simulation.launch.py

import os

from launch_ros.actions import Node
from launch import LaunchDescription
from launch.conditions import IfCondition
from launch.substitutions import LaunchConfiguration
from launch.actions import DeclareLaunchArgument, ExecuteProcess, IncludeLaunchDescription
from ament_index_python.packages import get_package_share_directory
from launch.launch_description_sources import PythonLaunchDescriptionSource


def generate_launch_description():

    # Get package dirs
    launch_dir = get_package_share_directory('hollander_bringup')

    # Default values
    default_rviz_config_path = os.path.join(launch_dir, 'rviz/urdf_config.rviz')

    # Parameters
    configurable_parameters = [
        {'name': 'need_rviz',     'default': 'False',                  'description': 'Whether launch or not rviz'},
        {'name': 'rvizconfig',    'default': default_rviz_config_path, 'description': 'Absolute path to rviz config file'},
        {'name': 'use_sim_time',  'default': 'True',                   'description': 'Flag to enable use_sim_time'},
    ]

    def declare_configurable_parameters(parameters):
        return [DeclareLaunchArgument(param['name'], default_value=param['default'], description=param['description']) for param in parameters]

    description = IncludeLaunchDescription(
        PythonLaunchDescriptionSource(os.path.join(get_package_share_directory('hollander_bringup'), 'launch', 'description.launch.py')),
        condition=IfCondition(LaunchConfiguration('need_description'))
    )

    """ NODES """
    rviz_node = Node(
        package='rviz2',
        executable='rviz2',
        name='rviz2',
        output='screen',
        arguments=['-d', LaunchConfiguration('rvizconfig')],
    )

    spawn_entity = Node(
        package='gazebo_ros',
        executable='spawn_entity.py',
        arguments=['-entity', 'hollander', '-topic', 'robot_description'],
        output='screen'
    )

    return LaunchDescription(declare_configurable_parameters(configurable_parameters) + [

        ExecuteProcess(cmd=['gazebo', '--verbose', '-s', 'libgazebo_ros_init.so', '-s', 'libgazebo_ros_factory.so'], output='screen'),

        description,

        spawn_entity,
        rviz_node,
    ])