Typescript 'matformfield' 不是已知元素 Angular 5 & Material2

我试图在一个使用material 的Angular 项目中使用<mat-form-field>，但我遇到了麻烦.

正在获取下面的错误消息.

Uncaught Error: Template parse errors:
'mat-form-field' is not a known element:
1. If 'mat-form-field' is an Angular component, then verify that it is part of this module.
2. If 'mat-form-field' is a Web Component then add 'CUSTOM_ELEMENTS_SCHEMA' to the '@NgModule.schemas' of this component to suppress this message. ("[ERROR ->]<mat-form-field>
  <input matInput placeholder="Simple placeholder" required>
</mat-form-field>"): ng:///MaterialModule/SearchComponent.html@0:0
    at syntaxError (compiler.js:485)
    at TemplateParser.parse (compiler.js:24660)
    at JitCompiler._parseTemplate (compiler.js:34471)
    at JitCompiler._compileTemplate (compiler.js:34446)
    at eval (compiler.js:34347)
    at Set.forEach (<anonymous>)
    at JitCompiler._compileComponents (compiler.js:34347)
    at eval (compiler.js:34217)
    at Object.then (compiler.js:474)
    at JitCompiler._compileModuleAndComponents (compiler.js:34216)

这是我的密码.

app.module.ts

import { BrowserModule } from '@angular/platform-browser';
import { NgModule, CUSTOM_ELEMENTS_SCHEMA } from '@angular/core';
import { FormGroup, FormControl, FormsModule, ReactiveFormsModule } from '@angular/forms';

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

import {
  MatButtonModule,
  MatFormFieldModule,
  MatInputModule,
  MatRippleModule
} from '@angular/material';
import { BrowserAnimationsModule } from '@angular/platform-browser/animations';

import { AppComponent } from './app.component';
import { YahooService } from './yahoo.service';
import { SearchComponent } from './search/search.component';

@NgModule({
  exports: [
    MatButtonModule,
    MatFormFieldModule,
    MatInputModule,
    MatRippleModule,
  ],
  declarations: [
    SearchComponent,
  ],
})
export class MaterialModule {};

@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
    MaterialModule,
    BrowserModule,
    BrowserAnimationsModule,
    FormsModule,
    HttpModule,
    HttpClientModule,
  ],
  providers: [
    YahooService,
  ],
  bootstrap: [
    AppComponent,
  ],
  schemas: [
    CUSTOM_ELEMENTS_SCHEMA,
  ],
})
export class AppModule { }

search.component.html

<mat-form-field>
   <input matInput placeholder="Simple placeholder" required>
</mat-form-field>

search.component.ts

import { Component, OnInit } from '@angular/core';
import { FormBuilder, FormGroup } from '@angular/forms';

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

  options: FormGroup;

  constructor(fb: FormBuilder) {
    this.options = fb.group({
      floatLabel: 'never',
    });
  }

  ngOnInit() {
  }

}

package.json

{
  "name": "forecast",
  "version": "0.0.0",
  "license": "MIT",
  "scripts": {
    "ng": "ng",
    "start": "ng serve",
    "build": "ng build",
    "test": "ng test",
    "lint": "ng lint",
    "e2e": "ng e2e"
  },
  "private": true,
  "dependencies": {
    "@angular-devkit/schematics": "0.0.40",
    "@angular/animations": "^5.1.3",
    "@angular/cdk": "^5.0.3",
    "@angular/common": "^5.1.3",
    "@angular/compiler": "^5.1.3",
    "@angular/core": "^5.1.3",
    "@angular/forms": "^5.1.3",
    "@angular/http": "^5.1.3",
    "@angular/material": "^5.0.3",
    "@angular/platform-browser": "^5.1.3",
    "@angular/platform-browser-dynamic": "^5.1.3",
    "@angular/router": "^5.1.3",
    "axios": "^0.17.1",
    "body-parser": "^1.18.2",
    "core-js": "^2.5.3",
    "express": "^4.16.2",
    "node-sass": "^4.7.2",
    "nodemon": "^1.14.7",
    "q": "^1.5.1",
    "rxjs": "^5.5.6",
    "zone.js": "^0.8.4"
  },
  "devDependencies": {
    "@angular/cli": "^1.6.3",
    "@angular/compiler-cli": "^5.1.3",
    "@types/jasmine": "2.5.38",
    "@types/node": "~6.0.60",
    "codelyzer": "~2.0.0",
    "jasmine-core": "~2.5.2",
    "jasmine-spec-reporter": "~3.2.0",
    "karma": "~1.4.1",
    "karma-chrome-launcher": "~2.0.0",
    "karma-cli": "~1.0.1",
    "karma-coverage-istanbul-reporter": "^0.2.0",
    "karma-jasmine": "~1.1.0",
    "karma-jasmine-html-reporter": "^0.2.2",
    "protractor": "~5.1.0",
    "ts-node": "~2.0.0",
    "tslint": "~4.5.0",
    "typescript": "~2.4.0"
  }
}