从 angular 6 材质树中的子节点获取父层次结构 [英] Get parent hierarchy from a child node in angular 6 material tree

问题描述

我正在按照 教程 在 angular 6 中实现 cdk 树.我创建了一个树结构，现在我想通过使其可点击来从子节点获取父层次结构，而像 getDescendants 这样的方法可以获取节点的子节点，反之亦然.如何从子节点或叶节点获取父层次结构.

I am following a tutorial to implement cdk tree in angular 6. I created a tree structure, now I want to get the parent hierarchy from from the child by making it clickable, while there are methods like getDescendants to get children of a node, vice versa is not available. How can I get the parent hierarchy from a child or leaf node.

推荐答案

我已将这些方法添加到我的树组件中.请注意，我使用的是扁平树，这不适用于嵌套树.

I've added these methods to my tree component. Note that I use the flat tree, this won't work for a nested tree.

@Component({
  selector: 'es-outline-tree',
  // ...
})
export class OutlineTreeComponent implements OnInit {
  treeControl: FlatTreeControl<FlatTreeNode>;

  // other code...

  /**
   * Recursively expand all parents of the passed node.
   */
  expandParents(node: FlatTreeNode) {
    const parent = this.getParent(node);
    this.treeControl.expand(parent);

    if (parent && parent.level > 0) {
      this.expandParents(parent);
    }
  }

  /**
   * Iterate over each node in reverse order and return the first node that has a lower level than the passed node.
   */
  getParent(node: FlatTreeNode) {
    const { treeControl } = this;
    const currentLevel = treeControl.getLevel(node);

    if (currentLevel < 1) {
      return null;
    }

    const startIndex = treeControl.dataNodes.indexOf(node) - 1;

    for (let i = startIndex; i >= 0; i--) {
      const currentNode = treeControl.dataNodes[i];

      if (treeControl.getLevel(currentNode) < currentLevel) {
        return currentNode;
      }
    }
  }
}

我打算创建我自己的 FlatTreeControl(通过扩展 Angular CDK 的 FlatTreeControl)并将这个逻辑移到那里.

I'm planning to create my own FlatTreeControl (by extending Angular CDK's FlatTreeControl) and move this logic there.

更新

我已将上述逻辑移至我自己的 FlatTreeControl 实现:

I've moved the above logic to my own FlatTreeControl implementation:

import { FlatTreeControl } from '@angular/cdk/tree';

export class CustomTreeControl<T> extends FlatTreeControl<T> {
  /**
   * Recursively expand all parents of the passed node.
   */
  expandParents(node: T) {
    const parent = this.getParent(node);
    this.expand(parent);

    if (parent && this.getLevel(parent) > 0) {
      this.expandParents(parent);
    }
  }

  /**
   * Iterate over each node in reverse order and return the first node that has a lower level than the passed node.
   */
  getParent(node: T) {
    const currentLevel = this.getLevel(node);

    if (currentLevel < 1) {
      return null;
    }

    const startIndex = this.dataNodes.indexOf(node) - 1;

    for (let i = startIndex; i >= 0; i--) {
      const currentNode = this.dataNodes[i];

      if (this.getLevel(currentNode) < currentLevel) {
        return currentNode;
      }
    }
  }
}

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