Putting objects onto Frames

问题

I am creating a simple die rolling simulation that rolls dice when a button is pressed. I didn't add the action listener yet because I have a problem with showing up an object onto my frame. I created a class that generates a dice and gets an image of the dice with the number rolled but I can't seem to add the object onto my frame.

public class DieFrame extends JComponent 
{
    private static final int FRAME_WIDTH = 500;
    private static final int FRAME_HEIGHT = 240;
    private JButton rollButton;
    private JLabel player1Score,player2Score, playerTurn;

    Die die1 = new Die(1);
    Die die2 = new Die(1);

    public DieFrame()
    {
        JPanel panel = new JPanel();
        player1Score = new JLabel("Player 1 score:  ");
        player2Score = new JLabel("Player 2 score:  ");
        panel.add(player1Score);
        panel.add(player2Score);
        panel.setBackground(Color.yellow);
        add(panel, BorderLayout.NORTH);
        setSize(FRAME_WIDTH, FRAME_HEIGHT);
        createPlayerTurnPanel();
        createDiePanel();

    }
    public void createPlayerTurnPanel()
    {
        JPanel turnPanel = new JPanel();
        playerTurn = new JLabel("Player ");
        rollButton = new JButton("Roll");
        turnPanel.add(playerTurn);
        turnPanel.add(rollButton);

        add(turnPanel, BorderLayout.SOUTH);
    }

    public void createDiePanel()
    {
        JPanel diePanel = new JPanel();
        diePanel.add(die1);
        diePanel.setBackground(Color.BLACK);
        add(diePanel, BorderLayout.CENTER);
    }
}

回答1:

public class DieFrame extends JComponent 

Your class is extending JComponent.

 add(panel, BorderLayout.NORTH);

You are assuming the component will use a BorderLayout. Well it doesn't. It doesn't use any layout manager.

Only the content pane of a JFrame (JDialog) will use a BorderLayout by default.

Don't extend JComponent. It is not designed to be used as a container and will not work properly if you attempt to use it as a container.

Instead you can extend JPanel which is designe to be used as a containter, although its layout manager is a FlowLayout, so you will need to set the layout to a BorderLayout.

Although you really should not be extending JPanel either since you are not adding new functionality to the panel. Instead you should create a class that will return you a panel with the components. Read the section from the Swing tutorial on How to Use Menus. The MenuLookDemo has a working example using this approach.

来源：https://stackoverflow.com/questions/62354207/putting-objects-onto-frames