfix.2上测试
