Focusing

To focus the camera to a specific point, simply use the Camera's focus(...) function:

await camera.current.focus({ x: tapEvent.x, y: tapEvent.y })

The focus function expects a Point parameter which represents the location relative to the Camera view where you want to focus the Camera to (in points). If you use react-native-gesture-handler, this will consist of the x and y properties of the tap event payload.

So for example, { x: 0, y: 0 } will focus to the upper left corner, while { x: VIEW_WIDTH, y: VIEW_HEIGHT } will focus to the bottom right corner.

Focussing adjusts auto-focus (AF) and auto-exposure (AE).

note

focus(...) will fail if the selected Camera device does not support focusing (see CameraDevice.supportsFocus)

Example (Gesture Handler)

This is an Example on how to use react-native-gesture-handler to focus the Camera to a specific point on the screen:

import { Camera, useCameraDevice } from 'react-native-vision-camera'
import { Gesture, GestureDetector } from 'react-native-gesture-handler'

export function App() {
  const camera = useRef<Camera>(null)
  const device = useCameraDevice('back')

  const focus = useCallback((point: Point) => {
    const c = camera.current
    if (c == null) return
    c.focus(point)
  }, [])

  const gesture = Gesture.Tap()
    .onEnd(({ x, y }) => {
      runOnJS(focus)({ x, y })
    })

  if (device == null) return <NoCameraDeviceError />
  return (
    <GestureDetector gesture={gesture}>
      <Camera
        ref={camera}
        style={StyleSheet.absoluteFill}
        device={device}
        isActive={true}
      />
    </GestureDetector>
  )
}

🚀 Next section: Exposure