# Widget Event Capability Overview

For dynamic ATS widgets, the **postCardAction()** API is provided for interaction between the widget internal and the provider application. Currently, this API supports the router, message, and call events and can be called only in the widget.

For static ATS widgets, the [FormLink](../../application-dev/reference/arkui-ts/ts-container-formlink.md) component is provided for interaction between the widget internal and the provider application.

## Dynamic Widget Event Capability
![WidgetPostCardAction](figures/WidgetPostCardAction.png)

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

**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**


| Key | Value | 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()](../reference/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](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/permission-list.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.

Sample code of the **postCardAction()** API:

```typescript
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.
      }
    });
  })
```

## Static Widget Event Capability
See [FormLink](../../application-dev/reference/arkui-ts/ts-container-formlink.md).