angular material scrolling not showing up

Question

I am trying to use angular material scrolling.

Here is my code:

app.module.ts:

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

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

import {BrowserAnimationsModule} from '@angular/platform-browser/animations';
import {ScrollDispatchModule} from '@angular/cdk/scrolling';
import {ScrollingModule} from '@angular/cdk/scrolling';

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

app.component.ts:

import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  items = Array.from({length: 10}).map((_, i) => `Item #${i}`);
}

app.component.html:

<cdk-virtual-scroll-viewport itemSize="50" class="example-viewport">
        <div *cdkVirtualFor="let item of items" class="example-item">{{item}}</div>
</cdk-virtual-scroll-viewport>

But the scroll bar does show up. Did I miss anything? I installed angular material and cdk, checked all of them in my package.json. should be working.

Answer 1

Solved, turns our that the CSS file is the solution. I did not include CSS file before.

Here is my app.component.css file:

.example-viewport {
    height: 200px;
    width: 200px;
    border: 1px solid black;
  }

  .example-item {
    height: 50px;
  }