# Key Event

A key event is triggered when a focusable component, such as **Button**, interacts with a keyboard, remote control, or any other input device with keys. To use a key event for components that are not focusable by default, such as **Text** and **Image**, first set their **focusable** attribute to **true**.
For details about the process and specific timing of the key event triggering, see [Key Event Data Flow](../../../ui/arkts-common-events-device-input-event.md#key-event-data-flow).

>  **NOTE**
>
>  The APIs of this module are supported since API version 7. Updates will be marked with a superscript to indicate their earliest API version.

## onKeyEvent

onKeyEvent(event: (event: KeyEvent) => void): T

Triggered when a key event occurs.

**Atomic service API**: This API can be used in atomic services since API version 11.

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

**Parameters** 

| Name | Type                         | Mandatory | Description              |
| ------ | ----------------------------- | ---- | ------------------ |
| event  | [KeyEvent](#keyevent)  | Yes  | **KeyEvent** object. |

**Return value**

| Type | Description |
| -------- | -------- |
| T | Current component. |

## onKeyPreIme<sup>12+</sup>

onKeyPreIme(event: Callback<KeyEvent, boolean>): T

Triggered before other callbacks when a key event occurs.

If the return value of this callback is **true**, it is considered that the key event has been consumed, and subsequent event callbacks (**keyboardShortcut**, input method events, **onKeyEvent**) will be intercepted and no longer triggered.

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

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

**Parameters** 

| Name | Type                         | Mandatory | Description              |
| ------ | ----------------------------- | ---- | ------------------ |
| event  | [Callback](./ts-types.md#callback12)<[KeyEvent](#keyevent), boolean> | Yes  | Callback for processing the key event. |

**Return value**

| Type | Description |
| -------- | -------- |
| T | Current component. |

## KeyEvent

**Atomic service API**: This API can be used in atomic services since API version 11.

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

| Name                                   | Type                                      | Description                        |
| ------------------------------------- | ---------------------------------------- | -------------------------- |
| type                                  | [KeyType](ts-appendix-enums.md#keytype)  | Key type.                    |
| [keyCode](../../apis-input-kit/js-apis-keycode.md#keycode) | number                                   | Key code.                    |
| keyText                               | string                                   | Key value.                    |
| keySource                             | [KeySource](ts-appendix-enums.md#keysource) | Type of the input device that triggers the key event.            |
| deviceId                              | number                                   | ID of the input device that triggers the key event.            |
| metaKey                               | number                                   | State of the metakey (that is, the **WIN** key on the Windows keyboard or the **Command** key on the Mac keyboard) when the key is pressed. The value **1** indicates the pressed state, and **0** indicates the unpressed state. |
| timestamp                             | number                                   | Timestamp of the event. It is the interval between the time when the event is triggered and the time when the system starts, in nanoseconds. |
| stopPropagation                       | () => void                               | Stops the event from bubbling upwards or downwards.                 |
| intentionCode<sup>10+</sup>           | [IntentionCode](../../apis-input-kit/js-apis-intentioncode.md) | Intention corresponding to the key.      |
| getModifierKeyState<sup>12+</sup> | (Array&lt;string&gt;) => bool | Obtains the pressed status of modifier keys. For details about the error message, see the following error codes. The following modifier keys are supported: 'Ctrl'\|'Alt'\|'Shift'\|'Fn'. This API does not work for the Fn key on an externally connected keyboard.<br>**Atomic service API**: This API can be used in atomic services since API version 12.|

**Error codes**

For details about the error codes, see [Universal Error Codes](../../errorcode-universal.md).

| ID | Error Message |
| ------- | -------- |
| 401 | Parameter error. Possible causes: 1. Incorrect parameter types. 2. Parameter verification failed. |

## Example

```ts
// xxx.ets
@Entry
@Component
struct KeyEventExample {
  @State text: string = ''
  @State eventType: string = ''

  build() {
    Column() {
      Button('KeyEvent')
        .onKeyEvent((event?: KeyEvent) => {
          if(event){
            if (event.type === KeyType.Down) {
              this.eventType = 'Down'
            }
            if (event.type === KeyType.Up) {
              this.eventType = 'Up'
            }
            this.text = 'KeyType:' + this.eventType + '\nkeyCode:' + event.keyCode + '\nkeyText:' + event.keyText + '\nintentionCode:' + event.intentionCode
          }
        })
      Text(this.text).padding(15)
    }.height(300).width('100%').padding(35)
  }
}
```

 ![keyEvent](figures/keyEvent.gif)