Flutter-隐藏FloatingActionButton

Flutter-隐藏FloatingActionButton

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