JSF ValueChangeEvent：如何根據上一個SelectOneMenu上的選擇更改一個SelectOneMenu上的選項？

Question

好的，我已經堅持了幾天（輕描淡寫）。

說我有一個selectOneMenu

  <h:selectOneMenu id="selectFamily" valueChangeListener="#{menuBean.changeFamily}" onclick="submit()" immediate="true" > <f:selectItems id="familyNames" value="#{menuBean.familyNames}" /> </h:selectOneMenu> 

我想基於在先前的selectOneMenu中選擇的選項來更改另一個selectOneMenu上的選項。

  <h:selectOneMenu id="selectFunction" immediate="true"> <f:selectItems id="functions" value="#{menuBean.functions}" /> </h:selectOneMenu> 

我該如何做？閱讀后，我對如何做有一些想法，但我似乎無法正確地做到這一點。 對不起，我將bean類轉儲到這里，希望有人可以指導我。

公共類MenuBean {

/** Creates a new instance of MenuBean */
public MenuBean() {
} 

private SelectItem[] familyNames = {
    new SelectItem((Integer) 1,"Operations"),
    new SelectItem((Integer) 2, "Special"),
    new SelectItem((Integer) 3, "Support")};

public SelectItem[] getFamilyNames() {
    return familyNames;
}

private SelectItem[] functions = {new SelectItem("Select Function")};

private SelectItem[] operationsFunctions = {
    new SelectItem("Air/Ocean Freight"),
    new SelectItem("Customs"),
    new SelectItem("Land Transport"),
    new SelectItem("Logistics/SCM"),
    new SelectItem("Rail Transport"),
    new SelectItem("Special")
};

private SelectItem[] specialFunctions = {
    new SelectItem("General Management"),
    new SelectItem("Quality & Processes")
};

private  SelectItem[] supportFunctions = {
    new SelectItem("Finance/Controlling"),
    new SelectItem("Human Resources"),
    new SelectItem("ICT"),
    new SelectItem("Legal Affairs"),
    new SelectItem("Marketing/Public Relations"),
    new SelectItem("Procurement"),
};

public SelectItem[] getFunctions(int n) {

    if (n==1) {
        functions = operationsFunctions;
    } else if (n==2) {
        functions = specialFunctions;
    } else if (n==3) {
        functions = supportFunctions;
    }

    return functions;
}

public void setFunctions(SelectItem[] function) {
    this.functions = function;
}

public void changeFamily(ValueChangeEvent event) {
    FacesContext context = FacesContext.getCurrentInstance();
    int value = (Integer) event.getNewValue();
    setFunctions(getFunctions(value));

    context.renderResponse();        
}}

Answer 1

我認為這里的問題是getFunctions（int i）需要一個參數。 由於它是由下面的EL表達式調用的，因此它不應帶有參數。

 <f:selectItems id="functions" value="#{menuBean.functions}" /> 

另外，ValueChangeEvent中的值需要轉換為字符串，而不是整數。 從您的問題中不確定是否已將selectItem包裝在表單中，否則，您也必須這樣做。 我能想到的最后一件事是backingBean的范圍，它需要在回發中生存下來。

我嘗試了以下示例，該示例的會話范圍為ManagedBean和JSF 1.2，並且可以正常工作：

   <h:form>
        <h:selectOneMenu id="selectFamily"
                         valueChangeListener="#{menuBean.changeFamily}"
                         immediate="true"
                         onchange="submit()">
            <f:selectItems id="familyNames" value="#{menuBean.familyNames}"/>
        </h:selectOneMenu>

        <h:selectOneMenu id="selectFunction" immediate="true">
            <f:selectItems id="functions" value="#{menuBean.functions}"/>
        </h:selectOneMenu>
    </h:form>

public class MenuBean {
    private SelectItem[] familyNames = {
            new SelectItem(1, "Operations"),
            new SelectItem(2, "Special"),
            new SelectItem(3, "Support")};

    public SelectItem[] getFamilyNames() {
        return familyNames;
    }

    private SelectItem[] functions = {new SelectItem("Select Function")};

    private SelectItem[] operationsFunctions = {
            new SelectItem("Air/Ocean Freight"),
            new SelectItem("Customs"),
            new SelectItem("Land Transport"),
            new SelectItem("Logistics/SCM"),
            new SelectItem("Rail Transport"),
            new SelectItem("Special")
    };

    private SelectItem[] specialFunctions = {
            new SelectItem("General Management"),
            new SelectItem("Quality & Processes")
    };

    private SelectItem[] supportFunctions = {
            new SelectItem("Finance/Controlling"),
            new SelectItem("Human Resources"),
            new SelectItem("ICT"),
            new SelectItem("Legal Affairs"),
            new SelectItem("Marketing/Public Relations"),
            new SelectItem("Procurement"),
    };

    public SelectItem[] getFunctions() {
        return functions;
    }

    private void switchSelectedFunctions(int n) {
        if (n == 1) {
            setFunctions(operationsFunctions);
        } else if (n == 2) {
            setFunctions(specialFunctions);
        } else if (n == 3) {
            setFunctions(supportFunctions);
        }
    }

    public void setFunctions(SelectItem[] function) {
        this.functions = function;
    }

    public void changeFamily(ValueChangeEvent event) {
        FacesContext context = FacesContext.getCurrentInstance();
        int value = Integer.valueOf(((String) event.getNewValue()));
        switchSelectedFunctions(value);
        context.renderResponse();
    }
}