你能从 p:ajax 监听器更新 h:outputLabel 吗? [英] Can you update an h:outputLabel from a p:ajax listener?

问题描述

我正在尝试使用 p:ajax 标记，然后在该侦听器中，我设置了一个名为periodRendered"的值.然后我试图通过来自 p:ajax 标签的更新来更新 h:outputLabel 标签.它没有更新ajaxily，我认为这是因为primefaces ajax 标签无法更新标准jsf outputLabel 标签.

I'm trying to use a p:ajax tag and then in that listener, i'm setting a value called "periodRendered". then i'm trying to update an h:outputLabel tag via an update from the p:ajax tag. It's not updating ajaxily and i'm thinking it's because a primefaces ajax tag can't update a standard jsf outputLabel tag.

我的假设是否正确，是否应该使用更合适的标签代替 h:outputLabel ?

Is my assumption correct and is there a more appropriate tag i should be using instead of h:outputLabel ?

<h:outputLabel for="addProgramTo" value="Add Program To" />
<p:selectOneMenu value="#{ppBacker.grantProgram.grant_project_id}" id="addProgramTo" size="1" styleClass="listBoxMedium">
    <p:ajax process=":addProgram:addProgramTo" update=":addProgram:periodGrid, :addProgram:periodLabel" event="change" listener="#{ppBacker.addProgramListener}" />
    <f:selectItems value="#{ppBacker.grantProjectDropDownList}" />
</p:selectOneMenu>            

<h:outputLabel for="period" value="Period" id="periodLabel" rendered="#{ppBacker.periodRendered}"> 

推荐答案

您不能更新未呈现的元素，rendered=false是一种 JSF 方式"以从 DOM 树中删除元素,

You cannot update elements which are not rendered , rendered=false "is a JSF way to" to remove elements from the DOM Tree ,

它不像 css display:none 或 visibility:hidden <- 这两个将元素保留在 DOM 树中但隐藏，而 JSF render=false 甚至不会渲染(保留)DOM 树中的元素(您甚至不会在页面的查看源代码"中看到它)

its not like css display:none or visibility:hidden <- this two will keep the elements in the DOM tree but hidden , while the JSF rendered=false wont even render (keep) the element in the DOM tree (you wont even see it in the "view source" of the page)

因此，在您的情况下，您需要使用 `panelGroup' 包装 outputLabel 并更新包装器的 id

So in you case you need to wrap the outputLabel with `panelGroup' and update the id of the wrapper

<h:panelGroup id="periodLabelWrapper">
    <h:outputLabel for="period" value="Period" id="periodLabel" rendered="#{ppBacker.periodRendered}">
</h:panelGroup>

并在 <p:ajax update 属性中引用包装器(它总是在 DOM 树中)id，如下所示:

and refer to the wrapper (which always be in the DOM tree) id in the <p:ajax update attribute, like this:

<p:ajax process=":addProgram:addProgramTo" update=":addProgram:periodGrid, :addProgram:periodLabelWrapper" event="change" listener="#{ppBacker.addProgramListener}" />

另一个解决方案是像这样更新整个表单 <p:ajax update="@form" ... 这样你就不需要包装 outputLabel

Another solution would be the update the entire form like this <p:ajax update="@form" ... that way you don't need the wrap the outputLabel

关于你的评论问题

@form 如何更新未渲染的元素，但不直接通过 id 定位它们?

how does @form update the un-rendered elements, but targeting them directly through id's does not?

您不能在 update 中定位页面中不存在的元素(rendered=false)它不存在"

You can't target an element in update which is not present in the page (rendered=false) "its not there"

但是当您使用 update="@form" 或 update="someWrapperID" 时，表单/包装器会重新评估"其所有内部元素，包括带有rendered="#{someBean.someCondition}" 并且条件被重新评估"，所以如果结果为 true 元素将被显示...

But when you use update="@form" or update="someWrapperID" the form/wrapper "re evaluates" all its inner elements , including the ones with rendered="#{someBean.someCondition}" and the condition gets "re evaluated" so if it result to true the elemet will be displayed...

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