Flutter具有预定义的方式来更改应用程序中支架的背景颜色。
只需在main.dart（主文件）内的MaterialApp Widget中更改即可。

MaterialApp(
      title: 'Flutter',
      theme: ThemeData(
          scaffoldBackgroundColor: const Color(0xFF332F43),
           ),
      );

Color color = Colors.blue; // make it at root level

void main() {
  runApp(MaterialApp(home: Page1()));
}

在page1类中，导入上述文件。

class Page1 extends StatefulWidget {
  @override
  _Page1State createState() => _Page1State();
}

class _Page1State extends State<Page1> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: color,
      appBar: AppBar(title: Text("Page 1")),
      body: Center(
        child: Column(
          children: <Widget>[
            RaisedButton(
              onPressed: () => Navigator.push(context, MaterialPageRoute(builder: (c) => Page2())),
              child: Text("Go to Page 2"),
            ),
            RaisedButton(
              child: Text("Change color"),
              onPressed: () => setState(() => color = Colors.red),
            ),
          ],
        ),
      ),
    );
  }
}

在page2类中，导入第一个文件。

class Page2 extends StatefulWidget {
  @override
  _Page2State createState() => _Page2State();
}

class _Page2State extends State<Page2> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: color,
      appBar: AppBar(title: Text("Page 2")),
      body: Center(
        child: Column(
          children: <Widget>[
            RaisedButton(
              onPressed: () => Navigator.pop(context),
              child: Text("Back"),
            ),
            RaisedButton(
              child: Text("Change color"),
              onPressed: () => setState(() => color = Colors.green),
            ),
          ],
        ),
      ),
    );
  }
}