docs: public void setDragView(View dragView) {
          if (mDragView != null) {
              mDragView.setOnClickListener(null);
          }
          mDragView = dragView;
          if (mDragView != null) {
              mDragView.setClickable(true);
              mDragView.setFocusable(false);
              mDragView.setFocusableInTouchMode(false);
              mDragView.setOnClickListener(new OnClickListener() {
                  @Override
                  public void onClick(View v) {
                      if (!isEnabled() || !isTouchEnabled()) return;
                      if (mSlideState != PanelState.EXPANDED && mSlideState != PanelState.ANCHORED) {
                          if (mAnchorPoint < 1.0f) {
                              setPanelState(PanelState.ANCHORED);
                          } else {
                              setPanelState(PanelState.EXPANDED);
                          }
                      } else {
                          setPanelState(PanelState.COLLAPSED);
                      }
                  }
              });
              ;
          }
      }