AngularJS之定时器无法停止

1、问题背景

AngularJS设置定时器后，再次点击按钮触发定时器，这时会出现：前一个定时器未停止，后一个定时器又启动了，导致出现多个定时器同时在运行。

2、问题源码

<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title>AngularJS之定时器无法停止</title>
		<script src="http://apps.bdimg.com/libs/angular.js/1.4.6/angular.min.js"></script>
		<script>
			var app = angular.module("btnApp",[]);
			app.controller("btnCon",function($scope,$interval){
				$scope.count = 0;
				$scope.getDayTime = function(){
					var date = new Date();
					var year = date.getFullYear();
					var month = date.getMonth()+1;
					var day = date.getDate();
					var hour = date.getHours();
					var minute = date.getMinutes();
					var second = date.getSeconds();
					var thisTime = year+"-"+(month<10?"0"+month:month)+"-"+(day<10?"0"+day:day)+" "+(hour<10?"0"+hour:hour)+":"+(minute<10?"0"+minute:minute)+":"+(second<10?"0"+second:second);
					
					return thisTime;
				};
				$scope.dayTime = $scope.getDayTime();
				$scope.queryData = function(){
					var timer = $interval(function(){  
	                    $scope.count++;  
	                    console.log($scope.count);
	                },4000);
	                
	                $scope.$on("destroy",function(){
					   $interval.cancel($scope.timer);
					}); 
				};
			});
		</script>
	</head>
	<body ng-app="btnApp">
		<div ng-controller="btnCon">
			<button ng-click="queryData();">查询</button>
			<div>
				<label>{{count}}</label>
			</div>
		</div>
	</body>
</html>

3、问题结果

4、解决源码

5、解决结果