Calling a method of Service directly instead of using startService()

Issue

I'm trying to connect to a Service using bindService(). I am able to obtain reference to the Service in onServiceConnected() method of ServiceConnection.

My question is if I declare a method say downloadFile() in Service and call it through the Service object from an Activity rather than calling startService() and then calling downloadFile() from onStartCommand(), then what is the difference between the two approaches ?

Solution

What is the difference between the two approaches ?

The method you are proposing is a wrong-headed approach, for three reasons:

• In Android, Activitys and Services are considered to be app components. A component should be treated as an independent entity whose internal methods are not directly called by other components/classes. Such a component should be started using an Intent and then left to do its own work.

• If you don't call startService(), you literally never start the Service. How then would you call a method defined inside it ? And manually creating instances of classes that are app components is frowned upon in Android. You should never do something like

  new Service()
  

  or

  new Activity()
  

  That's just bad and you're inviting a whole lot of trouble.

• If you are going to call downloadFile() directly from your Activity, then why put it in a Service in the first place ? Isn't that redundant ? The reason for putting it in a Service is that the download operation is a non-UI task that requires no user interaction, which is what a Service is meant for. An Activity, on the other hand, is a UI-based component that is explicitly meant for user interaction. If the user dismisses your Activity while the download is in progress, then a NullPointerException gets thrown when the download completes and your code tries to post the data on the UI.

Answered By - Yash Sampat