build_item_categoria.dart

Widget _buildCategoryItem(index){

    return new GestureDetector(
      onTap: (){
        onTabCategory(index);
      },
      child: new Center(
        child: new Container(
          margin: new EdgeInsets.only(left: 10.0),
          child: new Material(
            elevation: 2.0,
            borderRadius: const BorderRadius.all(const Radius.circular(25.0)),
            child:  new Container(
              padding: new EdgeInsets.only(left: 12.0,top: 7.0,bottom: 7.0,right: 12.0),
              color: _category_selected == index ? Colors.blue[800]:Colors.blue[500],
              child: new Text(_categorys[index],
                style: new TextStyle(
                    color: Colors.white),
              ),
            ),
          ),
        ),
      ),
    );

  }

  onTabCategory(index){

    setState(() {
      _category_selected = index;
    });

    //Realiza chamada de serviço para atualizar as noticias de acordo com a categoria selecionada

  }