角度6“垫按钮切换”不是已知元素

我检查过这些问题:

• 'mat-toolbar' is not a known element - Angular 5
• Jhipster / md-button is not a known element
• Template parse errors: 'mat-icon' is not a known element
• Meterial 2 md-datepicker-toggle is not a known element
• How to bind to model with Angular Material <mat-button-toggle>?

我遵循了这个教程:

• https://material.angular.io/components/button-toggle/overview

编译器.js:1016未捕获错误:模板分析错误: “mat button toggle”不是已知元素:

应用模块ts

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { TRANSLATION_PROVIDERS } from './translations';
import { TranslateService } from './services/translator.service';
import { AppComponent } from './app.component';
import { MatButtonModule, MatCheckboxModule, MatFormFieldModule, MatInputModule, MatRippleModule, MatDatepickerModule, MatNativeDateModule } from '@angular/material';
import { BrowserAnimationsModule } from '@angular/platform-browser/animations';
import { FormsModule } from '@angular/forms';

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


@NgModule({
  imports: [
    BrowserModule,
    FormsModule,
    MatButtonModule,
    MatCheckboxModule,
    MatFormFieldModule,
    MatInputModule,
    MatRippleModule,
    BrowserAnimationsModule,
    MatDatepickerModule,
  ],
  exports: [
    BrowserModule,
    FormsModule,
    MatButtonModule,
    MatCheckboxModule,
    MatFormFieldModule,
    MatInputModule,
    MatRippleModule,
    BrowserAnimationsModule,
    MatDatepickerModule,
  ],
  declarations: [AppComponent],
  providers: [TRANSLATION_PROVIDERS, TranslateService],
  bootstrap: [AppComponent]
})
export class AppModule { }

....

  <div>
      <mat-button-toggle-group name="fontStyle" aria-label="Font Style">
          <mat-button-toggle value="bold">Bold</mat-button-toggle>
          <mat-button-toggle value="italic">Italic</mat-button-toggle>
          <mat-button-toggle value="underline">Underline</mat-button-toggle>
        </mat-button-toggle-group>
  </div>

样式.css

@import '~@angular/material/prebuilt-themes/deeppurple-amber.css';

body { 
  font-family: Roboto, Arial, sans-serif;
  margin: 0;
}

.basic-container {
  padding: 30px;
}

.version-info {
  font-size: 8pt;
  float: right;
}

html, body { height: 100%; }
body { margin: 0; font-family: 'Roboto', sans-serif; }