Activity not registered in the manifest Lint warning

You should make your BaseActivity as an Abstract class. No need to register such Activities in manifest, they are just simple java classes extending Activity class not an Activity of your application.

  public abstract class BaseActivity extends Activity {
    @Override
    public void onCreate(bundle) {
    super.onCreate(bundle);
    setContentView(getLayoutResourceId());
    }

    protected abstract int yourmethods();
  }

 public class Activity1 extends BaseActivity {
   @Override
   public void onCreate(bundle) {
    super.onCreate(bundle);
    // do extra stuff on your resources, using findViewById on your layout_for_activity1
}

   @Override
   protected int yourmethod() {
     //implemetation
   }
 }

You'll only need to list activities that are entry points to your app in the manifest. That is, activities that are invoked with an Intent.

You should not have activities that are in fact not instantiable entry points. Make such activity classes abstract. This will also get rid of the lint warning.