primeng 下拉组件错误（“p-dropdown”不是已知元素）

遵循指南：https://www.primefaces.org/primeng/ https://www.primefaces.org/primeng/我尝试按照上面详述的步骤安装 PrimeNG 以与 Angular4 一起使用，但出现错误：

'p-dropdown' is not a known element:

我尝试按照其他帖子中的建议重建项目，但它对我不起作用。有什么提示吗？

以下是所有详细信息：

-- PrimeNg 安装

npm install primeng --save

-- 文件：testdropdown.component.html

<p-dropdown [options]="cities" [(ngModel)]="selectedCity"></p-dropdown>

-- 文件：testdropdown.component.ts

import { DropdownModule } from 'primeng/primeng';
import { Component, OnInit } from '@angular/core';
import { SelectItem } from 'primeng/primeng';

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

  cities: SelectItem[];

  selectedCity: string;

  constructor() {

  this.cities = [];
    this.cities.push({ label: 'Select City', value: null });
    this.cities.push({ label: 'New York', value: { id: 1, name: 'New York', code: 'NY' } });
    this.cities.push({ label: 'Rome', value: { id: 2, name: 'Rome', code: 'RM' } });
  }

  ngOnInit() {
  }

}

- 错误：

VM1128:185 [CodeLive] HTTP detected: Connecting using WS
zone.js:630 Unhandled Promise rejection: Template parse errors:
Can't bind to 'options' since it isn't a known property of 'p-dropdown'.
1. If 'p-dropdown' is an Angular component and it has 'options' input, then verify that it is part of this module.
2. If 'p-dropdown' is a Web Component then add 'CUSTOM_ELEMENTS_SCHEMA' to the '@NgModule.schemas' of this component to suppress this message.
3. To allow any property add 'NO_ERRORS_SCHEMA' to the '@NgModule.schemas' of this component. ("<p-dropdown [ERROR ->][options]="cities" [(ngModel)]="selectedCity"></p-dropdown>
"): ng:///AppModule/TestdropdownComponent.html@0:12
'p-dropdown' is not a known element:
1. If 'p-dropdown' is an Angular component, then verify that it is part of this module.
2. If 'p-dropdown' is a Web Component then add 'CUSTOM_ELEMENTS_SCHEMA' to the '@NgModule.schemas' of this component to suppress this message. ("[ERROR ->]<p-dropdown [options]="cities" [(ngModel)]="selectedCity"></p-dropdown>

在声明组件的模块中导入下拉模块。

   import { DropdownModule } from 'primeng/dropdown';


@NgModule({
  imports: [
   DropdownModule
  ],
  declarations: [TestdropdownComponent ]
 
})
export class myModule { }