# @ohos.app.form.FormExtensionAbility (FormExtensionAbility)

The **FormExtensionAbility** module provides lifecycle callbacks invoked when a widget is created, destroyed, or updated.

> **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.
> The APIs of this module can be used only in the stage model.

## Modules to Import

```ts
import FormExtensionAbility from '@ohos.app.form.FormExtensionAbility';
```

## Attributes

**System capability**: SystemCapability.Ability.Form

| Name   | Type                                                        | Readable| Writable| Description                                                        |
| ------- | ------------------------------------------------------------ | ---- | ---- | ------------------------------------------------------------ |
| context | [FormExtensionContext](js-apis-inner-application-formExtensionContext.md) | Yes  | No  | Context of the FormExtensionAbility. This context is inherited from [ExtensionContext](js-apis-inner-application-extensionContext.md).|

## onAddForm

onAddForm(want: Want): formBindingData.FormBindingData

Called to notify the widget provider that a **Form** instance (widget) is being created.

**System capability**: SystemCapability.Ability.Form

**Parameters**

| Name| Type                                  | Mandatory| Description                                                        |
| ------ | -------------------------------------- | ---- | ------------------------------------------------------------ |
| want   | [Want](js-apis-app-ability-want.md) | Yes  | Want information related to the FormExtensionAbility, including the widget ID, name, and style. The information must be managed as persistent data to facilitate subsequent widget update and deletion.|

**Return value**

| Type                                                        | Description                                                       |
| ------------------------------------------------------------ | ----------------------------------------------------------- |
| [formBindingData.FormBindingData](js-apis-app-form-formBindingData.md#formbindingdata) | A **formBindingData.FormBindingData** object containing the data to be displayed on the widget.|

**Example**

```ts
import FormExtensionAbility from '@ohos.app.form.FormExtensionAbility';
import formBindingData from '@ohos.app.form.formBindingData';
import Want from '@ohos.app.ability.Want';

export default class MyFormExtensionAbility extends FormExtensionAbility {
  onAddForm(want: Want) {
    console.log(`FormExtensionAbility onAddForm, want: ${want.abilityName}`);
    let dataObj1 = new Map<string, string>();
    dataObj1.set('temperature', '11c');
    dataObj1.set('time', '11:00');

    let obj1: formBindingData.FormBindingData = formBindingData.createFormBindingData(dataObj1);
    return obj1;
  }
}
```

## onCastToNormalForm

onCastToNormalForm(formId: string): void

Called to notify the widget provider that a temporary widget is being converted to a normal one.

**System capability**: SystemCapability.Ability.Form

**Parameters**

| Name| Type  | Mandatory| Description                    |
| ------ | ------ | ---- | ------------------------ |
| formId | string | Yes  | ID of the widget that requests to be converted to a normal one.|

**Example**

```ts
import FormExtensionAbility from '@ohos.app.form.FormExtensionAbility';

export default class MyFormExtensionAbility extends FormExtensionAbility {
  onCastToNormalForm(formId: string) {
    console.log(`FormExtensionAbility onCastToNormalForm, formId: ${formId}`);
  }
};
```

## onUpdateForm

onUpdateForm(formId: string): void

Called to notify the widget provider that a widget is being updated. After obtaining the latest data, your application should call [updateForm](js-apis-app-form-formProvider.md#updateform) of **formProvider** to update the widget data.

**System capability**: SystemCapability.Ability.Form

**Parameters**

| Name| Type  | Mandatory| Description              |
| ------ | ------ | ---- | ------------------ |
| formId | string | Yes  | ID of the widget that requests to be updated.|

**Example**

```ts
import FormExtensionAbility from '@ohos.app.form.FormExtensionAbility';
import formBindingData from '@ohos.app.form.formBindingData';
import formProvider from '@ohos.app.form.formProvider';
import Base from '@ohos.base';

export default class MyFormExtensionAbility extends FormExtensionAbility {
  onUpdateForm(formId: string) {
    console.log(`FormExtensionAbility onUpdateForm, formId: ${formId}`);
    let param: Record<string, string> = {
      'temperature': '22c',
      'time': '22:00'
    }
    let obj2: formBindingData.FormBindingData = formBindingData.createFormBindingData(param);
    formProvider.updateForm(formId, obj2).then(() => {
      console.log(`FormExtensionAbility context updateForm`);
    }).catch((error: Base.BusinessError) => {
      console.error(`FormExtensionAbility context updateForm failed, data: ${error}`);
    });
  }
};
```

## onChangeFormVisibility

onChangeFormVisibility(newStatus: { [key: string]: number }): void

Called to notify the widget provider that the widget visibility status is being changed.

**System capability**: SystemCapability.Ability.Form

**Parameters**

| Name   | Type                     | Mandatory| Description                        |
| --------- | ------------------------- | ---- | ---------------------------- |
| newStatus | { [key: string]: number } | Yes  | ID and visibility status of the widget to be changed.|

**Example**

```ts
import FormExtensionAbility from '@ohos.app.form.FormExtensionAbility';
import formBindingData from '@ohos.app.form.formBindingData';
import formProvider from '@ohos.app.form.formProvider';
import Base from '@ohos.base';

// There is no Object.keys in ArkTS, and the for..in... syntax cannot be used.
// If an error is reported, extract this API to a .ts file and expose it. Then import the API to the required .ets file.
function getObjKeys(obj: Object): string[] {
  let keys = Object.keys(obj);
  return keys;
}

export default class MyFormExtensionAbility extends FormExtensionAbility {
  onChangeFormVisibility(newStatus: Record<string, number>) {
    console.log(`FormExtensionAbility onChangeFormVisibility, newStatus: ${newStatus}`);
    let param: Record<string, string> = {
      'temperature': '22c',
      'time': '22:00'
    }
    let obj2: formBindingData.FormBindingData = formBindingData.createFormBindingData(param);

    let keys: string[] = getObjKeys(newStatus);

    for (let i: number = 0; i < keys.length; i++) {
      console.log(`FormExtensionAbility onChangeFormVisibility, key: ${keys[i]}, value= ${newStatus[keys[i]]}`);
      formProvider.updateForm(keys[i], obj2).then(() => {
        console.log(`FormExtensionAbility context updateForm`);
      }).catch((error: Base.BusinessError) => {
        console.error(`Operation updateForm failed. Cause: ${JSON.stringify(error)}`);
      });
    }
  }
};
```

## onFormEvent

onFormEvent(formId: string, message: string): void

Called to instruct the widget provider to process the widget event.

**System capability**: SystemCapability.Ability.Form

**Parameters**

| Name | Type  | Mandatory| Description                  |
| ------- | ------ | ---- | ---------------------- |
| formId  | string | Yes  | ID of the widget that requests the event.|
| message | string | Yes  | Event message.            |

**Example**

```ts
import FormExtensionAbility from '@ohos.app.form.FormExtensionAbility';

export default class MyFormExtensionAbility extends FormExtensionAbility {
  onFormEvent(formId: string, message: string) {
    console.log(`FormExtensionAbility onFormEvent, formId: ${formId}, message: ${message}`);
  }
};
```

## onRemoveForm

onRemoveForm(formId: string): void

Called to notify the widget provider that a **Form** instance (widget) is being destroyed.

**System capability**: SystemCapability.Ability.Form

**Parameters**

| Name| Type  | Mandatory| Description              |
| ------ | ------ | ---- | ------------------ |
| formId | string | Yes  | ID of the widget to be destroyed.|

**Example**

```ts
import FormExtensionAbility from '@ohos.app.form.FormExtensionAbility';

export default class MyFormExtensionAbility extends FormExtensionAbility {
  onRemoveForm(formId: string) {
    console.log(`FormExtensionAbility onRemoveForm, formId: ${formId}`);
  }
};
```

## onConfigurationUpdate

onConfigurationUpdate(newConfig: Configuration): void;

Called when the configuration of the environment where the FormExtensionAbility is running is updated.

**System capability**: SystemCapability.Ability.Form

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| newConfig | [Configuration](js-apis-application-configuration.md) | Yes| New configuration.|

**Example**

```ts
import FormExtensionAbility from '@ohos.app.form.FormExtensionAbility';
import { Configuration } from '@ohos.app.ability.Configuration';

export default class MyFormExtensionAbility extends FormExtensionAbility {
  onConfigurationUpdate(config: Configuration) {
    console.log(`onConfigurationUpdate, config: ${JSON.stringify(config)}`);
  }
};
```

## onAcquireFormState

onAcquireFormState?(want: Want): formInfo.FormState;

Called to notify the widget provider that the widget host is requesting the widget state. By default, the initial state is returned.

**System capability**: SystemCapability.Ability.Form

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| want | [Want](js-apis-app-ability-want.md) | Yes| Description of the widget state, including the bundle name, ability name, module name, widget name, and widget dimension.|

**Example**

```ts
import FormExtensionAbility from '@ohos.app.form.FormExtensionAbility';
import formInfo from '@ohos.app.form.formInfo';
import Want from '@ohos.app.ability.Want';

export default class MyFormExtensionAbility extends FormExtensionAbility {
  onAcquireFormState(want: Want) {
    console.log(`FormExtensionAbility onAcquireFormState, want: ${want}`);
    return formInfo.FormState.UNKNOWN;
  }
};
```

## onShareForm

onShareForm?(formId: string): { [key: string]: Object }

Called to notify the widget provider that the widget host is sharing the widget data.

**System API**: This is a system API.

**System capability**: SystemCapability.Ability.Form

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| formId | string | Yes  | Widget ID.|

**Return value**

| Type                                                        | Description                                                       |
| ------------------------------------------------------------ | ----------------------------------------------------------- |
| {[key: string]: any} | Data to be shared by the widget, in the form of key-value pairs.|

**Example**

```ts
import FormExtensionAbility from '@ohos.app.form.FormExtensionAbility';

export default class MyFormExtensionAbility extends FormExtensionAbility {
  onShareForm(formId: string) {
    console.log(`FormExtensionAbility onShareForm, formId: ${formId}`);
    let wantParams: Record<string, Object> = {
      'temperature': '20',
      'time': '2022-8-8 09:59',
    };
    return wantParams;
  }
};
```

## onAcquireFormData<sup>10+</sup>

onAcquireFormData?(formId: string): { [key: string]: Object }

Called to notify the widget provider that the widget host is requesting the custom data.

**System API**: This is a system API.

**System capability**: SystemCapability.Ability.Form

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| formId | string | Yes  | Widget ID.|

**Return value**

| Type                                                        | Description                                                       |
| ------------------------------------------------------------ | ----------------------------------------------------------- |
| {[key: string]: any} | Custom data of the widget, in the form of key-value pairs.|

**Example**

```ts
import FormExtensionAbility from '@ohos.app.form.FormExtensionAbility';

export default class MyFormExtensionAbility extends FormExtensionAbility {
  onAcquireFormData(formId: string) {
    console.log(`FormExtensionAbility onAcquireFormData, formId: ${formId}`);
    let wantParams: Record<string, Object> = {
      'temperature': '20',
      'time': '2022-8-8 09:59',
    };
    return wantParams;
  }
};
```