Running ROS on an Android device

This project should enable a full version of ROS running on Android.

Introduction

Rosjava (ROS1)

This project is not up-to-date, therefore we encountered many problems due to version incompability. A big problem was that only Android NDKs up to 12 were supported. This is not feasible for an implementation with current smartphones, therefore we decided to find a different approach.

ROS2 Mobile

The ROS2-Mobile App for Android enables the development of Widgets in Java using the ROS2 communication on the same Network using DSS. The widgets can be defined as a publisher or subscriber. The problem we encountered in this implementation is, that we can not use already implemented ROS packages, e.g. ROS control package.

The ROS2_Mobile app is a forked repo trying to port the official ROS-Mobile-Android app to ROS2. The functionalities/widgets supported by this implementation are:

• battery
• button
• camera (ros2_java related issues)
• debug
• gps
• gridmap
• joystick
• label
• laserscan
• logger
• path
• pose
• rqtplot
• switchbutton
• touchgoal
• viz2d
• gps sender
• imu sender

Installation

This part shows how to build ROS2 packages for the use with Java. Please refer to this repo for more details.
Steps:

• Change directory

cd ./ROS2_rosjava_build

• Build docker image

docker build -t ros2java-android-build ./

• Build

python3 run.py ./out/soOut ./out/jarOut

The files in the folders ./out/jarOut and ./out/soOut need to be copied to the Android project according this file-tree:

app (e.g. ROS2_Mobile)
 -libs
    - .jar files
 - src
    - main
        - java
        - jniLibs
            - arm64-v8a
                - .so files
        - res
        - AndroidManifest.xml

Now you are ready to use the Android project with the imported ROS2 packages. Refer to the example project for testing: https://github.com/YasuChiba/ros2-android-test-app

Note: There is also the option to use the Maven artifact repository, currently only available for ROS1.

Creating new widgets

In order to create a new widget for the ROS2_Mobile app you need to follow these steps:

• Open the project folder ./ROS2_Mobile in Android Studio.
• Duplicate an existing widget package in the directory java/com.schneewittchen.rosandroid/widgets/ and name it, e.g. testWidget
• Rename the files in the package, e.g. testWidgetData, testWidgetView, ...
• Add your new widget name to the file res/values/widgets.xml, first to the string-array "widget_names" and then add the Description at the end of the file according to the other widget implementations.
• Duplicate the widget detail xml-file of another widget and name it accordingly, e.g. res/layout/widget_detail_gps.xml

The widget package consists of four main classes:

• Data: Representation of the data structure of this widget
• DetailVH: This class is used for the settings of the widget
• Entity: Here the entity class is defined, such as publisher or subscriber.
• View: This class describes how the widget looks like

Concluding the ROS2_Mobile app could be very useful for future implementations with a ROS "Master" device and not as a standalone option.

Dockerized ROS1 on Android

The third approach was to use a dockerized version of ROS1 on Android using "Linux on Android" such as Termux or Alpine Term.
Note: This android device used in this approach does not need root rights.

Install the Alpine-Term app

Download and install the APK. Unfortunately this app is not available in the Google PlayStore, an alternative link is found here: https://apkcombo.com/alpine-term/alpine.term/

Install Docker on Alpine-Term

Follow these steps to install docker on your Android device in Alpine-Term:

# add docker package
sudo apk add docker

sudo rc-update add docker boot

# start docker deamon
sudo service docker start

For more details, watch this video (starting at 2:11).

Pull and start ROS noetic docker image

Next up, we pull a ROS docker image, e.g. noetic-base.

docker pull ros:noetic-ros-base

Then we run the docker container

docker run -it --network=host ros:noetic-ros-base

And source the ROS workspace

cd /
source ros_.sh

Check ROS installation using a remote ROS Master

For testing purposes we start a ROS Master on another Device "DEVICE MASTER" and set the ROS_MASTER_URI environment variable accordingly.

# DEVICE MASTER
export ROS_MASTER_URI=http://192.168.170.1:11311/
roscore

On the Android device in the Docker container we set the ROS_MASTER_URI from the Host-Device "DEVICE MASTER" and check the current rostopics published to the network:

# DEVICE ANDROID
export ROS_MASTER_URI=http://192.168.170.1:11311/
rostopic list

The output should look like this:

/rosout
/rosout_agg

This means that we successfully receive the topics published by the master.

ROS Master on the Android device

In order to run the ROS core on an Android device we execute the command

roscore

Here an error occurs that could not be solved. Error msg:

RLException: ERROR: could not contact master ...

process[master]: started with pid [71]
RLException: ERROR: could not contact master [http://alpine-term:11311/]
The traceback for the exception was written to the log file
[master] killing on exit
Traceback (most recent call last):
  File "/opt/ros/noetic/bin/rosmaster", line 34, in <module>
    import rosmaster
  File "/opt/ros/noetic/lib/python3/dist-packages/rosmaster/_init_.py", line 35, in <module>
    from .main import rosmaster_main
  File "/opt/ros/noetic/lib/python3/dist-packages/rosmaster/main.py", line 43, in <module>
    import rosmaster.master
  File "/opt/ros/noetic/lib/python3/dist-packages/rosmaster/master.py", line 45, in <module>
    import rosgraph.xmlrpc
  File "/opt/ros/noetic/lib/python3/dist-packages/rosgraph/_init_.py", line 36, in <module>
    from . masterapi import Master, MasterFailure, MasterError, MasterException
  File "/opt/ros/noetic/lib/python3/dist-packages/rosgraph/masterapi.py", line 45, in <module>
    from . names import make_caller_id
  File "<frozen importlib._bootstrap>", line 991, in _find_and_load
  File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 671, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 844, in exec_module
  File "<frozen importlib._bootstrap_external>", line 956, in get_code
  File "<frozen importlib._bootstrap_external>", line 1037, in get_data
KeyboardInterrupt