Attribute property binding for background-image url in Angular 2

问题

I have been struggling to figure out the best way to dynamically change the background-image attribute in a number of Angular 2 components.

In the following example, I am attempting to set the background-image of a div to an @Input value using [ngStyle] directive:

import {Component, Input} from '@angular/core';
import { User } from '../models';

// exporting type aliases to enforce better type safety (https://github.com/ngrx/example-app)
export type UserInput = User;

@Component({
  selector: 'profile-sidenav',
  styles: [ `
    .profile-image {
      background-repeat: no-repeat;
      background-position: 50%;
      border-radius: 50%;
      width: 100px;
      height: 100px;
    }
  `],
  template: `  
    <div class="profile-image" [ngStyle]="{ 'background-image': url({{image}})">
    <h3>{{ username }}</h3>
  `
})

export class ProfileSidenav {
  @Input() user: UserInput;
  blankImage: string = '../assets/.../camera.png';

  // utilizing "getters" to keep templates clean in 'dumb' components (https://github.com/ngrx/example-app) 
  get username() {
    return this.user.username;
  }
  get image() {
    if (!this.user.image) { return this.cameraImage;
    } else { return this.user.image; }
  }

I don't think the issue is with the observable, since username displays and doing something like <img *ngIf="image" src="{{ image }}"> renders the image. I have to access the background-image attribute because apparently that is the best way to make a circular image, but in general would like to know how to do this.

EDIT:

My original [ngStyle] declaration had unnecessary curly brackets (ngStyle is a directive that can take a variable), and was missing string tags around url() and image. The correct way is (as answered below) is:

<div class="profile-image" [ngStyle]="{'background-image': 'url(' + image + ')'}"></div>`.

As stated in the original edit, a solution can also be achieved with the Renderer class in Angular 2. I have yet to do it but think there should be a way with setElementStylesor something like that. I will try to post an example but would love if someone else showed me (and others) how to for the time being.

回答1:

I think that you should use something like that:

<div class="profile-image"
     [ngStyle]="{ 'background-image': 'url(' + image + ')'}">

where image is a property of your component.

See this question:

How to add background-image using ngStyle (angular2)?

回答2:

You don't need to use NgStyle. You can also do this:

[style.background-image]="'url(' + image + ')'"

See more at How to add background-image using ngStyle (angular2)?

回答3:

The main reason is very simple you declared global variable as blankImage but in your template you typed image . thats two different variable

your ts code **blankImage**: string = '../assets/.../camera.png';

your template code **<div class="profile-image" [ngStyle]="{'background-image': 'url(' + **image** + ')'}"></div>.`

just change the image to blankImage or viceversa

回答4:

that's wrong

I think you should add:

<div class="profile-image" [ngStyle]="{ 'backgroundImage': url({{image}})">

Regards

来源：https://stackoverflow.com/questions/37577343/attribute-property-binding-for-background-image-url-in-angular-2

标签

css

angular

typescript

angular-directive