加载图像时显示加载图标

问题描述

我想在 div 中显示一个背景图像/加载微调器，它将在其中加载一个图像，图像将在完全加载后显示，执行如下操作:

I want to show a background image/loading spinner inside a div that will load an image inside of it, the image will show once it's fully loaded doing something like this:

   <div style="background-image:url('imageThatWillAppearBeforeLoad')"></div>

演示(在 jQuery 中)

如何使用 Angular2/Ionic2 获得相同的效果?

How can I have the same using Angular2/Ionic2?

推荐答案

创建一个组件，在加载请求的图像之前显示占位符图像，并隐藏请求的图像.加载图像后，隐藏占位符并显示图像.

Create a component that shows the placeholder image until the requested image is loaded, and hides the requested image. Once the image is loaded, you hide the placeholder and show the image.

@Component({
  selector: 'image-loader',
  template: `<img *ngIf="!loaded" src="url-to-your-placeholder"/>
    <img [hidden]="!loaded" (load)="loaded = true" [src]="src"/>`
})
export class ImageLoader {
  @Input() src;
}

查看它在 Plunker 中的工作.

See it working in Plunker.

更新

现在我更好地理解了要求，这里有一个带有背景图片的解决方案.有点hacky，我更喜欢原来的...

Now that I understand the requirements better, here's a solution with background image. It's a little hacky, and I like the original one better...

@Directive({
  selector: '[imageLoader]'
})
export class ImageLoader {
  @Input() imageLoader;

  constructor(private el:ElementRef) {
    this.el = el.nativeElement;
    this.el.style.backgroundImage = "url(http://smallenvelop.com/demo/image-loading/spinner.gif)";
  }

  ngOnInit() {
    let image = new Image();
    image.addEventListener('load', () => {
      this.el.style.backgroundImage = `url(${this.imageLoader})`;
    });
    image.src = this.imageLoader;
  }
}

更新插件.

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