@Override
    public void initialize(AppStateManager stateManager, Application app) {
        if (!super.isInitialized()) {
            inputManager = app.getInputManager();
            inputManager.addMapping("ScreenShot", new KeyTrigger(KeyInput.KEY_SYSRQ));
            inputManager.addListener(this, "ScreenShot");

            List<ViewPort> vps = app.getRenderManager().getPostViews();
            last = vps.get(vps.size() - 1);
            last.addProcessor(this);

            if (shotName == null) {
                shotName = app.getClass().getSimpleName();
            }
        }

        super.initialize(stateManager, app);
    }
Sets if the filename should be appended with a number representing the
current sequence.
@param numberedWanted If numbering is wanted.
jme3-core/src/main/java/com/jme3/app/state/ScreenshotAppState.java