更改事件在selectOneMenu中不起作用

Question

我有2个下拉列表：Country＆amp;州。我想在更改国家/地区列表的选择时重新加载状态列表。 我试过了How to pass value into Listener in selectOneMenu。 但是，我的代码中的更改事件不起作用。任何人都可以帮助我吗？谢谢。

<h:selectOneMenu id="ddlCountry" value="#{Bean.companyCountry}" >
    <f:selectItems value="#{Bean.countries}" var="country" itemValue="#{country.value}" itemLabel="#{country.name}" />
    <f:ajax event="change" listener="#{Bean.loadStates}" render="ddlState" execute="@this"/>
</h:selectOneMenu>

<h:selectOneMenu id="ddlState" value="#{Bean.companyState}">
    <f:selectItems value="#{Bean.states}" var="state" itemValue="#{state.value}" itemLabel="#{state.name}" />
</h:selectOneMenu>

Java Bean类sscce

private ArrayList<State> states;
public ArrayList<State> getStates() {
    return states;
}
public void loadStates(AjaxBehaviorEvent event) {
    states = new ArrayList<State>();
    if(companyCountry.equals("USA")){
        states.add(new State("1","UT"));
        states.add(new State("2","WA"));
        states.add(new State("3","CA"));
    }
}

---

jsf ajax监听器仍无法在我的项目中工作。所以我使用了primefaces标签，它可以解决我的问题。

<h:selectOneMenu id="ddlCountry" value="#{Bean.companyCountry}"  >
    <f:selectItems value="#{Bean.countries}" var="country" itemValue="#{country.value}" itemLabel="#{country.name}" />
    <p:ajax event="valueChange" update="ddlState" process="@this"/>
</h:selectOneMenu>

<h:selectOneMenu id="ddlState" value="#{Bean.companyState}">
    <f:selectItems value="#{Bean.states}" var="state" itemValue="#{state.value}" itemLabel="#{state.name}" />
</h:selectOneMenu>

Java Bean类sscce

private ArrayList<State> states;
public ArrayList<State> getStates() {
    states = new ArrayList<State>();
    if(companyCountry.equals("USA")){
        states.add(new State("1","UT"));
        states.add(new State("2","WA"));
        states.add(new State("3","CA"));
    }
    else{
        states.clear();
    }
    return states;
}

Answer 1

将您的bean范围从@RequestScoped更改为@ViewScoped

否则，在您调用listener方法之后，将创建一个新的bean实例，而另一个h:selectOneMenu将填充空值