between extends Activity and extends AndroidApplication

between extends Activity and extends AndroidApplication

I want to call
public class main3D extends AndroidApplication {
public void onCreate (android.os.Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
initialize(new genarate3D(), false);
}
}
by this class
public class mainPage extends Activity
{
private ImageView mHome;
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main_page);
mHome = (ImageView) findViewById(R.id.imgVtownHome);
mHome.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Intent i = new Intent(mainPage.this, main3D.class);
startActivity(i);
}
});
}
but there is error because extends between Activity and AndroidApplication
how could I fix this? thank you.