Not able to create an array of buttons in javafx in controller

Question

I am creating a grid of 4x4 buttons. I am trying to do this is in the controller. This is my code in initialize method.

    Button[][] gridButtons = new Button[4][4];
    for(int i=0; i<4; i++) {
        for (int j = 0; j<4; j++) {
            mainGrid.add(gridButtons[i][j], i, j);
            gridButtons[i][j].setText("1");
            gridButtons[i][j].minWidth(34.0);
            gridButtons[i][j].setMnemonicParsing(false);
            gridButtons[i][j].prefHeight(38.0);
            gridButtons[i][j].prefWidth(41.0);
            gridButtons[i][j].setTextAlignment(TextAlignment.CENTER);
        }
    }

The above code throws a NullPointerException at mainGrid.add(gridButtons[i][j], i, j);. But when I try to do the following, it works.

    Button gridButtons = new Button();
    gridButtons.setText("1");
    gridButtons.minWidth(34.0);
    gridButtons.setMnemonicParsing(false);
    gridButtons.prefHeight(38.0);
    gridButtons.prefWidth(41.0);
    gridButtons.setTextAlignment(TextAlignment.CENTER);
    mainGrid.add(gridButtons, 1, 1);

I'm not knowing what exactly is causing this issue.

awksp · Accepted Answer · 2014-05-17 04:24:04Z

4

When you create Button[][], you're creating the array of buttons. NOT the buttons inside the array. In other words, the array elements are still null after you create the array.

Simply add in gridButtons[i][j] = new Button(); as the first thing in your loop to initialize the Button and you should be good.

answered May 17, 2014 at 4:24

awksp

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