IntentService Error: No default Constructor

Seems that you need a no parameter constructor, like so:

public DisplayNotification() { 
    super("DisplayNotification");
}

Let me know if it helps.

Just add a default constructor

public DisplayNotification() {
    super("DisplayNotification");
}

That means a constructor with no parameter

See android developer guide for creating background services https://developer.android.com/training/run-background-service/create-service.html

From what I gather all you need to do is to create the intent service by creating a class that extends IntentService and within it, define a method that overrides onHandleIntent().

You need to remove the constructor you have defined for your DisplayNotification class or add a default constructor like so:

public DisplayNotification() {
    super("DisplayNotification");
}