TextBox not firing valueChangedEvent in GWT -

i have code , action never fired

  textbox textbox = new textbox();     textbox .addvaluechangehandler(new valuechangehandler<string>() {                 @override                 public void onvaluechange(valuechangeevent<string> event) {                     //do action                 }              }); 

what doing wrong ?

one information forgot textbox setenable(true), reason don't use other handler. find solution way fire event when textbox set , use couttotal.settext("sometext") fire event need use couttotal.setvalue("sometext", true)

private void computetotal() {             double total = 0.0;             (int = 0; < discloserpanel.getwidgetcount(); i++) {                 if (discloserpanel.getwidget(i) instanceof lignecout) {                     lignecout lignecout = (lignecout) discloserpanel.getwidget(i);                     total += lignecout.getsoustotal();                 }             }             couttotal.setvalue(formhelper.preparedoubleforform(total, 0), true);         }