Getting NullPointerExceptions when accessing animation controller from the outside

General Discussion
1

I have the following code:

public class Simulator extends SimpleApplication implements AnimEventListener {
    private AnimChannel animationChannel;
    private AnimControl animationController;
    private Node avatar;

    // Constructor, getters/setters, etc.

    @Override
    public void simpleInitApp() {
        viewPort.setBackgroundColor(ColorRGBA.LightGray);
        DirectionalLight directionalLight = new DirectionalLight();
        rootNode.addLight(directionalLight);

        avatar = (Node)assetManager.loadModel("models/Ninja.mesh.xml");
        avatar.localScale = 0.025f;
        rootNode.attachChild(avatar);
        animationController = avatar.getControl(AnimControl);
        animationController.addListener(this);
        animationChannel = animationController.createChannel();

        flyCam.setDragToRotate(true);

        setDisplayFps(false);
        setDisplayStatView(false);

        animationChannel.setAnim("Walk", 0.5f);
    }

    @Override
    public void yeehaw() {
        animationChannel.setAnim("Backflip", 0.5f);
    }

    @Override
    public void onAnimCycleDone(AnimControl control, AnimChannel channel, String animName) {
        channel.setAnim('Idle1');
        channel.setLoopMode(LoopMode.DontLoop);
        channel.setSpeed(1f);
    }

    @Override
    public void onAnimChange(AnimControl control, AnimChannel channel, String animName) {
        // No-op for now
    }
}

When I run:

public class Driver {
    public static void main(String[] args) {
        Simulator simulator = new SImulator();
        simulator.start();
    }
}

Everything runs perfectly. But the minute I try to invoke animationController from outside the Simulator like so:

public class Driver {
    public static void main(String[] args) {
        Simulator simulator = new SImulator();
        simulator.start();
        simulator.yeehaw();
    }
}

I start getting null NPEs:

java.lang.NullPointerException: Cannot invoke method setAnim() on null object

Any idea why this is?

2

You are calling simulator.yeehaw() before the app is done initializing. You souldn’t be calling anything runtime related on application from there anyway. In fact, in new versions of JME, start() never returns.