# AccessibilityExtensionContext (System API)

The **AccessibilityExtensionContext** module, inherited from **ExtensionContext**, provides context for **AccessibilityExtensionAbility**.

You can use the APIs of this module to configure the concerned information, obtain root information, and inject gestures.

> **NOTE**
>
> - The initial APIs of this module are supported since API version 12. Newly added APIs will be marked with a superscript to indicate their earliest API version.
> - The current page contains only the system APIs of the current module. For details about other public APIs, see [AccessibilityExtensionContext](js-apis-inner-application-accessibilityExtensionContext.md).

## How to Use

Before using the **AccessibilityExtensionContext** module, you must define a child class that inherits from **AccessibilityExtensionAbility**.

```ts
import { AccessibilityExtensionAbility } from '@kit.AccessibilityKit';

class EntryAbility extends AccessibilityExtensionAbility {
  onConnect(): void {
    let axContext = this.context; 
  } 
}
```

### enableScreenCurtain<sup>12+</sup>

enableScreenCurtain(isEnable: boolean): void;

Enables or disables the screen curtain.

**System capability**: SystemCapability.BarrierFree.Accessibility.Core

**Parameters**

| Name        | Type                                    | Mandatory  | Description            |
| ----------- | ---------------------------------------- | ---- | -------------- |
| isEnable | boolean | Yes   | The value **true** indicates enabled; **false** indicates disabled.|

**Error codes**

For details about the error codes, see [Accessibility Error Codes](errorcode-accessibility.md).

| ID  | Error Message                                    |
| ------- | ---------------------------------------- |
| 202 | Permission verification failed. A non-system application calls a system API. |
| 401  | Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed. |
| 9300003 | No accessibility permission to perform the operation. |

**Example**

```ts
import { AccessibilityElement } from '@kit.AccessibilityKit';
import { BusinessError } from '@kit.BasicServicesKit';

let rootElement: AccessibilityElement;

axContext.getWindowRootElement().then((data: AccessibilityElement) => {
  rootElement = data;
  console.log(`Succeeded in get root element of the window, ${JSON.stringify(data)}`);
  await rootElement.enableScreenCurtain(true);
  console.log(`Succeeded in enableScreenCurtain}`);
}).catch((err: BusinessError) => {
  console.error(`failed to enableScreenCurtain, Code is ${err.code}, message is ${err.message}`);
});
```

### findElement('elementId')<sup>12+</sup>

findElement(type: 'elementId', condition: number): Promise\<AccessibilityElement>;

Queries the node elements in the current active window based on the **elementId**. This API uses a promise to return the result.

**System capability**: SystemCapability.BarrierFree.Accessibility.Core

**Parameters**

| Name      | Type                               | Mandatory  | Description                                      |
| --------- | --------------------------------- | ---- | ---------------------------------------- |
| type      | string                            | Yes   | Type of element finding. The value is fixed at **'elementId'**.|
| condition | number | Yes   | **elementId** of the node element.                          |

**Return value**

| Type                                 | Description                              |
| ----------------------------------- | -------------------------------- |
| Promise&lt;[AccessibilityElement](js-apis-inner-application-accessibilityExtensionContext.md#accessibilityelement9)&gt; | Promise used to return the result.|

**Error codes**

For details about the error codes, see [Accessibility Error Codes](errorcode-accessibility.md).

| ID  | Error Message                         |
| ------- | ----------------------------- |
| 401  | Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed. |

**Example**

```ts
import { BusinessError } from '@kit.BasicServicesKit';

// elementId is 10.
let condition = 10;

// rootElement is an instance of AccessibilityElement.
rootElement.findElement('elementId', condition).then((data: AccessibilityElement) => {
  console.log(`Succeeded in find element, ${JSON.stringify(data)}`);
}).catch((err: BusinessError) => {
  console.error(`failed to find element, Code is ${err.code}, message is ${err.message}`);
});
```

### findElement('textType')<sup>12+</sup>

findElement(type: 'textType', condition: string): Promise\<Array\<AccessibilityElement>>;

Queries all node elements based on the **accessibilityTextHint** text type configured for a node. This API uses a promise to return the result.

**System capability**: SystemCapability.BarrierFree.Accessibility.Core

**Parameters**

| Name      | Type    | Mandatory  | Description                           |
| --------- | ------ | ---- | ----------------------------- |
| type      | string | Yes   | Type of element finding. The value is fixed at **'textType'**.|
| condition | string | Yes   | Search criteria.                     |

**Return value**

| Type                                      | Description                           |
| ---------------------------------------- | ----------------------------- |
| Promise&lt;Array&lt;[AccessibilityElement](js-apis-inner-application-accessibilityExtensionContext.md#accessibilityelement9)&gt;&gt; | Promise used to return the result.|

**Error codes**

For details about the error codes, see [Accessibility Error Codes](errorcode-accessibility.md).

| ID  | Error Message                         |
| ------- | ----------------------------- |
| 401  | Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed. |

**Example**

```ts
import { BusinessError } from '@kit.BasicServicesKit';

// The content of condition must be the same as the type value in the accessibilityTextHint attribute of the target component.
let condition = 'location'; 

// rootElement is an instance of AccessibilityElement.
rootElement.findElement('textType', condition).then((data: AccessibilityElement[]) => {
  console.log(`Succeeded in find element, ${JSON.stringify(data)}`);
}).catch((err: BusinessError) => {
  console.error(`failed to find element, Code is ${err.code}, message is ${err.message}`);
});
```

### getCursorPosition<sup>12+</sup>

getCursorPosition(): Promise\<number>;

Obtains the cursor position in the **Text** component. This API uses a promise to return the result.

**System capability**: SystemCapability.BarrierFree.Accessibility.Core

**Return value**

| Type                 | Description              |
| ------------------- | ---------------- |
| Promise&lt;number&gt; | Promise used to return the result.|

**Example**

```ts
import { BusinessError } from '@kit.BasicServicesKit';

// rootElement is an instance of AccessibilityElement.
rootElement.getCursorPosition().then((data: number) => {
  console.info(`Succeeded in getCursorPosition, ${data}`);
}).catch((err: BusinessError) => {
  console.error(`failed to getCursorPosition, Code is ${err.code}, message is ${err.message}`);
});
```

### getCursorPosition<sup>12+</sup>

getCursorPosition(callback: AsyncCallback\<number>): void;

Obtains the cursor position in the **Text** component. This API uses an asynchronous callback to return the result.

**System capability**: SystemCapability.BarrierFree.Accessibility.Core

**Parameters**

| Name        | Type                                    | Mandatory  | Description            |
| ----------- | ---------------------------------------- | ---- | -------------- |
| callback | AsyncCallback&lt;number&gt; | Yes   | Callback function used to return the result.|

**Example**

```ts
import { BusinessError } from '@kit.BasicServicesKit';

// rootElement is an instance of AccessibilityElement.
rootElement.getCursorPosition((err: BusinessError, data: number) => {
  if (err && err.code) {
    console.error(`failed to getCursorPosition, Code is ${err.code}, message is ${err.message}`);
    return;
  }
  console.info(`Succeeded in getCursorPosition, ${data}`);
});
```

### startAbility<sup>12+</sup>

startAbility(want: Want): void;

Starts the foreground page.

**System capability**: SystemCapability.BarrierFree.Accessibility.Core

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| want | [Want](../../reference/apis-ability-kit/js-apis-app-ability-want.md) | Yes| Want information about the target ability, such as the ability name and bundle name.|

**Error codes**

For details about the error codes, see [Accessibility Error Codes](errorcode-accessibility.md).

| ID  | Error Message                                    |
| ------- | ---------------------------------------- |
| 201 | Permission denied. Interface caller does not have permission. |
| 401 | Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed. |

**Example**

```ts
import { BusinessError } from '@kit.BasicServicesKit';

let want: Want = {
  bundleName: 'com.huawei.hmos.photos'
  abilityName: 'com.huawei.hmos.photos.MainAbility'
}

axContext.startAbility(want).then(() => {
  console.info(`startAbility Succeeded enable ability`);
}).catch((err: BusinessError) => {
  console.error(`startAbility failed to enable ability, Code is ${err.code}, message is ${err.message}`);
});
```

### getElements<sup>18+</sup>

getElements(windowId: number, elementId?: number): Promise<Array&lt;AccessibilityElement&gt;>;

Obtains node elements in batches.

**System capability**: SystemCapability.BarrierFree.Accessibility.Core

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| windowId | number | Yes| Window ID to be obtained.|
| elementId | number | No| Element ID to be obtained. If this parameter is passed in, the list of all child nodes under the current node is obtained. Otherwise, all nodes in the window are obtained.|

**Return value**
| Type                                 | Description                    |
| ----------------------------------- | ---------------------- |
| Promise<Array&lt;AccessibilityElement&gt;> | Promise used to return the result.|

**Error codes**

For details about the error codes, see [Accessibility Error Codes](errorcode-accessibility.md).

| ID  | Error Message                                    |
| ------- | ---------------------------------------- |
| 201 | Permission verification failed. The application does not have the permission required to call the API. |
| 401 | Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed. |
| 9300003 | No accessibility permission to perform the operation. |

**Example**

```ts
import { AccessibilityElement } from '@kit.AccessibilityKit';
import { BusinessError } from '@kit.BasicServicesKit';

let windowId: number = 10;
let elementId: number = 10;

axContext.getElements(windowId, elementId).then((data:AccessibilityElement[]) => {
  console.log(`Succeeded in find element, ${JSON.stringify(data)}`);
}).catch((err: BusinessError) => {
  console.error(`failed to find element, Code is ${err.code}, message is ${err.message}`);
});
```

### getDefaultFocusedElementIds<sup>18+</sup>

getDefaultFocusedElementIds(windowId: number): Promise<Array&lt;number&gt;>;

Obtains the custom default focuses of an application.

**System capability**: SystemCapability.BarrierFree.Accessibility.Core

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| windowId | number | Yes| Window ID to be obtained.|

**Return value**
| Type                                 | Description                    |
| ----------------------------------- | ---------------------- |
| Promise<Array&lt;number&gt;> | Promise used to return the result.|

**Error codes**

For details about the error codes, see [Accessibility Error Codes](errorcode-accessibility.md).

| ID  | Error Message                                    |
| ------- | ---------------------------------------- |
| 202 | Permission verification failed. A non-system application calls a system API. |
| 401 | Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2. Incorrect parameter types; 3. Parameter verification failed. |
| 9300003 | No accessibility permission to perform the operation. |

**Example**

```ts
import { AccessibilityElement } from '@kit.AccessibilityKit';
import { BusinessError } from '@kit.BasicServicesKit';

let windowId: number = 10;

axContext.getDefaultFocusedElementIds(windowId).then((data: number[]) => {
  console.log(`Succeeded in get default focus, ${JSON.stringify(data)}`);
}).catch((err: BusinessError) => {
  console.error(`failed to get default focus, Code is ${err.code}, message is ${err.message}`);
});
```