我想知道图像何时完成加载。有没有办法通过回调来做到这一点？
如果没有，有没有办法做到这一点？
matt
问问题
217427 次
10 回答
187
.complete+ 回调
这是一种符合标准的方法，没有额外的依赖项，并且无需等待：
var img = document.querySelector('img')
function loaded() {
alert('loaded')
}
if (img.complete) {
loaded()
} else {
img.addEventListener('load', loaded)
img.addEventListener('error', function() {
alert('error')
})
}
于 2014-06-13T08:48:11.587 回答
82
Image.onload()通常会起作用。
要使用它，您需要确保在设置 src 属性之前绑定事件处理程序。
相关链接：
示例用法：
window.onload = function () {
var logo = document.getElementById('sologo');
logo.onload = function () {
alert ("The image has loaded!");
};
setTimeout(function(){
logo.src = 'https://edmullen.net/test/rc.jpg';
}, 5000);
}; <html>
<head>
<title>Image onload()</title>
</head>
<body>
<img src="#" alt="This image is going to load" id="sologo"/>
<script type="text/javascript">
</script>
</body>
</html>于 2008-11-11T05:19:46.893 回答
21
You can use the .complete property of the Javascript image class.
I have an application where I store a number of Image objects in an array, that will be dynamically added to the screen, and as they're loading I write updates to another div on the page. Here's a code snippet:
var gAllImages = [];
function makeThumbDivs(thumbnailsBegin, thumbnailsEnd)
{
gAllImages = [];
for (var i = thumbnailsBegin; i < thumbnailsEnd; i++)
{
var theImage = new Image();
theImage.src = "thumbs/" + getFilename(globals.gAllPageGUIDs[i]);
gAllImages.push(theImage);
setTimeout('checkForAllImagesLoaded()', 5);
window.status="Creating thumbnail "+(i+1)+" of " + thumbnailsEnd;
// make a new div containing that image
makeASingleThumbDiv(globals.gAllPageGUIDs[i]);
}
}
function checkForAllImagesLoaded()
{
for (var i = 0; i < gAllImages.length; i++) {
if (!gAllImages[i].complete) {
var percentage = i * 100.0 / (gAllImages.length);
percentage = percentage.toFixed(0).toString() + ' %';
userMessagesController.setMessage("loading... " + percentage);
setTimeout('checkForAllImagesLoaded()', 20);
return;
}
}
userMessagesController.setMessage(globals.defaultTitle);
}
于 2008-11-11T06:12:33.120 回答
14
jquery 的生命太短暂了。
function waitForImageToLoad(imageElement){
return new Promise(resolve=>{imageElement.onload = resolve})
}
var myImage = document.getElementById('myImage');
var newImageSrc = "https://pmchollywoodlife.files.wordpress.com/2011/12/justin-bieber-bio-photo1.jpg?w=620"
myImage.src = newImageSrc;
waitForImageToLoad(myImage).then(()=>{
// Image have loaded.
console.log('Loaded lol')
});<img id="myImage" src="">于 2018-01-11T13:38:20.510 回答
12
您可以在 jQuery 中使用 load() 事件，但如果图像是从浏览器缓存中加载的，它不会总是触发。这个插件https://github.com/peol/jquery.imgloaded/raw/master/ahpi.imgload.js可以用来解决这个问题。
于 2011-02-06T12:05:55.990 回答
4
这是 jQuery 等价物：
var $img = $('img');
if ($img.length > 0 && !$img.get(0).complete) {
$img.on('load', triggerAction);
}
function triggerAction() {
alert('img has been loaded');
}
于 2017-03-22T08:43:14.277 回答
3
不适合 2008 年问这个问题，但这些天这对我来说效果很好：
async function newImageSrc(src) {
// Get a reference to the image in whatever way suits.
let image = document.getElementById('image-id');
// Update the source.
img.src = src;
// Wait for it to load.
await new Promise((resolve) => { image.onload = resolve; });
// Done!
console.log('image loaded! do something...');
}
于 2020-06-04T00:42:19.407 回答
2
如果目标是在浏览器渲染图像后设置 img 样式，您应该：
const img = new Image();
img.src = 'path/to/img.jpg';
img.decode().then(() => {
/* set styles */
/* add img to DOM */
});
因为浏览器首先loads the compressed version of image，然后decodes it，最后paints它。因为在浏览器具有img 标签paint后，您应该运行您的逻辑没有任何事件。decoded
于 2020-04-01T12:39:53.223 回答
0
这些函数将解决问题，您需要实现该DrawThumbnails函数并有一个全局变量来存储图像。我喜欢让它与具有ThumbnailImageArray作为成员变量的类对象一起工作，但我很挣扎！
称为addThumbnailImages(10);
var ThumbnailImageArray = [];
function addThumbnailImages(MaxNumberOfImages)
{
var imgs = [];
for (var i=1; i<MaxNumberOfImages; i++)
{
imgs.push(i+".jpeg");
}
preloadimages(imgs).done(function (images){
var c=0;
for(var i=0; i<images.length; i++)
{
if(images[i].width >0)
{
if(c != i)
images[c] = images[i];
c++;
}
}
images.length = c;
DrawThumbnails();
});
}
function preloadimages(arr)
{
var loadedimages=0
var postaction=function(){}
var arr=(typeof arr!="object")? [arr] : arr
function imageloadpost()
{
loadedimages++;
if (loadedimages==arr.length)
{
postaction(ThumbnailImageArray); //call postaction and pass in newimages array as parameter
}
};
for (var i=0; i<arr.length; i++)
{
ThumbnailImageArray[i]=new Image();
ThumbnailImageArray[i].src=arr[i];
ThumbnailImageArray[i].onload=function(){ imageloadpost();};
ThumbnailImageArray[i].onerror=function(){ imageloadpost();};
}
//return blank object with done() method
//remember user defined callback functions to be called when images load
return { done:function(f){ postaction=f || postaction } };
}
于 2012-10-24T16:43:41.190 回答
-3
如果你使用 React.js，你可以这样做：
render() {
// ...
<img
onLoad={() => this.onImgLoad({ item })}
onError={() => this.onImgLoad({ item })}
src={item.src} key={item.key}
ref={item.key} />
// ... }
在哪里：
于 2018-05-28T15:30:52.570 回答