Hi i\'m trying to create a application related to the Augmented Reality (AR) and was able to configure my application with Metaio SDK and OpenCV library successfully in two sepa
I suggest you to integrate the sdk of Opencv4android, and to see the samples come with, they are very good examples to teach you how to use the camera easily
For your objective probably face detection example is good to check.
Here is the tuto that help you to install and configure opencv SDK
For AR I can't help you so much, but have look at this discussion, it could be helpful.