【转载】分享一个HTML5的drag and drop API实现的图片拖拽分组效果

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今天我们介绍HTML5的拖拽功能。基本目前所有的现代浏览器(Firefox，Chrome，Safari，或者Opera)都支持这个实用的功能。这意味着我们可以考虑在我们的项目和网站中使用这个功能。更重要的是代码编写非常简单。我们这里将使用拖拽API开发一个图片的分组排序功能 ，希望能够给大家比较直观的使用感受。希望大家喜欢！

HTML标签

<div>
    <div id="drop_1" droppable="true"><h2>Album 1</h2></div>
    <div id="drop_2" droppable="true"><h2>Album 1</h2></div>
    <div id="drop_3" droppable="true"><h2>Album 3</h2></div>
</div>
<div style="clear:both"></div>
<div>
    <a id="1" draggable="true"><img src="images/1.jpg"></a>
    <a id="2" draggable="true"><img src="images/2.jpg"></a>
    <a id="3" draggable="true"><img src="images/3.jpg"></a>
    <a id="4" draggable="true"><img src="images/4.jpg"></a>
    <a id="5" draggable="true"><img src="images/5.jpg"></a>
    <a id="6" draggable="true"><img src="images/6.jpg"></a>
    <a id="7" draggable="true"><img src="images/7.jpg"></a>
    <a id="8" draggable="true"><img src="images/8.jpg"></a>
    <a id="9" draggable="true"><img src="images/9.jpg"></a>
    <a id="10" draggable="true"><img src="images/10.jpg"></a>
    <a id="11" draggable="true"><img src="images/11.jpg"></a>
    <a id="12" draggable="true"><img src="images/12.jpg"></a>
</div>
<script src="js/main.js"></script>

你可以看到这里我们设定了3个开放的drop对象和12个图片。我们将可drop的区域使用属性droppable来标示，并且将可drag的对象用draggable来标示。

CSS代码

接下来我们设置页面的样式。

/* Photo Gallery styles */
.gallery {
    margin: 50px auto 0;
     840px;
}
.gallery a {
    display: inline-block;
    height: 135px;
    margin: 10px;
    opacity: 1;
    position: relative;
     180px;

    -khtml-user-drag: element;

    /* CSS3 Prevent selections */
    -moz-user-select: none;
    -webkit-user-select: none;
    -khtml-user-select: none;
    user-select: none;

    /* CSS3 transition rules */
    -webkit-transition: all 0.5s ease;
    -moz-transition: all 0.5s ease;
    -o-transition: all 0.5s ease;
    transition: all 0.5s ease;
}
.gallery a img {
    border: 8px solid #fff;
    border-bottom: 20px solid #fff;
    cursor: pointer;
    display: block;
    height: 100%;
    left: 0px;
    position: absolute;
    top: 0px;
     100%;
    z-index: 1;

    /* CSS3 Box sizing property */
    -moz-box-sizing: border-box;
    -webkit-box-sizing: border-box;
    -o-box-sizing: border-box;
    box-sizing: border-box;

    /* CSS3 transition rules */
    -webkit-transition: all 0.5s ease;
    -moz-transition: all 0.5s ease;
    -o-transition: all 0.5s ease;
    transition: all 0.5s ease;

    /* CSS3 Box Shadow */
    -moz-box-shadow: 2px 2px 4px #444;
    -webkit-box-shadow: 2px 2px 4px #444;
    -o-box-shadow: 2px 2px 4px #444;
    box-shadow: 2px 2px 4px #444;
}

/* Custom CSS3 rotate transformation */
.gallery a:nth-child(1) img {
    -moz-transform: rotate(-25deg);
    -webkit-transform: rotate(-25deg);
    transform: rotate(-25deg);
}
.gallery a:nth-child(2) img {
    -moz-transform: rotate(-20deg);
    -webkit-transform: rotate(-20deg);
    transform: rotate(-20deg);
}
.gallery a:nth-child(3) img {
    -moz-transform: rotate(-15deg);
    -webkit-transform: rotate(-15deg);
    transform: rotate(-15deg);
}
.gallery a:nth-child(4) img {
    -moz-transform: rotate(-10deg);
    -webkit-transform: rotate(-10deg);
    transform: rotate(-10deg);
}
.gallery a:nth-child(5) img {
    -moz-transform: rotate(-5deg);
    -webkit-transform: rotate(-5deg);
    transform: rotate(-5deg);
}
.gallery a:nth-child(6) img {
    -moz-transform: rotate(0deg);
    -webkit-transform: rotate(0deg);
    transform: rotate(0deg);
}
.gallery a:nth-child(7) img {
    -moz-transform: rotate(5deg);
    -webkit-transform: rotate(5deg);
    transform: rotate(5deg);
}
.gallery a:nth-child(8) img {
    -moz-transform: rotate(10deg);
    -webkit-transform: rotate(10deg);
    transform: rotate(10deg);
}
.gallery a:nth-child(9) img {
    -moz-transform: rotate(15deg);
    -webkit-transform: rotate(15deg);
    transform: rotate(15deg);
}
.gallery a:nth-child(10) img {
    -moz-transform: rotate(20deg);
    -webkit-transform: rotate(20deg);
    transform: rotate(20deg);
}
.gallery a:nth-child(11) img {
    -moz-transform: rotate(25deg);
    -webkit-transform: rotate(25deg);
    transform: rotate(25deg);
}
.gallery a:nth-child(12) img {
    -moz-transform: rotate(30deg);
    -webkit-transform: rotate(30deg);
    transform: rotate(30deg);
}
.gallery a:hover img {
    z-index: 5;

    /* CSS3 transition rules */
    -webkit-transition: all 0.5s ease;
    -moz-transition: all 0.5s ease;
    -o-transition: all 0.5s ease;
    transition: all 0.5s ease;

    /* CSS3 transform rules */
    -moz-transform: rotate(0deg);
    -webkit-transform: rotate(0deg);
    -o-transform: rotate(0deg);
    transform: rotate(0deg);
}
.gallery a.hidden {
    height: 0;
    margin: 0;
    opacity: 0;
     0;
}
.albums {
    margin: 40px auto 0;
    overflow: hidden;
     840px;
}
.album {
    border: 3px dashed #ccc;
    float: left;
    margin: 10px;
    min-height: 100px;
    padding: 10px;
     220px;

    /* CSS3 transition rules */
    -webkit-transition: all 1.0s ease;
    -moz-transition: all 1.0s ease;
    -o-transition: all 1.0s ease;
    transition: all 1.0s ease;
}
.album a {
    display: inline-block;
    height: 56px;
    margin: 15px;
    opacity: 1;
    position: relative;
     75px;

    -khtml-user-drag: element;
    -webkit-user-drag: element;
    -khtml-user-select: none;
    -webkit-user-select: none;

    /* CSS3 Prevent selections */
    -moz-user-select: none;
    -webkit-user-select: none;
    -khtml-user-select: none;
    user-select: none;

    /* CSS3 transition rules */
    -webkit-transition: all 0.5s ease;
    -moz-transition: all 0.5s ease;
    -o-transition: all 0.5s ease;
    transition: all 0.5s ease;
}
.album a img {
    border: 4px solid #fff;
    border-bottom: 10px solid #fff;
    cursor: pointer;
    display: block;
    height: 100%;
    left: 0px;
    position: absolute;
    top: 0px;
     100%;
    z-index: 1;

    /* CSS3 Box sizing property */
    -moz-box-sizing: border-box;
    -webkit-box-sizing: border-box;
    -o-box-sizing: border-box;
    box-sizing: border-box;

    /* CSS3 transition rules */
    -webkit-transition: all 0.5s ease;
    -moz-transition: all 0.5s ease;
    -o-transition: all 0.5s ease;
    transition: all 0.5s ease;

    /* CSS3 Box Shadow */
    -moz-box-shadow: 2px 2px 4px #444;
    -webkit-box-shadow: 2px 2px 4px #444;
    -o-box-shadow: 2px 2px 4px #444;
    box-shadow: 2px 2px 4px #444;
}

Javascript代码

// add event handler
var addEvent = (function () {
  if (document.addEventListener) {
    return function (el, type, fn) {
      if (el && el.nodeName || el === window) {
        el.addEventListener(type, fn, false);
      } else if (el && el.length) {
        for (var i = 0; i < el.length; i++) {
          addEvent(el[i], type, fn);
        }
      }
    };
  } else {
    return function (el, type, fn) {
      if (el && el.nodeName || el === window) {
        el.attachEvent('on' + type, function () { return fn.call(el, window.event); });
      } else if (el && el.length) {
        for (var i = 0; i < el.length; i++) {
          addEvent(el[i], type, fn);
        }
      }
    };
  }
})();

// inner variables
var dragItems;
updateDataTransfer();
var dropAreas = document.querySelectorAll('[droppable=true]');

// preventDefault (stops the browser from redirecting off to the text)
function cancel(e) {
  if (e.preventDefault) {
    e.preventDefault();
  }
  return false;
}

// update event handlers
function updateDataTransfer() {
    dragItems = document.querySelectorAll('[draggable=true]');
    for (var i = 0; i < dragItems.length; i++) {
        addEvent(dragItems[i], 'dragstart', function (event) {
            event.dataTransfer.setData('obj_id', this.id);
            return false;
        });
    }
}

// dragover event handler
addEvent(dropAreas, 'dragover', function (event) {
    if (event.preventDefault) event.preventDefault();

    // little customization
    this.style.borderColor = "#000";
    return false;
});

// dragleave event handler
addEvent(dropAreas, 'dragleave', function (event) {
    if (event.preventDefault) event.preventDefault();

    // little customization
    this.style.borderColor = "#ccc";
    return false;
});

// dragenter event handler
addEvent(dropAreas, 'dragenter', cancel);

// drop event handler
addEvent(dropAreas, 'drop', function (event) {
    if (event.preventDefault) event.preventDefault();

    // get dropped object
    var iObj = event.dataTransfer.getData('obj_id');
    var oldObj = document.getElementById(iObj);

    // get its image src
    var oldSrc = oldObj.childNodes[0].src;
    oldObj.className += 'hidden';

    var oldThis = this;

    setTimeout(function() {
        oldObj.parentNode.removeChild(oldObj); // remove object from DOM

        // add similar object in another place
        oldThis.innerHTML += '<a id="'+iObj+'" draggable="true"><img src="'+oldSrc+'" /></a>';

        // and update event handlers
        updateDataTransfer();

        // little customization
        oldThis.style.borderColor = "#ccc";
    }, 500);

    return false;
});

可以看到以上代码并不复杂。开始我们选择所有的可拖放的元素。然后将’dragstart’事件绑定到所有的draggable元素上，这样讲数据设定到dataTransfer对象中。对于所有的droppable区域我们绑定这些事件：’dragover’,'dragleave’和’drop’。针对前两个方法我们执行一个小的CSS自定义来激活drop区域。当我们放置可拖放的元素的时候，我们的脚本会复制可拖放元素并且将它们放置到活动的droppable区域（即相册），并且删除那个dropped元素。最后我们更新事件处理。

希望大家喜欢这个HTML5的图片拖放展示效果。