main_launch.py

import os
from ament_index_python.packages import get_package_share_directory
from launch import LaunchDescription
from launch.actions import (DeclareLaunchArgument, GroupAction,
                            IncludeLaunchDescription, SetEnvironmentVariable)
from launch.conditions import IfCondition
from launch.launch_description_sources import PythonLaunchDescriptionSource
from launch.substitutions import LaunchConfiguration, PythonExpression
from launch_ros.actions import PushRosNamespace
from launch.actions import DeclareLaunchArgument, EmitEvent, RegisterEventHandler
from launch.conditions import IfCondition, UnlessCondition
from launch.event_handlers import OnProcessExit
from launch.events import Shutdown
from launch_ros.actions import Node
from nav2_common.launch import ReplaceString


def generate_launch_description():
    # Get the launch directory
    bringup_dir = get_package_share_directory('nav2_bringup')
    launch_dir = os.path.join(bringup_dir, 'launch')

    # Create the launch configuration variables
    namespace = LaunchConfiguration('namespace')
    use_namespace = LaunchConfiguration('use_namespace')
    slam = LaunchConfiguration('slam')
    map_yaml_file = LaunchConfiguration('map')
    use_sim_time = LaunchConfiguration('use_sim_time')
    params_file = LaunchConfiguration('params_file')
    autostart = LaunchConfiguration('autostart')

    stdout_linebuf_envvar = SetEnvironmentVariable(
        'RCUTILS_LOGGING_BUFFERED_STREAM', '1')

    declare_namespace_cmd = DeclareLaunchArgument(
        'namespace',
        default_value='',
        description='Top-level namespace')

    declare_use_namespace_cmd = DeclareLaunchArgument(
        'use_namespace',
        default_value='false',
        description='Whether to apply a namespace to the navigation stack')

    declare_slam_cmd = DeclareLaunchArgument(
        'slam',
        default_value='False',
        description='Whether run a SLAM')

    declare_map_yaml_cmd = DeclareLaunchArgument(
        'map',
        default_value = '/home/hp/navigation2/nav2_bringup/bringup/maps/map_02.yaml',
        description='Full path to map yaml file to load')

    declare_use_sim_time_cmd = DeclareLaunchArgument(
        'use_sim_time',
        default_value='false',
        description='Use simulation (Gazebo) clock if true')

    declare_params_file_cmd = DeclareLaunchArgument(
        'params_file',
        default_value=os.path.join(bringup_dir, 'params', 'nav2_params.yaml'),
        description='Full path to the ROS2 parameters file to use for all launched nodes')

    declare_autostart_cmd = DeclareLaunchArgument(
        'autostart', default_value='true',
        description='Automatically startup the nav2 stack')

    # Specify the actions
    bringup_cmd_group = GroupAction([
        PushRosNamespace(
            condition=IfCondition(use_namespace),
            namespace=namespace),

        IncludeLaunchDescription(
            PythonLaunchDescriptionSource(os.path.join(launch_dir, 'slam_launch.py')),
            condition=IfCondition(slam),
            launch_arguments={'namespace': namespace,
                              'use_sim_time': use_sim_time,
                              'autostart': autostart,
                              'params_file': params_file}.items()),

        IncludeLaunchDescription(
            PythonLaunchDescriptionSource(os.path.join(launch_dir,
                                                       'localization_launch.py')),
            condition=IfCondition(PythonExpression(['not ', slam])),
            launch_arguments={'namespace': namespace,
                              'map': map_yaml_file,
                              'use_sim_time': use_sim_time,
                              'autostart': autostart,
                              'params_file': params_file,
                              'use_lifecycle_mgr': 'false'}.items()),

        IncludeLaunchDescription(
            PythonLaunchDescriptionSource(os.path.join(launch_dir, 'navigation_launch.py')),
            launch_arguments={'namespace': namespace,
                              'use_sim_time': use_sim_time,
                              'autostart': autostart,
                              'params_file': params_file,
                              'use_lifecycle_mgr': 'false',
                              'map_subscribe_transient_local': 'true'}.items()),
    ])

    # Create the launch description and populate
    ld = LaunchDescription()

    # Set environment variables
    ld.add_action(stdout_linebuf_envvar)

    # Declare the launch options
    ld.add_action(declare_namespace_cmd)
    ld.add_action(declare_use_namespace_cmd)
    ld.add_action(declare_slam_cmd)
    ld.add_action(declare_map_yaml_cmd)
    ld.add_action(declare_use_sim_time_cmd)
    ld.add_action(declare_params_file_cmd)
    ld.add_action(declare_autostart_cmd)

    # Add the actions to launch all of the navigation nodes
    ld.add_action(bringup_cmd_group)


    # Create the launch configuration variables
    namespace = LaunchConfiguration('namespace')
    use_namespace = LaunchConfiguration('use_namespace')
    rviz_config_file = LaunchConfiguration('rviz_config')

    # Declare the launch arguments
    declare_namespace_cmd = DeclareLaunchArgument(
        'namespace',
        default_value='navigation',
        description=('Top-level namespace. The value will be used to replace the '
                     '<robot_namespace> keyword on the rviz config file.'))

    declare_use_namespace_cmd = DeclareLaunchArgument(
        'use_namespace',
        default_value='false',
        description='Whether to apply a namespace to the navigation stack')

    declare_rviz_config_file_cmd = DeclareLaunchArgument(
        'rviz_config',
        default_value=os.path.join(bringup_dir, 'rviz', 'nav2_default_view.rviz'),
        description='Full path to the RVIZ config file to use')

    # Launch rviz
    start_rviz_cmd = Node(
        condition=UnlessCondition(use_namespace),
        package='rviz2',
        executable='rviz2',
        name='rviz2',
        arguments=['-d', rviz_config_file],
        output='screen')

    namespaced_rviz_config_file = ReplaceString(
            source_file=rviz_config_file,
            replacements={'<robot_namespace>': ('/', namespace)})

    start_namespaced_rviz_cmd = Node(
        condition=IfCondition(use_namespace),
        package='rviz2',
        executable='rviz2',
        name='rviz2',
        namespace=namespace,
        arguments=['-d', namespaced_rviz_config_file],
        output='screen',
        remappings=[('/tf', 'tf'),
                    ('/tf_static', 'tf_static'),
                    ('/goal_pose', 'goal_pose'),
                    ('/clicked_point', 'clicked_point'),
                    ('/initialpose', 'initialpose')])

    exit_event_handler = RegisterEventHandler(
        condition=UnlessCondition(use_namespace),
        event_handler=OnProcessExit(
            target_action=start_rviz_cmd,
            on_exit=EmitEvent(event=Shutdown(reason='rviz exited'))))

    exit_event_handler_namespaced = RegisterEventHandler(
        condition=IfCondition(use_namespace),
        event_handler=OnProcessExit(
            target_action=start_namespaced_rviz_cmd,
            on_exit=EmitEvent(event=Shutdown(reason='rviz exited'))))

    # Create the launch description and populate
    ld = LaunchDescription()

    # Declare the launch options
    ld.add_action(declare_namespace_cmd)
    ld.add_action(declare_use_namespace_cmd)
    ld.add_action(declare_rviz_config_file_cmd)

    # Add any conditioned actions
    ld.add_action(start_rviz_cmd)
    ld.add_action(start_namespaced_rviz_cmd)

    # Add other nodes and processes we need
    ld.add_action(exit_event_handler)
    ld.add_action(exit_event_handler_namespaced)

    return ld