Setting Up OpenCV library in Eclipse for Android Development
To develop Android apps using OpenCV Library, we need the following tools (all of these are either Open Source or free software, or both) -
Eclipse with ADT Bundle (You can choose any other IDE like Android Studio or even the puissant command line!!, but ADT bundle is a must.)
OpenCV4Android (although, you can compile from source code, it is recommended for novice users to download the binaries.)
Caveat - Download the file named OpenCV-2.4.9-android-sdk.zip and not opencv-2.4.9.zip. (Version might differ)
CygWin (Only for Windows, not needed on Linux or Mac)
Java JDK (JRE would not be sufficient)
Android Native Development Toolkit (NDK)
You will need to set environment variables on your OS for the tools to correctly configure. For the sake of brevity, I would not discuss each step in detail but you can follow the link[1] given at the bottom of this post for detailed instructions.
Alternatively, nVidia also provides a suite of developing tools -- TADP. The advantage of TADP over the piece-by-piece method is that you don't need to follow the often perplexing task of setting up the development environment. The default installation will download a lot of superfluous packages that are not needed (The download size can be greater than 2GB and on slow internet connections, it can turn into a prolonged activity.), rather select the packages manually at the time of download (A dialog box will appear, asking you to select either Complete, Custom or Manually.)
Nota Bene - [1] For meticulous installation instructions, refer to the official OpenCV installation instructions.