[英]Javascript wait for image to load before calling Ajax
function dropResource() {
var imgIndex = getImageIndexByID(currentDragImageID);
var newImgID = resourceData.length;
// Create the image
$('#thePage').append('<img alt="Big" id="imgA' + newImgID + '" src="' + uploadFolder + '/' + imgData[imgIndex][1] + '" class="mediaImg" />');
// Get properties
var imgW = $('#imgA' + newImgID).width();
var imgH = $('#imgA' + newImgID).height();
var imgX = $('#imgA' + newImgID).position().left;
var imgY = $('#imgA' + newImgID).position().top;
// Add to array (dbID, imgarrIndex, width, height, x, y)
resourceData[newImgID] = new Array(0, imgIndex, imgW, imgH, imgX, imgY);
//alert('artworkAjaxHandler.ashx?type=addResource&uploadID=' + currentDragImageID + '&page=' + currentPage + '&w=' + imgW + '&h=' + imgH + '&x=' + imgX + '&y=' + imgY);
// Save this as a resource
$.ajax({
url: 'artworkAjaxHandler.ashx?type=addResource&uploadID=' + currentDragImageID + '&page=' + currentPage + '&w=' + imgW + '&h=' + imgH + '&x=' + imgX + '&y=' + imgY,
一旦插入縮略圖,此代碼會將圖像添加到放置區域。問題是圖像的寬度和高度顯示為0,0,因為在加載圖像之前調用了ajax。 ..如果我取消對警報的注釋,並等到圖像完全加載,則它將正常工作。
反正有解決這個問題的方法嗎?
設置src屬性時,瀏覽器將立即開始下載圖像。 您必須在插入之前在其中定義后加載代碼的情況下定義加載事件:
$('<img alt="Big" id="imgA' + newImgID + '" class="mediaImg" />').load(function() {
// you can do things here, after the image loads
var imgW = $(this).width();
var imgH = $(this).height();
// ...
}).appendTo('#thePage').attr('src',uploadFolder + '/' + imgData[imgIndex][1]);
我可能會重新整理一下:
function dropResource() {
var imgIndex = getImageIndexByID(currentDragImageID);
var newImgID = resourceData.length;
var newImage;
// Create the image
newImage = $('<img alt="Big" id="imgA' + newImgID + '" src="' + uploadFolder + '/' + imgData[imgIndex][1] + '" class="mediaImg" />');
newImage.load(function() {
// Get properties
var imgW = newImage.width();
var imgH = newImage.height();
var imgPos = newImage.position();
var imgX = imgPos.left;
var imgY = imgPos.top;
// Add to array (dbID, imgarrIndex, width, height, x, y)
resourceData[newImgID] = new Array(0, imgIndex, imgW, imgH, imgX, imgY);
//alert('artworkAjaxHandler.ashx?type=addResource&uploadID=' + currentDragImageID + '&page=' + currentPage + '&w=' + imgW + '&h=' + imgH + '&x=' + imgX + '&y=' + imgY);
// Save this as a resource
$.ajax({
url: 'artworkAjaxHandler.ashx?type=addResource&uploadID=' + currentDragImageID + '&page=' + currentPage + '&w=' + imgW + '&h=' + imgH + '&x=' + imgX + '&y=' + imgY,
});
$('#thePage').append(newImage);
這樣做是創建img
元素,鈎住其load
事件,然后將其添加到DOM中(通過將其添加到#thePage
元素中)。 所有其他動作都在load
處理程序中進行。 請注意,在添加到DOM之前,請確保鈎掛load
處理程序,因此在掛接它之前不會觸發load
事件。
如果您確實要小心,則甚至可以確定設置src
屬性,直到我們鈎住load
之后。 為此,請更改:
newImage = $('<img alt="Big" id="imgA' + newImgID + '" src="' + uploadFolder + '/' + imgData[imgIndex][1] + '" class="mediaImg" />');
newImage.load(function() {
// ...
});
$('#thePage').append(newImage);
至
newImage = $('<img alt="Big" id="imgA' + newImgID + '" class="mediaImg" />');
newImage.load(function() {
// ...
});
newImage[0].src = uploadFolder + '/' + imgData[imgIndex][1];
$('#thePage').append(newImage);
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