未应用材质树样式

Question

我正在尝试复制此处找到的材质树示例。

它应该看起来像这样：

但我的结果是这样的：

这是我的 HTML：

<mat-tree [dataSource]="dataSource" [treeControl]="treeControl">
  <!-- This is the tree node template for leaf nodes -->
  <mat-tree-node *matTreeNodeDef="let node" matTreeNodePadding>
    <!-- use a disabled button to provide padding for tree leaf -->
    <button mat-icon-button disabled></button>
    {{node.name}}
  </mat-tree-node>
  <!-- This is the tree node template for expandable nodes -->
  <mat-tree-node *matTreeNodeDef="let node;when: hasChild" matTreeNodePadding>
    <button mat-icon-button matTreeNodeToggle
            [attr.aria-label]="'toggle ' + node.name">
      <mat-icon class="mat-icon-rtl-mirror">
        {{treeControl.isExpanded(node) ? 'expand_more' : 'chevron_right'}}
      </mat-icon>
    </button>
    {{node.name}}
  </mat-tree-node>
</mat-tree>

TS：

import { Component, HostListener, OnInit, ViewChild, ElementRef } from '@angular/core';
import { ScreenshotService } from './screenshot.service';

import { DomSanitizer, SafeResourceUrl, SafeUrl} from '@angular/platform-browser';

import {FlatTreeControl} from '@angular/cdk/tree';
import {MatTreeFlatDataSource, MatTreeFlattener} from '@angular/material/tree';

/**
 * Food data with nested structure.
 * Each node has a name and an optiona list of children.
 */
interface FoodNode {
  name: string;
  children?: FoodNode[];
}

const TREE_DATA: FoodNode[] = [
  {
    name: 'Fruit',
    children: [
      {name: 'Apple'},
      {name: 'Banana'},
      {name: 'Fruit loops'},
    ]
  }, {
    name: 'Vegetables',
    children: [
      {
        name: 'Green',
        children: [
          {name: 'Broccoli'},
          {name: 'Brussel sprouts'},
        ]
      }, {
        name: 'Orange',
        children: [
          {name: 'Pumpkins'},
          {name: 'Carrots'},
        ]
      },
    ]
  },
];

/** Flat node with expandable and level information */
interface ExampleFlatNode {
  expandable: boolean;
  name: string;
  level: number;
}

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent implements OnInit {


  private transformer = (node: FoodNode, level: number) => {
    return {
      expandable: !!node.children && node.children.length > 0,
      name: node.name,
      level: level,
    };
  }

  treeControl = new FlatTreeControl<ExampleFlatNode>(
    node => node.level, node => node.expandable);

  treeFlattener = new MatTreeFlattener(
      this.transformer, node => node.level, node => node.expandable, node => node.children);

  dataSource = new MatTreeFlatDataSource(this.treeControl, this.treeFlattener);

  hasChild = (_: number, node: ExampleFlatNode) => node.expandable;

  constructor(private screenshotService: ScreenshotService, private sanitizer: DomSanitizer) {

    this.dataSource.data = TREE_DATA;

  }

}

应用程序模块.ts：

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';

import { AppRoutingModule } from './app-routing.module';
import { AppComponent } from './app.component';

import { HttpClientModule } from '@angular/common/http';

import {MatTreeModule} from '@angular/material/tree';
import {MatIconModule} from '@angular/material';
import {BrowserAnimationsModule} from '@angular/platform-browser/animations';
import {MatButtonModule} from '@angular/material';
import {FlatTreeControl} from '@angular/cdk/tree';
import {MatTreeFlatDataSource, MatTreeFlattener} from '@angular/material/tree';



@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
    BrowserAnimationsModule,
    BrowserModule,
    AppRoutingModule,
    HttpClientModule,
    MatTreeModule,
    MatIconModule,
    MatButtonModule
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

Answer 1

我在 Angular 10 中遇到了同样的问题。此外，MatTreeModule我还必须将MatIconModule和 MatButtonModule导入app.module.ts：

import {MatButtonModule} from '@angular/material/button';
import {MatIconModule} from '@angular/material/icon';
import {MatTreeModule} from '@angular/material/tree';
//...
imports: [
  //...
  MatButtonModule,
  MatIconModule,
  MatTreeModule
]