我有一个问题，我需要你的帮助！我想要得到的p值选择：selectOneListbox当我点击一棵树，但价值总是空的，即使我点击号码：selectOneListbox第一。这是我的XHTML code：

I have a problem and I need your helps!!! I want to get selected value of p:selectOneListbox when I click on a tree, but the value is always null, even though I clicked on p:selectOneListbox first. Here is my xhtml code:

<h:form>
<p:selectOneListbox id="selectRole"
            value="#{grandUseAuthoritiesBean.selectedRoleId}"               
            filter="true" filterMatchMode="contains">
            <f:selectItems value="#{grandUseAuthoritiesBean.roleList}"
                var="role" itemLabel="#{role.code}" itemValue="#{role.roleId}" />
</p:selectOneListbox>
<p:tree value="#{grandUseAuthoritiesBean.root}"
                selectionMode="single" var="node"
                style="font-size:13px; width:100%;border-width:0">
                <p:treeNode icon="ui-icon-calculator">
                    <h:outputText value="#{node}" />
                </p:treeNode>
                <p:ajax event="select" update="@([id$=privilegeChecbox])"
                    listener="#{grandUseAuthoritiesBean.onNodeSelect()}">
                </p:ajax>
            </p:tree>
</h:form>

和这里是我的管理bean的code：

and here is my manage bean's code:

public String selectedRoleId;
public String getSelectedRoleId() {
    return selectedRoleId;
}
public void setSelectedRoleId(String selectedRoleId) {
    this.selectedRoleId = selectedRoleId;
}
public void onNodeSelect(NodeSelectEvent event) {
    if (selectedRoleId!=null)
     System.out.println("selected Role Id: "+ this.selectedRoleId);
}

我不能打印变量selectedRoleId怎么把它为空，但如果我用一个button'method来调用这个变量，我可以得到它的价值。我该怎么办？感谢您阅读我的问题！

I can't print the variable "selectedRoleId" coz it is null but if I use a button'method to call this variable, I can get its value. What should I do? Thanks for reading my question!

推荐答案

当你选择一些从列表框中，直到您发送的形式或做部分发这么因此空值，它不支持bean里面看到的东西是。加入部分处理为＆LT;电话号码：selectOneListbox＆GT; ，并再次检查：

The thing is when you choose something from listbox it is not visible inside backing bean until you send a form or do a partial sending so hence null value. Add partial processing to <p:selectOneListbox> and check again:

＆LT;电话号码：AJAX程序=@这个partialSubmit =真/＆GT;

<p:ajax process="@this" partialSubmit="true" />

还有类似的话题： http://stackoverflow.com/a/14988129/3803447