请帮忙？当元素被拖动拾取时，它只能从中间拾取？

Question

例如，我有一个 div，当您拿起它开始拖动时，它会捕捉 div，使光标/鼠标位于其中间。

这是代码。

// DEFINE DEFAULT VARIABLES
var _target=null, _dragx=null, _dragy=null, _rotate=null, _resort=null;
var _dragging=false, _sizing=false, _animate=false;
var _rotating=0, _width=0, _height=0, _left=0, _top=0, _xspeed=0, _yspeed=0;
var _zindex=1000;

jQuery.fn.touch = function(settings) {

    // DEFINE DEFAULT TOUCH SETTINGS
    settings = jQuery.extend({
        animate: true,
        sticky: false,
        dragx: true,
        dragy: true,
        rotate: false,
        resort: true,
        scale: false
    }, settings);

    // BUILD SETTINGS OBJECT
    var opts = [];
    opts = $.extend({}, $.fn.touch.defaults, settings);

    // ADD METHODS TO OBJECT
    this.each(function(){
        this.opts = opts;
        this.ontouchstart = touchstart;
        this.ontouchend = touchend;
        this.ontouchmove = touchmove;
        this.ongesturestart = gesturestart;
        this.ongesturechange = gesturechange;
        this.ongestureend = gestureend;
    });
};
function touchstart(e){
    _target = this.id;
    _dragx = this.opts.dragx;
    _dragy = this.opts.dragy;
    _resort = this.opts.resort;
    _animate = this.opts.animate;
    _xspeed = 0;
    _yspeed = 0;

    $(e.changedTouches).each(function(){

        var curLeft = ($('#'+_target).css("left") == 'auto') ? this.pageX : parseInt($('#'+_target).css("left"));
        var curTop = ($('#'+_target).css("top") == 'auto') ? this.pageY : parseInt($('#'+_target).css("top"));

        if(!_dragging && !_sizing){
            _left = (e.pageX - curLeft);
            _top = (e.pageY - curTop);
            _dragging = [_left,_top];
            if(_resort){
                _zindex = ($('#'+_target).css("z-index") == _zindex) ? _zindex : _zindex+1;
                $('#'+_target).css({ zIndex: _zindex });
            }
        }
    });
};
function touchmove(e){

    if(_dragging && !_sizing && _animate) {

        var _lastleft = (isNaN(parseInt($('#'+_target).css("left")))) ? 0:parseInt($('#'+_target).css("left"));
        var _lasttop = (isNaN(parseInt($('#'+_target).css("top")))) ? 0:parseInt($('#'+_target).css("top"));
    }

    $(e.changedTouches).each(function(){

        e.preventDefault();

        _left = (this.pageX-(parseInt($('#'+_target).css("width"))/2));
        _top = (this.pageY-(parseInt($('#'+_target).css("height"))/2));

        if(_dragging && !_sizing) {

            if(_animate){
                _xspeed = Math.round((_xspeed + Math.round( _left - _lastleft))/1.5);
                _yspeed = Math.round((_yspeed + Math.round( _top - _lasttop))/1.5);
            }

            if(_dragx || _dragy) $('#'+_target).css({ position: "absolute" });
            if(_dragx) $('#'+_target).css({ left: _left+"px" });
            if(_dragy) $('#'+_target).css({ top: _top+"px" });

        }
    });
};
function touchend(e){
    $(e.changedTouches).each(function(){
        if(!e.targetTouches.length){
            _dragging = false;
            if(_animate){
                _left = ($('#'+_target).css("left") == 'auto') ? this.pageX : parseInt($('#'+_target).css("left"));
                _top = ($('#'+_target).css("top") == 'auto') ? this.pageY : parseInt($('#'+_target).css("top"));

                var animx = (_dragx) ? (_left+_xspeed)+"px" : _left+"px";
                var animy = (_dragy) ? (_top+_yspeed)+"px" : _top+"px";

                if(_dragx || _dragy) $('#'+_target).animate({ left: animx, top: animy }, "fast");
            }
        }
    });

    setTimeout(changeBack,5000,_target);
};
function gesturestart(e){
    _sizing = [$('#'+this.id).css("width"), $('#'+this.id).css("height")];
};
function gesturechange(e){
    if(_sizing){
        _width = (this.opts.scale) ? Math.min(parseInt(_sizing[0])*e.scale, 300) : _sizing[0];
        _height = (this.opts.scale) ? Math.min(parseInt(_sizing[1])*e.scale, 300) : _sizing[1];
        _rotate = (this.opts.rotate) ? "rotate(" + ((_rotating + e.rotation) % 360) + "deg)" : "0deg";      
        $('#'+this.id).css({ width: _width+"px", height: _height+"px", webkitTransform: _rotate });
    }
};
function gestureend(e){
    _sizing = false;
    _rotating = (_rotating + e.rotation) % 360;
};

这仅在您开始拖动时发生，而不是在您第一次单击时发生。

有人告诉我将：更改

_left = (this.pageX-(parseInt($('#'+_target).css("width"))/2));
_top = (this.pageY-(parseInt($('#'+_target).css("height"))/2));

为：

_left = (this.pageX);
_top = (this.pageY);

但这只会使其从顶部恢复。
如何让它从鼠标点击的地方拾取？

编辑： 这是针对ipad的，在电脑上测试不起作用。 但任何帮助都会很棒，我被困住了

Answer 1

我对 _top 和 _left 变量了解不多，但也许您可以在 onclick 事件期间将它们设置为鼠标位置。该页面有一些用于选择鼠标位置的代码：
使用 Javascript 进行鼠标跟踪