问使AppBar透明并显示设置为全屏的背景图像

EN

import 'package:flutter/material.dart';

void main() => runApp(new MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      home: new Home(),
    );
  }
}

class Home extends StatefulWidget {
  @override
  _HomeState createState() => _HomeState();
}

class _HomeState extends State<Home> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Stack(
        children: <Widget>[
          Scaffold(
            backgroundColor: Colors.transparent,
            appBar: new AppBar(
              title: new Text(
                "Hello World",
                style: TextStyle(color: Colors.amber),
              ),
              backgroundColor: Colors.transparent,
              elevation: 0.0,
            ),
            body: new Container(
              color: Colors.red,
            ),
          ),
        ],
      ),
    );
  }
}

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      extendBodyBehindAppBar: true,
      backgroundColor: Colors.red,
      appBar: AppBar(
//        backgroundColor: Colors.transparent,
        backgroundColor: Color(0x44000000),
        elevation: 0,
        title: Text("Title"),
      ),
      body: Center(child: Text("Content")),
    );
  }

  @Override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(
          widget.title,
          style: TextStyle(color: Colors.black),
        ),
        backgroundColor: Colors.transparent,
        elevation: 0.0,
      ),
      extendBodyBehindAppBar: true,
      body: Container(
        width: double.infinity,
        height: double.infinity,
        decoration: BoxDecoration(
          image: DecorationImage(
            image: AssetImage('assets/background/home.png'),
            fit: BoxFit.cover,
          ),
        ),
        child: SafeArea(
            child: Center(
          child: Container(
            width: 300,
            height: 300,
            decoration: BoxDecoration(
              color: Colors.green,
            ),
            child: Center(child: Text('Test')),
          ),
        )),
      ),
    );
  }