小编K.c*_*ine的帖子

我尝试使用角度材料 5 上传文件（角度 5）。

应用程序组件.html

    <mat-horizontal-stepper [linear]="isLinear" #stepper="matHorizontalStepper">

  <mat-step [stepControl]="firstFormGroup">
    <form [formGroup]="firstFormGroup">
      <ng-template matStepLabel>Upload your audio file</ng-template>
      <mat-form-field>
          <input matInput  
          style="display: none" 
          type="file" (change)="onFileSelected($event)" 
          #fileInput name ="file" formControlName="firstCtrl" required>
      <button mat-button (click)="fileInput.click()" >Select File</button>
  </mat-form-field>
  <div>
    <button mat-button matStepperNext>Next</button>
  </div>
</form>

应用程序组件.ts

export class AppComponent {
  selectedFile: File=null;
  isLinear = true;
  firstFormGroup: FormGroup;
  secondFormGroup: FormGroup;
  constructor(private _formBuilder: FormBuilder, private http: HttpClient) {}
  ngOnInit() {
   this.firstFormGroup = this._formBuilder.group({
     firstCtrl: ['', Validators.required]
    });
   this.secondFormGroup = this._formBuilder.group({
      secondCtrl: ['', Validators.required]
    });
  }

但我收到了这个错误 …