## postCardAction

postCardAction(component: Object, action: Object): void

Provides information for interaction between the widget and widget provider. Currently, router, message, and call events are supported. This API can only be called within the widget.

> **NOTE**
>
> This API is supported since API version 9.

**System capability**: SystemCapability.ArkUI.ArkUI.Full

**Parameters**


| **Name**| **Type**| **Mandatory**| **Description**|
| -------- | -------- | -------- | -------- |
| component | Object | Yes| Instance of the current custom component. Generally, **this** is passed in.|
| action | Object | Yes| Action description. For details, see the following table.|


Description of the action parameter


| **Name**| **Type**| **Description**|
| -------- | -------- | -------- |
| action | string | Action type.<br>- **"router"**: redirection to the specified UIAbility of the widget provider.<br>- **"message"**: custom message. If this type of action is triggered, the [onFormEvent()](../apis/js-apis-app-form-formExtensionAbility.md#onformevent) lifecycle callback of the provider FormExtensionAbility is called.<br>- **"call"**: launch of the widget provider in the background. If this type of action is triggered, the specified UIAbility (whose [launch type](../../application-models/uiability-launch-type.md) must be singleton) of the widget provider is started in the background, but not displayed in the foreground. This action type requires that the widget provider should have the [ohos.permission.KEEP_BACKGROUND_RUNNING](../../security/AccessToken/permissions-for-all.md#ohospermissionkeep_background_running) permission.|
| bundleName | string | Name of the target bundle when **action** is **"router"** or **"call"**. This parameter is optional.|
| moduleName | string | Name of the target module when **action** is **"router"** or **"call"**. This parameter is optional.|
| abilityName | string | Name of the target UIAbility when **action** is **"router"** or **"call"**. This parameter is mandatory.|
| params | Object | Additional parameters carried in the current action. The value is a key-value pair in JSON format. This parameter is mandatory.|

>**NOTE**
>
>When **action** is **"router"** or **"call"**, **'method'** of the string type must be passed to **params** to trigger the corresponding method in the UIAbility.

**Example**

```ts
Button ('Redirect')
  .width('40%')
  .height('20%')
  .onClick(() => {
    postCardAction(this, {
      action: 'router',
      bundleName: 'com.example.myapplication',
      abilityName: 'EntryAbility',
      params: {
        message: 'testForRouter' // Customize the message to send.
      }
    });
  })

Button ('Start in Background')
  .width('40%')
  .height('20%')
  .onClick(() => {
    postCardAction(this, {
      action: 'call',
      bundleName: 'com.example.myapplication',
      abilityName: 'EntryAbility',
      params: {
        method: 'fun', // Set the name of the method to call. It is mandatory.
        message: 'testForCall' // Customize the message to send.
      }
    });
  })
```