PowenKo, Android, Tutorial 84-3, map, display map zoom

package com.looptek.GoogleMapsZoomView;


import android.os.Bundle;
import android.view.KeyEvent;
import android.view.View;
import android.widget.LinearLayout;

import com.google.android.maps.MapActivity;
import com.google.android.maps.MapController;
import com.google.android.maps.MapView;
import com.google.android.maps.MapView.LayoutParams;
 

public class GoogleMapsZoomView extends MapActivity 
{    
    MapView mapView; 
 
    
    public boolean onKeyDown(int keyCode, KeyEvent event) 
    {
        MapController mc = mapView.getController(); 
        switch (keyCode) 
        {
            case KeyEvent.KEYCODE_VOLUME_UP:
                mc.zoomIn();
                break;
            case KeyEvent.KEYCODE_VOLUME_DOWN :
                mc.zoomOut();
                break;
        }
        return super.onKeyDown(keyCode, event);
    }    
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
 
 
        mapView = (MapView) findViewById(R.id.mapView);
        LinearLayout zoomLayout = (LinearLayout)findViewById(R.id.zoom);  
        View zoomView = mapView.getZoomControls(); 
 
        zoomLayout.addView(zoomView, 
            new LinearLayout.LayoutParams(
                LayoutParams.WRAP_CONTENT, 
                LayoutParams.WRAP_CONTENT)); 
        mapView.displayZoomControls(true);
 
    }
 
    @Override
    protected boolean isRouteDisplayed() {
        // TODO Auto-generated method stub
        return false;
    }
}

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent">
 
    <com.google.android.maps.MapView 
        android:id="@+id/mapView"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:enabled="true"
        android:clickable="true"
        android:apiKey="0aCAkNUz85Bmk0EVw95hI2_P2PWbHWRNNtacuVw"
        />
 
    <LinearLayout android:id="@+id/zoom" 
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:layout_alignParentBottom="true" 
        android:layout_centerHorizontal="true" 
        /> 
 
</RelativeLayout>

sample code:

GoogleMapsZoomView