JavaFX - Array of Controls

Question

I want to create an Array of JavaFX controllers in order to be easier to work with them e.g. you could loop adding/setting elements in a GridPane.

But despite of the compiler/IDE not displaying any error this code below doesn't work:

public GridPane drawPane(){
    GridPane grid = new GridPane();
    Button[] btn = new Button[10];
    grid.add(btn[0], 0,0);
    return grid;
}

however this one does work:

public GridPane drawPane(){
    GridPane grid = new GridPane();
    Button btn = new Button();
    grid.add(btn, 0,0);
    return grid;
}

Am I instancing the controllers wrong? Why this code doesn't work with arrays ?

Where do you fill your arrays with Controls in the first example? — Tactical Downvote
– Tactical Downvote, Commented May 7, 2014 at 6:57
I tried it with a for loop, but I am trying to point out that even with a single instance of that array it doesn't works. — Mansueli
– Mansueli, Commented May 7, 2014 at 7:23
Of course your first example does not work. btn[0] is null. Initialize it properly and it will work. — Tactical Downvote
– Tactical Downvote, Commented May 7, 2014 at 8:32

Patrick · Accepted Answer · 2014-05-07 08:39:19Z

Try this... It will create an Array of Buttons and if you call your getGrid() Method it iterates through this Array of Buttons and adds them to the GridPane.

import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.Pane;
import javafx.stage.Stage;

public class App extends Application {

    private Button[] btns = new Button[10];

    @Override
    public void start(Stage primaryStage) {

        initBtnsArray();
        Group root = new Group();

        root.getChildren().add(getGrid());
        Scene scene = new Scene(root, 800, 600);

        primaryStage.setTitle("Hello Controller-Array-World!");
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        launch(args);
    }

    private Pane getGrid() {
        int i = 0;
        GridPane gridPane = new GridPane();
        for(Button b : btns) {
            // do something with your button
            // maybe add an EventListener or something
            gridPane.add(b, i*(i+(int)b.getWidth()), 0);
            i++;
        }
        return gridPane;
    }

    private void initBtnsArray() {
        for(int i = 0; i < btns.length; i++) {
            btns[i] = new Button("Button-"+i);
        }
    }
}

Patrick

Simulant · Accepted Answer · 2014-05-20 10:40:17Z

5

Your Array does not contain any Objects, so you will get a NullPointerException. Fill the array with an initialized Object to get it working.

public GridPane drawPane(){
    GridPane grid = new GridPane();
    Button[] btn = new Button[10];
    btn[0] = new Button(); //add this line
    grid.add(btn[0], 0,0);
    return grid;
}

edited May 20, 2014 at 10:40

answered May 7, 2014 at 8:34

Simulant

20.2k10 gold badges68 silver badges106 bronze badges

Collectives™ on Stack Overflow

JavaFX - Array of Controls

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related