java - How to select one of GWT CellTree nodes after first data fetch? -

i'm trying select first root node of celltree after asynchronous data fetching server. here code:

public class mytreemodel implements treeviewmodel{  private myserviceasync myservice = gwt.create(myservice.class);      public <t> nodeinfo<?> getnodeinfo(t value) {          cell<myto> cell = new abstractcell<myto>() {             @override             public void render(context context, myto value, safehtmlbuilder sb) {                 //rendering node...             }         };          return new defaultnodeinfo<myto>(value instanceof myto ?                 createbranchdataprovider((myto)value) : //fetching child nodes                 ceraterootdataprovider(), cell); //fetching root nodes     }  @override public boolean isleaf(object value) {      if (value instanceof myto) {         myto = (myto)value;         return to.isleafnode();     }     return false; }  private abstractdataprovider<myto> ceraterootdataprovider() {     asyncdataprovider<myto> dataprovider = new asyncdataprovider<myto>() {         @override         protected void onrangechanged(hasdata<myto> display) {             asynccallback<list<myto>> callback = new asynccallback<list<myto>>() {                 @override                 public void onsuccess(list<myto> result) {                     updaterowcount(result.size(), true);                     updaterowdata(0, result);                 }                 @override                 public void onfailure(throwable caught) {                     window.alert(caught.tostring());                 }             };             myservice.getrootnodes(callback);         }     };      return dataprovider; }  private abstractdataprovider<myto> createbranchdataprovider(final myto value) {     asyncdataprovider<myto> dataprovider = new asyncdataprovider<myto>() {         @override         protected void onrangechanged(hasdata<myto> display) {             asynccallback<list<myto>> callback = new asynccallback<list<myto>>() {                 @override                 public void onsuccess(list<myto> result) {                     updaterowcount(result.size(), true);                     updaterowdata(0, result);                 }                 @override                 public void onfailure(throwable caught) {                     window.alert(caught.tostring());                 }             };             myservice.getchildnodes(value.getid(), callback);         }     };     return dataprovider; } 

for data stored on client side solution looks pretty simple: call

tree.getroottreenode().setchildopen(0, true, true); 

but if want fetch data asynchronously catch indexoutofboundsexception in case try same after creation tree, because data not obtained yet. how can know when onsuccess() event fired in ceraterootdataprovider()? or use solution? please suggest something.

i see 2 options calling

tree.getroottreenode().setchildopen(0, true, true); 

in right moment:

1. direct dependency on presenter: add constructor mytreemodel object. send corresponding presenter parameter. add , call presenter.ondataloadingcomplete() @ end of onsuccess method.

2. custom event: create custom event. fire @ end of onsuccess method. subscribe in place can call access `tree``object. call necessary code.