How to set fixed focus area in Android camera?

Question

I'm developing an Android app that use camera to capture image for futher step. For good result camera should focus on fixed area (like center area of the image).

I'm using

params.setFocusMode(Camera.Parameters.FOCUS_MODE_AUTO); mCamera.setParameters(params);

but it seem not the best choice for my app.

Please tell me how can I set camera focus on fixed area?

Thanks in advance.