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Merge pull request #16398 from wxy/20191115-Developing-a-Simple-Web-Application-Using-Flutter
PRF&PUB:20191115 Developing a Simple Web Application Using Flutter
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[#]: collector: (lujun9972)
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[#]: translator: (geekpi)
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[#]: reviewer: (wxy)
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[#]: publisher: (wxy)
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[#]: url: (https://linux.cn/article-11604-1.html)
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[#]: subject: (Developing a Simple Web Application Using Flutter)
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[#]: via: (https://opensourceforu.com/2019/11/developing-a-simple-web-application-using/)
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[#]: author: (Jis Joe Mathew https://opensourceforu.com/author/jis-joe/)
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使用 Flutter 开发简单的 Web 应用
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======
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![][2]
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> 本文指导读者如何使用 Flutter 运行和部署第一个 Web 应用。
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Flutter 在 Android 和 iOS 开发方面走了很长一段路之后，已经迈入了一个新的阶段，即 Web 开发。Google 发布了 Flutter 1.5，同时支持 Web 应用开发。
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### 为 Web 开发配置 Flutter
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为了使用 Web 包，输入命令 `flutter upgrade` 更新到 Flutter 1.5.4。
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* 打开终端
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* 输入 `flutter upgrade`
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* 输入 `flutter –version` 检查版本
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![图 1: 升级 Flutter 到最新版][3]
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也可以将 Android Studio 3.0 或更高版本用于 Flutter Web 开发，但在本教程中，我们使用 Visual Studio Code。
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### 使用 Flutter Web 创建新项目
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打开 Visual Studio Code，然后按 `Shift+Ctrl+P` 开始一个新项目。输入 `flutter` 并选择 “New Web Project”。
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![图 2：在 VSC 中开始一个新的 Flatter 项目][4]
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现在，为项目命名。我将其命名为 `open_source_for_you`。
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![图 3: 给项目命名][5]
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在 VSC 中打开终端窗口，然后输入以下命令：
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```
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flutter packages pub global activate webdev
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flutter packages upgrade
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```
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现在，使用以下命令在 localhost 上运行网站，IP 地址是 127.0.0.1。
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```
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flutter packages pub global run webdev serve
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```
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打开任何浏览器，然后输入 `http://127.0.0.1:8080/`。
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![图 4：运行于 8080 端口的 Flutter 演示应用][6]
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在项目目录中有个 Web 文件夹，其中包含了 `index.html`。`dart` 文件被编译成 JavaScript 文件，并使用以下代码包含在 HTML 文件中：
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```
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<script defer src="main.dart.js" type="application/javascript"></script>
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```
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### 编码和修改演示页面
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让我们创建一个简单的应用，它会在网页上打印 “Welcome to OSFY”。
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现在打开 Dart 文件，它位于 `lib` 文件夹 `main.dart`（默认名）中（参见图 5）。
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![图 5：main.dart 文件的位置][7]
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现在，我们可以在 `MaterialApp` 的属性中删除调试标记，如下所示：
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```
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debugShowCheckedModeBanner: false
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```
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现在，向 Dart 中添加更多内容与用 Dart 编写 Flutter 很类似。为此，我们可以声明一个名为 `MyClass` 的类，它继承了 `StatelessWidget`。
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我们使用 `Center` 部件将元素定位到中心。我们还可以添加 `Padding` 部件来添加填充。使用以下代码获得图 5 所示的输出。使用刷新按钮查看更改。
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```
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class MyClass extends StatelessWidget {
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@override
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Widget build(BuildContext context) {
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return Scaffold(
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body: Center(
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child: Column(
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mainAxisAlignment: MainAxisAlignment.center,
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children: <Widget>[
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Padding(
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padding: EdgeInsets.all(20.0),
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child: Text(
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'Welcome to OSFY',
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style: TextStyle(fontSize: 24.0, fontWeight: FontWeight.bold),
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),
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),
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],
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),
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),
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);
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}
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}
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```
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![图 6：MyClass 的输出][8]
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让我们从互联网中添加一张图片，我已经从一个杂志网站选择了一张 “Open Source for You” 徽标。我们使用 `Image.network`。
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```
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Image.network(
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'https://opensourceforu.com/wp-content/uploads/2014/03/OSFY-Logo.jpg',
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height: 100,
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width: 150
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),
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```
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最终输出如图 7 所示。
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![图 7：最终输出][9]
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--------------------------------------------------------------------------------
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via: https://opensourceforu.com/2019/11/developing-a-simple-web-application-using/
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作者：[Jis Joe Mathew][a]
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选题：[lujun9972][b]
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译者：[geekpi](https://github.com/geekpi)
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校对：[wxy](https://github.com/wxy)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]: https://opensourceforu.com/author/jis-joe/
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[b]: https://github.com/lujun9972
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[1]: https://i1.wp.com/opensourceforu.com/wp-content/uploads/2019/11/Screenshot-from-2019-11-15-16-20-30.png
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[2]: https://i1.wp.com/opensourceforu.com/wp-content/uploads/2019/11/Screenshot-from-2019-11-15-16-20-30.png
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[3]: https://i0.wp.com/opensourceforu.com/wp-content/uploads/2019/11/Figure-1-Upgrading-Flutter-to-the-latest-version.jpg
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[4]: https://i0.wp.com/opensourceforu.com/wp-content/uploads/2019/11/Figure-2-Starting-a-new-Flutter-Web-project-in-VSC.jpg
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[5]: https://i2.wp.com/opensourceforu.com/wp-content/uploads/2019/11/Figure-3-Naming-the-project.jpg
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[6]: https://i0.wp.com/opensourceforu.com/wp-content/uploads/2019/11/Figure-4-The-Flutter-demo-application-running-on-port-8080.jpg
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[7]: https://i2.wp.com/opensourceforu.com/wp-content/uploads/2019/11/Figure-5-Location-of-main.dart-file.jpg
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[8]: https://i2.wp.com/opensourceforu.com/wp-content/uploads/2019/11/Figure-6-Output-of-MyClass.jpg
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[9]: https://i0.wp.com/opensourceforu.com/wp-content/uploads/2019/11/Figure-7-Final-output.jpg
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[10]: https://secure.gravatar.com/avatar/64db0e07799ae14fd1b51d0633db6593?s=100&r=g
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[11]: https://opensourceforu.com/author/jis-joe/
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[12]: mailto:jisjoemathew@gmail.com
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[13]: https://opensourceforu.com/wp-content/uploads/2019/11/assoc.png
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[14]: https://feedburner.google.com/fb/a/mailverify?uri=LinuxForYou&loc=en_US
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@ -1,150 +0,0 @@
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[#]: collector: (lujun9972)
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[#]: translator: (geekpi)
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[#]: reviewer: ( )
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[#]: publisher: ( )
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[#]: url: ( )
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[#]: subject: (Developing a Simple Web Application Using Flutter)
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[#]: via: (https://opensourceforu.com/2019/11/developing-a-simple-web-application-using/)
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[#]: author: (Jis Joe Mathew https://opensourceforu.com/author/jis-joe/)
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使用 Flutter 开发简单的 Web 应用
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======
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[![][1]][2]
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|
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_本文指导读者如何使用 Flutter 运行和部署第一个 Web 应用。_
|
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|
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Flutter 在 Android 和 iOS 开发方面走了很长一段路之后，已经迈入了一个新的阶段，即 Web。Google 发布了 Flutter 1.5，同时支持 Web 应用开发。
|
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|
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**为 Web 配置 Flutter**
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为了使用 Web 包，输入命令 _flutter upgrade_ 更新到 Flutter 1.5.4。
|
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|
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* 打开终端
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* 输入 flutter upgrade
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* 输入 _flutter –version_ 检查版本
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![Figure 1: Upgrading Flutter to the latest version][3]
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![Figure 2: Starting a new Flutter Web project in VSC][4]
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也可以将 Android Studio 3.0 或更高版本用于 Flutter Web 开发，但在本教程中，我们使用 Visual Studio Code。
|
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**使用 Flutter Web 创建新项目**
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打开 Visual Studio Code，然后按 _Shift+Ctrl+P_ 开始一个新项目。输入 flutter 并选择 _New Web Project_。
|
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现在，为项目命名。我将其命名为 _open_source_for_you_。
|
||||
在 VSC 中打开终端窗口，然后输入以下命令：
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|
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```
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flutter packages pub global activate webdev
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flutter packages upgrade
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```
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现在，使用以下命令在 localhost 上运行网站，IP 地址是 127.0.0.1。
|
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```
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flutter packages pub global run webdev serve
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||||
```
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打开任何浏览器，然后输入 _<http://127.0.0.1:8080/>_。
|
||||
在项目目录中有个 Web 文件夹，其中包含了 _index.html_。 _dart_ 文件被编译成 JavaScript 文件，并使用以下代码包含在 HTML 文件中：
|
||||
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```
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||||
<script defer src="main.dart.js" type="application/javascript"></script>
|
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```
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||||
|
||||
**编码和修改演示页面**
|
||||
让我们创建一个简单的应用，它会在网页上打印 “ Welcome to OSFY”。
|
||||
现在打开 Dart 文件，它位于 _lib_ 文件夹 _main.dart_（默认名）中（参见图 5）。
|
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现在，我们可以在 _MaterialApp_ 的属性中删除调试标记，如下所示：
|
||||
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```
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debugShowCheckedModeBanner: false
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```
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![Figure 3: Naming the project][5]
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![Figure 4: The Flutter demo application running on port 8080][6]
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![Figure 5: Location of main.dart file][7]
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现在，向 Dart 中添加更多内容与在 Dart 中编写 Flutter 类似。为此，我们可以声明一个名为 _MyClass_ 的类，它继承了 _StatelessWidget_。
|
||||
我们使用 _Center_ 部件将元素定位到中心。我们还可以添加 _Padding_ 部件来添加填充。使用以下代码获得图 5 所示的输出。使用刷新按钮查看更改。
|
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```
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class MyClass extends StatelessWidget {
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@override
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Widget build(BuildContext context) {
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return Scaffold(
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body: Center(
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child: Column(
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mainAxisAlignment: MainAxisAlignment.center,
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children: <Widget>[
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Padding(
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padding: EdgeInsets.all(20.0),
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child: Text(
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'Welcome to OSFY',
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style: TextStyle(fontSize: 24.0, fontWeight: FontWeight.bold),
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),
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),
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],
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),
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),
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);
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}
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}
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```
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![Figure 6: Output of MyClass][8]
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![Figure 7: Final output][9]
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让我们从互联网中添加一张图片，我已经从一个杂志网站选择了一张 “Open Source for You” 的 logo。我们使用 _Image.network_。
|
||||
|
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```
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Image.network(
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'https://opensourceforu.com/wp-content/uploads/2014/03/OSFY-Logo.jpg',
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height: 100,
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width: 150
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),
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```
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最终输出如图 7 所示。
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![Avatar][10]
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[Jis Joe Mathew][11]
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作者是喀拉拉邦卡尼拉帕利阿玛尔·乔蒂学院的计算机科学与工程助理教授。可以通过 [jisjoemathew@gmail.com][12] 与他联系。
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[![][13]][14]
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--------------------------------------------------------------------------------
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via: https://opensourceforu.com/2019/11/developing-a-simple-web-application-using/
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作者：[Jis Joe Mathew][a]
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选题：[lujun9972][b]
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||||
译者：[geekpi](https://github.com/geekpi)
|
||||
校对：[校对者ID](https://github.com/校对者ID)
|
||||
|
||||
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
|
||||
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||||
[a]: https://opensourceforu.com/author/jis-joe/
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[b]: https://github.com/lujun9972
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[1]: https://i1.wp.com/opensourceforu.com/wp-content/uploads/2019/11/Screenshot-from-2019-11-15-16-20-30.png?resize=696%2C495&ssl=1 (Screenshot from 2019-11-15 16-20-30)
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[2]: https://i1.wp.com/opensourceforu.com/wp-content/uploads/2019/11/Screenshot-from-2019-11-15-16-20-30.png?fit=900%2C640&ssl=1
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[3]: https://i0.wp.com/opensourceforu.com/wp-content/uploads/2019/11/Figure-1-Upgrading-Flutter-to-the-latest-version.jpg?resize=350%2C230&ssl=1
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[4]: https://i0.wp.com/opensourceforu.com/wp-content/uploads/2019/11/Figure-2-Starting-a-new-Flutter-Web-project-in-VSC.jpg?resize=350%2C93&ssl=1
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[5]: https://i2.wp.com/opensourceforu.com/wp-content/uploads/2019/11/Figure-3-Naming-the-project.jpg?resize=350%2C147&ssl=1
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[6]: https://i0.wp.com/opensourceforu.com/wp-content/uploads/2019/11/Figure-4-The-Flutter-demo-application-running-on-port-8080.jpg?resize=350%2C111&ssl=1
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[7]: https://i2.wp.com/opensourceforu.com/wp-content/uploads/2019/11/Figure-5-Location-of-main.dart-file.jpg?resize=350%2C173&ssl=1
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[8]: https://i2.wp.com/opensourceforu.com/wp-content/uploads/2019/11/Figure-6-Output-of-MyClass.jpg?resize=350%2C173&ssl=1
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[9]: https://i0.wp.com/opensourceforu.com/wp-content/uploads/2019/11/Figure-7-Final-output.jpg?resize=350%2C167&ssl=1
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[10]: https://secure.gravatar.com/avatar/64db0e07799ae14fd1b51d0633db6593?s=100&r=g
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[11]: https://opensourceforu.com/author/jis-joe/
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[12]: mailto:jisjoemathew@gmail.com
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[13]: https://opensourceforu.com/wp-content/uploads/2019/11/assoc.png
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[14]: https://feedburner.google.com/fb/a/mailverify?uri=LinuxForYou&loc=en_US
|
||||
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