Problems with asynchronous methods

I'm working with Flex 4 invoking webservices from JVM 1.6

I'm trying to make asynchronous calls to java to populate three comboboxes that will display country, states and cities, these three are related (master-slave relationship) but sometimes the calls are not met, or they are not completed, and I think this is because they are asynchronous, how can I be sure that I'm making the call to fill the next combobox when the master combobox (country) is filled?

protected function comboCountry_changeHandler(idCombo:String):void {

            selectedComboCountry= idCombo;
            var countryId:String; 
            if(selectedComboCountry == comboCountry.id){
                countryId = String(comboCountry.selectedItem.countryId);                
            }else if(selectedCombocountry == combocountrySuc.id){
                countryId = String(comboCountrySuc.selectedItem.countryId);
            }



            obtainStatesResult.token = wsfacturas.obtainStates(countryId);


        }

protected function obtainStatesResult_resultHandler(event:ResultEvent):void { var StateListVo:ArrayCollection = obtainStatesResult.token.result as ArrayCollection;

            if(selectedComboCountry == "comboCountrySuc"){

                StateListsSuc.removeAll();
                CityListsSuc.removeAll();
                for (var d:int = 0; d < StateListVo.length; d++){
                    var estSuc:State = StateListVo[d];
                    StateListsSuc.addItem(estSuc);                                          
                }       

                comboStateSuc.dataProvider = StateListsSuc;
            }
            else if(selectedCombocountry == "combocountry"){
                StateListsEmp.removeAll();
                CityListsEmp.removeAll();
                for (var i:int = 0; i < StateListVo.length; i++){
                    var estEmp:State = StateListVo[i];
                    StateListsEmp.addItem(estEmp);      
                }                   
                comboState.dataProvider = StateListsEmp;
            } else {

                for (var f:int = 0; f < StateListVo.length; f++){
                    var est:State = StateListVo[f];
                    StateListsSuc.addItem(est); 
                    StateListsEmp.addItem(est); 
                }                           
                comboState.dataProvider = StateListsEmp;
                comboStateSuc.dataProvider = StateListsSuc;

  开发者_如何学Python          }
        } 

---

Wouldn't it mean that you probably need to load the country and wait for change event on the country combobox to update state and so on? If you do that, you dont have to worry about asynchronicity of your requests? Otherwise, you might be able to use DataProviders and they might provide Event:Complete.. I am not sure though, I definitely am not an expert.. :)

---

You might want to give slightly more details in your question. But I am just playing with whatever details you have provided.

1_ First asynchronous calls never caused me any problem with dynamic data binding. Sometimes a SOAP call can take reasonable amount of time, in that case, make sure to show a busy cursor till the web service call returns.

2_Combobox has always had problem with dynamic data binding. You can create a custom combobox that extends a combobox and override the setValue method Or Else you have to iterate over the dataProvider of the combobox and look for a match in the data field and then sets the combo box to that item.

So in summary, the problem mostly have to do with binding of the new data to the rendered combobox not asynchronous calls or any latency.