未定义的watchHeading in compass插件，用于离子/ phonegap

Question

好吧，我正在研究一个用离子法制作的小项目。我正在使用ngCordova添加一些很酷的插件，比如指南针的设备方向。但我不能强迫它发挥作用。我已经安装了ngCordova并添加了插件（地理位置插件工作）。我没有想到为什么这样做不起作用。

代码如下所示：

.controller('GeoLocationCtrl', function($scope, $cordovaGeolocation, $cordovaDeviceOrientation, $ionicPlatform, $document) {
$scope.lat = 0;
$scope.long = 0;
$scope.position = {};


$ionicPlatform.ready(function() {
var options = {frequency: 1000}; // Update every 1 second
var watch2 = $cordovaDeviceOrientation.watchHeading(options); ///LINE 53!

watch2.promise.then(function (result) { /* unused */
    },
    function (err) {
        // An error occurred
    }, function (position) {
        // Heading comes back in
        // position.magneticHeading
        $scope.position = position.magneticHeading;
    });

    $cordovaDeviceOrientation.clearWatch(watch2.watchId)
        .then(function (result) {
            // Success!
        }, function (err) {
            // An error occurred
        });

  });
})

但我得到的只是：

ripple.js:37
TypeError: Cannot read property 'watchHeading' of undefined
    at Object.watchHeading (http://localhost:8080/lib/ngCordova/dist/ng-        cordova.min.js:1:14565)
    at http://localhost:8080/js/controllers.js:53:44
    at http://localhost:8080/lib/ionic/js/ionic.bundle.js:37388:19
    at Object.ionic.Platform.ready     (http://localhost:8080/lib/ionic/js/ionic.bundle.js:1915:9)
    at Object.self.ready (http://localhost:8080/lib/ionic/js/ionic.bundle.js:37386:26)
    at new <anonymous> (http://localhost:8080/js/controllers.js:15:20)
    at invoke (http://localhost:8080/lib/ionic/js/ionic.bundle.js:11591:17)
    at Object.instantiate (http://localhost:8080/lib/ionic/js/ionic.bundle.js:11602:23)
    at http://localhost:8080/lib/ionic/js/ionic.bundle.js:14906:28
    at updateView (http://localhost:8080/lib/ionic/js/ionic.bundle.js:42986:30) ionic.bundle.js:17696

感谢您的帮助！