How to place adView below?

I create a game which has a custom view derived from surfaceView. and in the game I want to place adView below the gameView. but the problem is , if I place adView below the gameView , the adView wont show up.. I do all the layouting in the code because its easier to maintain..

here is the code..

If i place the adView above the gameView it will show up

private RelativeLayout layout;   //the gameView container
private LinearLayout mainLayout;  //the main layout
private RocketView rocketView;   //the gameView
private AdView adView;             //the adView
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

        mainLayout = new LinearLayout(this);
        mainLayout.setOrientation(LinearLayout.VERTICAL);

        adView = new AdView(this, AdSize.BANNER, "a14d9e9ea3740e8");
       开发者_JAVA百科 adView.setVisibility(AdView.VISIBLE);
        adView.loadAd(new AdRequest());
        mainLayout.addView(adView);   // -->> here i place the adView first

        layout = new RelativeLayout(this);
        mainLayout.addView(layout);   //--->> then i place the gameView later

        rocketView = new RocketView(this);
        layout.addView(rocketView);
        setContentView(mainLayout);
}

But if i place the adView below it won't show up.

private RelativeLayout layout;
private LinearLayout mainLayout;
private RocketView rocketView;
private Launcher launcher;

private AdView adView;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
        mainLayout = new LinearLayout(this);
        mainLayout.setOrientation(LinearLayout.VERTICAL);

        layout = new RelativeLayout(this);
        mainLayout.addView(layout);

        rocketView = new RocketView(this);
        layout.addView(rocketView);

        adView = new AdView(this, AdSize.BANNER, "a14d9e9ea3740e8");
        adView.setVisibility(AdView.VISIBLE);
        adView.loadAd(new AdRequest());
        mainLayout.addView(adView);
        setContentView(mainLayout);

}

I think I know what happen.. after adView loading the adRequest and get the ads, its not streching above, but it streching below, so it not showing in the screen. but I don't know how to solve this problem. please help me..

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First, there is no need for your linear layout, mainLayout. Add both rocketView and adView to your relativelayout, layout. Give adView the attributes align_parent_bottom, wrap_content (height) and wrap_content or fill_parent for width. Then give rocketView fill_parent for width and height and have it be "above" adView.