Draw a rectangle on image frames received via Android Camera

edit

First of all use the Java docs to see what is implemented on http://docs.opencv.org/java/2.4.5/

Look there at the core library, go to method summary and then look for your drawing function. This is what I found.

rectangle(Mat img, Point pt1, Point pt2, Scalar color)
// Draws a simple, thick, or filled up-right rectangle.

Hope this will solve your problem :)