我是第一次开发Flutter应用程序。我在添加图片时遇到问题。我有以下问题：

1. 在哪里创建图片文件夹？
2. 在pubspec.ymal中的哪里添加资产标签？
3. 为此需要任何资产文件夹吗？

我试过了

 assets:
    - images/lake.jpg

在pubspec.ymal内部：

完整档案：

name: my_flutter_app
description: A new Flutter application.

dependencies:
  flutter:
    sdk: flutter

  cupertino_icons: ^0.1.2

dev_dependencies:
  flutter_test:
    sdk: flutter

flutter:
  uses-material-design: true,
  assets:
    - images/lake.jpg

错误日志：

#/properties/flutter/properties/uses-material-design: type: wanted [boolean] got true,
Error detected in pubspec.yaml:
Error building assets

FAILURE: Build failed with an exception.

* Where:
Script '/home/abc/Downloads/flutter/packages/flutter_tools/gradle/flutter.gradle' line: 435

* What went wrong:
Execution failed for task ':app:flutterBuildDebug'.
> Process 'command '/home/abc/Downloads/flutter/bin/flutter'' finished with non-zero exit value 1

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

* Get more help at https://help.gradle.org

BUILD FAILED in 1s
Finished with error: Gradle build failed: 1

我的main.dart代码：

// Copyright 2017 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:flutter/material.dart';
// Uncomment lines 7 and 10 to view the visual layout at runtime.
//import 'package:flutter/rendering.dart' show debugPaintSizeEnabled;

void main() {
  //debugPaintSizeEnabled = true;
  runApp(new MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    Widget titleSection = new Container(
      padding: const EdgeInsets.all(32.0),
      child: new Row(
        children: [
          new Expanded(
            child: new Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: [
                new Container(
                  padding: const EdgeInsets.only(bottom: 8.0),
                  child: new Text(
                    'Oeschinen Lake Campground',
                    style: new TextStyle(
                      fontWeight: FontWeight.bold,
                    ),
                  ),
                ),
                new Text(
                  'Kandersteg, Switzerland',
                  style: new TextStyle(
                    color: Colors.grey[500],
                  ),
                ),
              ],
            ),
          ),
          new Icon(
            Icons.star,
            color: Colors.red[500],
          ),
          new Text('41'),
        ],
      ),
    );

    Column buildButtonColumn(IconData icon, String label) {
      Color color = Theme.of(context).primaryColor;

      return new Column(
        mainAxisSize: MainAxisSize.min,
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          new Icon(icon, color: color),
          new Container(
            margin: const EdgeInsets.only(top: 8.0),
            child: new Text(
              label,
              style: new TextStyle(
                fontSize: 12.0,
                fontWeight: FontWeight.w400,
                color: color,
              ),
            ),
          ),
        ],
      );
    }

    Widget buttonSection = new Container(
      child: new Row(
        mainAxisAlignment: MainAxisAlignment.spaceEvenly,
        children: [
          buildButtonColumn(Icons.call, 'CALL'),
          buildButtonColumn(Icons.near_me, 'ROUTE'),
          buildButtonColumn(Icons.share, 'SHARE'),
        ],
      ),
    );

    Widget textSection = new Container(
      padding: const EdgeInsets.all(32.0),
      child: new Text(
        '''
Lake Oeschinen lies at the foot of the Blüemlisalp in the Bernese Alps. Situated 1,578 meters above sea level, it is one of the larger Alpine Lakes. A gondola ride from Kandersteg, followed by a half-hour walk through pastures and pine forest, leads you to the lake, which warms to 20 degrees Celsius in the summer. Activities enjoyed here include rowing, and riding the summer toboggan run.
        ''',
        softWrap: true,
      ),
    );

    return new MaterialApp(
      title: 'Flutter Demo',
      home: new Scaffold(
        appBar: new AppBar(
          title: new Text('Top Lakes'),
        ),
        body: new ListView(
          children: [
            new Image.asset(
              'images/lake.jpg',
              width: 600.0,
              height: 240.0,
              fit: BoxFit.cover,
            ),
            titleSection,
            buttonSection,
            textSection,
          ],
        ),
      ),
    );
  }
}

我指的是本教程
https://flutter.io/tutorials/layout/

我也想问一问，有什么工具可以在flutter中进行干净的重建，因为我找不到任何选择。

任何帮助，将不胜感激。

谢谢 ！