Question

我正在使用下拉列表中的选项动态构建面包屑作为菜单项值，但我遇到了一个奇怪的行为。以下是我正在使用的代码：

breadcrumb.xhtml：

<h:form>                        
    <p:breadCrumb id="breadcrumb" model="#{breadcrumbVO.menuModel}">
    </p:breadCrumb>
    <p:selectOneMenu id="select-box" value="#{breadcrumbVO.selectedOption}">
        <p:ajax listener="#{breadcrumbVO.selectionChanged}" update="@form" />
        <f:selectItem itemLabel="- Select -" itemValue="" noSelectionOption="true" />
        <f:selectItems value="#{breadcrumbVO.selectItems}" />
    </p:selectOneMenu>
</h:form>

BreadcrumbVO.java

import java.util.ArrayList;
import java.util.List;

import javax.faces.bean.ManagedBean;
import javax.faces.bean.ViewScoped;
import javax.faces.model.SelectItem;

import org.primefaces.model.menu.DefaultMenuItem;
import org.primefaces.model.menu.DefaultMenuModel;
import org.primefaces.model.menu.MenuElement;
import org.primefaces.model.menu.MenuModel;

@ManagedBean
@ViewScoped
public class BreadcrumbVO implements Serializable {

    private static final long serialVersionUID = -4419933664561553404L;

    private MenuModel menuModel;
    private List<SelectItem> selectItems;

    private String selectedOption; 

    public BreadcrumbVO() {
        menuModel = new DefaultMenuModel();     
        DefaultMenuItem menuItem = new DefaultMenuItem();
        menuItem.setValue("USA");       
        menuItem.setCommand("#{breadcrumbVO.onBredcrumbMenuClick()}");
        menuItem.setUpdate("@form");
        menuModel.addElement(menuItem);                     
        initSelectMenu();    
    }   

    public void selectionChanged() {        
        if(this.selectedOption != ""){
            DefaultMenuItem menuItem = new DefaultMenuItem();
            menuItem.setValue(this.selectedOption);
            menuItem.setCommand("#{breadcrumbVO.onBredcrumbMenuClick()}");
            menuItem.setUpdate("@form");
            this.menuModel.addElement(menuItem);

            refreshSelectMenu();
        }               
    }


    private void refreshSelectMenu() {
        this.selectedOption = null;

        selectItems = new ArrayList<SelectItem>();  
        selectItems.add(new SelectItem("New Item3", "New Item3"));
        selectItems.add(new SelectItem("New Item4", "New Item4"));      
    }

    private void initSelectMenu(){
        this.selectItems = new ArrayList<SelectItem>();         
        selectItems.add(new SelectItem("New Item1", "New Item1"));
        selectItems.add(new SelectItem("New Item2", "New Item2"));
    }

    public void onBredcrumbMenuClick(){
        List<MenuElement> menuElements = this.menuModel.getElements();      
        menuElements.remove(menuElements.size()-1);
        initSelectMenu();
    }

    public List<SelectItem> getSelectItems() {
        return selectItems;
    }

    public void setSelectItems(List<SelectItem> selectItems) {
        this.selectItems = selectItems;
    }

    public MenuModel getMenuModel() {
        return menuModel;
    }

    public void setMenuModel(MenuModel menuModel) {
        this.menuModel = menuModel;
    }

    public String getSelectedOption() {
        return selectedOption;
    }

    public void setSelectedOption(String selectedOption) {
        this.selectedOption = selectedOption;
    }              
}

我观察到的奇怪行为是我在构造函数中添加到menuItem的{{1}}正常工作并正确调用bean中的方法menuModel。但是，由于用户从下拉列表中选择了某个值而添加的其他menuItem，不会在单击时调用此方法。即使我对菜单项使用相同的配置，但它们的行为也有所不同，具体取决于它们在onBredcrumbMenuClick中的添加时间。

感谢您的解释。

动态面包屑菜单项不调用操作方法

0 个答案: