在web開發中，我們要實現拖放效果，需要借助Javascript。今天讓我們使用Html5實現它：
先看Html核心代碼:
復制代碼代碼如下:
www.mb5u.com
<div>
<p>把黃色小方塊拖入到紅色大方框中</p>
</div>
<div id="item" draggable="true">
</div>
<div id="drop">
</div>
draggable屬性是Html5/">Html5新增加的，它有三個值true,false,auto. true是可以拖，false是不可以，auto由用戶浏覽器是否支持而定。更多請可以參考官方文檔.
加上一點兒樣式:
復制代碼代碼如下:
www.mb5u.com
<style type="text/CSS">
#drop
{
width: 300px;
height: 200px;
background-color: #ff0000;
padding: 5px;
border: 2px solid #000000;
}
#item
{
width: 100px;
height: 100px;
background-color: #ffff00;
padding: 5px;
margin: 20px;
border: 1px dashed #000000;
}
*[draggable=true] {
-moz-user-select:none;
-kHtml-user-drag: element;
cursor: move;
}
*:-kHtml-drag {
background-color: rgba(238,238,238, 0.5);
}
</style>
然後我們來看Javascript:
復制代碼代碼如下:
www.mb5u.com
function listenEvent(eventTarget, eventType, eventHandler) {
if (eventTarget.addEventListener) {
eventTarget.addEventListener(eventType, eventHandler,false);
} else if (eventTarget.attachEvent) {
eventType = "on" + eventType;
eventTarget.attachEvent(eventType, eventHandler);
} else {
eventTarget["on" + eventType] = eventHandler;
}
}
// cancel event
function cancelEvent (event) {
if (event.preventDefault) {
event.preventDefault();
} else {
event.returnValue = false;
}
}
// cancel propagation
function cancelPropagation (event) {
if (event.stopPropagation) {
event.stopPropagation();
} else {
event.cancelBubble = true;
}
}
window.onload=function() {
var target = document.getElementById("drop");
listenEvent(target,"dragenter",cancelEvent);
listenEvent(target,"dragover", dragOver);
listenEvent(target,"drop",function (evt) {
cancelPropagation(evt);
evt = evt || window.event;
evt.dataTransfer.dropEffect = 'copy';
var id = evt.dataTransfer.getData("Text");
target.appendChild(document.getElementById(id));
});
var item = document.getElementById("item");
item.setAttribute("draggable", "true");
listenEvent(item,"dragstart", function(evt) {
evt = evt || window.event;
evt.dataTransfer.effectAllowed = 'copy';
evt.dataTransfer.setData("Text",item.id);
});
};
function dragOver(evt) {
if (evt.preventDefault) evt.preventDefault();
evt = evt || window.event;
evt.dataTransfer.dropEffect = 'copy';
return false;
}
由上面的代碼我們看使用一組Html5 提供的拖放Events,直接來看下面:
dragstart
Drag event starts.
drag
During the drag Operation.
dragenter
Drag is over the target; used to determine if target will accept drop.
dragover
Drag is over target; used to determine feedback to user.
drop
Drop occurs.
dragleave
Drag leaves target.
dragend
Drag Operation ends.
定義了相關的事件，來實現想要功能。上面的JS不難看懂。
你可以自己試一下，目前在Opera支持最好，IE效果並不好。
希望對您web開發有幫助.