public void ClearImageViews() {
  final ImageView image_a = (ImageView)findViewById(R.id.image_a);
  image_a.setVisibility(View.INVISIBLE);
 }

MainActivity mainActivity = new MainActivity();
 mainActivity.ClearImageViews();

final ImageView image_a = (ImageView)findViewById(R.id.image_a);
 image_a.setVisibility(View.INVISIBLE);

MainActivity.ClearImageViews()

class AnotherClass extends Activity{


 OriginalClass o;

 public AnotherClass(OriginalClass oo){

   this.o = oo;


}


final ImageView image_a = (ImageView)this.o.findViewById(R.id.image_a);

                // Use this.o.findViewById like above.

}