使用angular.js导航到其他页面之前无法获取任何消息

Question

我需要在使用Angular.js和Ui-router导航到另一个页面之前显示一条警报消息。我正在解释下面的代码。

<form name="billdata" id="billdata" confirm-on-exit  enctype="multipart/form-data" novalidate>
    <div id="SHOWDATA">
        <div id="transactionsPortlet" class="panel-collapse collapse in">
            <div class="portlet-body">
                <div class="totalaligndiv">
                    <div class="col-md-6">
                       <div class="input-group bmargindiv1 col-md-12">
                        <span class="input-group-addon ndrftextwidth text-right" style="width:180px">First Name :</span>
                        <input type="text" name="itemname" id="contactno" class="form-control" placeholder="user Name" ng-model="first_name" >
                    </div> 
                    <div class="input-group bmargindiv1 col-md-12">
                        <span class="input-group-addon ndrftextwidth text-right" style="width:180px">Last Name :</span>
                        <input type="text" name="itemname" id="contactno" class="form-control" placeholder="user Name" ng-model="last_name" >
                    </div> 
                    <div class="input-group bmargindiv1 col-md-12">
                        <input type="button" class="btn btn-success" ng-click="addUserData(billdata);"  id="addProfileData" ng-value="buttonName"  />
                    </div>
                    <div class="clearfix"></div>           
                </div>
            </div>
        </div>
    </div>  
</form>

我的控制器页面代码如下所示。

var dashboard=angular.module('Channabasavashwara');
dashboard.directive('confirmOnExit', function() {
   return {
    link: function($scope, elem, attrs) {
           /* window.onbeforeunload = function(){
                if ($scope.billdata.$dirty) {
                    return "The form is not saved, do you want to stay on the page?";
                }
            }*/
            $scope.$on('$locationChangeStart', function(event, next, current) {
                if ($scope.myForm.$dirty) {
                    if(!confirm("The form is not saved, do you want to stay on the page?")) {
                        event.preventDefault();
                    }
                }
            });
        }
    };
});

这里我的要求是假设用户填写了表单中的2个给定字段并突然导航到另一个页面而没有提交。在这种情况下，用户应该收到确认消息以留在此页面上。我在使用{{1导航视图。请帮我解决这个问题。