Could you be more precise? Where is the problem? Do you want to design a method that recognizes the three-in-a-row situation? If so than it can be done in more ways than one, but it still is a bit tricky if you are a begginer. Also, you did not say how the cards are moved, so it is hard to picture what you are working on. You should post some of the work you already have done, and then say where the problem is.

You could switch the image of the card with a transparent image, or an image that is filled with the color of the playing table