flutter中的动画

1、AnimatedOpacity

控制widget淡入或淡出效果  

　　

栗子是点击MaterialButton后，通过更新opacity变量，控制details的opacity;

import 'package:flutter/material.dart';

const owl_url =
    'https://raw.githubusercontent.com/flutter/website/master/src/images/owl.jpg';

class FadeInDemo extends StatefulWidget {
  _FadeInDemoState createState() => _FadeInDemoState();
}

class _FadeInDemoState extends State<FadeInDemo> {
  double opacity = 0.0;

  @override
  Widget build(BuildContext context) {
    return Column(children: <Widget>[
      Image.network(owl_url),
      MaterialButton(
        child: Text(
          'Show details',
          style: TextStyle(color: Colors.blueAccent),
        ),
        onPressed: () => setState(() {
          opacity = opacity == 1 ? 0.0 : 1;
        }),
      ),
      AnimatedOpacity(
        opacity: opacity,
        duration: Duration(seconds: 2),
        child: Column(
          children: <Widget>[
            Text('Type: Owl'),
            Text('Age: 39'),
            Text('Employment: None'),
          ],
        ),
      )
    ]);
  }
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: Center(
          child: FadeInDemo(),
        ),
      ),
    );
  }
}

void main() {
  runApp(
    MyApp(),
  );
}

2、AnimatedContainer

控制widget的样式属性

栗子是通过点击changebutton使AnimatedContainer widget随即获取新的样式

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

double randomBorderRadius() {
  return Random().nextDouble() * 64;
}

double randomMargin() {
  return Random().nextDouble() * 64;
}

Color randomColor() {
  return Color(0xFFFFFFFF & Random().nextInt(0xFFFFFFFF));
}

const  _duration = Duration(milliseconds: 1000);

class AnimatedContainerDemo extends StatefulWidget {
  _AnimatedContainerDemoState createState() => _AnimatedContainerDemoState();
}

class _AnimatedContainerDemoState extends State<AnimatedContainerDemo> {
  Color color;
  double borderRadius;
  double margin;

  @override
  initState() {
    super.initState();
    color = randomColor();
    borderRadius = randomBorderRadius();
    margin = randomMargin();
  }

  void change() {
    setState(() {
      color = randomColor();
      borderRadius = randomBorderRadius();
      margin = randomMargin();
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          children: <Widget>[
            SizedBox(
               128,
              height: 128,
              child: AnimatedContainer(
                margin: EdgeInsets.all(margin),
                duration: _duration,
                decoration: BoxDecoration(
                  color: color,
                  borderRadius: BorderRadius.circular(borderRadius),
                ),
              ),
            ),
            MaterialButton(
              color: Theme.of(context).primaryColor,
              child: Text(
                'change',
                style: TextStyle(color: Colors.white),
              ),
              onPressed: () => change(),
            ),
          ],
        ),
      ),
    );
  }
}

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

void main() async {
  runApp(
    MyApp(),
  );
}

3、FadeInImage

一般用于网络图片未加载完的placeholder与加载后的图片替换动画

栗子很简单，就是上面的描述

FadeInImage.assetNetwork(
              placeholder:'images/pic8.jpg',///本地图片
              image:'http://pics.sc.chinaz.com/files/pic/pic9/201909/zzpic19910.jpg',
            )

3、FadeInImage