Angular 6 Material Nested Tree is not working with dynamic data

Question

I am using mat-tree with mat-nested-tree-node in Angular 6. What I want is to load the data dynamically when the user toggles expand icon.

Answer 1

Add Remove Update element with Angular 6 Nested Tree Material

addmodifymilestone.component.ts

    import { Component, Injectable, AfterViewInit, ViewChild } from '@angular/core';
import { NestedTreeControl } from '@angular/cdk/tree';
import { MatTreeNestedDataSource } from '@angular/material/tree';
import { BehaviorSubject, Observable, of as observableOf } from 'rxjs';


/**
 * Json node data with nested structure. Each node has a filename and a value or a list of children
 */
export class ItemNode {
  children: ItemNode[];
  filename: string;
  type: any;
  expanded: boolean;
}


@Component({
  selector: 'app-addmodifymilestone',
  templateUrl: './addmodifymilestone.component.html',
  styleUrls: ['./addmodifymilestone.component.scss'],
})
export class AddmodifymilestoneComponent implements AfterViewInit {
  @ViewChild('tree') tree;
  updateNodeItemName: any = 'null';
  updateItemNameInput: any;
  nestedTreeControl: NestedTreeControl;
  nestedDataSource: MatTreeNestedDataSource;
  dataChange: BehaviorSubject = new BehaviorSubject([]);


  constructor() {
    this.nestedTreeControl = new NestedTreeControl(this._getChildren);
    this.nestedDataSource = new MatTreeNestedDataSource();

    this.dataChange.subscribe(data => this.nestedDataSource.data = data);
    this.dataChange.next([
      // {
      //   filename: 'Milestones',
      //   type: '',
      //   'expanded': false,
      //   children: [
      //     {
      //       filename: 'Milestone1',
      //       type: '',
      //       'expanded': false,
      //       children: []
      //     }
      //   ]
      // }
    ]);

    // this.dataChange.next([
    //   {
    //     filename: 'Milestones',
    //     type: '',
    //     children: [
    //       {
    //         filename: 'Milestone1',
    //         type: '',
    //         children: [
    //           {
    //             filename: 'To do list',
    //             type: '',
    //             children: [
    //               {
    //                 filename: 'Suggestion',
    //                 type: 'suggetion1, suggestion 2',
    //                 children: []
    //               }
    //             ],
    //           },
    //         ],
    //       }
    //     ],
    //   },
    // ]);
  }


  private _getChildren = (node: ItemNode) => {
    return observableOf(node.children);
  }


  hasNestedChild = (_: number, nodeData: ItemNode) => {
    return !(nodeData.type);
  }

  ngAfterViewInit(): void {
    this.nestedTreeControl = new NestedTreeControl(this._getChildren);
    this.nestedDataSource = new MatTreeNestedDataSource();

    this.dataChange.subscribe(data => this.nestedDataSource.data = data);
  }

  changeState(node) {
    console.log('change state called :::');
    node.expanded = !node.expanded;
    console.log(node);
  }

  addNewMilestone() {
    this.nestedTreeControl = new NestedTreeControl(this._getChildren);
    this.nestedDataSource = new MatTreeNestedDataSource();
    this.dataChange.subscribe(data => this.nestedDataSource.data = data);

    let tempData: any[];
    this.dataChange.subscribe(data => tempData = data);
    const data = new ItemNode();
    data.filename = 'New Milestone';
    data.type = '',
      data.children = [
        {
          filename: 'AddToDoList',
          type: 'AddToDoList',
          'expanded': false,
          children: [],
        },
        {
          filename: 'To do list',
          type: '',
          'expanded': false,
          children: [
            {
              filename: 'AddSuggestion',
              type: 'AddSuggestion',
              'expanded': false,
              children: [],
            },
            {
              filename: 'suggestions',
              type: 'suggestion1, suggestion2, suggestion3',
              'expanded': false,
              children: []
            },
          ],
        },
      ];

    tempData.push(data);
    this.dataChange.next(tempData);
  }


  addNewToDoList(node: ItemNode) {
    this.nestedTreeControl = new NestedTreeControl(this._getChildren);
    this.nestedDataSource = new MatTreeNestedDataSource();

    this.dataChange.subscribe(data => this.nestedDataSource.data = data);

    const nodeChiledren: any[] = node.children;
    const data = {
      filename: 'To do list',
      type: '',
      children: [
        {
          filename: 'AddSuggestion',
          type: 'AddSuggestion',
          'expanded': false,
          children: [],
        }
      ],
    };
    nodeChiledren.push(data);

    let tempData: any[];
    this.dataChange.subscribe(data => tempData = data);

    tempData = tempData.map((value, index, array) => {
      if (value.filename === node.filename) {
        value.children = nodeChiledren;
      }
      return value;
    });


    const dataStringfy = JSON.stringify(tempData);
    const json: ItemNode[] = JSON.parse(dataStringfy);
    this.dataChange.next(json);
  }

  addNewSuggestion(node: ItemNode) {
    this.nestedTreeControl = new NestedTreeControl(this._getChildren);
    this.nestedDataSource = new MatTreeNestedDataSource();

    this.dataChange.subscribe(data => this.nestedDataSource.data = data);

    const nodeChiledren: any[] = node.children;
    const data = {
      filename: 'Suggestion',
      type: 'suggestion11, suggestion22',
      'expanded': false,
      children: [],
    };
    nodeChiledren.push(data);

    let tempData: any[];
    this.dataChange.subscribe(data => tempData = data);

    tempData = tempData.map((value, index, array) => {
      if (value.filename === node.filename) {
        value.children = nodeChiledren;
      }
      return value;
    });


    const dataStringfy = JSON.stringify(tempData);
    const json: ItemNode[] = JSON.parse(dataStringfy);
    this.dataChange.next(json);
  }


  enableUpdateNode(node: ItemNode) {
    console.log('updateNode :::');
    console.log(node);
    this.updateNodeItemName = node.filename;
  }

  updateNode(node: ItemNode) {

    this.updateNodeItemName = 'null';
    console.log(this.updateItemNameInput);
    console.log(node);


    this.nestedTreeControl = new NestedTreeControl(this._getChildren);
    this.nestedDataSource = new MatTreeNestedDataSource();

    this.dataChange.subscribe(data => this.nestedDataSource.data = data);

    node.filename = this.updateItemNameInput;
    let tempData: any[];
    this.dataChange.subscribe(data => tempData = data);

    tempData = tempData.map((value, index, array) => {
      if (value.filename === node.filename) {
        value = node;
      }
      return value;
    });


    const dataStringfy = JSON.stringify(tempData);
    const json: ItemNode[] = JSON.parse(dataStringfy);
    this.dataChange.next(json);

  }

  deleteNode(node: any) {

    this.nestedTreeControl = new NestedTreeControl(this._getChildren);
    this.nestedDataSource = new MatTreeNestedDataSource();

    this.dataChange.subscribe(data => this.nestedDataSource.data = data);

    node.filename = this.updateItemNameInput;
    let tempData: any[];
    this.dataChange.subscribe(data => tempData = data);

    const index = tempData.findIndex(value => value.filename === node.filename);

    tempData.splice(index, 1);


    const dataStringfy = JSON.stringify(tempData);
    const json: ItemNode[] = JSON.parse(dataStringfy);
    this.dataChange.next(json);

  }
}

addmodifymilestone.component.html

Add New Milestone 

  
    

      
      {{node.filename}}: {{node.type }}
      
      
    
  


  
    
    


      

        
          
            {{node.expanded ? 'expand_more' : 'chevron_right'}}
          
        
        

          {{node.filename}}
        
        
          
            
          

        

        
        
        
      
      


        

          

            
Add To do list 
          
          

            
Add Suggestion
          
        

        
      
    
  

addmodifymilestone.component.scss

.example-tree-invisible {
  display: none;
}

.example-tree ul,
.example-tree li {
  margin-top: 0;
  margin-bottom: 0;
  list-style-type: none;
}

.example-tree li {
  margin-left: 25px;
}

.fa {
margin:5px;
}

.fa-trash{
color: red;
}

.mat-tree-node {
  display: flex;
  align-items: center;
  min-height: 0px;
  flex: 1;
  overflow: hidden;
  word-wrap: break-word;
}

.paragraphMargingLeft{
  margin-left: 46px;
}