ros2-android-tutorial

This is a short tutorial for developing Android apps for ROS2 Java bindings based on ros2_java and ros2_android_examples.

Installation (Only for Linux)

Download Android Studio from here.

Download the latest stable version Android NDK from the official website then unpack it to ~/Android/Sdk/, name it as ndk-bundle, so the path will be ~/Android/Sdk/ndk-bundle.

Check your JAVA version:

update-java-alternatives -l

You might be able to spot the path from output, it will be something like this:

/usr/lib/jvm/java-1.8.0-openjdk-amd64

Copy the path from the output. Then, add following lines to the bottom of /etc/environment.

JAVA_HOME="[###REPLACE THIS WITH YOUR JAVA PATH###]"
ANDROID_HOME=~/Android/Sdk
ANDROID_NDK=~/Android/Sdk/ndk-bundle

Build ROS2_JAVA on Linux computer.

# define paths
ROOT_DIR = ${HOME}
AMENT_WORKSPACE=${ROOT_DIR}/ament_ws
ROS2_ANDROID_WORKSPACE=${ROOT_DIR}/ros2_android_ws

# pull and build ament
mkdir -p ${AMENT_WORKSPACE}/src
cd ${AMENT_WORKSPACE}
wget https://raw.githubusercontent.com/esteve/ament_java/master/ament_java.repos
vcs import ${AMENT_WORKSPACE}/src < ament_java.repos
src/ament/ament_tools/scripts/ament.py build --symlink-install --isolated

# android build configuration
export PYTHON3_EXEC="$( which python3 )"
export ANDROID_ABI=armeabi-v7a
export ANDROID_NATIVE_API_LEVEL=android-21
export ANDROID_TOOLCHAIN_NAME=arm-linux-androideabi-clang

# pull and build ros2 for android
mkdir -p ${ROS2_ANDROID_WORKSPACE}/src
cd ${ROS2_ANDROID_WORKSPACE}
wget https://raw.githubusercontent.com/esteve/ros2_java/master/ros2_java_android.repos
vcs import ${ROS2_ANDROID_WORKSPACE}/src < ros2_java_android.repos
source ${AMENT_WORKSPACE}/install_isolated/local_setup.sh
ament build --isolated --skip-packages test_msgs \
  --cmake-args \
  -DPYTHON_EXECUTABLE=${PYTHON3_EXEC} \
  -DCMAKE_TOOLCHAIN_FILE=$ANDROID_NDK/build/cmake/android.toolchain.cmake \
  -DANDROID_FUNCTION_LEVEL_LINKING=OFF \
  -DANDROID_NATIVE_API_LEVEL=${ANDROID_NATIVE_API_LEVEL} \
  -DANDROID_TOOLCHAIN_NAME=${ANDROID_TOOLCHAIN_NAME} \
  -DANDROID_STL=gnustl_shared \
  -DANDROID_ABI=${ANDROID_ABI} \
  -DANDROID_NDK=${ANDROID_NDK} \
  -DTHIRDPARTY=ON \
  -DCOMPILE_EXAMPLES=OFF \
  -DCMAKE_FIND_ROOT_PATH="$AMENT_WORKSPACE/install_isolated;$ROS2_ANDROID_WORKSPACE/install_isolated" \
  -- \
  --parallel \
  --ament-gradle-args \
  -Pament.android_stl=gnustl_shared -Pament.android_abi=$ANDROID_ABI -Pament.android_ndk=$ANDROID_NDK --

For more instruction: https://github.com/esteve/ros2_java#android

Try out Android examples

Github repo: https://github.com/esteve/ros2_android_examples

Method1: Install APK through Android Studio

Firstly, plug in your android phone to your computer via USB cable and make sure you have enable developer options and USB debugging in your phone settings.

After that, open ros2_talker_android or ros2_listener_android in Android Studio, click 'Build', then click 'Run' and choose your device.

Method2: Install APK through command line

Firstly, plug in your android phone to your computer via USB cable and make sure you have enable developer options and USB debugging in your phone settings.

After that, run the following commands on your computer:

Talker:

adb install ~/ros2_android_ws/install_isolated/ros2_talker_android/ros2_talker_android-debug.apk

Listener:

adb install ~/ros2_android_ws/install_isolated/ros2_listener_android/ros2_listener_android-debug.apk

Add ROS2 packages

When you want to develop your own ROS2 Android app, you might want to import additional ROS2 packages for additional features.

To import ROS2 library into your Android project:

In your gradle.properties, add the package path to ament.dependencies and ament.exec_dependency_paths_in_workspace variables:

For example:

//...
ament.dependencies=...\:/home/rmf/ros2_android_ws/install_isolated/geometry_msgs/share/geometry_msgs
//...
ament.exec_dependency_paths_in_workspace=...\:/home/rmf/ros2_android_ws/install_isolated/geometry_msgs/share/geometry_msgs
//...

ROS2 Node in Java

To start a ROS2 Node:

talkerNode = new TalkerNode("android_talker_node", "chatter");

To add a node:

getExecutor().addNode(talkerNode);

To remove a node:

getExecutor().removeNode(talkerNode);

Import Android library

Open your project in Android Studio
Download the library (using Git, or a zip archive to unzip)
Create a folder "subProject" in your project
Copy and paste the FreemiumLibrary folder to your subProject folder
On the root of your project directory create/modify the settings.gradle file. It should contain something like the following:

include ':virtualjoystick'
project(':virtualjoystick').projectDir = new File('libs/virtual-joystick-android/virtualjoystick')

gradle clean & build/close the project and reopen/re-import it.
Edit your project's build.gradle to add this in the "depencies" section:

dependencies {
// ...
  compile project(':virtualjoystick')
}