JAVA BEGINNERS Create and roll Dice

Question

I want to create a Dice Rolling Simulator. This is what I've gotten so far.

public class RollDice {
    private static class rollDice extends JPanel {
        public void paintComponent(Graphics g) {
            super.paintComponent(g);
            // custom draw code goes here
        }
    }

    public static void main(String[] args) { 
        JLabel message = new JLabel ("\nRoll the Die!\n", JLabel.CENTER); 
        message.setForeground(Color.BLACK); 
        message.setBackground(Color.WHITE); 
        message.setFont(new Font("Courier", Font.PLAIN, 25));
        message.setOpaque(true);

        JButton roll = new JButton("ROLL");

        JPanel content = new JPanel(); 
        content.setLayout(new BorderLayout()); 
        content.add(message, BorderLayout.NORTH);
        content.add(roll, BorderLayout.SOUTH);

        JFrame window = new JFrame("Roll Dice"); 
        window.setContentPane(content); 
        window.setSize(250,300); 
        window.setLocation(300,300); 
        window.setVisible(true);
    }
}

I have gotten a JFrame, JLabel, and the Button which says roll, the simple things.

What I am trying to figure out is how to create two dice in the JPanel, and also how to make it roll when the button "ROLL" is clicked, using math.Random and Graphics.

I would appreciate if it was as simple as possible, since I am not very advanced in the programming world and recently started. I would appreciate it if you would try to explain as detailed as possible before you give me the answer, so that I have a chance to try and figure it out myself beforehand.

Thanks!

score 1 · Answer 1 · edited Jun 20 '20 at 09:12

Like fd. said, you need components for the die. Let's use JLabel as the components. They can be arranged like this:

+==============================+
|        Roll the Die!         |
|   +---------+  +---------+   |
|   |         |  |         |   |
|   |  dice1  |  |  dice2  |   |
|   |         |  |         |   |
|   +---------+  +---------+   |
| +--------------------------+ |
| |           ROLL           | |
| +--------------------------+ |
+==============================+

You can set an ImageIcon on the label (Check out: Java: how to add image to Jlabel?), so create 6 images of the different positions of the dice. When the button is pushed, a random number (between 1 and 6) will be generated (using Math.random). Each number represents an image. Set the image of the JLabel based on this number.

For this to happen you need a ActionListener. Create a custom ActionListener like below (Note I did it for one die):

public class RollDiceActionListener implements ActionListener {

    private JLabel dice;
    
    public RollDiceActionListener(JLabel dice) {
        this.dice = dice;
    }
    
    @Override
    public void actionPerformed(ActionEvent e) {
        int rnd = (int)(Math.random() * 6) + 1;
        
        switch (rnd) {
        case 1:
            dice.setIcon(new ImageIcon("/path/to/dice_1.png"));
            break;
        case 2:
            dice.setIcon(new ImageIcon("/path/to/dice_2.png"));
            break;
        case 3:
            dice.setIcon(new ImageIcon("/path/to/dice_3.png"));
            break;
        case 4:
            dice.setIcon(new ImageIcon("/path/to/dice_4.png"));
            break;
        case 5:
            dice.setIcon(new ImageIcon("/path/to/dice_5.png"));
            break;
        case 6:
            dice.setIcon(new ImageIcon("/path/to/dice_6.png"));
            break;
        }
    }
}

Each time the button is pressed, the ActionPerformed method will be invoked and randomly change the icons of each JLabel, simulating a roll of the die.

To add your custom ActionListener to the button:

roll.addActionListener(new RollDiceActionListener(die));

The ActionListener needs to modify the Jlabels representing the dice, so don't forget to add it as a parameter to the constructor of you listener.

Hope this helps. Good luck!

score 0 · Answer 2 · answered Apr 23 '15 at 09:22

If we ignore having some kind of custom draw/animation for the dice for now, then your code is missing a few functional elements:

instantiating objects for the UI components for the 2 dice
adding those components to your layout (you may need to create a nested layout object here as well, depending on how you'd like them positioned)
defining an ActionListener object to generate the random numbers for your dice rolls and update the dice UI components
adding the ActionListener to your roll button

Let me know if you have any questions (add a comment here) and I will refine my answer. — Mike Tunnicliffe, Apr 23 '15 at 09:23

JAVA BEGINNERS Create and roll Dice

2 Answers2