OpenCV for Android 3.1 from OpenCV Webs Site.

To import OpenCV you have to import new module by File > New > Import Module... > then locate your sdk folder for me is ~/Library/Android/OpenCV-android-sdk-3.1/sdk/java

Right click at your project folder in Android Studio > Open Modules Setting > 'Module' app > Dependencies 'tab' > + > Module Dependencies > select :libraries:OpenCV.

You need to create a JNI folder to /app/src/main/jniLibs and copy all folders with *.so files eg. arm64-v8a, armeabi, armeabi-v7a, mips, mips64, x86, x86_64 (choose CPU architecture you supported) into the jniLibs folder from the OpenCV SDK

• The folder you can find in OpenCV SDK/sdk/native/libs/
• You can delete all other non *.so files in the folders