如何在JSF中的表中动态添加行? [英] How to Dynamically add a row in a table in JSF?

问题描述

在我的应用程序中，我需要单击一个按钮添加一行，并且该按钮将出现在所有行中.需要帮助吗?

In my application i need to add a row on a click of a button and this button will be in all the rows. Need help to do this?

物品类别

public class Item {
 public Item()
{

}
private String value;
public Item(String value) { this.value = value; }
public void setValue(String value) { this.value = value; }
public String getValue() { return value; }
}

管理Bean类

public class MyMB 
{
private List<Item> list;    

public void addItem() { // JSF action method
    list.add(new Item("Default"));
    Iterator<Item> iterator = list.iterator();
    while(iterator.hasNext())
    {
        Item item = (Item)iterator.next();
        System.out.println(item.getValue());
    }
    System.out.println();
    }
/**
 * @return the list
 */
public List<Item> getList() {
    if(list==null)
    {
        loadList();
    }
    return list;
}
private void loadList() {
    list = new ArrayList<Item>();
    list.add(new Item("Data"));
}

}

JSF代码

<h:form>
   <rich:dataTable value="#{myMB.list}" var="item" id="tabel">
    <h:column><h:inputText value="#{item.value}" /></h:column>
    <h:column><a4j:commandButton value="Add"  actionListener="#{myMB.addItem}" reRender="tabel"/></h:column>

推荐答案

基本上，您所需要做的只是在h:dataTable的value属性后面的数据模型中添加一个空对象.

All you need to do is basically indeed just adding an empty object to the datamodel behind the value attribute of h:dataTable.

但是在随后的请求中也需要保留相同的空行.如果支持bean是请求范围的，那么将重新加载数据模型而没有空行.当bean在会话范围内时，所有这些都应该起作用.

But the same empty row needs to be preserved in the subsequent request as well. If the backing bean is request scoped, then the datamodel get reloaded without the empty row. This all should work when the bean is session scoped.

此外，您的JSF代码中有几个错误. h:dataTable var属性丢失，列内容必须在h:column内部.

Further there are several errors in your JSF code. The h:dataTable var attribute is missing and the column content needs to be inside a h:column.

<h:form>
    <h:dataTable value="#{bean.list}" var="item">
        <h:column><h:inputText value="#{item.value}" /></h:column>
    </h:dataTable>
    <h:commandButton value="Add" action="#{bean.add}"/>
</h:form>

会话或视图作用域 bean可能看起来像这样:

A session or view scoped bean can look like this:

public class Bean {
    private List<Item> list;

    public Bean() {
        list = new ArrayList<Item>();
    }

    public void add() {
        list.add(new Item());
    }

    public List<Item> getList() {
        return list;
    }
}

Item类当然应该具有默认的无参数构造函数.通常，它已经隐式可用，但是如果您使用参数定义自己的构造函数，那么它将不再可用.您需要明确定义它，否则就不能再执行Item item = new Item();.

The Item class should of course have a default no-arg constructor. Normally this is already implicitly available, but if you define your own constructor with arguments, then it is not available anymore. You'll need to explicitly define it, otherwise you cannot do Item item = new Item(); anymore.

public class Item {

    private String value;

    public Item() {
        // Keep default constructor alive.
    }

    public Item(String value) {
        this.value = value;
    }

    // ...
}

如果您希望将Bean保留在请求范围中，则需要保持新添加的项的数量，以便Bean可以在加载时保持相同的数量.

If you prefer to keep the bean in the request scope, then you'll need to maintain the amount of newly added items, so that the bean can preserve the same amount on load.

public class Bean {
    private List<Item> list;
    private HtmlInputHidden count = new HtmlInputHidden();

    public Bean() {
        count.setValue(0);
    }

    public void add() {
        list.add(new Item());
    }

    public List<Item> getList() {
        if (list == null) loadList();
        return list;
    }

    public HtmlInputHidden getCount() {
        return count;
    }

    public void setCount(HtmlInputHidden count) {
        this.count = count;
    }

    private void loadList() {
        list = new ArrayList<Item>();

        // Preserve list with newly added items.
        for (int i = 0; i < (Integer) count.getValue(); i++) {
            list.add(new Item());
        }
    }
}

您只需要将以下内容添加到JSF页面的<h:form>:

You'll only need to add the following to the <h:form> of the JSF page:

<h:inputHidden binding="#{bean.count}" converter="javax.faces.Integer" />

有关以任何方式使用数据表的更多见解，您可能会发现本文有用:使用数据表.它还包含一个WAR文件，在请求和会话范围内都有很多示例.

For more insights about using datatables in any way you may find this article useful: Using Datatables. It also contains a WAR file with lot of examples in both request and session scope.

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