Angular：mat-form-field 必须包含一个 MatFormFieldControl

Question

我正在尝试添加带有自定义电话号码输入控件的表单字段。我以https://material.angular.io/components/form-field/examples的手机为例。

代码如下：

<mat-form-field>
  <example-tel-input placeholder="Phone number" required></example-tel-input>
  <mat-icon matSuffix>phone</mat-icon>
  <mat-hint>Include area code</mat-hint>
</mat-form-field>

import {FocusMonitor} from '@angular/cdk/a11y';
import {coerceBooleanProperty} from '@angular/cdk/coercion';
import {Component, ElementRef, Input, OnDestroy} from '@angular/core';
import {FormBuilder, FormGroup} from '@angular/forms';
import {MatFormFieldControl} from '@angular/material';
import {Subject} from 'rxjs';

/** @title Form field with custom telephone number input control. */
@Component({
  selector: 'form-field-custom-control-example',
  templateUrl: 'form-field-custom-control-example.html',
  styleUrls: ['form-field-custom-control-example.css'],
})
export class FormFieldCustomControlExample {}

/** Data structure for holding telephone number. */
export class MyTel {
  constructor(public area: string, public exchange: string, public subscriber: string) {}
}

/** Custom `MatFormFieldControl` for telephone number input. */
@Component({
  selector: 'example-tel-input',
  templateUrl: 'example-tel-input-example.html',
  styleUrls: ['example-tel-input-example.css'],
  providers: [{provide: MatFormFieldControl, useExisting: MyTelInput}],
  host: {
    '[class.example-floating]': 'shouldLabelFloat',
    '[id]': 'id',
    '[attr.aria-describedby]': 'describedBy',
  }
})
export class MyTelInput implements MatFormFieldControl<MyTel>, OnDestroy {
  static nextId = 0;

  parts: FormGroup;
  stateChanges = new Subject<void>();
  focused = false;
  ngControl = null;
  errorState = false;
  controlType = 'example-tel-input';
  id = `example-tel-input-${MyTelInput.nextId++}`;
  describedBy = '';

  get empty() {
    const {value: {area, exchange, subscriber}} = this.parts;

    return !area && !exchange && !subscriber;
  }

  get shouldLabelFloat() { return this.focused || !this.empty; }

  @Input()
  get placeholder(): string { return this._placeholder; }
  set placeholder(value: string) {
    this._placeholder = value;
    this.stateChanges.next();
  }
  private _placeholder: string;

  @Input()
  get required(): boolean { return this._required; }
  set required(value: boolean) {
    this._required = coerceBooleanProperty(value);
    this.stateChanges.next();
  }
  private _required = false;

  @Input()
  get disabled(): boolean { return this._disabled; }
  set disabled(value: boolean) {
    this._disabled = coerceBooleanProperty(value);
    this.stateChanges.next();
  }
  private _disabled = false;

  @Input()
  get value(): MyTel | null {
    const {value: {area, exchange, subscriber}} = this.parts;
    if (area.length === 3 && exchange.length === 3 && subscriber.length === 4) {
      return new MyTel(area, exchange, subscriber);
    }
    return null;
  }
  set value(tel: MyTel | null) {
    const {area, exchange, subscriber} = tel || new MyTel('', '', '');
    this.parts.setValue({area, exchange, subscriber});
    this.stateChanges.next();
  }

  constructor(fb: FormBuilder, private fm: FocusMonitor, private elRef: ElementRef<HTMLElement>) {
    this.parts = fb.group({
      area: '',
      exchange: '',
      subscriber: '',
    });

    fm.monitor(elRef, true).subscribe(origin => {
      this.focused = !!origin;
      this.stateChanges.next();
    });
  }

  ngOnDestroy() {
    this.stateChanges.complete();
    this.fm.stopMonitoring(this.elRef);
  }

  setDescribedByIds(ids: string[]) {
    this.describedBy = ids.join(' ');
  }

  onContainerClick(event: MouseEvent) {
    if ((event.target as Element).tagName.toLowerCase() != 'input') {
      this.elRef.nativeElement.querySelector('input')!.focus();
    }
  }


  }

example-tel-input-example.html

  <div [formGroup]="parts" class="example-tel-input-container">
      <input class="example-tel-input-element" formControlName="area" size="3">
      <span class="example-tel-input-spacer">&ndash;</span>
      <input class="example-tel-input-element" formControlName="exchange" size="3">
      <span class="example-tel-input-spacer">&ndash;</span>
      <input class="example-tel-input-element" formControlName="subscriber" size="4">
    </div>

但我收到以下错误：

错误错误：mat-form-field 必须包含 MatFormFieldControl。

Answer 1

需要import两个模块并在导入和导出部分添加。

import { MatFormFieldModule } from '@angular/material/form-field';
import { MatInputModule } from '@angular/material/input';

@NgModule ({
  imports: [ MatFormFieldModule, MatInputModule ],
  exports: [ MatFormFieldModule, MatInputModule ]
})

最让大家怀念的是'/'这个角色。如果您看到 Angular Material Documentation ，他们也会错过这个（上次检查时间为 2020 年 6 月 16 日，甚至不知道他们是否更新了）。我举个例子说明一下

<!-- Wrong -->
<mat-form-field>
  <input matInput>
</mat-form-field>

<!-- Right -->
<mat-form-field>
  <input matInput />
</mat-form-field>

仔细查看sn-p。当<input 开始时，它必须以/> 结尾，但大多数人会错过/（反斜杠）字符。

Answer 2

确保 MatInputModule 已导入，并且 <mat-form-field> 包含 <input> 和 matInput / matSelect 指令。

https://github.com/angular/material2/issues/7898

Answer 3

导入MatInputModule，解决了我的错误

Answer 4

你需要将你的类指定为MatFormFieldControl的提供者

https://material.angular.io/guide/creating-a-custom-form-field-control#providing-our-component-as-a-matformfieldcontrol

@Component({
  selector: 'form-field-custom-control-example',
  templateUrl: 'form-field-custom-control-example.html',
  styleUrls: ['form-field-custom-control-example.css'],
  providers: [
    { provide: MatFormFieldControl, useExisting: FormFieldCustomControlExample }   
  ]
})

Answer 5

另外，别忘了在输入标签中写上name属性：

name="yourName"

Answer 6

关闭输入标签的另一个可能问题。如果您从 Angular 示例之一 (https://material.angular.io/components/datepicker/overview) 复制代码，您最终可能会得到以下代码：

<mat-form-field appearance="fill">
  <mat-label>Choose a date</mat-label>
  <input matInput [matDatepicker]="picker">
  <mat-datepicker-toggle matSuffix [for]="picker"></mat-datepicker-toggle>
  <mat-datepicker #picker></mat-datepicker>
</mat-form-field>

输入应该有结束标记（斜杠）：

<input matInput [matDatepicker]="picker" />

Answer 7

1. 如果您在代码中使用任何“输入”标签和“mat-form-field”，请确保在输入标签中包含“matInput”

2. 如果'mat-form-field'的子标签中存在任何*ngIf，则在'mat-form-field'标签中指定*ngIf条件

Answer 8

这将解决您的问题

 import {
      MatFormFieldModule, 
      MatInputModule
    } from "@angular/material";

Answer 9

错误提示mat-form-field 应至少包含一个从中获取输入的表单字段。

例如：matInput mat-select 等

在您的情况下，您可以在 example-tel-input-example.html 中的输入字段中添加 matInput 标签。您还可以将mat-form-field 移动到example-tel-input-example 组件中，并将其添加到每个matInput 字段中。

<div [formGroup]="parts" class="example-tel-input-container">
      <mat-form-field>
         <input matInput class="example-tel-input-element" formControlName="area" size="3">
      </mat-form-field>
      <span class="example-tel-input-spacer">&ndash;</span>
      <mat-form-field>
          <input matInput class="example-tel-input-element" formControlName="exchange" size="3">
      </mat-form-field>
      <span class="example-tel-input-spacer">&ndash;</span>
      <mat-form-field>
          <input matInput class="example-tel-input-element" formControlName="subscriber" size="4">
      </mat-form-field>
</div>

注意：mat-icon 或 mat-hint 不能被视为表单域