How to scheduled an UI update

Flow
1

I’m going to implement a session scheduler for a conference which displays the schedule on a big screen. It shows the running sessions and the following sessions. It will run on a Raspberry Pi attached to the HDMI of the display.

What is the recommended way to update parts of the view regularly, e.g. every minute? I want to update the countdown (“8 minutes left”), remove sessions from the view when ended and add new sessions.

I’m using Vaadin 24.3.8 with Spring Boot 3.2.4 and Java 21.0.2.

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2

You can enable Push on the application and the scheduler from Spring Boot then you can use this code in your MainLayout (or only for this view):

@Scheduled(fixedRate = 1000)
public void scheduleFixedRateTask() {
	getUI().ifPresent(ui -> {
			ui.access(() -> {
       // refresh your page
       }
    }
}

For a countdown, you can probably use a custom component that does the countdown on the client side but that’s probably premature optimization :slight_smile:

1 Like
3

Thank you very much, this works very well! Maybe you’ll see this at a conference at work soon… :grinning:

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4

I don’t like the annotation as it’s not flexible and cannot be stopped.

I prefer to inject TaskScheduler and then use

taskScheduler.scheduleAtFixedRate(...)

3 Likes
5

Thank you very much for your hint, I refactored my code accordingly. Looks good now and no more exceptions when I close the browser tab. :grinning:

1 Like