Android : Expandable Listview customization

I want reduce the Expandable list view child list view divider height, the problem is when ever I tried to increase the main view divider height it result in increasing the child list divider height, Now what I want is Parent list view height should be more than the child list view.

The Code I tried 1,

       Elv.setGroupIndicator(null);
    Elv.setChildIndicator(null);
    Elv.setChildDivider(getResources().getDrawable(R.drawable.dividermore));  
    Elv.setDividerHeight(1);

2,

           android:id="@+id/expandableListView1"
          android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:divider="@drawable/transparentimage80"
    android:dividerHeight="25dp" 
    android:layout_margin="5dp"
    android:childDivider="@drawable/dividermore"
    >
</ExpandableListView>

Both didn't worked