Issue in setting Value in Select Item from RPC Call in GWT - gwt

Question

I am facing issue in Setting the Value of Select Box in Grid .
Scenario: in the ListGrid i am having two Combo box .
For One combo box i am getting the value in the list during the onload and displaying .
On change value of first combo i need to fetch data from a list with input value from frst combo. i am getting the value from list but when i try to set in the second combo its not loading
Please find my code below.
//Properly Loading Combo
TaskName=new ListGridField("task_name","task_label);
SelectItem taskItem=new SelectItem("task_name","task_label);
taskNameList=populateTaskName();//Getting while onload
taskItem.setValueMap(taskNameList);
taskItem.addChangedHandler(...);
TaskName.setEditorType(taskItem);
TaskName.setValueMap(taskNameList);
TaskName.setRequired(true);
TaskName.setCanEdit(true);
//Not Loading Combo
SubTaskName=new ListGridField("Sub_task_name","Sub_task_label);
SelectItem subTaskItem=new SelectItem("Sub_task_name","Sub_task_label);
subTaskItem.addChangedHandler(...);
SubTaskName.setEditorType(taskItem);
TaskName.setRequired(true);
TaskName.setCanEdit(true);
//ChangeHandlerFor taskItem-FirstCombo
onChange(){
Form item=event.getItem();
item.setTooltip(item.getDisplayValue());
String taskId=String.valueOf(item.getValue());
populateSubTaskname(taskId);
subTaskItem.setValueMap(subtaskNameList);//getting the subtaskname List from RPC Call
SubTaskName.setValueMap(subtaskNameList);
populateSubTaskname(){
getting the value and loads in List
//subtaskNameList
subTaskItem.setValueMap(subtaskNameList);//getting the subtaskname List
SubTaskName.setValueMap(subtaskNameList);
}
//ChangeHandlerFor taskItem-Second Combo
onChange(){
Form item=event.getItem();
item.setTooltip(item.getDisplayValue());
}//Here also Name in the Map is not setting instead setting the value alone sometimes
Please help me where im wrong.

Answer 1

Once value in the combobox/select item changes, you need to assign it again to List grid field.
eg: listGridField.setEditorProperties(selectItem)