Flutter双击退出应用

WillPopScope 注册一个回调 onWillPop 用来自定义用户对路由的操作

（1）自定义双击退出回调函数

int _lastClickTime = 0;

Future<bool> _doubleClickExit() {
  int nowTime = new DateTime.now().microsecondsSinceEpoch;
  if (_lastClickTime != 0 && nowTime - _lastClickTime > 1500) {
    return new Future.value(true);
  } else {
    print('Click again to exist!');
    _lastClickTime = new DateTime.now().microsecondsSinceEpoch;
    new Future.delayed(const Duration(milliseconds: 1500), () {
      _lastClickTime = 0;
    });
    return new Future.value(false);
  }
}

（2）将事先创建好的子节点 _getBody() 嵌套在 WillPopScope 中

class _HomePageState extends State<HomePage> {
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(title: new Text('Home'),),
      body: WillPopScope(
        onWillPop: _doubleClickExit,
        child: _getBody(),
      )
    );
  }