Develop Reference

randomly displaying circles within gridPane cells in javaFX

I am creating am application that displays circles (of different colors) randomly within each cell of a gridPane.
What i want to do is create a "shuffle" button that changes the position of each circle randomly within the gridPane. However, I keep running into a slurry of problems.
Here is what i have so far. My two classes (have not added XML file):
Controller Class
public class viewController {
//My two Variables, a gridPane and a button
#FXML
private GridPane matrix;
#FXML
private Button shuffleBut;
//my eventHandler event that should (1) add circles to all the cells, and
(2) shuffle them amongst the cells in the gridPane.
void shuffle(ActionEvent e) {
Random r = new Random ();
int rowShuffle = r.next((4-0)+1);
int colShuffle = r.next((4-0)+1);
Circle newCircle = new Circle ();
matrix.add(newCircle, rowShuffle, colShuffle );
}
Main Class
public class Main extends Application {
#Override
public void start(Stage primaryStage) throws Exception {
// just load fxml file and display it in the stage:
Parent root = FXMLLoader.Load(getClass().getResource("mainUI.fxml"));
Scene scene = new Scene(root);
primaryStage.setScene(scene);
primaryStage.show();
}
// main method to support non-JavaFX-aware environments:
public static void main(String[] args) {
// starts the FX toolkit, instantiates this class,
// and calls start(...) on the FX Application thread:
launch(args);
}

Here is an example that demos how to shuffle Circles around in a GridPane. If you add the Circles to an ArrayList, you can remove the Circles from the GridPane. Then you can shuffle the List. Finally, you can add the shuffled list back to the GridPane.
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Random;
import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Control;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.StackPane;
import javafx.scene.layout.VBox;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.stage.Stage;
/**
*
* #author blj0011
*/
public class JavaFXApplication314 extends Application
{
Random random = new Random();
int numberOfRows = 25;
int numberOfColumns = 25;
#Override
public void start(Stage primaryStage)
{
List<Circle> circles = new ArrayList();
for (int i = 0; i < numberOfColumns * numberOfRows; i++) {
circles.add(new Circle(10, getRandomColor()));
}
GridPane gridPane = new GridPane();
addCirclesToGridPane(gridPane, circles);
gridPane.setPadding(new Insets(20, 20, 20, 20));
Button btn = new Button();
btn.setText("Say 'Hello World'");
btn.setOnAction((ActionEvent event) -> {
Collections.shuffle(circles);//Shuffle the List of Circles.
for(int i = 0; i < numberOfColumns * numberOfRows; i++)
{
Circle c = circles.get(i);
GridPane.setColumnIndex(c, i % numberOfColumns);
GridPane.setRowIndex(c, i / numberOfColumns);
}
});
VBox vBox = new VBox(gridPane, new StackPane(btn));
vBox.setMaxSize(Control.USE_COMPUTED_SIZE, Control.USE_COMPUTED_SIZE);
StackPane root = new StackPane(vBox);
root.setMaxSize(Double.MAX_VALUE, Double.MAX_VALUE);
Scene scene = new Scene(root);
primaryStage.setTitle("Hello World!");
primaryStage.setScene(scene);
primaryStage.show();
}
/**
* #param args the command line arguments
*/
public static void main(String[] args)
{
launch(args);
}
public void addCirclesToGridPane(GridPane gridPane, List<Circle> circles)
{
for (int i = 0; i < numberOfColumns * numberOfRows; i++) {
gridPane.add(circles.get(i), i % numberOfColumns, i / numberOfColumns);
}
}
public Color getRandomColor()
{
int r = random.nextInt(255);
int g = random.nextInt(255);
int b = random.nextInt(255);
return Color.rgb(r, g, b);
}
}

Thread stops updating display after a while

I am trying to do a neural network training visualization with JavaFX 8. The network cells are shown as dots changing their color depending on the output value. The calculations and the drawing are done in a thread that can be started or stopped by clicking a button. For a while everything works fine but after a number of iterations the display is no longer updated.
What needs to be done to reliably update the display?
I am using JRE version 1.8.0_45.
Here's a simplified version of my code:
import javafx.application.*;
import javafx.concurrent.Task;
import javafx.geometry.Insets;
import javafx.stage.Stage;
import javafx.scene.control.Button;
import javafx.scene.control.ScrollPane;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.GridPane;
import javafx.scene.paint.Color;
import javafx.scene.*;
import javafx.scene.canvas.Canvas;
import javafx.scene.canvas.GraphicsContext;
public class TestView extends Application {
public static final int SCENE_WIDTH = 1000;
public static final int SCENE_HEIGHT = 800;
public static final int BUTTON_PANEL_HEIGHT = 80;
private Canvas canvas;
private GraphicsContext gc;
private Task<Void> task = null;
public static void main(String[] args) {
launch(args);
}
#Override
public void start(Stage primaryStage) throws Exception {
primaryStage.setTitle("MLP");
BorderPane borderPane = new BorderPane();
canvas = new Canvas( SCENE_WIDTH, 3*SCENE_HEIGHT-BUTTON_PANEL_HEIGHT );
gc = canvas.getGraphicsContext2D();
borderPane.setCenter(new ScrollPane(canvas));
GridPane buttonPanel = new GridPane();
Button buttonTrain = new Button("Train");
buttonTrain.setMinWidth(SCENE_WIDTH/2);
buttonPanel.setPadding(new Insets(0, 0, 0, 0));
buttonPanel.add(buttonTrain, 1, 0);
borderPane.setBottom(buttonPanel);
buttonTrain.setOnMouseClicked( e -> {
if (task != null) {
task.cancel();
task = null;
}
else {
task = new Task<Void>() {
#Override
protected Void call() throws Exception {
for (int i = 1; i <= 10000000; i++) {
if (isCancelled()) {
break;
}
// dummy calculation
doSomeStuff();
// dummy graphics update
gc.setFill(Color.GREEN);
gc.fillOval(50, 50, 20, 20);
gc.clearRect(200, 10, 200, 100);
gc.setFill(Color.BLACK);
gc.fillText("" + i, 200, 50);
}
return null;
}
};
new Thread(task).start();
}
});
Scene scene = new Scene( borderPane, SCENE_WIDTH, SCENE_HEIGHT );
primaryStage.setScene(scene);
primaryStage.show();
}
private double doSomeStuff() {
double r = 0.5;
for ( int i = 0; i < 10000; i++ ) {
r = Math.sin(r);
}
return r;
}
}

How to display a 10-by-10square matrix with JavaFX?

JavaFX Basics write a program that displays a 10-by-10 square matrix. Each element in the matrix is 0 or 1, randomly generated. Display each number centered in a text field. Use TextField setText method to set value 0 or 1 as a string.
As of now I can only print one random number. How can I make display a 10-by-10 matrix?
import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.GridPane;
import javafx.stage.Stage;
import java.util.Random;
public class Matrix extends Application {
public class Matrix extends Application {
Button[][] matrix; //names the grid of buttons
#Override
public void start(Stage primaryStage) {
int SIZE = 10;
int length = SIZE;
int width = SIZE;
GridPane root = new GridPane();
matrix = new Button[width][length];
for(int y = 0; y < length; y++)
{
for(int x = 0; x < width; x++)
{
Random rand = new Random();
int rand1 = rand.nextInt(2);
matrix[x][y] = new Button(/*"(" + rand1 + ")"*/);
matrix[x][y].setText("(" + rand1 + ")"); //
matrix[x][y].setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent event) {
System.out.println("Random Binary Matrix (JavaFX)");
}
});
root.getChildren().add(matrix[x][y]);
}
}
Scene scene = new Scene(root, 500, 500);
primaryStage.setTitle("Random Binary Matrix (JavaFX)");
primaryStage.setScene(scene);
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}

You actually did most of the hard work already and the only thing you missed is looking up the GridPaneAPI. What your code does is add 40 buttons on top of each other because you never change the row or column of the GridPane!
import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.TextField;
import javafx.scene.layout.GridPane;
import javafx.stage.Stage;
import javax.xml.soap.Text;
import java.util.ArrayList;
import java.util.Random;
public class Main extends Application {
#Override
public void start(Stage primaryStage) {
int SIZE = 10;
int length = SIZE;
int width = SIZE;
GridPane root = new GridPane();
for(int y = 0; y < length; y++){
for(int x = 0; x < width; x++){
Random rand = new Random();
int rand1 = rand.nextInt(2);
// Create a new TextField in each Iteration
TextField tf = new TextField();
tf.setPrefHeight(50);
tf.setPrefWidth(50);
tf.setAlignment(Pos.CENTER);
tf.setEditable(false);
tf.setText("(" + rand1 + ")");
// Iterate the Index using the loops
root.setRowIndex(tf,y);
root.setColumnIndex(tf,x);
root.getChildren().add(tf);
}
}
Scene scene = new Scene(root, 500, 500);
primaryStage.setTitle("Random Binary Matrix (JavaFX)");
primaryStage.setScene(scene);
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}

Chessboard with automatic resizing

So, I am trying to display a chessboard in javaFX. I will have to perform different operations and draw on some of the tiles so I chose to use a Canvas for each tile and a GridPane to arrange them for me in a grid fashion.
Unfortunately I am having some problems with the resizing of the grid tiles; I want my whole chessboard to automatically adapt its size to the Scene. Therefore, I have added a ChangeListener to both the height and width properties of the GridPane which takes care of resizing the tiles. This only works when the window gets bigger, when the window is reduced to a smaller size everything still gets bigger!
Here's the shortest SSCCE I came up with which reproduces my problem:
package chessboardtest;
import javafx.application.Application;
import javafx.beans.value.*;
import javafx.geometry.*;
import javafx.scene.*;
import javafx.scene.canvas.*;
import javafx.scene.control.*;
import javafx.scene.layout.*;
import javafx.scene.paint.*;
import javafx.stage.Stage;
public class ChessboardTest extends Application {
final int size = 10;
#Override
public void start(Stage primaryStage) {
VBox root = new VBox();
final GridPane chessboard = new GridPane();
fillChessboard(chessboard, size);
ChangeListener<Number> resizeListener = new ChangeListener<Number>() {
#Override
public void changed(ObservableValue<? extends Number> ov, Number t, Number t1) {
double newWidth = chessboard.getWidth() / size;
double newHeight = chessboard.getHeight() / size;
for(Node n: chessboard.getChildren()) {
Canvas canvas = (Canvas)n;
canvas.setWidth(newWidth);
canvas.setHeight(newHeight);
}
}
};
chessboard.widthProperty().addListener(resizeListener);
chessboard.heightProperty().addListener(resizeListener);
root.getChildren().add(chessboard);
root.setPadding(new Insets(10));
VBox.setVgrow(chessboard, Priority.ALWAYS);
Scene scene = new Scene(root, 300, 250);
primaryStage.setTitle("chessboard");
primaryStage.setScene(scene);
primaryStage.show();
}
void fillChessboard(GridPane pane, int size) {
class RedrawListener implements ChangeListener<Number> {
Color color;
Canvas canvas;
public RedrawListener(Canvas c, int i) {
if(i % 2 == 0) {
color = Color.BLACK;
}
else {
color = Color.WHITE;
}
canvas = c;
}
#Override
public void changed(ObservableValue<? extends Number> ov, Number t, Number t1) {
canvas.getGraphicsContext2D().setFill(color);
canvas.getGraphicsContext2D().fillRect(0, 0, canvas.getWidth(), canvas.getHeight());
}
}
for(int row = 0; row < size; row++) {
for(int col = 0, i = row; col < size; col++, i++) {
Canvas c = new Canvas();
RedrawListener rl = new RedrawListener(c, i);
c.widthProperty().addListener(rl);
c.heightProperty().addListener(rl);
pane.add(c, row, col);
}
}
}
public static void main(String[] args) {
launch(args);
}
}

If you don't need a canvas (and you probably don't), just use StackPanes for the squares and make them fill the width and the height. You can always add a canvas (or anything else) to the StackPanes to display their content.
import javafx.application.Application;
import javafx.geometry.HPos;
import javafx.geometry.VPos;
import javafx.scene.Scene;
import javafx.scene.control.Control;
import javafx.scene.layout.ColumnConstraints;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.Priority;
import javafx.scene.layout.RowConstraints;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
public class Chessboard extends Application {
#Override
public void start(Stage primaryStage) {
GridPane root = new GridPane();
final int size = 8 ;
for (int row = 0; row < size; row++) {
for (int col = 0; col < size; col ++) {
StackPane square = new StackPane();
String color ;
if ((row + col) % 2 == 0) {
color = "white";
} else {
color = "black";
}
square.setStyle("-fx-background-color: "+color+";");
root.add(square, col, row);
}
}
for (int i = 0; i < size; i++) {
root.getColumnConstraints().add(new ColumnConstraints(5, Control.USE_COMPUTED_SIZE, Double.POSITIVE_INFINITY, Priority.ALWAYS, HPos.CENTER, true));
root.getRowConstraints().add(new RowConstraints(5, Control.USE_COMPUTED_SIZE, Double.POSITIVE_INFINITY, Priority.ALWAYS, VPos.CENTER, true));
}
primaryStage.setScene(new Scene(root, 400, 400));
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}

This is a nice solution, but resizing is so much easier with data binding in Java FX. You can hide all listener business this way.
Here is a solution much like James D's, but using Rectangles insread of Canvases for the squares:
public class ResizeChessboard extends Application {
GridPane root = new GridPane();
final int size = 8;
public void start(Stage primaryStage) {
for (int row = 0; row < size; row++) {
for (int col = 0; col < size; col++) {
Rectangle square = new Rectangle();
Color color;
if ((row + col) % 2 == 0) color = Color.WHITE;
else color = Color.BLACK;
square.setFill(color);
root.add(square, col, row);
square.widthProperty().bind(root.widthProperty().divide(size));
square.heightProperty().bind(root.heightProperty().divide(size));
}
}
primaryStage.setScene(new Scene(root, 400, 400));
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}

Dynamically add elements to a fixed-size GridPane in JavaFX

I would like to display a grid containing a various number of rectangles in JavaFX. It is important that this grid cannot be resized.
I chose the GridPane layout. I dynamically add javafx.scene.shape.Rectangle to it. Here's how my grid looks like with 2 rows and 4 columns.
Upon resizing, I would like it to keep the same overall shape, that is to say each Rectangle having the same size and keeping an horizontal and vertical gaps between my Rectangles.
However, here's what I get with a 4x4 grid:
The problems being:
The last row and last column do not have the same size as the rest of the Rectangles.
The gaps have disappeared.
Here is my code responsible for refreshing the display:
public void refreshConstraints() {
getRowConstraints().clear();
getColumnConstraints().clear();
for (int i = 0; i < nbRow; i++) {
RowConstraints rConstraint = new RowConstraints();
// ((nbRow - 1) * 10 / nbRow) = takes gap into account (10% of height)
rConstraint.setPercentHeight(100 / nbRow - ((nbRow - 1) * 10 / nbRow));
getRowConstraints().add(rConstraint);
}
for (int i = 0; i < nbColumn; i++) {
ColumnConstraints cConstraint = new ColumnConstraints();
cConstraint.setPercentWidth(100 / nbColumn - ((nbColumn - 1) * 10 / nbColumn));
getColumnConstraints().add(cConstraint);
}
}
Using the setFillWidth and setHgrow yields no result either, the gap is kept between my Rectangles, but the Rectangles aren't resized and they overlap the rest of my GUI elements.
EDIT: MCVE code:
import javafx.application.Application;
import javafx.application.Platform;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.ColumnConstraints;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.HBox;
import javafx.scene.layout.RowConstraints;
import javafx.scene.paint.Paint;
import javafx.scene.shape.Rectangle;
import javafx.stage.Stage;
public class DynamicGrid extends Application {
//Class containing grid (see below)
private GridDisplay gridDisplay;
#Override
public void start(Stage primaryStage) {
//Represents the grid with Rectangles
gridDisplay = new GridDisplay(400, 200);
//Fields to specify number of rows/columns
TextField rowField = new TextField();
TextField columnField = new TextField();
//Function to set an action when text field loses focus
buildTextFieldActions(rowField, columnField);
HBox fields = new HBox();
fields.getChildren().add(rowField);
fields.getChildren().add(new Label("x"));
fields.getChildren().add(columnField);
BorderPane mainPanel = new BorderPane();
mainPanel.setLeft(gridDisplay.getDisplay());
mainPanel.setBottom(fields);
Scene scene = new Scene(mainPanel);
primaryStage.setTitle("Test grid display");
primaryStage.setScene(scene);
primaryStage.show();
}
/**
* #param args the command line arguments
*/
public static void main(String[] args) {
launch(args);
}
private void buildTextFieldActions(final TextField rowField, final TextField columnField) {
rowField.focusedProperty().addListener(new ChangeListener<Boolean>() {
#Override
public void changed(ObservableValue<? extends Boolean> ov, Boolean t, Boolean t1) {
if (!t1) {
if (!rowField.getText().equals("")) {
try {
int nbRow = Integer.parseInt(rowField.getText());
gridDisplay.setRows(nbRow);
gridDisplay.updateDisplay();
} catch (NumberFormatException nfe) {
System.out.println("Please enter a valid number.");
}
}
}
}
});
columnField.focusedProperty().addListener(new ChangeListener<Boolean>() {
#Override
public void changed(ObservableValue<? extends Boolean> ov, Boolean t, Boolean t1) {
if (!t1) {
if (!columnField.getText().equals("")) {
try {
int nbColumn = Integer.parseInt(columnField.getText());
gridDisplay.setColumns(nbColumn);
gridDisplay.updateDisplay();
} catch (NumberFormatException nfe) {
System.out.println("Please enter a valid number.");
}
}
}
}
});
}
//Class responsible for displaying the grid containing the Rectangles
public class GridDisplay {
private GridPane gridPane;
private int nbRow;
private int nbColumn;
private int width;
private int height;
private double hGap;
private double vGap;
public GridDisplay(int width, int height) {
this.gridPane = new GridPane();
this.width = width;
this.height = height;
build();
}
private void build() {
this.hGap = 0.1 * width;
this.vGap = 0.1 * height;
gridPane.setVgap(vGap);
gridPane.setHgap(hGap);
gridPane.setPrefSize(width, height);
initializeDisplay(width, height);
}
//Builds the first display (correctly) : adds a Rectangle for the number
//of rows and columns
private void initializeDisplay(int width, int height) {
nbRow = height / 100;
nbColumn = width / 100;
for (int i = 0; i < nbColumn; i++) {
for (int j = 0; j < nbRow; j++) {
Rectangle rectangle = new Rectangle(100, 100);
rectangle.setStroke(Paint.valueOf("orange"));
rectangle.setFill(Paint.valueOf("steelblue"));
gridPane.add(rectangle, i, j);
}
}
}
//Function detailed in post
//Called in updateDisplay()
public void refreshConstraints() {
gridPane.getRowConstraints().clear();
gridPane.getColumnConstraints().clear();
for (int i = 0; i < nbRow; i++) {
RowConstraints rConstraint = new RowConstraints();
rConstraint.setPercentHeight(100 / nbRow - ((nbRow - 1) * 10 / nbRow));
gridPane.getRowConstraints().add(rConstraint);
}
for (int i = 0; i < nbColumn; i++) {
ColumnConstraints cConstraint = new ColumnConstraints();
cConstraint.setPercentWidth(100 / nbColumn - ((nbColumn - 1) * 10 / nbColumn));
gridPane.getColumnConstraints().add(cConstraint);
}
}
public void setColumns(int newColumns) {
nbColumn = newColumns;
}
public void setRows(int newRows) {
nbRow = newRows;
}
public GridPane getDisplay() {
return gridPane;
}
//Function called when refreshing the display
public void updateDisplay() {
Platform.runLater(new Runnable() {
#Override
public void run() {
//The gridpane is cleared of the previous children
gridPane.getChildren().clear();
//A new rectangle is added for row*column
for (int i = 0; i < nbColumn; i++) {
for (int j = 0; j < nbRow; j++) {
Rectangle rectangle = new Rectangle(100, 100);
rectangle.setStroke(Paint.valueOf("orange"));
rectangle.setFill(Paint.valueOf("steelblue"));
gridPane.add(rectangle, i, j);
}
}
//Call to this function to update the grid's constraints
refreshConstraints();
}
});
}
}
}

Seems like a TilePane is a better fit for this use case than a GridPane.
import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.HBox;
import javafx.scene.layout.TilePane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Rectangle;
import javafx.stage.Stage;
// java 8 code
public class DynamicTiles extends Application {
//Class containing grid (see below)
private GridDisplay gridDisplay;
//Class responsible for displaying the grid containing the Rectangles
public class GridDisplay {
private static final double ELEMENT_SIZE = 100;
private static final double GAP = ELEMENT_SIZE / 10;
private TilePane tilePane = new TilePane();
private Group display = new Group(tilePane);
private int nRows;
private int nCols;
public GridDisplay(int nRows, int nCols) {
tilePane.setStyle("-fx-background-color: rgba(255, 215, 0, 0.1);");
tilePane.setHgap(GAP);
tilePane.setVgap(GAP);
setColumns(nCols);
setRows(nRows);
}
public void setColumns(int newColumns) {
nCols = newColumns;
tilePane.setPrefColumns(nCols);
createElements();
}
public void setRows(int newRows) {
nRows = newRows;
tilePane.setPrefRows(nRows);
createElements();
}
public Group getDisplay() {
return display;
}
private void createElements() {
tilePane.getChildren().clear();
for (int i = 0; i < nCols; i++) {
for (int j = 0; j < nRows; j++) {
tilePane.getChildren().add(createElement());
}
}
}
private Rectangle createElement() {
Rectangle rectangle = new Rectangle(ELEMENT_SIZE, ELEMENT_SIZE);
rectangle.setStroke(Color.ORANGE);
rectangle.setFill(Color.STEELBLUE);
return rectangle;
}
}
#Override
public void start(Stage primaryStage) {
//Represents the grid with Rectangles
gridDisplay = new GridDisplay(2, 4);
//Fields to specify number of rows/columns
TextField rowField = new TextField("2");
TextField columnField = new TextField("4");
//Function to set an action when text field loses focus
buildTextFieldActions(rowField, columnField);
HBox fields = new HBox(10);
fields.getChildren().add(rowField);
fields.getChildren().add(new Label("x"));
fields.getChildren().add(columnField);
BorderPane mainPanel = new BorderPane();
mainPanel.setCenter(gridDisplay.getDisplay());
mainPanel.setTop(fields);
Scene scene = new Scene(mainPanel, 1000, 800);
primaryStage.setTitle("Test grid display");
primaryStage.setScene(scene);
primaryStage.show();
}
/**
* #param args the command line arguments
*/
public static void main(String[] args) {
launch(args);
}
private void buildTextFieldActions(final TextField rowField, final TextField columnField) {
rowField.focusedProperty().addListener((ov, t, t1) -> {
if (!t1) {
if (!rowField.getText().equals("")) {
try {
int nbRow = Integer.parseInt(rowField.getText());
gridDisplay.setRows(nbRow);
} catch (NumberFormatException nfe) {
System.out.println("Please enter a valid number.");
}
}
}
});
columnField.focusedProperty().addListener((ov, t, t1) -> {
if (!t1) {
if (!columnField.getText().equals("")) {
try {
int nbColumn = Integer.parseInt(columnField.getText());
gridDisplay.setColumns(nbColumn);
} catch (NumberFormatException nfe) {
System.out.println("Please enter a valid number.");
}
}
}
});
}
}

Thanks a lot for your answer. TilePanes are indeed a lot easier to use, although what you've written does not completely answer my question.
I wanted to have a pane in which the children would resize, and not the pane itself. It seems setting the maxSize and prefSize doesn't have any effect.
EDIT: I managed to do it using two JavaFX Property in my GridDisplay class, corresponding to the fixed height and width of my grid:
public class GridDisplay {
private ReadOnlyDoubleProperty heightProperty;
private ReadOnlyDoubleProperty widthProperty;
...
}
Then I assign to these members the values corresponding to the desired fixed size in the constructor. The size of the children inside the grid correspond to a fraction of the height and width of the grid, depending on the number of rows and columns. Here's what my updateDisplay() looks like:
public void updateDisplay() {
gridPane.getChildren().clear();
for (int i = 0; i < nbColumn; i++) {
for (int j = 0; j < nbRow; j++) {
Rectangle rectangle = new Rectangle(100, 100);
//Binding the fraction of the grid size to the width
//and heightProperty of the child
rectangle.widthProperty().bind(widthProperty.divide(nbColumn));
rectangle.heightProperty().bind(heightProperty.divide(nbRow));
gridPane.add(rectangle, i, j);
}
}
}