小编map*_*rup的帖子

他大家，

我有以下代码的问题：

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Stack(
      children: <Widget>[
        Expanded(
          child: PageView(
            children: <Widget>[
              Container(
                color: Colors.red,
              ),
              Container(
                color: Colors.yellow,
              ),
              Container(
                color: Colors.green,
              ),
              Container(
                color: Colors.blue,
              ), …