如何删除mat datepicker文本框中的默认值？

<mat-form-field>
  <input matInput [matDatepicker]="picker" [(ngModel)]="selectedDate">
  <mat-datepicker-toggle matSuffix [for]="picker"></mat-datepicker-toggle>
  <mat-datepicker #picker></mat-datepicker>
</mat-form-field>

import { Component, ViewChild } from '@angular/core';
import { MatDatepicker } from '@angular/material/datepicker';

@Component({
  selector: 'app-datepicker',
  templateUrl: './datepicker.component.html',
  styleUrls: ['./datepicker.component.css']
})
export class DatepickerComponent {
  @ViewChild(MatDatepicker) datepicker: MatDatepicker<any>;
  selectedDate: Date;

  clearDate() {
    this.selectedDate = null;
    this.datepicker._datepickerInput.value = ''; // 清空文本框中的值
    this.datepicker.close(); // 关闭日期选择器
  }
}