Documentation / FAQ / The graph viewer

Why do I get NullPointerException with JavaFX UI?

I get this error:

    at (
    at$PulseTask.set (
    at (
    at (
    at com.sun.scenario.animation.AbstractMasterTimer$MainLoop.updateAnimationRunnable (
    at com.sun.scenario.animation.AbstractMasterTimer.addPulseReceiver (
    at javafx.animation.Animation.addPulseReceiver (
    at javafx.animation.Animation.startReceiver (
    at (
    at org.graphstream.ui.fx_viewer.FxViewer.lambda$init$1 (
    at (

Somehow, your java program starts before the JavaFX engine. Use the following system property in order to delay the start of the viewer: