Array of objects in JavaFX

Question

I am supposed to create an array of objects of type Buttons but the output it's just one button not multiple as it is supposed to. What Should I do?

int numberOfButtons = 20;

for (int i = 0; i < numberOfButtons; ++i) {    
    Button[] btn = new Button[numberOfButtons];
    btn[i] = new Button();
    btn[i].setText("Safe!");

    btn[i].setOnAction(new EventHandler<ActionEvent>() {
        @Override
        public void handle(ActionEvent event) {
            System.out.println("Hello World!");
        }
    });

    FlowPane root = new FlowPane();
    root.getChildren().addAll(btn[i]);

    Scene scene = new Scene(root, 300, 250); 
    primaryStage.setTitle("Button Blast!");
    primaryStage.setScene(scene);
    primaryStage.show();
}

You should probably close your for loop before you create root. You should also move Button[] btn = new Button[numberOfButtons] before the for loop. Otherwise you're creating every variable within the for loop 20 times. — Jonny Henly
– Jonny Henly, Commented Oct 28, 2016 at 21:22
Ok, so I did that... But then the method root.getChildren().add(btn[i]); doesn't work anymore. — Oscar Chavez
– Oscar Chavez, Commented Oct 28, 2016 at 22:03
So add another for loop like: for(Button b : btn) { root.getChildren().add(b); }. Or you could probably just do root.getChildren().addAll(btn) without the for loop. — Jonny Henly
– Jonny Henly, Commented Oct 28, 2016 at 22:07

Timothy Truckle · Accepted Answer · 2016-10-28 21:31:24Z

1

When you run in such problems the best thing is to get a paper and a pen and to write down what each line of your code does.

your complete code is within the loop. you should narrow it down so that in only contains this:

btn[i] = new Button();
btn[i].setText("Safe!");

btn[i].setOnAction(new EventHandler<ActionEvent>() {
    @Override
    public void handle(ActionEvent event) {
        System.out.println("Hello World!");
    }
});

answered Oct 28, 2016 at 21:31

Timothy Truckle

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Comments

Sergej Isbrecht · Accepted Answer · 2016-10-28 21:47:21Z

0

I used JavaFx with Java8 (Stream) in order to solve your issue:

    FlowPane fPane = IntStream.range(1, 20)
            .mapToObj(value -> {

                Button button = new Button("Safe!");

                button.setOnAction(event -> {
                    System.out.println("Hello World!");
                });

                return button;

            }).reduce(new FlowPane(), (p, b) -> {

                p.getChildren().add(b);

                return p;
            }, (flowPane, flowPane2) -> flowPane2);

    Scene scene = new Scene(fPane, 300, 250);

    primaryStage.setTitle("Button Blast!");
    primaryStage.setScene(scene);
    primaryStage.show();

answered Oct 28, 2016 at 21:47

Sergej Isbrecht

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