i2pd/docs/build_notes_android.md

Pre-requesties

You need to install Android SDK, NDK and QT with android support.

SDK (choose command line tools only)
https://developer.android.com/studio/index.html
NDK https://developer.android.com/ndk/downloads/index.html

QT
https://www.qt.io/download-open-source/ Choose one for your platform for android For example QT 5.6 under Linux would be http://download.qt.io/official_releases/qt/5.6/5.6.1-1/qt-opensource-linux-x64-android-5.6.1-1.run

You also need Java JDK and Ant.

QT-Creator

Open QT-creator that should be installed with QT.
Go to Settings/Anndroid and specify correct paths to SDK and NDK. If everything is correct you will see two set avaiable:
Android for armeabi-v7a (gcc, qt) and Android for x86 (gcc, qt).

Dependencies

Take following pre-compiled binaries from PurpleI2P's repositories.
git clone https://github.com/PurpleI2P/Boost-for-Android-Prebuilt.git
git clone https://github.com/PurpleI2P/OpenSSL-for-Android-Prebuilt.git
git clone https://github.com/PurpleI2P/MiniUPnP-for-Android-Prebuilt.git
git clone https://github.com/PurpleI2P/android-ifaddrs.git

Building the app

Open qt/i2pd_qt/i2pd_qt.pro in the QT-creator. Change line MAIN_PATH = /path/to/libraries to actual path where did you put the dependancies to. Select appropriate project (usually armeabi-v7a) and build. You will find an .apk file in android-build/bin folder.