在launch目录里创建launch文件或py文件后，ros2 launch不能直接找到，会报错

file 'file.launch' was not found in the share directory of package 'package_name' which is at '/home/user/catkin_ws/install/package_name/share/package_name'

需要在CMakeLists里加一句

install(DIRECTORY launch
DESTINATION share/${PROJECT_NAME})

再编译后，会把launch文件复制到share目录里。

• 使用xml

<launch>
    <node pkg="nav2_map_server" exec="map_server" name="map_server">
        <param name="yaml_filename" value="/home/zzp/catkin_ws/maps/test.yaml"/>
    </node>

    <node pkg="nav2_planner" exec="planner_server" name="planner_server" >
    </node>
</launch>

args的写法一直查不到，按ROS1的写法是错的，节点会退出: <node pkg ="tf2_ros" exec="static_transform_publisher" name="map_odom_tf" args="1 0 0 0 0 0 map odom 100" />

• 使用python

cd ~/ros2_ws
mkdir launch
vim launch/both_launch.py

加入下面内容:

from launch import LaunchDescription
from launch_ros.actions import Node
 
def generate_launch_description():
    return LaunchDescription([
        Node(
            package='duckiebot',
            namespace='duckietown',
            executable='duckiebot_node',
            name='duckiebot_node1'
        ),
        Node(
            package='control',
            namespace='duckietown',
            executable='control_node',
            name='control_node1'
        )
    ])