如何在angular2中使用微调器加载图像 [英] How to load image with spinner in angular2

问题描述

我的应用有很多带有描述的图片.当用户导航时，这些文本首先出现并且图像加载有一些延迟.我想在这里添加一个微调器.在加载图像时显示微调器的指令，并显示像

my app got many images with descriptions. When user navigates these text is coming first and image is loading with some delay. I would like to add a spinner here. A directive which shows spinner while loading the image and shows image like

<myimgdir [src]='myimage.png'></myimgdir>

如何添加微调器并跟踪图像是否加载并显示?

How to add spinner and track the image is loaded or not and display it?

推荐答案

在你的控制器中，添加一个函数来处理 'onLoad' 事件，设置状态为 {loading: false}:

In your controller, add a function to to handle the 'onLoad' event, setting the state to {loading: false}:

loading: boolean = true
onLoad() {
    this.loading = false;
}

在您的模板中，在状态为 loading === true 时渲染加载 gif(或您想要的任何内容)，棘手的部分是您应该隐藏 img[hidden]="true/false" 的 code> 元素，而不是阻止它呈现，因此它实际上会加载 src，然后只需绑定 onLoad 将控制器中的函数添加到实际图像上的 (load) 事件:

In your template, render a loading gif (or whatever you want) while the state has loading === true, the tricky part is that you should just hide the img element with [hidden]="true/false" as opposed to prevent it from rendering so it will actually load the src, then just bind the onLoad function in your controller to the (load) event on the actual image:

<img *ngIf="loading" src="/assets/loading.gif" alt="loading" />
<img [hidden]="loading" (load)="onLoad()" src="{{ source }}" />

此解决方案在功能上与 AngJobs 的相同，但它更具声明性且 IMO 不那么繁琐.

This solution is functionally the same as AngJobs's, but it's more declarative and a little less cumbersome IMO.

PS:使用 [hidden]="boolean" 而不是 *ngIf 有点麻烦，你应该看看 http://angularjs.blogspot.com/2016/04/5-rookie-mistakes-to-avoid-with-angular.html 以了解原因以及如何安全应用它的解决方案.

PS: Using [hidden]="boolean" instead of *ngIf is a bit of a gotcha, you should look to http://angularjs.blogspot.com/2016/04/5-rookie-mistakes-to-avoid-with-angular.html to understand why and for a solution on how to apply it safely.

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