如何在双击时动态隐藏AppBar？

Question

我想在容器上的 DoubleTap 上动态隐藏和显示应用程序栏，并带有一些隐藏动画，但此链接的解决方案不适用于我的项目：Flutter - How can Idynamic show or hide App Bars onpages

该应用程序的图片：

代码：

import 'package:flutter/material.dart';

class GeneratedCouponScreen extends StatelessWidget {

  bool ShowAppBar = true;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: ShowAppBar ? AppBar(
        title: Text('Makdolan Flutter'),
      ) : null ,
      backgroundColor: Colors.white,
      body: GestureDetector(
        onDoubleTap: () {
          ShowAppBar = false;
        },
        child: Container(
        padding: EdgeInsets.all(16.0),
        child: Column(
          children: [
            Row(
            mainAxisAlignment: MainAxisAlignment.spaceBetween,
            children: [
              Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: [
                  Text('DATA WYDANIA:', style: TextStyle(color: Colors.black),),
                  Text('10/09/2019', style: TextStyle(color: Colors.black))
                ],
              ),
              Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: [
                  Text('UNIKALNY KOD:', style: TextStyle(color: Colors.black)),
                  Text('e-86-tC-9', style: TextStyle(color: Colors.black))
                ],
              )
              ],
            ),
            Column(
              children: [
                SizedBox(height: 8.0),
                Image.asset('assets/images/coupon_hamburger.png',)
              ],
            )
          ],
        )
      ),
    ));
  }
}

Answer 1

使用setState

onDoubleTap: () {
  setState(() => ShowAppBar = false); // you missed setState
}

更新（完整代码）：

void main() => runApp(MaterialApp(home: YourPage()));

class YourPage extends StatefulWidget {
  @override
  _YourPageState createState() => _YourPageState();
}

class _YourPageState extends State<YourPage> {
  bool _showAppBar = true;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: _showAppBar ? AppBar() : null,
      body: Center(
        child: GestureDetector(
          onDoubleTap: () => setState(() => _showAppBar = !_showAppBar),
          child: Container(
            width: 200,
            height: 200,
            color: Colors.blue,
          ),
        ),
      ),
    );
  }
}