code: boolean smoothSlideTo(float slideOffset, int velocity) {
          if (!isSlidingEnabled()) {
              // Nothing to do.
              return false;
          }
  
          int panelTop = computePanelTopPosition(slideOffset);
          if (mDragHelper.smoothSlideViewTo(mSlideableView, mSlideableView.getLeft(), panelTop)) {
              setAllChildrenVisible();
              ViewCompat.postInvalidateOnAnimation(this);
              return true;
          }
          return false;
      }
docs: Smoothly animate mDraggingPane to the target X position within its range.
  
  @param slideOffset position to animate to
  @param velocity initial velocity in case of fling, or 0.