import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { AppComponent } from './app.component';
import {BrowserAnimationsModule} from '@angular/platform-browser/animations';
import {MatTreeModule, MatIconModule, MatButtonModule} from '@angular/material'
import {FormsModule, ReactiveFormsModule} from '@angular/forms';
@NgModule({
   declarations: [
      AppComponent
   ],
   imports: [
      BrowserModule,
      BrowserAnimationsModule,
      MatTreeModule, MatIconModule, MatButtonModule,
      FormsModule,
      ReactiveFormsModule
   ],
   providers: [],
   bootstrap: [AppComponent]
})
export class AppModule { }

   
      
      {{node.filename}} : {{node.type}}
   
   
      
         
            {{treeControl.isExpanded(node) ? 'expand_more' : 'chevron_right'}}
         
      
      {{node.filename}}
   

import {FlatTreeControl} from '@angular/cdk/tree';
import {Component, Injectable} from '@angular/core';
import {MatTreeFlatDataSource, MatTreeFlattener} from '@angular/material/tree';
import {BehaviorSubject, Observable, of as observableOf} from 'rxjs';
export class FileNode {
   children: FileNode[];
   filename: string;
   type: any;
}
export class FileFlatNode {
   constructor(
      public expandable: boolean, public filename: string, public level: number, public type: any) {}
}
const TREE_DATA = JSON.stringify({
   Documents: {
      angular: {
         src: {
            compiler: 'ts',
            core: 'ts'
         }
      },
      material2: {
         src: {
            button: 'ts',
            checkbox: 'ts',
            input: 'ts'
         }
      }
   }
});
@Injectable()
export class FileDatabase {
   dataChange = new BehaviorSubject([]);
   get data(): FileNode[] { return this.dataChange.value; }
   constructor() {
      this.initialize();
   }
   initialize() {
      const dataObject = JSON.parse(TREE_DATA);   
      const data = this.buildFileTree(dataObject, 0);
      this.dataChange.next(data);
   } 
   buildFileTree(obj: {[key: string]: any}, level: number): FileNode[] {
      return Object.keys(obj).reduce((accumulator, key) => {
         const value = obj[key];
         const node = new FileNode();
         node.filename = key;
         if (value != null) {
            if (typeof value === 'object') {
               node.children = this.buildFileTree(value, level + 1);
            } else {
               node.type = value;
            }
         }
         return accumulator.concat(node);
      }, []);
   }
}
@Component({
   selector: 'app-root',
   templateUrl: 'app.component.html',
   styleUrls: ['app.component.css'],
   providers: [FileDatabase]
})
export class AppComponent {
   treeControl: FlatTreeControl;
   treeFlattener: MatTreeFlattener;
   dataSource: MatTreeFlatDataSource;
   constructor(database: FileDatabase) {
      this.treeFlattener = new MatTreeFlattener(this.transformer, this._getLevel,
      this._isExpandable, this._getChildren);
      this.treeControl = new FlatTreeControl(this._getLevel, this._isExpandable);
      this.dataSource = new MatTreeFlatDataSource(this.treeControl, this.treeFlattener);
      database.dataChange.subscribe(data => this.dataSource.data = data);
   }
   transformer = (node: FileNode, level: number) => {
      return new FileFlatNode(!!node.children, node.filename, level, node.type);
   }
   private _getLevel = (node: FileFlatNode) => node.level;
   private _isExpandable = (node: FileFlatNode) => node.expandable;
   private _getChildren = (node: FileNode): Observable => observableOf(node.children);
   hasChild = (_: number, _nodeData: FileFlatNode) => _nodeData.expandable;
}