Flutter學(xué)習(xí)筆記（26）--返回?cái)r截WillPopScope，實(shí)現(xiàn)1秒內(nèi)點(diǎn)擊兩次返回按鈕退出程序

const WillPopScope({
  Key key,
  @required this.child,
  @required this.onWillPop,//回調(diào)函數(shù)，當(dāng)用戶(hù)點(diǎn)擊返回按鈕時(shí)調(diào)用
})

DateTime.now()

DateTime.now().difference(_lastPressedAt)

DateTime.now().difference(_lastPressedAt) > Duration(seconds: 1)

import 'package:flutter/material.dart';

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

class DemoApp extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return new DemoAppState();
  }
}

class DemoAppState extends State<DemoApp> {
  DateTime _lastPressedAt;//上次點(diǎn)擊的時(shí)間
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'WillPopScope Demo',
      home: new Scaffold(
        appBar: new AppBar(
          title: new Text('WillPopScope Demo'),
        ),
        body: new WillPopScope(
            child: new Center(
              child: new Text('WillPopScope'),
            ),
            onWillPop: () async{
              if(_lastPressedAt == null || (DateTime.now().difference(_lastPressedAt) > Duration(seconds: 1))){
                //兩次點(diǎn)擊間隔超過(guò)1秒，重新計(jì)時(shí)
                _lastPressedAt = DateTime.now();
                print(_lastPressedAt);
                return false;
              }
              return true;
            }
        ),
      ),
    );
  }
}