$rootScope.$on('$stateChangeStart', function(event, toState){
  if(toState.name === 'view2'){
    $rootScope.stateTransition = "left";
  }
  if(toState.name === 'view1'){
    $rootScope.stateTransition = "right";
  }
  $rootScope.$apply();
});

<div ui-view class='{{stateTransition}}'></div>

<div ui-view class='left ng-enter ng-enter-active'></div>
<div ui-view class='right ng-leave ng-leave-active'></div>