@qooxdoo/framework/docs/widget/virtuallist.md

The JS Framework for Coders

Virtual List
============

The virtual List is a widget based on the framework's virtual infrastructure.

Preview Image
-------------

![virtuallist.png](virtuallist.png)

Description
-----------

The `qx.ui.list.List` is based on the virtual infrastructure and supports filtering, sorting, grouping, single selection, multi selection, data binding and custom rendering.

Using the virtual infrastructure has considerable advantages when there is a huge amount of model items to render: Widgets are created only for visible items and reused. This saves both creation time and memory.

With the [qx.ui.list.core.IListDelegate](apps://apiviewer/#qx.ui.list.core.IListDelegate) interface, it is possible to configure the list's behavior (item and group renderer configuration, filtering, sorting, grouping, etc.).

> **note**

> Only widget based rendering for list and group items is supported.

Code Example
------------

Here's an example. We create a simple list example with 2500 items, sort the items (ascending), select the 20th item and log each selection change.

    //create the model data
    var rawData = [];
    for (var i = 0; i < 2500; i++) {
      rawData[i] = "Item No " + i;
    }
    var model = qx.data.marshal.Json.createModel(rawData);

    //create the list
    var list = new qx.ui.list.List(model);

    //configure the lists's behavior
    var delegate = {
      sorter : function(a, b) {
        return a > b ? 1 : a < b ? -1 : 0;
      }
    };
    list.setDelegate(delegate);

    //Pre-Select "Item No 20"
    list.getSelection().push(model.getItem(20));

    //log selection changes
    list.getSelection().addListener("change", function(e) {
      this.debug("Selection: " + list.getSelection().getItem(0));
    }, this);

Demos
-----

Here are some links that demonstrate the usage of the widget:

-   [Example for the virtual List widget](apps://demobrowser/#virtual~List.html)
-   [Example showing the filtering feature](apps://demobrowser/#virtual~ListWithFilter.html)
-   [Example showing the custom rendering](apps://demobrowser/#virtual~ExtendedList.html)
-   [Example showing the grouping feature](apps://demobrowser/#virtual~GroupedList.html)

API
---

Here is a link to the API of the widget:
[qx.ui.list.List](apps://apiviewer/#qx.ui.list.List)