How to make buttons span mutiple columns/rows with GridPane JavaFX?

Question

I'm new to JavaFX and is trying to make a simple button design with GridPane.

I can't figure out how to make a button span multiple columns/rows without it pushing other buttons out of the way. I've been using HBox and VBox to group the other buttons together. I've tried setRowSpan on the buttons, but that didn't seem to work.

How it is looking

How i want it to look

Here is my code:

import javafx.stage.*;
import javafx.application.*;
import javafx.scene.*;
import javafx.scene.control.*;
import javafx.scene.layout.*;

public class SimpleGUI extends Application {
 public void start(Stage primaryStage) throws Exception {
  GridPane root = new GridPane();
  Scene scene = new Scene(root, 200, 200);

   //Buttons
   Button b1 = new Button("KNAPP 1");
   Button b2 = new Button("KNAPP 2");
   Button b3 = new Button("KNAPP 3");
   Button b4 = new Button("KNAPP 4");
   Button b5 = new Button("KNAPP 5");
   Button b6 = new Button("KNAPP 6");

   //Horizontal Box
   HBox topButtons = new HBox();
   topButtons.getChildren().add(b1);
   topButtons.getChildren().add(b2);
   topButtons.getChildren().add(b3);

   //Vertical Box
   VBox leftButtons = new VBox();
   leftButtons.getChildren().add(b4);
   leftButtons.getChildren().add(b5);

   //Placement
   GridPane.setConstraints(topButtons, 0,0);
   GridPane.setConstraints(leftButtons, 0,1);
   GridPane.setConstraints(b6, 1,1);

   //Length (3 Columns, 2 Rows)
   GridPane.setColumnSpan(topButtons, 3);
   GridPane.setRowSpan(leftButtons, 2);

   //Add them to the stage
   root.getChildren().add(topButtons);
   root.getChildren().add(leftButtons);
   root.getChildren().add(b6);

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

 public static void main(String[] args){
  launch(args);
 }
}

Solution

Since you're using a grid pane, you don't really need the HBox and VBox:

import javafx.stage.*;
import javafx.application.*;
import javafx.scene.*;
import javafx.scene.control.*;
import javafx.scene.layout.*;

public class SimpleGUI extends Application {
 public void start(Stage primaryStage) throws Exception {
  GridPane root = new GridPane();
  Scene scene = new Scene(root);

   //Buttons
   Button b1 = new Button("KNAPP 1");
   Button b2 = new Button("KNAPP 2");
   Button b3 = new Button("KNAPP 3");
   Button b4 = new Button("KNAPP 4");
   Button b5 = new Button("KNAPP 5");
   Button b6 = new Button("KNAPP 6");

   root.add(b1, 0, 0);
   root.add(b2, 1, 0);
   root.add(b3, 2, 0);

   root.add(b4, 0, 1);
   root.add(b5, 0, 2);

   // node, columnIndex, rowIndex, columnSpan, rowSpan:
   root.add(b6, 1, 1, 2, 2);

   // allow button to grow:
   b6.setMaxSize(Double.MAX_VALUE, Double.MAX_VALUE);

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

 public static void main(String[] args){
  launch(args);
 }
}