How can i know whether I have adds to show, which I get from admob server?

I have a adView in my application UI i don't want to display it when there is no ads to display.

How can i know whether my application have ads to display?

this is my layout

<LinearLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:myapp="http://schemas.android.com/apk/res/measurements.areaconvertor"
    android:id="@+id/root_layout"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">

        <com.admob.android.ads.AdView
            android:id="@+id/ad"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            myapp:backgroundColor="#000000"
            myapp:primaryTextColor="#FFFFFF"
            myapp:secondaryTextColor="#CCCCCC"/>


<FrameLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent">


    <ImageView
         开发者_开发技巧       .................

In my experience, an AdView automatically hides if no ads are present when you use wrap_content for height.

<com.admob.android.ads.AdView
    android:id="@+id/ad"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    myapp:backgroundColor="#000000"
    myapp:primaryTextColor="#FFFFFF"
    myapp:secondaryTextColor="#CCCCCC" />

i did it this way

    if(!isOnline()){
       LinearLayout li=(LinearLayout)findViewById(R.id.linearLayourID);
       AdView ad=(AdView)findViewById(R.id.adView);
       ad.setEnabled(false);
       li.setWeightSum(8);
    }


           public boolean isOnline() {
               ConnectivityManager cm =
               (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
               NetworkInfo netInfo = cm.getActiveNetworkInfo();
               if (netInfo != null && netInfo.isConnectedOrConnecting()) {
                    return true;
               }
               return false;
           }