adding button to a gridview in android

If you want the Button to be below the GridView, use something like this:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:ads="http://schemas.android.com/apk/lib/com.google.ads"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:gravity="center"
    android:orientation="vertical" >

    <GridView
        android:id="@+id/gridFriends"
        android:layout_width="fill_parent"
        android:layout_height="0dip"
        android:layout_weight="1"
        android:clipChildren="true"
        android:columnWidth="100dp"
        android:gravity="center"
        android:numColumns="auto_fit"
        android:scrollbars="none"
        android:stretchMode="columnWidth" >
    </GridView>

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:paddingBottom="5dp"
        android:paddingLeft="9dp"
        android:paddingRight="9dp"
        android:paddingTop="5dp" >

        <ImageButton
            android:id="@+id/imgbtnDemo"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_gravity="bottom|center"
            android:background="@null"
            android:gravity="center"
            android:src="@drawable/ic_contact_picture" >
        </ImageButton>
    </LinearLayout>

</LinearLayout>

If you want a Button in every cell in the GridView, you will have to use a Custom GridView that uses an Adapter. An exmaple XML snippet for the custom cell in the GridView:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/mainContainer"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:padding="5dp" >

    <FrameLayout
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:gravity="center" >

        <ImageView
            android:id="@+id/imgProfilePicture"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:adjustViewBounds="true"
            android:scaleType="centerCrop"
            android:src="@null" />

        <ImageButton
            android:id="@+id/imgbtnDemo"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_gravity="bottom|center"
            android:background="@null"
            android:gravity="center"
            android:src="@drawable/ic_contact_picture" >
        </ImageButton>
    </FrameLayout>

</RelativeLayout>

NOTE: In the XMLS snippets in the post, I am using ImageButton's. Change them and any necessary attributes to that of a Button. It is merely an illustration. You should be able to connect the dots though. ;-)

if you are familiar with the concept of custom ListViews, with a few modifications, you will be able to implement a custom GridView too. If you are not familiar with custom ListViews or GridViews, follow this tutorial to see how to create a custom GridView: http://www.coderzheaven.com/2012/02/29/custom-gridview-in-android-a-simple-example/.

Or use this Google Search for more tutorials on custom GridView's.

And this is a link to an answer of mine on SO. It has the complete solution. Use what logic suits your purpose.