dart - 为 flutter 小部件的高度设置动画

Question

我想在没有两只手的情况下为小部件的高度设置动画(:

我试过更改 Material 小部件的高度但没有任何改变

Answer 1

要为海拔设置动画，您需要使用 AnimationController 自行处理动画。这是一个完整的例子:

import 'package:flutter/material.dart';

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

class App extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: Center(
          child: AnimatedElevationButton(),
        ),
      ),
    );
  }
}

class AnimatedElevationButton extends StatefulWidget {
  @override
  _AnimatedElevationButtonState createState() =>
      _AnimatedElevationButtonState();
}

class _AnimatedElevationButtonState extends State<AnimatedElevationButton>
    with SingleTickerProviderStateMixin {
  AnimationController _animationController;
  Animation<double> _animationTween;

  @override
  void initState() {
    super.initState();

    _animationController = AnimationController(
      duration: Duration(milliseconds: 30),
      vsync: this,
    );
    _animationTween =
        Tween(begin: 20.0, end: 0.0).animate(_animationController);
    _animationController.addListener(() {
      setState(() {});
    });
  }

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onTapDown: _onTapDown,
      onTapUp: _onTapUp,
      child: Material(
        color: Colors.red,
        borderRadius: BorderRadius.circular(8.0),
        elevation: _animationTween.value,
        child: SizedBox(
          width: 100,
          height: 50,
        ),
      ),
    );
  }

  void _onTapDown(TapDownDetails details) {
    _animationController.forward();
  }

  void _onTapUp(TapUpDetails details) {
    _animationController.reverse();
  }
}