颤动 - 隐藏FloatingActionButton

Question

是否有任何内置的方式在扑隐藏FloatingActionButton在ListView向下滚动,然后显示在滚动起来了吗？

Answer 1

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) {
            /* only set when the previous state is false
             * Less widget rebuilds 
             */
            print("**** ${_isVisible} up"); //Move IO away from setState
            setState((){
              _isVisible = false;
            });
        }
      } else {
        if(_hideButtonController.position.userScrollDirection == ScrollDirection.forward){
          if(_isVisible == false) {
              /* only set when the previous state is false
               * Less widget rebuilds 
               */
               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),
        ),     
      ),
    );
  }
}

如果我没有使用listview,我很抱歉,因为我不知道如何使用listview滚动.我会回答你问题的其他部分.

首先,您需要创建一个将侦听scrollPostion 2事件的scrollcontroller 1

如果scrollcontroller设法找到向前或向后滚动方向3.您添加一个将状态设置为可见的状态.

绘制按钮时,将按钮包装在不透明度4类中.您将0.0设置为不可见或将1.0设置为可见.

编辑:我似乎无法添加到ScrollController,ScrollerPosition,ScrollDirection和Opacity的链接.我猜你可以自己搜索,也可以在链接中编辑

Answer 2

一个很老的问题，但是在我看来，随着最新的flutter 有一个更好（也更短）的解决方案。

其他解决方案确实有效，但如果您想要一个漂亮的动画（与 Android 中的默认动画相比），请执行以下操作：

每当用户滚动（向上/向下）时，NotificationListener 都会通知您。使用 AnimationController 您可以控制 FAB 的动画。

这是一个完整的例子：

class WidgetState extends State<Widget> with TickerProviderStateMixin<Widget> {
  AnimationController _hideFabAnimation;

  @override
  initState() {
    super.initState();
    _hideFabAnimation = AnimationController(vsync: this, duration: kThemeAnimationDuration);
  }

  @override
  void dispose() {
    _hideFabAnimation.dispose();
    super.dispose();
  }

  bool _handleScrollNotification(ScrollNotification notification) {
    if (notification.depth == 0) {
      if (notification is UserScrollNotification) {
        final UserScrollNotification userScroll = notification;
        switch (userScroll.direction) {
          case ScrollDirection.forward:
            if (userScroll.metrics.maxScrollExtent !=
                userScroll.metrics.minScrollExtent) {
              _hideFabAnimation.forward();
            }
            break;
          case ScrollDirection.reverse:
           if (userScroll.metrics.maxScrollExtent !=
                userScroll.metrics.minScrollExtent) {
              _hideFabAnimation.reverse();
            }
            break;
          case ScrollDirection.idle:
            break;
        }
      }
    }
    return false;
  }

  @override
  Widget build(BuildContext context) {
    return NotificationListener<ScrollNotification>(
      onNotification: _handleScrollNotification,
      child: Scaffold(
        appBar: AppBar(
          title: Text('Fabulous FAB Animation')
        ),
        body: Container(),
        floatingActionButton: ScaleTransition(
          scale: _hideFabAnimation,
          alignment: Alignment.bottomCenter,
          child: FloatingActionButton(
            elevation: 8,
            onPressed: () {},
            child: Icon(Icons.code),
          ),
        ),
      ),
    );
  }
}

Answer 3

floatingActionButton: Visibility(
  child: FloatingActionButton(...),
  visible: false, // set it to false
)

Answer 4

一个很好的方法来做到这一点...

import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';

class Home extends StatefulWidget {
  @override
  _HomeState createState() => _HomeState();
}

class _HomeState extends State<Home> {
  ScrollController controller;
  bool fabIsVisible = true;

  @override
  void initState() {
    super.initState();
    controller = ScrollController();
    controller.addListener(() {
      setState(() {
        fabIsVisible =
            controller.position.userScrollDirection == ScrollDirection.forward;
      });
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: ListView(
        controller: controller,
        children: List.generate(
            100,
            (index) => ListTile(
                  title: Text("Text $index"),
                )),
      ),
      floatingActionButton: AnimatedOpacity(
        child: FloatingActionButton(
          child: Icon(Icons.add),
          tooltip: "Increment",
          onPressed: () {
            print("Pressed");
          },
        ),
        duration: Duration(milliseconds: 100),
        opacity: fabIsVisible ? 1 : 0,
      ),
    );
  }
}

Answer 5

您可以使用以下代码保留默认动画

floatingActionButton: _isVisible
        ? FloatingActionButton(...)
        : null,

Answer 6

另一个非常好的方法是AnimatedOpacity

AnimatedOpacity(
          opacity: isEnabled ? 0.0 : 1.0,
          duration: Duration(milliseconds: 1000),
          child: FloatingActionButton(
             onPressed: your_method,
             tooltip: 'Increment',
             child: new Icon(Icons.add),
          ),
        )

Answer 7

您可以使用Visibility小部件来处理子小部件的可见性

样本：

  floatingActionButton:
            Visibility(visible: _visibilityFlag , child: _buildFAB(context)),