flutter 广告页-3秒读数后或者点击跳过广告按钮后跳转

/**
 * 广告页，3秒自动跳转到首页
 */

import 'dart:async';

import 'package:flutter/material.dart';
import 'package:zybdapp/youshang/main_screen.dart';

void main() {
  runApp(new MaterialApp(
    title: 'ad',
    home: new SplashScreen(),
    routes: <String, WidgetBuilder>{
      '/main': (BuildContext context) => new MainScreen()
    },
  ));
}

class SplashScreen extends StatefulWidget {
  @override
  _SplashScreenState createState() => new _SplashScreenState();
}

class _SplashScreenState extends State<SplashScreen> {
  Timer _timer;
  int count = 3;

  startTime() async {
    //设置启动图生效时间
    var _duration = new Duration(seconds: 1);
    new Timer(_duration, () {
      // 空等1秒之后再计时
      _timer = new Timer.periodic(const Duration(milliseconds: 1000), (v) {
        count--;
        if (count == 0) {
          navigationPage();
        } else {
          setState(() {});
        }
      });
      return _timer;
    });
  }

  void navigationPage() {
    _timer.cancel();
    Navigator.of(context).pushReplacementNamed('/main');
  }

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

  @override
  Widget build(BuildContext context) {
    return new Stack(
      alignment: const Alignment(1.0, -1.0), // 右上角对齐
      children: [
        new ConstrainedBox(
          constraints: BoxConstraints.expand(),
          child: new Image.asset(
            "assets/images/ad.jpg",
            fit: BoxFit.fill,
          ),
        ),
        new Padding(
          padding: new EdgeInsets.fromLTRB(0.0, 30.0, 10.0, 0.0),
          child: new FlatButton(
            onPressed: () {
              navigationPage();
            },
//            padding: EdgeInsets.all(0.0),
            color: Colors.grey,
            child: new Text(
              "$count 跳过广告",
              style: new TextStyle(color: Colors.white, fontSize: 12.0),
            ),
          ),
        )
      ],
    );
  }
}