how to use android ExpandableListView in xml?

Question

i'm trying to show an expandableListView with a button before it in xml. but somehow, i could not get it work in the code.

my xml (i uses RelativeLayout as parent layout) :

<FrameLayout
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_below="@id/mlt_file_titleFrame"
    android:background="#FF3300"
    android:padding="5dp"
    android:id="@+id/mlt_file_frameL"
    >

    <Button
        android:id="@+id/mlt_file_btn_edit"
        android:text="Edit"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
        android:layout_gravity="left"
        />

</FrameLayout>

<ExpandableListView 
    android:id="@android:id/list"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_below="@id/mlt_file_frameL"
    >

</ExpandableListView>

my code :

public class MLT_File extends ExpandableListActivity {

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.mlt_file_intent);
    // Set up our adapter
    ExpandableListAdapter listAdapter = new customListAdapter();

    ExpandableListView expLV = (ExpandableListView) findViewById(R.id.mlt_expList);//getExpandableListView();
    expLV.setAdapter(listAdapter);

    //registerForContextMenu(expLV);

}//onCreate

/**
 * A simple adapter which maintains an ArrayList of photo resource Ids. 
 * Each photo is displayed as an image. This adapter supports clearing the
 * list of photos and adding a new photo.
 *
 */
public class customListAdapter extends BaseExpandableListAdapter {
    // Sample data set.  children[i] contains the children (String[]) for groups[i].
    private File mapFolder = new File (Environment.getExternalStorageDirectory(),"/MLT/Map");
    private File recordFolder = new File (Environment.getExternalStorageDirectory(),"/MLT/Record");
    private File scribbleFolder = new File (Environment.getExternalStorageDirectory(),"/MLT/Scribble");
    private String[] groups = { "Map", "Record", "Scribble" };
    private String[][] children = { mapFolder.list(), recordFolder.list(), scribbleFolder.list() };

    public Object getChild(int groupPosition, int childPosition) {
        return children[groupPosition][childPosition];
    }

    public long getChildId(int groupPosition, int childPosition) {
        return childPosition;
    }

    public int getChildrenCount(int groupPosition) {
        return children[groupPosition].length;
    }

    public View getChildView(int groupPosition, int childPosition, boolean isLastChild,
                                View convertView, ViewGroup parent) {

        TextView textView = new TextView(MLT_File.this);
        textView.setBackgroundColor(Color.BLACK);
        textView.setGravity(Gravity.CENTER_VERTICAL | Gravity.LEFT);
        textView.setPadding(100, 0, 0, 0);
        textView.setTextColor(Color.WHITE);
        textView.setTextSize(20);
        textView.setText(getChild(groupPosition, childPosition).toString());
        return textView;
    }//getChildView

    public Object getGroup(int groupPosition) {
        return groups[groupPosition];
    }

    public int getGroupCount() {
        return groups.length;
    }

    public long getGroupId(int groupPosition) {
        return groupPosition;
    }

    public View getGroupView(int groupPosition, boolean isExpanded, View convertView,
            ViewGroup parent) {
        TextView textView = new TextView(MLT_File.this);
        textView.setBackgroundColor(Color.WHITE);
        textView.setGravity(Gravity.CENTER_VERTICAL | Gravity.LEFT);
        textView.setPadding(100, 0, 0, 0);
        textView.setTextColor(Color.BLACK);
        textView.setTextSize(25);
        textView.setText(getGroup(groupPosition).toString());

        /*Button btn = new Button(MLT_File.this);
        btn.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT,LayoutParams.WRAP_CONTENT));
        btn.setText("Edit");
        btn.setId(100+groupPosition);
        btn.setGravity(Gravity.CENTER_VERTICAL | Gravity.RIGHT);

        TableLayout layout = new TableLayout(MLT_File.this);
        layout.setBackgroundColor(Color.WHITE);
        layout.setColumnStretchable(1, true);
        layout.addView(textView);
        //layout.addView(btn);*/

        return textView;
    }

    public boolean isChildSelectable(int groupPosition, int childPosition) {
        return true;
    }

    public boolean hasStableIds() {
        return true;
    }

}//customListAdapter
}//class

my logcat :

java.lang.RuntimeException: Your content must have a ExpandableListView whose id attribute is 'android.R.id.list'

i tried to change the id to id="android:id/list", but i dont know how to create the ExpandableListView object with that id, as it gives an error saying its empty.

*impt : i wanted to create an ExpandableListView object is so that i can cast the onChildClickListener.