code: public void animateOpen() {
          prepareContent();
  
          if (onDrawerScrollListener != null) {
              onDrawerScrollListener.onScrollStarted();
          }
  
          animateOpen(vertical ? viewHandle.getTop() : viewHandle.getLeft());
  
          sendAccessibilityEvent(AccessibilityEvent.TYPE_WINDOW_STATE_CHANGED);
  
          if (onDrawerScrollListener != null) {
              onDrawerScrollListener.onScrollEnded();
          }
      }
docs: Opens the drawer with an animation.
  
  @see #animateToggle()
  @see #animateClose()
  @see #toggle()
  @see #open()
  @see #close()