如何添加加载“微调器”

Question

i have some very simple js (i'm still learning) that basically reads the elements of a form and creates a url string that is passed to an imaging server, that in turn renders the image.

var imgURL = "site.com/path/to/image";
var product = "BirthdayCard_End" + "?&";
var page = 2;
var format;
var data;

function setPage(inputID)
    {
        page = inputID;
        setJPG();
    }

function FormValues()
    {
        var str = '';
        var elem = document.getElementById('form1').elements;
        for(var i = 0; i < elem.length; i++)
        {
            str += "$" + elem[i].id + "=" + elem[i].value + "&";
        }
        data = str;         
    }

function genPDF()
    {
        var format = "fmt=pdf&mediaMargin=48&bleedMargin=48&printerMark=1,1,1,1,1,Illustrator,.25,1";
        fullURL = imgURL + product + data + format;
        window.open(fullURL);       

    }

function setJPG()
    {
        FormValues();
        var format = "imageRes=200&fmt=jpg&wid=550&page=" + page;
        fullURL = imgURL + product + data + format;
        document.getElementById('lblValues').innerHTML = fullURL;
        document.getElementById('image').src = fullURL;
    }

i'm trying to figure out how to show a simple loader like this ( http://fgnass.github.com/spin.js/#v1.2.5 ). how do I add something to the setJPG() function so that it pops up the loader everytime it is initialized, and then fades away once the image is loaded?

Answer 1

You guys are making this way more complicated than it needs to be. Put your image in a div and set the background of the div to be an animated gif.

<div style="background-image: url('spinner.gif')"><img src='bigImage.jpg'></div>

No need to use any JS at all, the image will simply load over the background spinner.

Answer 2

The easiest way to do it is to create two div one over the other. One div with the spinner covering the div with the content, and then when the page finishes loading to display the div with the content over it.

On this example I use it on window.load, so you might need to modify the event to be on image load. The rest should work fine.

CSS:

#preloader {
position:absolute;
top:0;
left:0;
width:100%;
height:100%;
background:white;
opacity:0.3;
z-index:2;
}
#spinner_container {
position:absolute;
width:100%;
top: 50%;
left:0px;
height:1px;
overflow:visible;
opacity: 1;
background: transparent;
}
#spinner {
width: 31px;
height:31px;
margin-left:-15px;
position:absolute;
top:-15px;
left:50%;
display:block;
}

HTML

<div id="preloader">
<div id="spinner_container">
<img id="spinner" src="/content/images/spinner_squares_circle.gif" alt="" />
</div>
</div>
<div id="wrapper">
content
</div>

jQuery

$(window).load(function(){

    $('#preloader').fadeOut(100, function() {
               $('body').css('overflow','auto');
               $(this).remove();
    });
});

Answer 3

Suggested solution

For images, using a "loading spinner" is problematic. See below.

Instead of a spinner, first send a low resolution (consider B&W too) of the image. This SO question tells how.

Spinners for image loading

A problem with showing a spinner while you're waiting for an image to be displayed is that the browsers do not reliably tell your JS when the image has loaded.

And if it doesn't fire then you're left looking at the spinner forever...

See the docs for the jQuery load event --

Caveats of the load event when used with images

A common challenge developers attempt to solve using the .load() shortcut is to execute a function when an image (or collection of images) have completely loaded. There are several known caveats with this that should be noted. These are:

• It doesn't work consistently nor reliably cross-browser
• It doesn't fire correctly in WebKit if the image src is set to the same src as before
• It doesn't correctly bubble up the DOM tree
• Can cease to fire for images that already live in the browser's cache

Answer 4

If you are using Spectre css , you can add this div to add a spinner :

 <link href="https://cdnjs.cloudflare.com/ajax/libs/spectre.css/0.3.1/spectre.min.css" rel="stylesheet"/> <div class="loading"></div>

Answer 5

I wrote loader code in a separate file so it will be reusable

file: Loader.js

export const elementString = {
    loader:'loader' // class name that I used in renderLoader function
}
export const renderLoader = parent =>{
    const loader = `
    <div class='${elementString.loader}'>
        <svg>
            <use href="img/icons.svg#icon-cw"></use>
        </svg>
    </div>
    `;
    parent.insertAdjacentHTML('afterbegin', loader);
};

export const clearLoader=()=>{
    const loader = document.querySelector(`.${elementString.loader}`);
    if(loader){
        loader.parentElement.removeChild(loader);
    }
}

file: style.css

.loader {
  margin: 5rem auto;
  text-align: center; }
  .loader svg {
    height: 5.5rem;
    width: 5.5rem;
    fill: #F59A83;
    transform-origin: 44% 50%;
    animation: rotate 1.5s infinite linear; }

    @keyframes rotate {
  0% {
    transform: rotate(0); }
  100% {
    transform: rotate(360deg); } }

file: icons.svg

<svg aria-hidden="true" style="position: absolute; width: 0; height: 0; overflow: hidden;" version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
<defs>
<symbol id="icon-cw" viewBox="0 0 20 20">
<title>cw</title>
<path d="M19.315 10h-2.372v-0.205c-0.108-4.434-3.724-7.996-8.169-7.996-4.515 0-8.174 3.672-8.174 8.201s3.659 8.199 8.174 8.199c1.898 0 3.645-0.65 5.033-1.738l-1.406-1.504c-1.016 0.748-2.27 1.193-3.627 1.193-3.386 0-6.131-2.754-6.131-6.15s2.745-6.15 6.131-6.15c3.317 0 6.018 2.643 6.125 5.945v0.205h-2.672l3.494 3.894 3.594-3.894z"></path>
</symbol>
</defs>
</svg>

file: app.js

renderLoader(document.querySelector('.results'));// .results is the parent of my searchlist which I am shoing in the view
await state.search.getResults();
clearLoader();

file: app.html

<body>
    <div class="container">
        <div class="results">
            <ul class="results__list">
            </ul>
        </div>
    </div>

</body>

Answer 6

Just add a spinning gif to the chart div, it will be replaced automatically by google chart when loaded. Like this, ""