1)创建来源项目
1.1)draggable属性的值:
true——此元素能被拖动;
false——此元素不能被拖动;
auto——浏览器可以自主决定某个元素是否能被拖动;
1.2)被拖动元素的事件:
dragstart——在元素开始被拖动时触发;
drag——在元素被拖动时反复触发;
dragend——在拖动操作完成时触发;
2)创建释放区
2.1)释放区事件:
dragenter——当被拖动元素进入释放区所占据的屏幕空间时触发;
dragover——当被拖动元素在释放区内触发时移动触发;
dragleave——当被拖动元素没有放入就离开释放区时触发;
drop——当被拖动元素在释放区放下时触发;
<!DOCTYPE HTML> <html> <head> <title>Example</title> <style> #src > * {float:left;} #src > img {border: thin solid black; padding: 2px; margin:4px;} #target {border: thin solid black; margin:4px;} #target { height: 81px; width: 81px; text-align: center; display: table;} #target > p {display: table-cell; vertical-align: middle;} img.dragged {background-color: lightgrey;} </style> </head> <body> <p id="src"> <img draggable="true" id="banana" src="banana100.png" alt="banana"/> <img draggable="true" id="apple" src="apple100.png" alt="apple"/> <img draggable="true" id="cherries" src="cherries100.png" alt="cherry"/> <p id="target"> <p id="msg">Drop Here</p> </p> </p> <script> var src = document.getElementById("src"); var target = document.getElementById("target"); var msg = document.getElementById("msg"); var draggedID; target.ondragenter = handleDrag; target.ondragover = handleDrag; function handleDrag(e) { e.preventDefault(); } target.ondrop = function(e) { var newElem = document.getElementById(draggedID).cloneNode(false); target.innerHTML = ""; target.appendChild(newElem); e.preventDefault(); } src.ondragstart = function(e) { draggedID = e.target.id; e.target.classList.add("dragged"); } src.ondragend = function(e) { var elems = document.querySelectorAll(".dragged"); for (var i = 0; i < elems.length; i++) { elems[i].classList.remove("dragged"); } } </script> </body> </html>
3)使用DataTransfer对象
3.1)与拖放操作所触发的事件同时派发的对象是DragEvent,它派生于MouseEvent。
DragEvent对象定义的额外属性:
dataTransfer——返回用于传输数据到释放区的对象(DataTransfer);
3.2)DataTransfer对象定义的属性:
types——返回数据的格式;
getData(
setData(
clearData(
files——返回已被拖动文件的列表;
<!DOCTYPE HTML> <html> <head> <title>Example</title> <style> #src > * {float:left;} #src > img {border: thin solid black; padding: 2px; margin:4px;} #target {border: thin solid black; margin:4px;} #target { height: 81px; width: 81px; text-align: center; display: table;} #target > p {display: table-cell; vertical-align: middle;} img.dragged {background-color: lightgrey;} </style> </head> <body> <p id="src"> <img draggable="true" id="banana" src="banana100.png" alt="banana"/> <img draggable="true" id="apple" src="apple100.png" alt="apple"/> <img draggable="true" id="cherries" src="cherries100.png" alt="cherry"/> <p id="target"> <p id="msg">Drop Here</p> </p> </p> <script> var src = document.getElementById("src"); var target = document.getElementById("target"); target.ondragenter = handleDrag; target.ondragover = handleDrag; function handleDrag(e) { e.preventDefault(); } target.ondrop = function(e) { var droppedID = e.dataTransfer.getData("Text"); var newElem = document.getElementById(droppedID).cloneNode(false); target.innerHTML = ""; target.appendChild(newElem); e.preventDefault(); } src.ondragstart = function(e) { e.dataTransfer.setData("Text", e.target.id); e.target.classList.add("dragged"); } src.ondragend = function(e) { var elems = document.querySelectorAll(".dragged"); for (var i = 0; i < elems.length; i++) { elems[i].classList.remove("dragged"); } } </script> </body> </html>
3.3)拖放文件:
File对象定义的属性
name——获取文件名;
type——获取文件类型,以MIME类型表示;
size——获取文件大小(以字节计算);
<!DOCTYPE HTML> <html> <head> <title>Example</title> <style> .table {display:table;} .row {display:table-row;} .cell {display: table-cell; padding: 5px;} .label {text-align: right;} #target {border: medium double black; margin:4px; height: 50px; width: 200px; text-align: center; display: table;} #target > p {display: table-cell; vertical-align: middle;} </style> </head> <body> <form id="fruitform" method="post" action="http://titan:8080/form"> <p class="table"> <p class="row"> <p class="cell label">Bananas:</p> <p class="cell"><input name="bananas" value="2"/></p> </p> <p class="row"> <p class="cell label">Apples:</p> <p class="cell"><input name="apples" value="5"/></p> </p> <p class="row"> <p class="cell label">Cherries:</p> <p class="cell"><input name="cherries" value="20"/></p> </p> <p class="row"> <p class="cell label">File:</p> <p class="cell"><input type="file" name="file"/></p> </p> <p class="row"> <p class="cell label">Total:</p> <p id="results" class="cell">0 items</p> </p> </p> <p id="target"> <p id="msg">Drop Files Here</p> </p> <button id="submit" type="submit">Submit Form</button> </form> <script> var target = document.getElementById("target"); var httpRequest; var fileList; document.getElementById("submit").onclick = handleButtonPress; target.ondragenter = handleDrag; target.ondragover = handleDrag; function handleDrag(e) { e.preventDefault(); } target.ondrop = function(e) { fileList = e.dataTransfer.files; e.preventDefault(); } function handleButtonPress(e) { e.preventDefault(); var form = document.getElementById("fruitform"); var formData = new FormData(form); if (fileList || true) { for (var i = 0; i < fileList.length; i++) { formData.append("file" + i, fileList[i]); } } httpRequest = new XMLHttpRequest(); httpRequest.onreadystatechange = handleResponse; httpRequest.open("POST", form.action); httpRequest.send(formData); } function handleResponse() { if (httpRequest.readyState == 4 && httpRequest.status == 200) { var data = JSON.parse(httpRequest.responseText); document.getElementById("results").innerHTML = "You ordered " + data.total + " items"; } } </script> </body> </html>
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