我想知道图像何时加载完成。是否有办法通过回调来实现?
如果没有,总体上有办法吗?
我想知道图像何时加载完成。是否有办法通过回调来实现?
如果没有,总体上有办法吗?
.complete
+ callback
这是一个符合标准且不需要额外依赖的方法,等待时间不会超过必要的时间:
var img = document.querySelector('img')
function loaded() {
alert('loaded')
}
if (img.complete) {
loaded()
} else {
img.addEventListener('load', loaded)
img.addEventListener('error', function() {
alert('error')
})
}
img.complete
调用和addEventListener
调用之间完成了图像,这会出现问题吗? - Thomas Ahleload
事件。也就是说,load
事件监听器必须在一个else
语句中,因为在load
事件被触发之前,img.complete
可能已经变为true,如果没有else
语句,你可能会有可能调用两次loaded
(请注意,相对来说img.complete
变为true的时机可能会发生改变)。 - gsneddersImage.onload()通常有效。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>
load
事件无效?https://html.spec.whatwg.org/multipage/webappapis.html#handler-onload 是 onload
事件处理程序的定义。 - gsneddersvar 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);
}
生命苦短,何必使用jquery。
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="">
myImage.src = https://pmchollywoodlife.files.wordpress.com/2011/12/justin-bieber-bio-photo1.jpg?w=620
就可以完成任务。 - Josiahconst img = new Image();
img.src = 'path/to/img.jpg';
img.decode().then(() => {
/* set styles */
/* add img to DOM */
});
以下是jQuery的等效代码:
var $img = $('img');
if ($img.length > 0 && !$img.get(0).complete) {
$img.on('load', triggerAction);
}
function triggerAction() {
alert('img has been loaded');
}
async function newImageSrc(src) {
// Get a reference to the image in whatever way suits.
let image = document.getElementById('image-id');
// Update the source.
image.src = src;
// Wait for it to load.
await new Promise((resolve) => { image.onload = resolve; });
// Done!
console.log('image loaded! do something...');
}
image.src = src;
。 - Simbiat这些函数将解决问题,您需要实现DrawThumbnails
函数并有一个全局变量来存储图像。我希望能够使用具有ThumbnailImageArray
作为成员变量的类对象使其工作,但是我遇到了困难!
调用方式如下: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 } };
}
addThumbnailImages
函数。将其精简为相关的代码,我会去掉 -1。 - Justin Morgan这对我起作用:
// Usage
let img = await image_on_load(parent_element_to_put_img, image_url);
img.hidden = true;
// Functions
async function image_on_load(parent, url) {
let img = element(parent, 'img');
img.src = url;
await new Promise((resolve, reject) => {
element_on(img, 'load', () => {
resolve();
});
element_on(img, 'error', () => {
reject();
});
});
return img;
}
function element(parent, tag_name, text = '') {
let result = document.createElement(tag_name);
element_child_append(parent, result);
element_html_inner(result, text);
return result;
}
function element_child_append(parent, result) {
parent.appendChild(result);
}
function element_html_inner(result, text) {
result.innerHTML = text;
}
function element_on(e, event, on_event) {
e.addEventListener(event, async () => {
await on_event();
});
}