two drop-down menus ajax refresh in primefaces

Question

I have a checkBox that renders 2 drop-down SelectOne Menus, the items in the first SelectOne Menu is static, but the second SelectOne Menu should update items based on selection from the first. How do I do this in primefaces?

For example country and towns, when i select the UK in first menu, I want to see in the second, towns only from UK.

    <h:selectBooleanCheckbox id="checkboxId" value="#{myBean.checkBoxSelected}" >
        <p:ajax event="CheckBoxEvent" update="panelId" />
    </h:selectBooleanCheckbox>

    <h:panelGrid id="panelId" style="border:solid 1px black;" >

        <h:outputText value="(country) First drop-down: " />  
            <p:selectOneMenu value="#{myBean.number}">  
                <f:selectItem itemLabel="Select One" itemValue="" />  
                <f:selectItem itemLabel="UK" itemValue="1" />  
                <f:selectItem itemLabel="SUA" itemValue="2" />  
                <f:selectItem itemLabel="Italy" itemValue="3" />  
            </p:selectOneMenu> 

        <h:outputText value="(region) Second drop-down: " />  
            <p:selectOneMenu value="#{myBean.number}">  
                <f:selectItem itemLabel="Select One" itemValue="" />  
                <f:selectItem itemLabel="country region 1" itemValue="1" />  
                <f:selectItem itemLabel="country region 2" itemValue="2" />  
                <f:selectItem itemLabel="country region 3" itemValue="3" />  
            </p:selectOneMenu>

    </h:panelGrid>

My Bean

private boolean checkBoxSelected=false;

public void CheckBoxEvent(ValueChangeEvent vcEvent){
    checkBoxSelected = Boolean.valueOf(vcEvent.getNewValue().toString()).booleanValue();        
}

Answer 1

try primeface's ajax event:

<h:outputText value="(country) First drop-down: " />  
    <p:selectOneMenu value="#{myBean.number}">  
        <f:selectItem itemLabel="UK" itemValue="1" />  
        <f:selectItem itemLabel="SUA" itemValue="2" />  
        <f:selectItem itemLabel="Italy" itemValue="3" />  
        <p:ajax update="dropdown2" listener="#{myBean.handleDropDownChange}" />
    </p:selectOneMenu> 

<h:outputText value="(region) Second drop-down: " />  
    <p:selectOneMenu value="#{myBean.number}" id="dropdown2">  
        <f:selectItems value="#{myBean.regions}" />  
    </p:selectOneMenu>

My Bean

private List<String> regions;
private int number;

public void handleDropDownChange(){
 //based on the number provided, change "regions" attribute.
}