Android Studio 0.8.2+ and above, could easily import modules. Thanks to TGMCains answer, is simplified, by using Android Studio itself to import OpenCV as a module.

1. Download latest OpenCV sdk for Android from OpenCV.org and decompress the zip file.
2. Import OpenCV to Android Studio, From File -> Import Module, choose sdk/java folder in the unzipped opencv archive.
3. Update build.gradle under imported OpenCV module to update 4 fields to match your project build.gradle a) compileSdkVersion b) buildToolsVersion c) minSdkVersion and 4) targetSdkVersion.
4. Add module dependency by Application -> Module Settings, and select the Dependenciestab. Click + icon at bottom, choose Module Dependency and select the imported OpenCV module.
5. Copy libs folder under sdk/native to Android Studio under app/src/main.
6. In Android Studio, rename the copied libs directory to jniLibs and we are done.

Step (6) is since Android studio expects native libs in app/src/main/jniLibs instead of older libs folder. For those new to Android OpenCV, don't miss below steps

• include static{ System.loadLibrary("opencv_java"); }
• For step(5), if you ignore any platform libs like x86, make sure your device/emulator is not on that platform.

OpenCV written is in C/C++. Java wrappers are

1. Android OpenCV SDK - OpenCV.org maintained Android Java wrapper. I suggest this one.
2. OpenCV Java - OpenCV.org maintained auto generated desktop Java wrapper.
3. JavaCV - Popular Java wrapper maintained by independent developer(s). Not Android specific. This library might get out of sync with OpenCV newer versions.