xref: /docs/en/application-dev/device/input/inputeventclient-guidelines.md (revision e41f4b71)

# Event Injection Development

## When to Use

The **inputEventClient** module provides the function of injecting input events, such as mouse click events and combination key events. For example, if you need to verify the combination key function of an application, you can listen for combination key events to serve that purpose.

## Modules to Import

```js
import { inputEventClient } from '@kit.InputKit';
```

## Available APIs

The following table lists the common APIs provided by the **inputEventClient** module. For details, see [ohos.multimodalInput.inputEventClient](../../reference/apis-input-kit/js-apis-inputeventclient-sys.md).

| API | Description|
| -------------------------------------------- | -------------------------- |
| injectEvent({KeyEvent: KeyEvent}): void |Injects keys (including single keys and combination keys).|
| injectMouseEvent(mouseEvent: MouseEventData): void |Injects a mouse/touchpad event.|
| injectTouchEvent(touchEvent: TouchEventData): void |Injects a touchscreen event.|

## How to Develop

Assume that an application calls the Home key to return to the home screen. When the Home key is pressed, check whether [injectEvent](../../reference/apis-input-kit/js-apis-inputeventclient-sys.md#inputeventclientinjectevent) is called to inject the Home key to determine if the Home key takes effect.

```js
try {
  let backKeyDown: inputEventClient.KeyEvent = {
    isPressed: true,
    keyCode: 2,
    keyDownDuration: 0,
    isIntercepted: false
  }// Home key pressing event

  class EventDown {
    KeyEvent: inputEventClient.KeyEvent | null = null
  }

  let eventDown: EventDown = { KeyEvent: backKeyDown }
  inputEventClient.injectEvent(eventDown);// Inject the Home key pressing event.

  let backKeyUp: inputEventClient.KeyEvent = {
    isPressed: false,
    keyCode: 2,
    keyDownDuration: 0,
    isIntercepted: false
  };// Home key release event.

  class EventUp {
    KeyEvent: inputEventClient.KeyEvent | null = null
  }

  let eventUp: EventUp = { KeyEvent: backKeyUp }
  inputEventClient.injectEvent(eventUp);// Inject the Home key release event and check whether the Home key function takes effect and whether the application returns to the home screen.
} catch (error) {
  console.log(`Failed to inject KeyEvent, error: ${JSON.stringify(error, [`code`, `message`])}`);
}
```