</robot>

import launch
import launch_ros
from ament_index_python.packages import get_package_share_directory
import os
import launch_ros.parameter_descriptions

def generate_launch_description():
#获取urdf路径
urdf_package_path = get_package_share_directory('fishbot_description')
default_urdf_path = os.path.join(urdf_package_path,'urdf','first_robot.xacro')
#声明一个urdf目录的参数,方便修改
action_declare_arg_mode_path = launch.actions.DeclareLaunchArgument(
name='model',
default_value=str(default_urdf_path),
description='加载的模型文件路径'
)
#通过文件路径，获取内容，并转换为参数值对象，以供传入robot_state_publisher
substitutions_command_result = launch.substitutions.Command(['xacro ',launch.substitutions.LaunchConfiguration('model')])
robot_description_value = launch_ros.parameter_descriptions.ParameterValue(
substitutions_command_result, value_type=str
)

#读取urdf文件中的内容
action_robot_state_publisher = launch_ros.actions.Node(
    package='robot_state_publisher' ,#可执行文件包的名字
    executable='robot_state_publisher' ,#可执行文件的名字
    parameters=[{'robot_description':robot_description_value}]
)

action_joint_state_publisher = launch_ros.actions.Node(
    package='joint_state_publisher' ,#可执行文件包的名字
    executable='joint_state_publisher' ,#可执行文件的名字
)

action_rviz_node = launch_ros.actions.Node(
    package='rviz2',
    executable='rviz2'
)

return launch.LaunchDescription([
    action_declare_arg_mode_path,
    action_robot_state_publisher,
    action_joint_state_publisher,
    action_rviz_node,

])