Lazy load in Kendo UI treeview with caching

Question

I am using Kendo UI TreeView to load hierarchical data in my webpage. By default, I am loading data upto 3 levels (ie Root -> Root directs -> Root directs' directs). I need a way to lazily load the remaining nodes as user expands further down the tree. Also, the already fetched data must be cached locally to avoid unnecessary calls for already expanded nodes. I am new to Kendo UI and do not have enough time to go through documentation. The json looks like

   {
      Id: '1',
      ParentId: '-1',
      Payload: {... }
      Children: [
          Id: '2',
          ParentId: '1',
          PayLoad: {...},
          Children: [{...}]
          ]
            ....
    }

Can someone point out to code samples ? How much of the above is supported out of box by Kendo ?

Thanks in advance.

Answer 1

That functionality is not supported by the out of the box configuration, but can be achieved through a custom transport. Here's how to create hybrid data sources that work with the localData array if the items are available, and otherwise perform requests to the server.

var localData = [
  { id: 1, text: "Node 1", hasChildren: true, items: [
    { id: 101, text: "Node 1.1", hasChildren: true, items: [
      { id: 10101, text: "Node 1.1.1" }
    ] }
  ] }, 
  { id: 2, hasChildren: true, text: "Node 2" },
  { id: 3, hasChildren: true, text: "Node 3" }
];

function get(data, id) {
  if (!id) {
    return data;
  } else {
    for (var i = 0; i < data.length; i++) {
      if (data[i].id == id) {
        return data[i].items;
      } else if (data[i].items) {
        var result = get(data[i].items, id);
        if (result) return result;
      }
    }
  }
}

var homogeneous = new kendo.data.HierarchicalDataSource({
  transport: {
    read: function (options) {
      var id = options.data.id;
      var data = get(localData, id);
      if (data) {
        options.success(data);
      } else {
        // mock call to server with static data
        // you can use $.ajax() and call options.success(data) on success
        setTimeout(function() {
          options.success([
            { id: id + 1, text: "Remote node 1", hasChildren: false },
            { id: id + 2, text: "Remote node 2", hasChildren: true }
          ]);
        }, 1000);
      }
    }
  },
  schema: {
    model: {
      id: "id"
    }
  }
});

$("#tree").kendoTreeView({
  dataSource: homogeneous
});

<link href="http://cdn.kendostatic.com/2013.1.319/styles/kendo.common.min.css" rel="stylesheet" />
<link href="http://cdn.kendostatic.com/2013.1.319/styles/kendo.default.min.css" rel="stylesheet" />
<script src="http://code.jquery.com/jquery-1.9.1.min.js"></script>
<script src="http://cdn.kendostatic.com/2013.1.319/js/kendo.web.min.js"></script>
<div id="tree"></div>