application-dev/quick-start/start-with-ets-fa.md

# Building the First ArkTS Application in FA Model


>  **NOTE**
>
>  To use ArkTS, your DevEco Studio must be V3.0.0.601 Beta1 or later.
>
>  For best possible results, use [DevEco Studio 3.1 Beta2](https://developer.harmonyos.com/cn/develop/deveco-studio) for your development.


## Creating an ArkTS Project

1. If you are opening DevEco Studio for the first time, click **Create Project**. If a project is already open, choose **File** > **New** > **Create Project** from the menu bar. On the **Choose Your Ability Template** page, select **Application** (or **Atomic Service**, depending on your project), select **Empty Ability** as the template, and click **Next**.

   ![createProject](figures/createProject.png)

2. In the project configuration page, set **Compile SDK** to **8** or **9** (in the latter case, you also need to set **Model** to **FA**) and **Language** to **ArkTS** and retain the default values for other parameters.

   ![chooseFAModel_ets](figures/chooseFAModel_ets.png)

   > **NOTE**
   >
   > If you are using DevEco Studio V3.0 Beta3 or later, you can use the low-code development mode apart from the traditional coding approach.
   >
   > On the low-code development pages, you can design your application UI in an efficient, intuitive manner, with a wide array of UI editing features.
   >
   > To use the low-code development mode, turn on **Enable Super Visual** on the page shown above.

3. Click **Finish**. DevEco Studio will automatically generate the sample code and resources that match your project type. Wait until the project is created.
4. After the project is created, in the **entry** > **build-profile.json5** file, change **runtimeOS** under **targets** to **OpenHarmony**, and click **Sync Now** in the upper right corner to start development.


## ArkTS Project Directory Structure (FA Model)

![en-us_image_0000001384652328](figures/en-us_image_0000001384652328.png)

- **entry**: OpenHarmony project module, which can be built into an OpenHarmony Ability Package ([HAP](../../glossary.md#hap)).
  - **src > main > ets**: a collection of ArkTS source code.
  - **src > main > ets > MainAbility**: entry to your application/service.
  - **src > main > ets > MainAbility > pages**: pages contained in **MainAbility**.
  - **src > main > ets > MainAbility > pages > index.ets**: the first page in the **pages** list, also referred to as the entry to the application.
  - **src > main > ets > MainAbility > app.ets**: 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. For details about resource files, see [Resource Categories and Access](resource-categories-and-access.md#resource-categories).
  - **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. For details, see [Application Configuration File Overview (FA Model)](application-configuration-file-overview-fa.md).
  - **build-profile.json5**: current module information and build configuration options, including **buildOption** and **targets**. Under **targets**, you can set **runtimeOS** to **HarmonyOS** (default) or **OpenHarmony**, depending on the OS of your application.
  - **hvigorfile.ts**: module-level build script. You can customize related tasks and code implementation.
- **build-profile.json5**: application-level configuration information, including the signature and product configuration.
- **hvigorfile.ts**: application-level build script.


## Building the First Page

1. Use the **\<Text>** component.

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

   ```ts
   // index.ets
   @Entry
   @Component
   struct Index {
     @State message: string = 'Hello World'

     build() {
       Row() {
         Column() {
           Text(this.message)
             .fontSize(50)
             .fontWeight(FontWeight.Bold)
         }
         .width('100%')
       }
       .height('100%')
     }
   }
   ```

2. Add a **\<Button>** component.

   On the default page, add a **\<Button>** component to respond to user clicks and implement redirection to another page. The sample code in the **index.ets** file is shown below:

   ```ts
   // index.ets
   @Entry
   @Component
   struct Index {
     @State message: string = 'Hello World'

     build() {
       Row() {
         Column() {
           Text(this.message)
             .fontSize(50)
             .fontWeight(FontWeight.Bold)
           // Add a button to respond to user clicks.
           Button() {
             Text('Next')
               .fontSize(30)
               .fontWeight(FontWeight.Bold)
           }
           .type(ButtonType.Capsule)
           .margin({
             top: 20
           })
           .backgroundColor('#0D9FFB')
           .width('40%')
           .height('5%')
         }
         .width('100%')
       }
       .height('100%')
     }
   }
   ```

3. On the toolbar in the upper right corner of the editing window, click **Previewer**. Below is how the first page looks in the Previewer.

   ![en-us_image_0000001311334976](figures/en-us_image_0000001311334976.png)


## Building the Second Page

1. Create the second page.

   - Create the second page file: In the **Project** window, choose **entry** > **src** > **main** > **ets** > **MainAbility**. Right-click the **pages** folder, choose **New** > **ArkTS File**, name the page **second**, and click **Finish**. Below is the structure of the **second** folder.
      ![en-us_image_0000001311334932](figures/en-us_image_0000001311334932.png)

      > **NOTE**
      >
      > You can also right-click the **pages** folder and choose **New** > **Page** from the shortcut menu. In this scenario, you do not need to manually configure page routes.
   - Configure the route for the second page, by setting **pages/second** under **module - js - pages** in the **config.json** file. The sample code is as follows:

      ```json
      {
        "module": {
          "js": [
            {
              "pages": [
                "pages/index",
                "pages/second"
              ]
              }
          ]
        }
      }
      ```

2. 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.ets** file is shown below:

   ```ts
   // second.ets
   @Entry
   @Component
   struct Second {
     @State message: string = 'Hi there'

     build() {
       Row() {
         Column() {
           Text(this.message)
             .fontSize(50)
             .fontWeight(FontWeight.Bold)
           Button() {
             Text('Back')
               .fontSize(25)
               .fontWeight(FontWeight.Bold)
           }
           .type(ButtonType.Capsule)
           .margin({
             top: 20
           })
           .backgroundColor('#0D9FFB')
           .width('40%')
           .height('5%')
         }
         .width('100%')
       }
       .height('100%')
     }
   }
   ```


## Implementing Page Redirection

You can implement page redirection through the [page router](../reference/apis/js-apis-router.md), which finds the target page based on the page URL. Import the **router** module and then perform the steps below:

1. Implement redirection from the first page to the second page.

   In the **index.ets** file of the first page, bind the **onClick** event to the **Next** button so that clicking the button redirects the user to the second page. The sample code in the **index.ets** file is shown below:

   ```ts
   // index.ets
   // Import the router module.
   import router from '@ohos.router';

   @Entry
   @Component
   struct Index {
     @State message: string = 'Hello World'

     build() {
       Row() {
         Column() {
           Text(this.message)
             .fontSize(50)
             .fontWeight(FontWeight.Bold)
           // Add a button to respond to user clicks.
           Button() {
             Text('Next')
               .fontSize(30)
               .fontWeight(FontWeight.Bold)
           }
           .type(ButtonType.Capsule)
           .margin({
             top: 20
           })
           .backgroundColor('#0D9FFB')
           .width('40%')
           .height('5%')
           // Bind the onClick event to the Next button so that clicking the button redirects the user to the second page.
           .onClick(() => {
             router.push({ url: 'pages/second' })
             // In a project of API version 9, you can use the API below instead:
             // router.pushUrl({ url: 'pages/second' })

           })
         }
         .width('100%')
       }
       .height('100%')
     }
   }
   ```

2. Implement redirection from the second page to the first page.

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

   ```ts
   // second.ets
   // Import the router module.
   import router from '@ohos.router';

   @Entry
   @Component
   struct Second {
     @State message: string = 'Hi there'

     build() {
       Row() {
         Column() {
           Text(this.message)
             .fontSize(50)
             .fontWeight(FontWeight.Bold)
           Button() {
             Text('Back')
               .fontSize(25)
               .fontWeight(FontWeight.Bold)
           }
           .type(ButtonType.Capsule)
           .margin({
             top: 20
           })
           .backgroundColor('#0D9FFB')
           .width('40%')
           .height('5%')
           // Bind the onClick event to the Back button so that clicking the button redirects the user back to the first page.
           .onClick(() => {
             router.back()
           })
         }
         .width('100%')
       }
       .height('100%')
     }
   }
   ```

3. Open the **index.ets** file and click ![en-us_image_0000001311015192](figures/en-us_image_0000001311015192.png) in the Previewer to refresh the file. The display effect is shown in the figure below.

   ![en-us_image_0000001364254729](figures/en-us_image_0000001364254729.png)


## Running the Application on a Real Device

1. Connect the development board running the OpenHarmony standard system to the computer.

2. Choose **File** > **Project Structure...** > **Project** > **SigningConfigs**, and select **Automatically generate signature**. Wait until the automatic signing is complete, and click **OK**. See the following figure.

   ![signConfig](figures/signConfig.png)

3. On the toolbar in the upper right corner of the editing window, click ![en-us_image_0000001364054485](figures/en-us_image_0000001364054485.png). The display effect is shown in the figure below.

   ![en-us_image_0000001364254729](figures/en-us_image_0000001364254729.png)

Congratulations! You have finished developing your OpenHarmony application in ArkTS in the FA model. To learn more about OpenHarmony application development, see [Application Development Overview](../application-dev-guide.md).