java 将文本添加到带有数据源的组合框
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adding text to a combobox with a datasource
提问by luuksen
I have a vaadin combobox that is filled with a containerdatasource
我有一个充满容器数据源的 vaadin 组合框
setContainerDataSource(container);
I now want to insert a static text somewhere in the list of results.
我现在想在结果列表中的某处插入一个静态文本。
For example:
例如：
A Combobox that is filled with a container of and the first entry that pops up in the result list is some kind of header:
一个 Combobox 填充了一个容器，结果列表中弹出的第一个条目是某种标题：
Persons:
Thomas S.
Lucas B.
Alex X.
人员：
Thomas S.
Lucas B.
Alex X.
Can i achieve that by either manipulating the container or the combobox?
我可以通过操作容器或组合框来实现吗？
I just tried to set the container source and add a String/Label via addItem() to the ComboBox, but that doesn't seem to work. I am kinda new to this, so I don't know how to continue.
我只是尝试设置容器源并通过 addItem() 向 ComboBox 添加字符串/标签，但这似乎不起作用。我对这个有点陌生，所以我不知道如何继续。
回答by miq
If you are using the ComboBox as immediate and don't want the "Person:" to be handled as a real person, you could use setNullSelectionItemIdto define the fake person as a true dummy object. This solution, however, has the limitation that you can only add one dummy object.
如果您直接使用 ComboBox 并且不希望将“人：”作为真人处理，您可以使用setNullSelectionItemId将假人定义为真正的虚拟对象。但是，此解决方案有一个限制，即您只能添加一个虚拟对象。
Here's my example which adds "Person:" on top of the list and handles it as a null value. Note that I'm using Vaadin 7.
这是我的示例，它在列表顶部添加“Person:”并将其作为空值处理。请注意，我使用的是 Vaadin 7。
import com.vaadin.data.Property;
import com.vaadin.data.Property.ValueChangeEvent;
import com.vaadin.data.util.BeanItemContainer;
import com.vaadin.server.VaadinRequest;
import com.vaadin.ui.AbstractSelect;
import com.vaadin.ui.ComboBox;
import com.vaadin.ui.Notification;
import com.vaadin.ui.UI;
import com.vaadin.ui.VerticalLayout;
/**
* The Application's "main" class
*/
@SuppressWarnings("serial")
public class MyVaadinUI extends UI {
@Override
protected void init(VaadinRequest request) {
final VerticalLayout layout = new VerticalLayout();
layout.setMargin(true);
setContent(layout);
BeanItemContainer<Person> container = new BeanItemContainer<Person>(Person.class);
Person nullPerson = new Person(0, "Person:");
container.addBean(nullPerson);
container.addBean(new Person(1, "Django"));
container.addBean(new Person(2, "Schultz"));
ComboBox combobox = new ComboBox();
combobox.setImmediate(true);
combobox.setNullSelectionItemId(nullPerson); // Define the null person as a dummy.
combobox.setContainerDataSource(container);
combobox.setItemCaptionMode(AbstractSelect.ItemCaptionMode.PROPERTY);
combobox.setItemCaptionPropertyId("name"); // the person's name field will be shown on the UI
combobox.addValueChangeListener(new Property.ValueChangeListener() {
@Override
public void valueChange(ValueChangeEvent event) {
// Will display 'null selected' when nullPerson is selected.
Notification.show(event.getProperty().getValue() + " selected");
}
});
layout.addComponent(combobox);
}
}
回答by kszk
If your code is similar to this:
如果您的代码与此类似：
BeanItemContainer<Person> container = new BeanItemContainer<Person>(Person.class);
container.addAll(myPersonList);
ComboBox combobox = new ComboBox();
combobox.setContainerDataSource(container);
combobox.setItemCaptionMode(Select.ITEM_CAPTION_MODE_PROPERTY);
combobox.setItemCaptionPropertyId("name"); // the person's name field will be shown on the UI
// imho if you want to add a static text (String) into a container
// which populated with Person objects then you have to make a fake Person object
Person staticText = new Person();
staticText.setName("My static text");
combobox.addItem(staticText);
// if you want to specify the index of the item, add them one by one in for cycle
// and insert the static text item in the appropritate place
回答by Ondrej Kvasnovsky
You should do the change in the container (for example: add items...) and call setContainerDataSource(container) again on the combobox (so it gets propagated to the client).
您应该在容器中进行更改（例如：添加项目...）并在组合框上再次调用 setContainerDataSource(container) （因此它会传播到客户端）。
