加载页面时选中Kendo Dropdowntree中的全部复选框

var treeData = [
  {
    text: "节点1",
    items: [
      { text: "子节点1", checked: true },
      { text: "子节点2", checked: true },
      // 其他子节点...
    ],
    checked: true
  },
  {
    text: "节点2",
    items: [
      { text: "子节点1", checked: true },
      { text: "子节点2", checked: true },
      // 其他子节点...
    ],
    checked: true
  },
  // 其他节点...
];

$("#dropdowntree").kendoDropDownTree({
  checkboxes: {
    checkChildren: true
  },
  dataSource: treeData
});

$("#dropdowntree").data("kendoDropDownTree").dataSource.bind("change", function() {
  var treeView = $("#dropdowntree").data("kendoDropDownTree");
  treeView.dataSource.view().forEach(function(node) {
    treeView.check(node);
  });
});