AngularJS doesn't send POST request from Ionic android app

I'm working on my first android app in Ionic framework. My app should communicate with a REST interface from AngularJS. When I'm testing the app in a browser on my pc then everything works just fine but when I'm running it as an android app from a virtual or a real android device then the POST request doesn't work at all. The GET requests work perfectly. I don't have a clue why it's happening so I appreciate any help!

Part of the code:

    $http({
        url: address,
        method: "POST",
        data: jsondata,
        transformRequest: false,
        headers: { 'Content-Type': undefined }
      })
      .success(function (data) {
         $scope.errormsg = "success";
         reloadComments();
      })
      .error(function (data) {
         $scope.errormsg = data;
      });

You have to convert all parameters in object then you have to call web services like following example.

$scope.submitForm = function($valid)
{
    myobject = {'email' : $scope.user.email, 'pass' : $scope.user.pass};
    Object.toparams = function ObjecttoParams(obj)
    {
        var p =[];
        for (var key in obj)
        {
            p.push(key + '=' + encodeURIComponent(obj[key]));
        }
        return p.join('&');
    };

    $http({
        url: WSURL + '/login',
        method: "POST",
        data: Object.toparams(myobject),
        headers: {'Content-Type': 'application/x-www-form-urlencoded'}
    }).success(function (data, status, headers, config)
    {

    }).error(function (data, status, headers, config) 
    {

    });
}

I hope its help to you