我的变量不会改变它的值

Question

我成功设计了一个带有mousedown和mousemove的拖放。这是代码：

$('.item').live( {
    mousedown : function() {
        var $elem = $(this);
        if (self.selectedItem != null) {
            self.selectedItem.removeClass('selected');
            self.selectedItem = null;
            firstSelectedItem = null;
            switchingItem = false;
        } else {
            self.selectedItem = $elem.addClass('selected');
            firstSelectedItem = $elem;
            switchingItem = true;
        }
    },
    mousemove : function() {
        var $elem = $(this);
        if (switchingItem === true && $elem.attr('id') != firstSelectedItem.attr('id')) {
            self._swap(firstSelectedItem, $elem);
            self.selectedItem.removeClass('selected');
            self.selectedItem = null;
            firstSelectedItem = null;
            switchingItem = false;
        }
    },
});

我试图用touchevents再次做到这一点。除了$ this这个值与touchstart和touchmove相同，所以交换不起作用：

$('.item').live( {
    touchstart : function(e) {
        e.stopPropagation();
        e.preventDefault();
        var $elem = $(this);
        if (self.selectedItem != null) {
            self.selectedItem.removeClass('selected');
            self.selectedItem = null;
            firstSelectedItem = null;
            switchingItem = false;
        } else {
            self.selectedItem = $elem.addClass('selected');
            firstSelectedItem = $elem;
            switchingItem = true;
            console.log (firstSelectedItem.attr('id'));
        }
    },
    touchmove : function (e) {
        e.stopPropagation();
        e.preventDefault();
        var elem = $(this);
        if (switchingItem === true && $elem.attr('id') != firstSelectedItem.attr('id')) {
            self._swap(firstSelectedItem, $elem);
            self.selectedItem.removeClass('selected');
            self.selectedItem = null;
            firstSelectedItem = null;
            switchingItem = false;
        }
    },
});

怎么办？

非常感谢