Flutter组件学习（22）导航返回拦截（WillPopScope）

简介

Flutter中可以通过WillPopScope来实现返回按钮拦截

onWillPop是一个WillPopScope的回调函数，当用户点击返回按钮时被调用

WillPopScope必须包含child，否则会报错

实现双击返退出APP

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:fluttertoast/fluttertoast.dart';

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

class MyApp extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return WillPopTest();
  }
}

class WillPopTest extends State {
  DateTime _lastTime;
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          backgroundColor: Colors.blue,
          centerTitle: true,
          title: Text(
            '实现二次点击退出',
            style: TextStyle(fontSize: 18, color: Colors.white),
          ),
        ),
        body: WillPopScope(
          onWillPop: ()async{
            if(_lastTime==null||DateTime.now().difference(_lastTime)>Duration(seconds: 1)){
              _lastTime=DateTime.now();
              Fluttertoast.showToast(msg: "再点击一次退出app",
                fontSize: 16,
                backgroundColor: Colors.blue,
                textColor: Colors.white
              );
              return false;
            }
            return true;
          },
          child: Container(
            alignment: Alignment.center,
            child: Text(
              "1秒内连续按两次返回键退出",
              style: TextStyle(fontSize: 30),
            ),
          ),
        ),
      ),
    );
  }
}

运行效果