public void setZoomableController(ZoomableController zoomableController) {
    Preconditions.checkNotNull(zoomableController);
    mZoomableController.setListener(null);
    mZoomableController = zoomableController;
    mZoomableController.setListener(mZoomableListener);
  }
Sets a custom zoomable controller, instead of using the default one.
samples/zoomable/src/main/java/com/facebook/samples/zoomable/ZoomableDraweeView.java