开源鸿蒙 Getting Started with JavaScript in the Traditional Coding Approach

2022-08-09
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Getting Started with JavaScript in the Traditional Coding Approach

NOTE
For best possible results, use DevEco Studio V3.0.0.900 Beta3 for your development.

Creating a JavaScript Project

In DevEco Studio, if no project is open, click Create Project; if a project is already open, choose File > New > Create Project. Then, select Empty Ability and click Next.

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On the project configuration page, set UI Syntax to JS and retain the default values for other parameters.

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Click Finish. DevEco Studio will automatically generate the sample code and resources that match your project type. Wait until the project is created.

JavaScript Project Files

entry: OpenHarmony project module, which can be built into an ability package (HAP).
- src > main > js: a collection of JS source code.
- src > main > js > MainAbility: entry to your application/service.
- src > main > js > MainAbility > i18n: resources in different languages, for example, UI strings and image paths.
- src > main > js > MainAbility > pages: pages contained in MainAbility.
- src > main > js > MainAbility > app.js: ability lifecycle file.
- src > main > resources: a collection of resource files used by your application/service, such as graphics, multimedia, character strings, and layout files.
- src > main > config.json: module configuration file. This file describes the global configuration information of the application/service, the device-specific configuration information, and the configuration information of the HAP file.
- build-profile.json5: current module information and build configuration options, including buildOption and targets.
- hvigorfile.js: module-level compilation and build task script. You can customize related tasks and code implementation.
build-profile.json5: application-level configuration information, including the signature and product configuration.
hvigorfile.js: application-level compilation and build task script.

Building the First Page

Use the Text component.

After the project synchronization is complete, choose entry > src > main > js > MainAbility > pages > index in the Project window and open the index.hml file. You can see that the file contains a <Text> component. The sample code in the index.hml file is shown below:

   <!--index.hml-->
   <div class="container">
       <text class="title">
           Hello World
       </text>
   </div>

Add a button and bind the onclick method to this button.

On the default page, add an <input> component of the button type to respond to user clicks and implement redirection to another page. The sample code in the index.hml file is shown below:

   <!--index.hml-->
   <div class="container">
       <text class="title">
           Hello World
       </text>
   
   <!-- Add a button, set its value to Next, and bind the onclick method to the button. -->
       <input class="btn" type="button" value="Next" onclick="onclick"></input>
   </div>

Set the page style in the index.css file.

From the Project window, choose entry > src > main > js > MainAbility > pages > index, open the index.css file, and set the page styles, such as the width, height, font size, and spacing. The sample code in the index.css file is shown below:

   .container {
       display: flex;
       flex-direction: column;
       justify-content: center;
       align-items: center;
       left: 0px;
       top: 0px;
       width: 100%;
       height: 100%;
   }
   
   .title {
       font-size: 100px;
       font-weight: bold;
       text-align: center;
       width: 100%;
       margin: 10px;
   }
   
   .btn {
       font-size: 60px;
       font-weight: bold;
       text-align: center;
       width: 40%;
       height: 5%;
       margin-top: 20px;
   }

On the toolbar in the upper right corner of the editing window, click Previewer to open the Previewer.

Below is how the first page looks on the Previewer.

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Building the Second Page

Create the second page.

In the Project window, choose entry > src > main > js > MainAbility, right-click the pages folder, choose New > Page, name the page second, and click Finish. Below, you can see the structure of the second folder.

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Add <Text> and <Button> components.

Add <Text> and <Button> components and set their styles, as you do for the first page. The sample code in the second.hml file is shown below:

   <!--second.hml-->
   <div class="container">
       <text class="title">
           Hi there
       </text>
   
   <!-- Add a button, set the value to Back, and bind the back method to the button.-->
       <input class="btn" type="button" value="Back" onclick="back"></input>
   </div>

Set the page style in the second.css file. The sample code in the second.css file is shown below:

   .container {
       display: flex;
       flex-direction: column;
       justify-content: center;
       align-items: center;
       left: 0px;
       top: 0px;
       width: 100%;
       height: 100%;
   }
   
   .title {
       font-size: 100px;
       font-weight: bold;
       text-align: center;
       width: 100%;
       margin: 10px;
   }
   
   .btn {
       font-size: 60px;
       font-weight: bold;
       text-align: center;
       width: 40%;
       height: 5%;
       margin-top: 20px;
   }

Implementing Page Redirection

You can implement page redirection through the page router, which finds the target page based on the page URL. Import the router module and then perform the steps below:

Implement redirection from the first page to the second page.

In the index.js file of the first page, bind the onclick method to the button so that clicking the button redirects the user to the second page. The sample code in the index.js file is shown below:

   // index.js
   import router from '@ohos.router';
   
   export default {
       onclick: function () {
           router.push({
               url: "pages/second/second"
           })
       }
   }

Implement redirection from the second page to the first page.

In the second.ets file of the second page, bind the back method to the Back button so that clicking the button redirects the user back to the first page. The sample code in the second.js file is shown below:

   // second.js
   import router from '@ohos.router';
   
   export default {
       back: function () {
           router.back()
       }
   }

Open any file in the index folder and click in the Previewer to refresh the file. The figure below shows the effect.

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Running the Application on a Real Device

Connect the development board running the OpenHarmony standard system to the computer.
Choose File > Project Structure > Project > Signing Configs, select Automatically generate signing, wait until the automatic signing is complete, and click OK, as shown below.

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On the toolbar in the upper right corner of the editing window, click . The display effect is shown in the figure below.

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Congratulations! You have finished developing your OpenHarmony application in JavaScript in the traditional coding approach. To learn more about OpenHarmony, see OpenHarmony Overview