How to use

setVisibleAmount

method

in

javafx.scene.control.ScrollBar

@Override
protected void layoutChildren() {
  double layoutWidth = getLayoutBounds().getWidth();
  double layoutHeight = getLayoutBounds().getHeight();
  boolean vbarVisible = vbar.isVisible();
  boolean hbarVisible = hbar.isVisible();
  double vbarWidth = vbarVisible ? vbar.prefWidth(-1) : 0;
  double hbarHeight = hbarVisible ? hbar.prefHeight(-1) : 0;
  double w = layoutWidth - vbarWidth;
  double h = layoutHeight - hbarHeight;
  content.resize(w, h);
  hbar.setVisibleAmount(w);
  vbar.setVisibleAmount(h);
  if(vbarVisible) {
    vbar.resizeRelocate(layoutWidth - vbarWidth, 0, vbarWidth, h);
  }
  if(hbarVisible) {
    hbar.resizeRelocate(0, layoutHeight - hbarHeight, w, hbarHeight);
  }
}

 @Override
public void start(Stage primaryStage) {
  ScrollBar scrollBar = new ScrollBar();
  scrollBar.setOrientation(Orientation.VERTICAL);

  scrollBar.setMax(100);
  scrollBar.setVisibleAmount(50);
  scrollBar.valueProperty().addListener((a,b,c) -> System.out.println(c));

  StackPane root = new StackPane();
  root.getChildren().add(scrollBar);

  Scene scene = new Scene(root, 200, 500);

  // do layout
  root.applyCss();
  root.layout();

  ScrollBarMark mark1 = new ScrollBarMark();
  ScrollBarMark mark2 = new ScrollBarMark();
  mark1.attach(scrollBar);
  mark2.attach(scrollBar);
  mark1.setPosition(50);
  mark2.setPosition(75);

  primaryStage.setScene(scene);
  primaryStage.show();
}

scrollBar.setMax(TOTAL_WIDTH - canvas.getWidth());
scrollBar.setVisibleAmount(scrollBar.getMax() * canvas.getWidth() / TOTAL_WIDTH);