Install Android SDK on headless Ubuntu linux machine via command line, so that you can compile open source Android apps.

ubuntu-cli-install-android-sdk.sh

#!/bin/bash

# Thanks to https://gist.github.com/wenzhixin/43cf3ce909c24948c6e7
# Execute this script in your home directory. Lines 17 and 21 will prompt you for a y/n

# Install Oracle JDK 8
apt install openjdk-8-jdk

# Get SDK tools (link from https://developer.android.com/studio/index.html#downloads)
wget https://dl.google.com/android/repository/sdk-tools-linux-4333796.zip
unzip sdk-tools-linux-*.zip
rm sdk-tools-linux-*.zip

# Let it update itself and install some stuff
cd tools
tools/sdkmanager --update

# Download every build-tools version that has ever existed
# This will save you time! Thank me later for this
./android update sdk --all --no-ui --filter $(seq -s, 27)

# If you need additional packages for your app, check available packages with:
# ./android list sdk --all

# install certain packages with:
# ./android update sdk --no-ui --all --filter 1,2,3,<...>,N
# where N is the number of the package in the list (see previous command)


# Add the directory containing executables in PATH so that they can be found
echo 'export ANDROID_HOME=$HOME/android-sdk-linux' >> ~/.bashrc
echo 'export PATH=$PATH:$ANDROID_HOME/tools:$ANDROID_HOME/platform-tools' >> ~/.bashrc

source ~/.bashrc

# Make sure you can execute 32 bit executables if this is 64 bit machine, otherwise skip this
dpkg --add-architecture i386
apt-get update
apt-get install -y libc6:i386 libstdc++6:i386 zlib1g:i386

# Add some swap space, useful if you've got less than 2G of RAM
fallocate -l 2G /swapfile 
chmod 600 /swapfile
mkswap /swapfile
swapon /swapfile

# Optionally run build system as daemon (speeds up build process)
mkdir ~/.gradle
echo 'org.gradle.daemon=true' >> ~/.gradle/gradle.properties
# See here: https://www.timroes.de/2013/09/12/speed-up-gradle/