This looks like you should use a VBox to hold your AnchorPanes and put them in a ScrollPane. Set fitToWidth to true on the ScrollPane and it should force the anchor panes to take up the whole width (and no more) of the scroll pane's viewport, assuming you don't change the maxWidth property on the AnchorPane from its default.
Mocked-up example (which can easily be done in FXML if you prefer):
import java.util.Random;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.ScrollPane;
import javafx.scene.layout.AnchorPane;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;
public class ScrollingVBox extends Application {
@Override
public void start(Stage primaryStage) {
final Random rng = new Random();
VBox content = new VBox(5);
ScrollPane scroller = new ScrollPane(content);
scroller.setFitToWidth(true);
Button addButton = new Button("Add");
addButton.setOnAction(e -> {
AnchorPane anchorPane = new AnchorPane();
String style = String.format("-fx-background: rgb(%d, %d, %d);"+
"-fx-background-color: -fx-background;",
rng.nextInt(256),
rng.nextInt(256),
rng.nextInt(256));
anchorPane.setStyle(style);
Label label = new Label("Pane "+(content.getChildren().size()+1));
AnchorPane.setLeftAnchor(label, 5.0);
AnchorPane.setTopAnchor(label, 5.0);
Button button = new Button("Remove");
button.setOnAction(evt -> content.getChildren().remove(anchorPane));
AnchorPane.setRightAnchor(button, 5.0);
AnchorPane.setTopAnchor(button, 5.0);
AnchorPane.setBottomAnchor(button, 5.0);
anchorPane.getChildren().addAll(label, button);
content.getChildren().add(anchorPane);
});
Scene scene = new Scene(new BorderPane(scroller, null, null, addButton, null), 400, 400);
primaryStage.setScene(scene);
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}
Another solution might be to use a ListView. (This would be preferable if you had many items to display.) Create a class representing the items you are displaying in each AnchorPane and a custom list cell to display them.