Java CardLayout IllegalArgumentException

Question

我正在制作一个使用 CardLayout 在四个 JPanel（gamePanel、startMenu、pauseMenu 和 levelMenu）之间切换的游戏。我收到异常 "java.lang.IllegalArgumentException: wrong parent for CardLayout"。但是，我将所有卡片添加到面板，面板具有布局管理器 CardLayout，所以我不明白为什么面板不是父级。我查看了 CardLayout 的 Java 教程以及涉及 IllegalArgumentException 的 Stack Overflow 问题，但我看不出我做错了什么。提前致谢。

游戏：

import java.awt.CardLayout;

import javax.swing.JFrame;
import javax.swing.JPanel;

/** Class Contains the main method and the game's logic */
public class Game {

    /** Field The JFrame for the game */
    public JFrame frame = new JFrame();

    /** Field The JPanel that uses CardLayout to only display one JPanel at a time */
    private JPanel panel;

    /** Field The CardLayout that controls which JPanel is showing */
    private CardLayout cardLayout;

    /** Field The JPanel that displays the playing field */
    private JPanel gamePanel = new JPanel();

    /** Field The first menu the player sees */
    private JPanel startMenu = new JPanel();

    /** Field The menu the player sees when the game is paused */
    private JPanel pauseMenu = new JPanel();

    /** Field The menu that allows the player to select which level to play */
    private JPanel levelMenu = new JPanel();

    /** Constructor for Game with no parameters */
    public Game() {
        initializeGame();
    }

    /** Main method of Game */
    public static void main(String argv[]) {
        new Game();
    }

    /** Sets up frame and panel */
    private void initializeGame() {
        panel = createPanel();

        panel = (JPanel) frame.getContentPane();

        cardLayout.show(panel, "startMenu");
    }

    private JPanel createPanel() {
        panel = new JPanel();
        cardLayout = new CardLayout();
        panel.setLayout(cardLayout);

        panel.add(startMenu, "startMenu");
        panel.add(pauseMenu, "pauseMenu");
        panel.add(levelMenu, "levelMenu");
        panel.add(gamePanel, "gamePanel");

        return panel;
    }

}

Answer 1

您已将 panel 变量分配给两个对象，一个是通过 createPanel() 方法创建的，另一个是通过获取 contentPane 创建的。一种是将组件添加到 GUI，另一种是调用 show 方法，因此 JVM 会报错。解决方案是不这样做，只将一个对象赋值给这个变量一次。

要了解我的意思，请在您的代码中搜索

 panel =

并查看弹出的行。

Java CardLayout IllegalArgumentException

Java CardLayout IllegalArgumentException

java

swing

layout-manager

cardlayout