拖拽组件

(function($){
        var defaults = {
            // 是否可拖拽默认为true
            enable : true,

            // 要拖动的对象，默认为handle的父级的父级元素
            target : null,

            // 回调
            callback : {
                // move时的回调
                onMove : function(e){

                },

                // drop时的回调
                onDrop : function(e){

                }
            }
        };

        $.fn.drag = function(options){
            var opts = $.extend({}, defaults, options);

            return this.each(function(){
                if(opts.enable){
                    var $this = $(this);

                    $this.bind(‘mousedown‘, function(e){
                        var target = opts.target || $this.parent().parent(), // 要拖拽的目标对象

                            height = target.outerHeight(),

                            width = target.outerWidth(),

                            offset = target.offset(),

                            left = offset.left,

                            top = offset.top,

                            lastElemLeft = left,

                            lastElemTop = top,

                            // 拖动开始时记录下鼠标的位置以及要拖动对象的位置
                            data = {
                                left : left,
                                top : top,
                                pageX : e.pageX,
                                pageY : e.pageY
                            },

                            // 辅助对象
                            help = $("<div></div>")
                                .appendTo(document.body),

                            $d = $(document),

                            body = document.documentElement || document.body,

                            cw = Math.max(body.scrollWidth, body.clientWidth),

                            ch = Math.max(body.scrollHeight, body.clientHeight),

                            // 拖动事件处理函数
                            handler = {
                                move : function(e){
                                    window.getSelection ? window.getSelection().removeAllRanges() : document.selection.empty();

                                    left = lastElemLeft + e.pageX - e.data.pageX;
                                    top = lastElemTop + e.pageY - e.data.pageY;
                                    // 防止拖出
                                    if(parseInt(left) < 0) left = 0;
                                    if(parseInt(top) < 0) top = 0;
                                    if(top > ch - height) top = ch - height;
                                    if(left > cw - width) left = cw - width;

                                    help.css({
                                        left: left,
                                        top: top
                                    });

                                    opts.callback.onMove(e);
                                },

                                drop : function(e){
                                    // 删除辅助对象
                                    help.remove();

                                    // 对目标对象进行定位
                                    target.css({
                                        left: left,
                                        top: top
                                    });

                                    var shim = target.data("shim");

                                    if(shim){
                                        shim.css({
                                            left: left,
                                            top: top
                                        });
                                    }

                                    $d.unbind("mousemove", handler.move).css("cursor", "");

                                    opts.callback.onDrop(e);
                                }
                            };

                        $d.css("cursor", "move");

                        /** 设置辅助div的样式 */
                        help.css({
                            height : target.outerHeight(),
                            width : target.outerWidth(),
                            border : "1px dotted #333",
                            position : "absolute",
                            zIndex : parseInt(target.css("z-index")) + 1,
                            left : left,
                            top : top
                        })

                        /** 监听document的mousemove和mouseup */
                        $d.bind(‘mousemove‘, data, handler.move).bind(‘mouseup‘, data, handler.drop);
                    });
                }
            });
        }
    })(jQuery);