# Functions
<!--Kit: AVSession Kit-->
<!--Subsystem: Multimedia-->
<!--Owner: @ccfriend; @liao_qian-->
<!--SE: @ccfriend-->
<!--TSE: @chenmingxi1_huawei-->

> **NOTE**
>
> The initial APIs of this module are supported since API version 9. Newly added APIs will be marked with a superscript to indicate their earliest API version.

## Modules to Import

```ts
import { avSession } from '@kit.AVSessionKit';
```

## avSession.createAVSession<sup>10+</sup>

createAVSession(context: Context, tag: string, type: AVSessionType): Promise\<AVSession>

Creates a media session. This API uses a promise to return the result. An ability can have only one session, and repeated calling of this API fails.

**Atomic service API**: This API can be used in atomic services since API version 12.

**System capability**: SystemCapability.Multimedia.AVSession.Core

**Parameters**

| Name| Type                           | Mandatory| Description                          |
| ------ | ------------------------------- | ---- | ------------------------------ |
| context| [Context](../apis-ability-kit/js-apis-inner-app-context.md) | Yes| Context of the UIAbility, which is used to obtain information about the application component.|
| tag    | string                          | Yes  | Custom session name.            |
| type   | [AVSessionType](arkts-apis-avsession-t.md#avsessiontype10) | Yes  | Session type.|

**Return value**

| Type                             | Description                                                        |
| --------------------------------- | ------------------------------------------------------------ |
| Promise<[AVSession](arkts-apis-avsession-AVSession.md)\> | Promise used to return the media session obtained, which can be used to obtain the session ID, set the metadata and playback state information, and send key events.|

**Error codes**

For details about the error codes, see [AVSession Management Error Codes](errorcode-avsession.md).

| ID| Error Message|
| -------- | ---------------------------------------- |
| 401 |  parameter check failed. 1.Mandatory parameters are left unspecified. 2.Parameter verification failed. |
| 6600101  | Session service exception. |

**Example**

```ts
import { BusinessError } from '@kit.BasicServicesKit';
import { avSession } from '@kit.AVSessionKit';
@Entry
@Component
struct Index {
  @State message: string = 'hello world';

  build() { 
    Column() {
        Text(this.message)
          .onClick(()=>{
            let currentAVSession: avSession.AVSession;
            let tag = "createNewSession";
            let context: Context = this.getUIContext().getHostContext() as Context;
            let sessionId: string;  // Used as an input parameter of subsequent functions.

            avSession.createAVSession(context, tag, "audio").then(async (data: avSession.AVSession) => {
            currentAVSession = data;
            sessionId = currentAVSession.sessionId;
            console.info(`CreateAVSession : SUCCESS : sessionId = ${sessionId}`);
            }).catch((err: BusinessError) => {
            console.error(`CreateAVSession BusinessError: code: ${err.code}, message: ${err.message}`);
            });
          })
      }
    .width('100%')
    .height('100%')
  }
}
```

## avSession.createAVSession<sup>10+</sup>

createAVSession(context: Context, tag: string, type: AVSessionType, callback: AsyncCallback\<AVSession>): void

Creates a media session. This API uses an asynchronous callback to return the result. An ability can have only one session, and repeated calling of this API fails.

**System capability**: SystemCapability.Multimedia.AVSession.Core

**Parameters**

| Name  | Type                                   | Mandatory| Description                                                        |
| -------- | --------------------------------------- | ---- | ------------------------------------------------------------ |
| context| [Context](../apis-ability-kit/js-apis-inner-app-context.md) | Yes| Context of the UIAbility, which is used to obtain information about the application component.    |
| tag      | string                                  | Yes  | Custom session name.                                          |
| type     | [AVSessionType](arkts-apis-avsession-t.md#avsessiontype10)         | Yes  | Session type.                              |
| callback | AsyncCallback<[AVSession](arkts-apis-avsession-AVSession.md)\> | Yes  | Callback used to return the media session obtained, which can be used to obtain the session ID, set the metadata and playback state information, and send key events.|

**Error codes**

For details about the error codes, see [AVSession Management Error Codes](errorcode-avsession.md).

| ID| Error Message|
| -------- | ---------------------------------------- |
| 401 |  parameter check failed. 1.Mandatory parameters are left unspecified. 2.Parameter verification failed. |
| 6600101  | Session service exception. |

**Example**

```ts
import { BusinessError } from '@kit.BasicServicesKit';
import { avSession } from '@kit.AVSessionKit';
@Entry
@Component
struct Index {
  @State message: string = 'hello world';

  build() {
    Column() {
      Text(this.message)
        .onClick(()=>{
          let currentAVSession: avSession.AVSession;
          let tag = "createNewSession";
          let context: Context = this.getUIContext().getHostContext() as Context;
          let sessionId: string;  // Used as an input parameter of subsequent functions.

          avSession.createAVSession(context, tag, "audio", async (err: BusinessError, data: avSession.AVSession) => {
            if (err) {
              console.error(`CreateAVSession BusinessError: code: ${err.code}, message: ${err.message}`);
            } else {
              currentAVSession = data;
              sessionId = currentAVSession.sessionId;
              console.info(`CreateAVSession : SUCCESS : sessionId = ${sessionId}`);
            }
          });
        })
    }
    .width('100%')
    .height('100%')
  }
}
```