更改后，Angular 8 值不会在视图中更新 [英] Angular 8 value won't update on view after change

问题描述

我在 Angular 中有一个小组件，其方法(目前)设置超时并更改变量的值.

import { Component, ChangeDetectionStrategy } from '@angular/core';@成分({选择器:'我的组件'，templateUrl: './my-view.html',styleUrls: ['./my-view.scss'],changeDetection: ChangeDetectionStrategy.Default})导出类 MyComponent {状态:布尔值 = 假；更改状态():无效{setTimeout(() => {this.status = true;}, 1500);}}

和 HTML

<form #myForm="ngForm"><input name="code" type="text" class="form-control" [(ngModel)]="code" #codeInput="ngModel" required placeholder="输入你的代码"/></表单>
<div class="row"><div class="col-md-5" (点击)="changeStatus()"><mat-icon aria-label="clear-all" *ngIf="!status">&#xe042;</mat-icon><a>更改状态</a>

<div class="col-md-7"><button type="button" class="btn-flat app-btn-flat">取消</button><button type="button" class="btn app-btn" [disabled]="myForm.invalid || myForm.pristine">保存</button>

如果我在组件中记录状态"的值.我得到了true"的新值，但它不会在视图上改变，除非我将光标放在输入上，然后单击它之外的任何地方.

为什么会这样?我该如何解决?

解决方案

为什么会这样?

您在祖先组件之一中将 changeDetection 设置为 OnPush.该属性不能被覆盖.参考:https://angular.io/api/core/ChangeDetectionStrategy

我该如何解决?

在祖先组件中取消设置 changeDetection，或者像 Adam 的回答那样手动检测变化.

constructor(private _cdr: ChangeDetectorRef) {}更改状态():无效{setTimeout(() => {this.status = true;this._cdr.detectChanges()}, 1500);}

I have a small component in Angular with a method that (for now) sets a timeout and changes the value of a variable.

import { Component, ChangeDetectionStrategy } from '@angular/core';

@Component({
  selector: 'my-component',
  templateUrl: './my-view.html',
  styleUrls: ['./my-view.scss'],
  changeDetection: ChangeDetectionStrategy.Default
})
export class MyComponent {

  status: boolean = false;

  changeStatus(): void {

    setTimeout(() => {
      this.status = true;
    }, 1500);
  }
}

And the HTML

<div>
  <form #myForm="ngForm">
    <input name="code" type="text" class="form-control" [(ngModel)]="code" #codeInput="ngModel" required placeholder="Enter your code" />
  </form>
</div>

<div class="row">
  <div class="col-md-5" (click)="changeStatus()">
    <mat-icon aria-label="clear-all" *ngIf="!status">&#xe042;</mat-icon>
    <a>Change status</a>
  </div>
  <div class="col-md-7">
    <button type="button" class="btn-flat app-btn-flat">Cancel</button>
    <button type="button" class="btn app-btn" [disabled]="myForm.invalid || myForm.pristine">Save</button>
  </div>
</div>

If I log the value of 'status' in the component. I get the new value of 'true' but it won't change on the view unless I focus the cursor on the input and then click anywhere outside it.

Why is that happening? how can I solve it?

解决方案

Why is that happening?

You set changeDetection to OnPush in one of the ancestor component. That property cannot be overridden. Ref: https://angular.io/api/core/ChangeDetectionStrategy

how can I solve it?

Unset changeDetection in the ancestor component, or manually detect changes like Adam's answer.

constructor(private _cdr: ChangeDetectorRef) {}

changeStatus(): void {
  setTimeout(() => {
    this.status = true;
    this._cdr.detectChanges()
  }, 1500);
}

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