JavaFX时间轴与ScheduledExecutorService

Question

In a JavaFX 8 project, you can use javafx.animation.Timeline like this:

Timeline timeline = new Timeline(
            new KeyFrame(Duration.millis(250),
                         actionEvent -> {
                               updateTemperature();
                         }
            )
    );
timeline.setCycleCount(Animation.INDEFINITE);
timeline.play();

Or you can something very similar using a ScheduledExecutorService :

executorService.scheduleAtFixedRate(this::updateTemperature, 0, 250, TimeUnit.SECONDS);

Are there any "best practises" for using one over the other?

Answer 1

As with most UI toolkits, in JavaFX you must not access UI components that are part of the display from any thread other than the dedicated UI thread (the FX Application Thread in the case of JavaFX). Additionally, code that takes (or may take) time to run (eg has blocking calls, as with I/O or networking) should not be executed on the UI thread as it will make the UI unresponsive.

The two code snippets you posted are quite different with regard to threading. The ScheduledExecutor will execute updateTemperature() on a background thread (ie not the FX Application Thread). This is appropriate if updateTemperature() takes a long time to run; but it will likely throw an exception (or, worse, have the potential of leaving the UI in an inconsistent state) if it accesses the UI.

By contrast, the Timeline creates no new threads and executes updateTemperature() on the FX Application Thread. If updateTemperature() accesses the UI, it must be performed on this thread and this is a convenient way to do so. If it takes a long time to run (which I assume it doesn't, since you're calling it 4 times per second), it will have the effect of making the UI unresponsive.