Angular-没有为FormBuilder提供程序

我正在使用Angular 9。

我收到以下错误：

没有FormBuilder的提供者

在许多情况下都已报告它，并且一般的解决方案似乎是将添加FormsModule到app.module.ts文件中。

例如

import { FormsModule } from '@angular/forms';

  imports: [
    FormsModule

我已经尝试过了，但是仍然出现错误。

ERROR Error: Uncaught (in promise): NullInjectorError: R3InjectorError(AppModule)[FormBuilder -> FormBuilder -> FormBuilder]:

  NullInjectorError: No provider for FormBuilder!
NullInjectorError: R3InjectorError(AppModule)[FormBuilder -> FormBuilder -> FormBuilder]: 
  NullInjectorError: No provider for FormBuilder!

题

我可能正在做一些在Angular 9中更改过的事情吗？我需要怎么做才能解决此问题？

我的代码：

login.component.ts

import { Component, OnInit } from '@angular/core';
import {Router} from '@angular/router';
import { FormGroup, FormBuilder } from '@angular/forms';
import { AuthService } from '../../services/auth.service';

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

  loginForm: FormGroup;

  constructor(private authService: AuthService, private formBuilder: FormBuilder, private router: Router) {
  }

  ngOnInit(): void {
    this.loginForm = this.formBuilder.group({
      username: [''],
      password: ['']
    });
  }

  get f() { return this.loginForm.controls; }

  login() {
    this.authService.login(
      {
        username: this.f.username.value,
        password: this.f.password.value
      }
    )
    .subscribe(success => {
      if (success) {
        this.router.navigate(['/secret-random-number']);
      }
    });
  }

}

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 { LoginComponent } from './auth/containers/login/login.component';
import { BrowserAnimationsModule } from '@angular/platform-browser/animations';
import { FlexLayoutModule } from '@angular/flex-layout';
import { MatFormFieldModule } from '@angular/material/form-field';
import { MatInputModule } from '@angular/material/input';
import { MatButtonModule } from '@angular/material/button';
import { MatCardModule } from '@angular/material/card';
import { MatToolbarModule } from '@angular/material/toolbar';
import { FormsModule } from '@angular/forms';
import { ApprovalListComponent } from './approval-list/component/approval-list.component';
import { MatTableModule } from '@angular/material/table';
import { MatPaginatorModule } from '@angular/material/paginator';
import { MatSortModule } from '@angular/material/sort';
import { MatTableExporterModule } from 'mat-table-exporter';

@NgModule({
  declarations: [
    AppComponent,
    LoginComponent,
    ApprovalListComponent
  ],
  imports: [
    BrowserModule,
    AppRoutingModule,
    HttpClientModule,
    BrowserAnimationsModule,
    FlexLayoutModule,
    MatFormFieldModule,
    MatInputModule,
    MatButtonModule,
    MatCardModule,
    MatToolbarModule,
    FormsModule,
    MatTableModule,
    MatPaginatorModule,
    MatSortModule,
    MatTableExporterModule
  ],
  providers: [LoginComponent],
  bootstrap: [AppComponent]
})
export class AppModule { }