title: Angular $watch not working, unless I click some were on the screen
body: <p>Am using angular $watch such as. </p>
  
  <p>Based on a trigger selectedIndex value changes.</p>
  
  <pre><code> $scope.selectedIndex = 1;
     Trigger.onReceivingTriger($scope,function(data){
           $scope.selectedIndex = 0;
      });
  
  
      $scope.$watch('selectedIndex', function(){
          console.log("am watching");
      });
  </code></pre>
  
  <p>I expect to work as once the trigger value set the watch should work as normal. But the problem is the $watch works only after I click some were on the screen. 
  I got stuck hear...
  any help please....</p>