JavaFX - Get GridPane to fit parent

Question

I have a simple GridPane showing a couple of labels and a button, but I cannot seem to get it to fit the parent StackPane. How would I go forth and make it so that it fills whatever container it is in?

    GridPane g = new GridPane();
    g.add(new Label("Categories"),0,0);
    g.add(new Label("Content"),1,0);        
    Button newCat = new Button("New Category");
    newCat.setOnAction(new EventHandler<ActionEvent>() {
        @Override public void handle(ActionEvent e) {
            System.out.println("Clicked");
        }
    });       
    g.add(newCat,0,1);
    g.setGridLinesVisible(true);
    StackPane root = new StackPane();
    root.getChildren().add(g);        
    Scene scene = new Scene(root, 300, 250);  
    primaryStage.setScene(scene);
    primaryStage.show();

UI is really not my forte and any help would be appreciated.

Answer 1

You should see this link, especially the part about Percentage Sizing. If you have only two columns, I have found that code to work:

GridPane grid = new GridPane();
/* your code */
ColumnConstraints column1 = new ColumnConstraints();
column1.setPercentWidth(50);
grid.getColumnConstraints().add(column1);

Answer 2

In case anyone will be looking for an answer, this is how it worked for me:

@Override
public void start(Stage stage) throws Exception {
    stage.setTitle("Window title");
    GridPane grid = new GridPane();

    gridSetup(grid); // Building my grid elements here (2 columns)

    // Setting columns size in percent
    ColumnConstraints column = new ColumnConstraints();
    column.setPercentWidth(30);
    grid.getColumnConstraints().add(column);

    column = new ColumnConstraints();
    column.setPercentWidth(70);
    grid.getColumnConstraints().add(column);

    grid.setPrefSize(WINDOW_WIDTH, WINDOW_HEIGHT); // Default width and height
    grid.setMaxSize(Region.USE_COMPUTED_SIZE, Region.USE_COMPUTED_SIZE);

    Scene scene = new Scene(grid, WINDOW_WIDTH, WINDOW_HEIGHT);
    stage.setScene(scene);
    stage.show();
}

With this setup the grid takes all space of the window and resizes automatically with the window.