由于源文件中没有实现，需要自己实现指令，以下即为该指令，亲测可以实现。
.directive('draggable', ['$document', function($document) {
return function(scope, element, attr) {
var startX = 0, startY = 0, x = 0, y = 0;
element= angular.element(document.getElementsByClassName("modal-dialog"));
element.css({
position: 'relative',
cursor: 'move'
});
element.on('mousedown', function(event) {
// Prevent default dragging of selected content
event.preventDefault();
startX = event.pageX - x;
startY = event.pageY - y;
$document.on('mousemove', mousemove);
$document.on('mouseup', mouseup);
});
function mousemove(event) {
y = event.pageY - startY;
x = event.pageX - startX;
element.css({
top: y + 'px',
left: x + 'px'
});
}
function mouseup() {
$document.off('mousemove', mousemove);
$document.off('mouseup', mouseup);
}
};
}]);