ZoomGestureDetector

@RequiresApi(value = 21)
class ZoomGestureDetector

Detector that interprets MotionEvents and notify users when a zooming gesture has occurred.

To use this class to do pinch-to-zoom on the viewfinder:

• In the OnZoomGestureListener.onZoomEvent, when receiving ZoomEvent.Move, get the ZoomEvent.Move.scaleFactor and use the value with CameraControl.setZoomRatio if the factor is in the range of ZoomState.getMinZoomRatio and ZoomState.getMaxZoomRatio. Then create an instance of the ZoomGestureDetector with the OnZoomGestureListener.

• In the View.onTouchEvent, call onTouchEvent and pass the MotionEvents to the ZoomGestureDetector.

import androidx.camera.viewfinder.core.ZoomGestureDetector
import androidx.camera.viewfinder.core.ZoomGestureDetector.ZoomEvent

val zoomGestureDetector = ZoomGestureDetector(context) { zoomEvent ->
    when (zoomEvent) {
        is ZoomEvent.Move -> {
            val zoomState = camera.cameraInfo.zoomState.value!!
            val ratio = zoomState.zoomRatio * zoomEvent.scaleFactor
            val minRatio = zoomState.minZoomRatio
            val maxRatio = zoomState.maxZoomRatio
            val clampedRatio = min(max(ratio, minRatio), maxRatio)
            camera.cameraControl.setZoomRatio(clampedRatio)
        }

        is ZoomEvent.Begin -> {
            // Handle the begin event. For example, determine whether this gesture
            // should be processed further.
        }

        is ZoomEvent.End -> {
            // Handle the end event. For example, show a UI indicator.
        }
    }
    true
}

return zoomGestureDetector.onTouchEvent(event)

Summary

ZoomGestureDetector(
    context: Context,
    spanSlop: @Px Int = ViewConfiguration.get(context).scaledTouchSlop * 2,
    minSpan: @Px Int = DEFAULT_MIN_SPAN,
    listener: ZoomGestureDetector.OnZoomGestureListener
)

@UiThread
fun onTouchEvent(event: MotionEvent): Boolean

var isQuickZoomEnabled: Boolean

var isStylusZoomEnabled: Boolean

val timeDelta: Long