如何解決在JavaSwing中顯示JPanel元素的問題？

我在顯示位于 JFrame 中另一個 JPanel 元素中的 JPanel (Page) 元素時遇到問題。

Abstract Class Page 正在擴展 JPanel 并為其提供一些新引數。

public abstract class Page extends JPanel implements KeyListener {
    protected String pageName;
    protected Color backgroundColor;

    public Page(String name, Color backgroundColor) {
        this.pageName = name;
        this.backgroundColor = backgroundColor;

        addKeyListener(this);
        this.setFocusable(true);
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        this.setSize((int) PAGE_WIDTH, (int) PAGE_HEIGHT);
        this.setBackgroundColor(backgroundColor);
    }

    /* keyTyped method is not needed in usage, so it is empty */
    @Override
    public void keyTyped(KeyEvent e) {}

    /* keyTyped method is not needed in usage, so it is empty */
    @Override
    public void keyReleased(KeyEvent e) {}

    @Override
    public abstract void keyPressed(KeyEvent e);

    public String getPageName() {
        return pageName;
    }

    public void setPageName(String name) {
        this.pageName = name;
    }

    public Color getBackgroundColor() {
        return backgroundColor;
    }

    public void setBackgroundColor(Color backgroundColor) {
        this.backgroundColor = backgroundColor;
    }
}

我在 Game Board 建構式中初始化 Page 物件，然后嘗試在 GameBoard 類的 printComponent() 方法中使用它。

public class GameBoard extends JPanel {
    private static GameBoard instance = null;
    private Page currentPage = new MainMenuPage();
    private JPanel dialog = Dialog.getInstance();

    private GameBoard() {}

    public static GameBoard getInstance() {
        if (instance == null) {
            instance = new GameBoard();
        }
        return instance;
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);

        this.setSize(WINDOW_WIDTH, WINDOW_HEIGHT);
        this.setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
        this.setBackground(Color.WHITE);

        JPanel container = new JPanel();
        container.setLayout(new BoxLayout(container, BoxLayout.X_AXIS));
        container.setSize(WINDOW_WIDTH, (int) PAGE_HEIGHT);
        container.setBackground(Color.decode("#333333"));

        container.add(currentPage);
        container.add(dialog);
        this.add(container);
    }

    public Page getCurrentPage() {
        return currentPage;
    }

    public void setCurrentPage(Page currentPage) {
        this.currentPage = currentPage;
    }

    public JPanel getDialog() {
        return dialog;
    }

    public void setDialog(JPanel dialog) {
        this.dialog = dialog;
    }
}

當視窗出現時，頁面元素不顯示，如下面的截圖所示。主類代碼：

public class GameApplication {
    private static JFrame window;
    private static GameBoard gameBoard;

    public static void main( String[] args ) {
        setupWindow();
        createGameBoard();
    }

    private static void setupWindow() {
        System.out.println("[GameApplication]: Creating window");
        window = new JFrame("Dungeon Master");
        window.setVisible(true);
        window.setResizable(false);
        window.setBounds(200, 80, WINDOW_WIDTH, WINDOW_HEIGHT);
        window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

    private static void createGameBoard() {
        System.out.println("[GameApplication]: Creating GameBoard");
        gameBoard = GameBoard.getInstance();
        window.add(gameBoard);
        gameBoard.requestFocusInWindow();
    }

    /* Game Init Method? */
}

uj5u.com熱心網友回復：

所以我通過洗掉容器解決了這個問題：

public class GameBoard extends JPanel {
    private static GameBoard instance = null;
    private Page currentPage = new MainMenuPage();
    private final JPanel dialog = Dialog.getInstance();

    private final JPanel keyInfo = new JPanel();
    private final JLabel keyInfoLabel = new JLabel("Q - quit the game | S - go to start menu | C - clear dialog");

    private GameBoard() {}

    public static GameBoard getInstance() {
        if (instance == null) {
            instance = new GameBoard();
        }
        return instance;
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        this.setSize(WINDOW_WIDTH, WINDOW_HEIGHT);

        currentPage.setBounds(0, 0, PAGE_WIDTH, PAGE_HEIGHT);
        currentPage.setBackground(Color.decode("#121212"));

        dialog.setBounds(PAGE_WIDTH, 0, DIALOG_WIDTH, PAGE_HEIGHT);
        dialog.setBackground(Color.decode("#333333"));

        keyInfo.setBounds(0, PAGE_HEIGHT, WINDOW_WIDTH, WINDOW_HEIGHT);
        keyInfo.setBackground(Color.decode("#f6f9f9"));
        keyInfo.setLayout(new BoxLayout(keyInfo, BoxLayout.X_AXIS));
        
        keyInfoLabel.setForeground(Color.decode("#121212"));
        keyInfo.add(keyInfoLabel);

        this.add(currentPage);
        this.add(dialog);
        this.add(keyInfo);
    }

    public Page getCurrentPage() {
        return currentPage;
    }

    public void setCurrentPage(Page currentPage) {
        this.currentPage = currentPage;
    }

    public JPanel getDialog() {
        return dialog;
    }
}

現在看起來像這樣：

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