步驟菜單不顯示在Primeng

嘗試primeng學習，我修改了cli生成的起始代碼如下。步驟菜單不顯示在Primeng

app.component.ts

import { Component } from '@angular/core'; 
import {StepsModule,MenuItem} from 'primeng/primeng'; 

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

    name: string; 

    message1: string; 

    private items: MenuItem[]; 

    ngOnInit() { 
     this.items = [ 
      {label: 'Step 1'}, 
      {label: 'Step 2'}, 
      {label: 'Step 3'} 
     ]; 
    } 

    onClick() { 
     this.message1 = 'Hello ' + this.name; 
    } 
}

app.component.html從而：

<input type="text" [(ngModel)]="name" pInputText> 
<button type="button" pButton label="Click" icon="fa fa-check" (click)="onClick($event)"></button> 

<div>{{message1}}</div> 
<p-fileUpload name="myfile[]" url="http://localhost/"></p-fileUpload> 


<p-steps [model]="items" [readonly]="false"></p-steps>

app.module.ts從而：

import { BrowserModule } from '@angular/platform-browser'; 
import { BrowserAnimationsModule } from '@angular/platform-browser/animations'; 
import { NgModule } from '@angular/core'; 
import { FormsModule } from '@angular/forms'; 
import { HttpModule } from '@angular/http'; 
import { InputTextModule, ButtonModule } from 'primeng/primeng'; 
import {FileUploadModule} from 'primeng/primeng'; 
import {StepsModule,MenuItem} from 'primeng/primeng'; 

import { AppComponent } from './app.component'; 

@NgModule({ 
    declarations: [ 
    AppComponent 
    ], 
    imports: [ 
    BrowserModule, 
    BrowserAnimationsModule, 
    FormsModule, 
    HttpModule, 
    InputTextModule, 
    ButtonModule, 
    FileUploadModule, 
    StepsModule 
    ], 
    providers: [], 
    bootstrap: [AppComponent] 
}) 
export class AppModule { }

它顯示此幾乎空白屏幕沒有控制檯錯誤：