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151 lines
5.9 KiB
Markdown
151 lines
5.9 KiB
Markdown
[#]: 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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Developing a Simple Web Application Using Flutter
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======
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[![][1]][2]
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_This article guides readers on how to run and deploy their first Web application using Flutter._
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Flutter has moved to a new stage, the Web, after having travelled a long way in Android and iOS development. Flutter 1.5 has been released by Google, along with support for Web application development.
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**Configuring Flutter for the Web**
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In order to use the Web package, enter the _flutter upgrade_ command to update to Flutter version 1.5.4.
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* Open a terminal
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* Type flutter upgrade
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* Check the version by typing _flutter –version_
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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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One can also use Android Studio 3.0 or later versions for Flutter Web development, but we will use Visual Studio Code for this tutorial.
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**Creating a new project with Flutter Web**
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Open Visual Studio Code and press _Shift+Ctrl+P_ to start a new project. Type flutter and select _New Web Project_.
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Now, name the project. I have named it _open_source_for_you_.
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Open the terminal window in VSC, and type in the following commands:
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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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Now use the following command to run the website, on localhost, with the IP address 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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Open any browser and type, _<http://127.0.0.1:8080/>_
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There is a Web folder inside the project directory which contains an _index.html_ file. The _dart_ file is compiled into a JavaScript file and is included in the HTML file using the following code:
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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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**Coding and making changes to the demo page**
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Let’s create a simple application, which will print ‘Welcome to OSFY’ on the Web page.
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Let’s now open the Dart file, which is located in the _lib_ folder _main.dart_ (the default name) (see Figure 5).
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We can now remove the debug tag using the property of _MaterialApp_, as follows:
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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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Now, adding more into the Dart file is very similar to writing code in Flutter in Dart. For that, we can declare a class titled _MyClass_, which extends the _StatelessWidget_.
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We use a _Center_ widget to position elements to the centre. We can also add a _Padding_ widget to add padding. Use the following code to obtain the output shown in Figure 5. Use the Refresh button to view the changes.
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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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Let’s add an image from the Internet – I’ve chosen the ‘Open Source for You’ logo from the magazine’s website. We use _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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The final output is shown in Figure 7.
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![Avatar][10]
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[Jis Joe Mathew][11]
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The author is assistant professor of computer science and engineering at Amal Jyoti College, Kanirapally, Kerala. He can be contacted at [jisjoemathew@gmail.com][12].
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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：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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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?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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