在提交时调用valueChangeListener，而不更改selectOneMenu中的选项 [英] valueChangeListener is invoked on submit without changing options in selectOneMenu

问题描述

在我的页面中，我有selectonemenu，并且注意到当我单击datatable的分页时，将调用valueChangeListener方法，而实际上并未更改selectonemenu中的值或选项.

In my page I have selectonemenu and I have noticed that when I click the pagination of datatable, valueChangeListener method is getting invoked without actually changing values or options in selectonemenu.

这是怎么回事，以及如何防止这种情况发生，因为仅当用户在selectonemenu中更改值时才需要调用valueChangeListener方法.

How is this happening and how could I prevent this from happening as I need to invoke valueChangeListener method only if user changes values in selectonemenu.

感谢并感谢您的帮助.

致谢

这是我的selectonemenu代码

Here is my code for selectonemenu

更新1

<ice:selectOneMenu value="#{list.selectedItem}"
            partialSubmit="true" valueChangeListener="#{list.val}">
                <f:selectItems value="#{list.selectItems}" />
                </ice:selectOneMenu>

还有bean方法

   public void val(ValueChangeEvent event) {
            logger.info("1");
            selectedValue = event.getNewValue().toString();
}

像这样添加值

public void loadItems(){
        selectItems.add(new SelectItem("1", "One"));
        selectItems.add(new SelectItem("2", "Two"));
        selectItems.add(new SelectItem("3", "Three"));
        selectItems.add(new SelectItem("4", "Four")); 

}

然后方法调用如下

 public List<SelectItem> getSelectItems() {
        if (selectItems == null) {
            loadItems;

        }
        return selectItems;
    }

推荐答案

JSF valueChangeListener与客户端事件无关.这是服务器端事件，当 submitted 值与 initial 值不同时，将调用该事件.

The JSF valueChangeListener is in no way related to the client-side events. It is a server-side event which will be invoked when the submitted value differs from the initial value.

列表的第一项的值为1，因此当用户不更改下拉菜单时，提交的值将为1.如果您不希望调用valueChangeListener，则需要确保初始值也等于1.那就是#{list.selectedItem}"后面的值.在bean的构造/初始化过程中，将其初始化为与第一项相同的值.

The first item of your list has a value of 1, so when the user doesn't change the dropdown, the submitted value will be 1. If you don't want the valueChangeListener to be invoked, then you need to ensure that the initial value also equals to 1. That is the value behind #{list.selectedItem}". Initialize it to the same value as the first item during bean's construction/initialization.

this.selectedItem = "1";

这篇关于在提交时调用valueChangeListener，而不更改selectOneMenu中的选项的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！