Async Method

Vaadin 6 / 7 / 8
1

Why the async method only works if he was the main method called?

If I call a method A and inside method A call a async method B don`t works?

2

Please show code

3 
public class MyView {
MyService myservice;
  public MyView(){
  myService = BeanLocator.find(MyService.class);
    myBtn.addClickListener(evt->btnProcessarArquivoListener());

}

    private void btnProcessarArquivoListener() {
        myService.processA();
    }
}
	
	
@Service	
public MyService {
   public void processA(){
      // process some code
       processB();
   }

  @Async
  public void processB(){
   // process some code  
  }
}

If I change the @Async to processA works fine, but with this sample don’t works (my view wait to all return)