flutter - 禁用脚手架 FAB 动画

Question

默认情况下，Flutter 中的脚手架会在应用程序运行时更改 FAB 时为 float 操作按钮 (FAB) 设置动画。

如何禁用此动画？

documentation引用 FloatingActionButtonAnimator.scaling 动画，它在按钮改变时缩放按钮:

/// Animator to move the [floatingActionButton] to a new [floatingActionButtonLocation]. /// /// If null, the [ScaffoldState] will use the default animator, [FloatingActionButtonAnimator.scaling]. final FloatingActionButtonAnimator floatingActionButtonAnimator;

但是，没有说明如何完全禁用缩放动画。

有问题的完整示例代码:

import 'dart:async';

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key}) : super(key: key);

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  Timer _timer;
  bool showFirst = true;

  @override
  void initState() {
    _timer = Timer.periodic(new Duration(seconds: 2), (Timer t) {
      setState(() {
        showFirst = !showFirst;
      });
    });
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(),
      floatingActionButtonLocation: showFirst
          ? FloatingActionButtonLocation.centerDocked
          : FloatingActionButtonLocation.endDocked,
      floatingActionButton: Padding(
        padding: EdgeInsets.only(top: 100.0),
        child: Column(
          children: <Widget>[
            Text('Floating Action Button Title'),
            showFirst
                ? FloatingActionButton.extended(
                    heroTag: 'unique',
                    icon: Icon(Icons.filter_1),
                    label: Text('First FAB'),
                    onPressed: () {},
                  )
                : FloatingActionButton.extended(
                    heroTag: 'unique2',
                    icon: Icon(Icons.filter_2),
                    label: Text('Second FAB'),
                    onPressed: () {},
                  ),
          ],
        ),
      ),
    );
  }

  @override
  void dispose() {
    _timer.cancel();
    super.dispose();
  }
}

为每个 FAB 添加不同的英雄标签不会影响动画。

Answer 1

你需要继承FloatingActionButtonAnimator并覆盖它的方法，检查下面的代码，

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

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key}) : super(key: key);

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  Timer _timer;
  bool showFirst = true;

  @override
  void initState() {
    _timer = Timer.periodic(new Duration(seconds: 2), (Timer t) {
      setState(() {
        showFirst = !showFirst;
      });
    });
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(),
      floatingActionButtonAnimator: NoScalingAnimation(),
      floatingActionButtonLocation: showFirst
          ? FloatingActionButtonLocation.centerDocked
          : FloatingActionButtonLocation.endDocked,
      floatingActionButton: Padding(
        padding: EdgeInsets.only(top: 100.0),
        child: Column(
          children: <Widget>[
            Text('Floating Action Button Title'),
            showFirst
                ? FloatingActionButton.extended(
              heroTag: 'unique',
              icon: Icon(Icons.filter_1),
              label: Text('First FAB'),
              onPressed: () {},
            )
                : FloatingActionButton.extended(
              heroTag: 'unique2',
              icon: Icon(Icons.filter_2),
              label: Text('Second FAB'),
              onPressed: () {},
            ),
          ],
        ),
      ),
    );
  }

  @override
  void dispose() {
    _timer.cancel();
    super.dispose();
  }
}

class NoScalingAnimation extends FloatingActionButtonAnimator{
  double _x;
  double _y;
  @override
  Offset getOffset({Offset begin, Offset end, double progress}) {
  _x = begin.dx +(end.dx - begin.dx)*progress ;
  _y = begin.dy +(end.dy - begin.dy)*progress;
    return Offset(_x,_y);
  }

  @override
  Animation<double> getRotationAnimation({Animation<double> parent}) {
    return Tween<double>(begin: 1.0, end: 1.0).animate(parent);
  }

  @override
  Animation<double> getScaleAnimation({Animation<double> parent}) {
    return Tween<double>(begin: 1.0, end: 1.0).animate(parent);
  }
}

您可以通过更改每个方法返回的内容来控制动画行为。例如。您可以通过将 getOffset 方法更改为

来使 fab 从左到右跳转而无需动画

  @override
  Offset getOffset({Offset begin, Offset end, double progress}) {
    if (progress == 1.0){
      return end;
    }else{
      return begin;
    }
  }