无法从PostFilterEvent

Question

目标是在用户过滤数据表时自动选择数据表的第一行。 实现PostFilter事件是为了选择第一行，但实际上它被事后发生的事件覆盖并重新设置初始选定行。

<h:form id="customerForm">
    <p:commandButton value="selection change" action="#{customerControllerv1.selectionChange}"/> 
    <p:commandButton value="selection show" action="#{customerControllerv1.selectionShow}"/>
    <p:dataTable id="dtCustomer" var="customer" value="#{customerControllerv1.customers}" rowKey="#{customer.id}" 
        selection="#{customerControllerv1.selectedCustomer}" selectionMode="single" 
        binding="#{customerControllerv1.uiCustomers}">

        <f:event type="org.primefaces.event.data.PostFilterEvent" listener="#{customerControllerv1.postFilter()}" />

        <p:column headerText="Id">
            <h:outputText value="#{customer.id}" />
        </p:column>
        <p:column headerText="First Name" filterBy="#{customer.firstName}" filterMatchMode="contains"  >
            <h:outputText value="#{customer.firstName}" />
        </p:column>
        <p:column headerText="Last Name" filterBy="#{customer.lastName}" filterMatchMode="contains">
            <h:outputText value="#{customer.lastName}" /> 
        </p:column>

    </p:dataTable>    
</h:form>

@ManagedBean(name = "customerControllerv1")
@ViewScoped

public class CustomerControllerv1 implements Serializable  {

    private static final long serialVersionUID = 1L;
    private Customer selectedCustomer;
    private DataTable uiCustomers;
    private List<Customer> customers = new ArrayList<Customer>();   

    public CustomerControllerv1() {
    }

    @PostConstruct
    void init() {        
        CustomerDAO custDAO = new CustomerDAO();
        customers = custDAO.getAllCustomers();         

        // select first row
        if (customers.size()>0) selectedCustomer=customers.get(0);
    }

   public void postFilter () {        
       selectionChange();
   }

   public void selectionChange () {
       RequestContext context = RequestContext.getCurrentInstance();
       List<Customer> sortedList = (List<Customer>)uiCustomers.getValue();
       // select first row of the filtered list and render the DataTable 
       if (sortedList.size()>0) selectedCustomer=sortedList.get(0);
       context.update("customerForm:dtCustomer");
   }

   public void selectionShow () {       
       System.out.println( "selectionShow: "+selectedCustomer.getId() );
   }


   // getters and setters
   ....
}

• selectionChange方法由postFilter以及xhtml页面中的按钮调用。单击选择更改按钮可按预期选择第一行。单击selectionShow按钮将证明它。
• 在xhtml页面的过滤器中输入数据也会调用相同的代码，但之后会覆盖第一行选择。单击selectionShow按钮将演示它。

有没有人知道如何解决这个问题？