Method insertNode

src/cdk/tree/tree.ts:595–627

* Create the embedded view for the data node template and place it in the correct index location * within the data node view container.

(nodeData: T, index: number, viewContainer?: ViewContainerRef, parentData?: T)

   * within the data node view container.
   */
  insertNode(nodeData: T, index: number, viewContainer?: ViewContainerRef, parentData?: T) {
    const levelAccessor = this._getLevelAccessor();

    const node = this._getNodeDef(nodeData, index);
    const key = this._getExpansionKey(nodeData);

    // Node context that will be provided to created embedded view
    const context = new CdkTreeNodeOutletContext<T>(nodeData);
    context.index = index;

    parentData ??= this._parents.get(key) ?? undefined;
    // If the tree is flat tree, then use the `getLevel` function in flat tree control
    // Otherwise, use the level of parent node.
    if (levelAccessor) {
      context.level = levelAccessor(nodeData);
    } else if (parentData !== undefined && this._levels.has(this._getExpansionKey(parentData))) {
      context.level = this._levels.get(this._getExpansionKey(parentData))! + 1;
    } else {
      context.level = 0;
    }
    this._levels.set(key, context.level);

    // Use default tree nodeOutlet, or nested node's nodeOutlet
    const container = viewContainer ? viewContainer : this._nodeOutlet.viewContainer;
    container.createEmbeddedView(node.template, context, index);

    // Set the data to just created `CdkTreeNode`.
    // The `CdkTreeNode` created from `createEmbeddedView` will be saved in static variable
    //     `mostRecentTreeNode`. We get it from static variable and pass the node data to it.
    if (CdkTreeNode.mostRecentTreeNode) {
      CdkTreeNode.mostRecentTreeNode.data = nodeData;
    }
  }

  /** Whether the data node is expanded or collapsed. Returns true if it's expanded. */
  isExpanded(dataNode: T): boolean {