code: public void setLineMorphingState(int state, boolean animation){
  		if(mIcon != null && mIcon instanceof LineMorphingDrawable)
              ((LineMorphingDrawable)mIcon).switchLineState(state, animation);
  	}
docs: Set the line state of LineMorphingDrawable that is used as this button's icon.
  @param state The line state.
  @param animation Indicate should show animation when switch line state or not.