@Override
  public void onGestureBegin(TransformGestureDetector detector) {
    FLog.v(TAG, "onGestureBegin");
    mPreviousTransform.set(mActiveTransform);
    onTransformBegin();
    // We only received a touch down event so far, and so we don't know yet in which direction a
    // future move event will follow. Therefore, if we can't scroll in all directions, we have to
    // assume the worst case where the user tries to scroll out of edge, which would cause
    // transformation to be corrected.
    mWasTransformCorrected = !canScrollInAllDirection();
  }
Notifies controller of the received touch event.
samples/zoomable/src/main/java/com/facebook/samples/zoomable/DefaultZoomableController.java