Notifications

By now you've probably already seen the notification bubbles that appear on the top right of the screen. Notifications are a way to provide updates about the state of your app. For example, they can inform you that a long running background process has been completed or a new message has arrived. In this section we are going to show you just how to get them to work in your app.

Making Preparations

Create a new Gtk.Application complete with a desktop launcher file, packaging, etc. You can review this in Our First App.

In your .desktop file, add the line X-GNOME-UsesNotifications=true to the end of the file. This is what will make your app appear in System Settings so that notification preferences can be set.

Sending Notifications

In your Application.vala file, in the activate () function, create a new and add it to a with some margins. Then set that box as the child widget for your app's main window.

Finally, connect to the signal of that button, and create a new Notification with body text, and then send it with .

Now build and run your app, and click the "Notify" button. Congratulations, you've learned how to send notifications!

Badge Icons

Notifications will automatically contain your app's icon, but you can add additional context by setting a badge icon. Right after the line containing var notification = New Notification, add:

Build and run your app again, and press the "Notify" button. As you can see, the notification now has a smaller badged icon placed over your app's icon. Using this method, you can set the icon to any of the named icons shipped with elementary OS.

Buttons

You can also add buttons to notifications that will trigger actions defined in the app namespace. To add a button, first define an action in your Application class as we did in .

Now, we can add a button to the notification with a label and the action ID.

Build and run your app again, and press the "Notify" button. Notice that the notification now has a button with the label "Quit" and clicking it will close your app.

Default Action

You may have noticed that when you click on a new notification, a new window pops up. This is happening because the notification has a default action that is executed when the user clicks on it. If you don't set it, it will activate your application, where we create a new window and present it.

You can change the default action using . The default action has to be in the app namespace. If you are unsure what that means, see .

If you want to avoid creating a new window every time your application is activated, you need to check if there is a window in and present it instead.

Priority

Notifications also have priority. When a notification is set as URGENT it will stay on the screen until either you interact with it, or your application withdraws it. To make an urgent notification, use the function

URGENT notifications should really only be used on the most extreme cases. There are also .

Replace

We now know how to send a notification, but what if you need to update it with new information? Thanks to the id argument of the function, we can replace a notification with a matching ID. This ID can be anything you like.

Make a new button with the label "Replace" that sends a new notification, this time with an ID. This button will replace a notification with a matching ID when clicked, instead of sending a new notification.

Build and run your app again. Click on the buttons, first on "Notify", then "Replace". See how the "Notify" button sends a new notification each time it's clicked, but the "Replace" button replaces the contents of the same notification when it's clicked.

Review

Let's review what all we've learned:

• We built .

• Notifications automatically get our app's icon, but we can also

• We can that trigger actions in the app namespace