How to scroll to make a Node within the content of a ScrollPane visible?
I created a slightly more elegant version for this case. However , I could only test on the y axis. Hope it helps
private static void ensureVisible(ScrollPane scrollPane, Node node) {
Bounds viewport = scrollPane.getViewportBounds();
double contentHeight = scrollPane.getContent().localToScene(scrollPane.getContent().getBoundsInLocal()).getHeight();
double nodeMinY = node.localToScene(node.getBoundsInLocal()).getMinY();
double nodeMaxY = node.localToScene(node.getBoundsInLocal()).getMaxY();
double vValueDelta = 0;
double vValueCurrent = scrollPane.getVvalue();
if (nodeMaxY < 0) {
// currently located above (remember, top left is (0,0))
vValueDelta = (nodeMinY - viewport.getHeight()) / contentHeight;
} else if (nodeMinY > viewport.getHeight()) {
// currently located below
vValueDelta = (nodeMinY + viewport.getHeight()) / contentHeight;
}
scrollPane.setVvalue(vValueCurrent + vValueDelta);
}
To get a perfect snap you need to account for the starting and stop position of the scrollbar. The viewport starts at half viewport from 0(Bounds scollpane) and stops a half viewport from max Bound. bounds vs viewport picture
so : node Y below a half viewport ->setVvalue to 0 node Y above maxheigh-half viewport -> set value to 1
and between that we need to calculate the total height -1viewport(half start half at end ) and the node y - half viewport. then (node y - half viewport) / (total height -1viewport)
double heightViewPort = scrollPane.getViewportBounds().getHeight();
double heightScrollPane = scrollPane.getContent().getBoundsInLocal().getHeight();
double y = Label.getBoundsInParent().getMaxY();
if (y<(heightViewPort/2)){
scrollPane.setVvalue(0);
// below 0 of scrollpane
}else if ((y>=(heightViewPort/2))&(y<=(heightScrollPane-heightViewPort/2))){
// between 0 and 1 of scrollpane
scrollPane.setVvalue((y-(heightViewPort/2))/(heightScrollPane-heightViewPort));
}
else if(y>= (heightScrollPane-(heightViewPort/2))){
// above 1 of scrollpane
scrollPane.setVvalue(1);
}
EDIT: code in the next example is more precise than mine: https://stackoverflow.com/a/23518314/1054140
You need to find a coordinates of this inner node inside content
and adjust ScrollPane
's vValue
and hValue
accordingly.
See ensureVisible()
method in next small app:
public class ScrollPaneEnsureVisible extends Application {
private static final Random random = new Random();
private static void ensureVisible(ScrollPane pane, Node node) {
double width = pane.getContent().getBoundsInLocal().getWidth();
double height = pane.getContent().getBoundsInLocal().getHeight();
double x = node.getBoundsInParent().getMaxX();
double y = node.getBoundsInParent().getMaxY();
// scrolling values range from 0 to 1
pane.setVvalue(y/height);
pane.setHvalue(x/width);
// just for usability
node.requestFocus();
}
@Override
public void start(Stage primaryStage) {
final ScrollPane root = new ScrollPane();
final Pane content = new Pane();
root.setContent(content);
// put 10 buttons at random places with same handler
final EventHandler<ActionEvent> handler = new EventHandler<ActionEvent>() {
@Override
public void handle(ActionEvent event) {
int index = random.nextInt(10);
System.out.println("Moving to button " + index);
ensureVisible(root, content.getChildren().get(index));
}
};
for (int i = 0; i < 10; i++) {
Button btn = new Button("next " + i);
btn.setOnAction(handler);
content.getChildren().add(btn);
btn.relocate(2000 * random.nextDouble(), 2000 * random.nextDouble());
}
Scene scene = new Scene(root, 300, 250);
primaryStage.setScene(scene);
primaryStage.show();
// run once to don't search for a first button manually
handler.handle(null);
}
public static void main(String[] args) { launch(); }
}