Android View align bottom (programmatically) without XML

I got a problem with setting aligning my view programatically to the bottom of the screen. Basically I just want to place my admob advert at the screen bottom. I can't do it with XML because it would be even more troublesome. Right now I already got the advert working, and added it manually to the RelativeLayout, but by default it appears at the top of the screen. I tried to use the gravity command, but couldn't get it working.

Here's the code snippet:

    _glSurfaceView = new CCGLSurfaceView(this);

    adView = new AdView(this, AdSize.BANNER, "a14e04559caea39");
    adView.loadAd(new AdRequest());
    adView.setGravity(Gravity.BOTTOM);

    RelativeLayout rl = new RelativeLayout(this);

    rl.addView(_glSurfaceView);
    rl.addView(adView);     

    setContentView(rl);
    adView.loadAd(new AdRequest());

Can anyone help me out?