# qooxdoo

## the new era of web development

### Navigation

- index
- next |
- previous |
- » Home »
- qooxdoo v1.5 documentation »
- References »
- Widget Reference »
- Widget Reference List »

# VirtualTree

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

## Preview Image

## Description

The `qx.ui.tree.VirtualTree` is based on the virtual infrastructure and supports 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.tree.core.IVirtualTreeDelegate interface it is possible to configure the tree's behavior (item renderer configuration, etc.).

Note

At the moment we only support widget based rendering for tree items, but we are planning to also support HTML based rendering in a future release.

## Code Example

Here's an example. We create a simple tree example with 2500 items and log each selection change.

    //create the model data
    var nodes = [];
    for (var i = 0; i < 2500; i++)
    {
      nodes[i] = {name : "Item " + i};

      // if its not the root node
      if (i !== 0)
      {
        // add the children in some random order
        var node = nodes[parseInt(Math.random() * i)];

        if(node.children == null) {
          node.children = [];
        }
        node.children.push(nodes[i]);
      }
    }
    // converts the raw nodes to qooxdoo objects
    nodes = qx.data.marshal.Json.createModel(nodes, true);

    // creates the tree
    var tree = new qx.ui.tree.VirtualTree(nodes.getItem(0), "name", "children").set({
      width : 200,
      height : 400
    });

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

## Demos

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

- Example for the VirtualTree widget
- Example with custom items as columns
- Example which loads items dynamically when a nodes is opened

## API

Here is a link to the API of the widget:
qx.ui.tree.VirtualTree