您没有使用动画对象。
import 'dart:async';import 'package:flutter/material.dart';void main() { runApp(new MaterialApp( debugShowCheckedModeBanner: false, home: new MyApp(), ));}class MyApp extends StatefulWidget { @override MyAppState createState() => new MyAppState();}class MyAppState extends State<MyApp> { @override Widget build(BuildContext context) { return new Scaffold( appBar: new AppBar( title: new Text('Slider Demo'), ), body: new Container( color: Colors.blueAccent, padding: new EdgeInsets.all(32.0), child: new ProgressIndicatorDemo(), ), ); }}class ProgressIndicatorDemo extends StatefulWidget { @override _ProgressIndicatorDemoState createState() => new _ProgressIndicatorDemoState();}class _ProgressIndicatorDemoState extends State<ProgressIndicatorDemo> with SingleTickerProviderStateMixin { AnimationController controller; Animation<double> animation; @override void initState() { super.initState(); controller = AnimationController( duration: const Duration(milliseconds: 2000), vsync: this); animation = Tween(begin: 0.0, end: 1.0).animate(controller) ..addListener(() { setState(() { // the state that has changed here is the animation object’s value }); }); controller.repeat(); } @override void dispose() { controller.stop(); super.dispose(); } @override Widget build(BuildContext context) { return new Center( child: new Container( child: LinearProgressIndicator( value: animation.value,), ) ); }}
