如何从多个外部类中提取JPanel？

Question

我目前正在制作一个主菜单和一个你实际玩的世界的游戏。

我有一个名为Game的类，它继承自JPanel，并实现了Runnable，MouseListener，KeyListener和ActionListener接口（仅包括重要部分）

我还有两个类，分别用于处理世界内部和外部的机制。

游戏课程：

public class Game extends JPanel implements Runnable, KeyListener, MouseListener, ActionListener
{
    protected JFrame frame;
    private Timer timer = new Timer(25, this);

    private World world;
    private Player player = new Player();

    private boolean draw;

    Game(World world)
    {
        frame = new JFrame("Minecraft 2D");
        this.world = world;
        player.enterWorld(world, this);
    }

    @Override
    protected void paintComponent(Graphics g)
    {
        Graphics2D g2d = (Graphics2D)g;

        if(draw)
        {
            g2d.setColor(new Color(255, 255, 255));
            g2d.fillRect(0, 0, frame.getWidth(), frame.getHeight());

            draw = false;
            //Here, the in-game mechanics should be handled
            if(player.inWorld())
            {
                Chunk chunk = player.getLoadedChunk();
                for(int x = 0; x < 16; x++)
                {
                    for(int y = 0; y < 16; y++)
                    {
                        Block block = chunk.getBlockAt(x, y);
                        BufferedImage texture = block.getTexture();

                        g2d.drawImage(block.getTexture(), x*32, y*32, texture.getWidth()*2, texture.getHeight()*2, null);
                    }
                }
            }
            //Here, the out-game mechanics should be handled
            else
            {

            }
        }
    }

    @Override
    public void actionPerformed(ActionEvent e)
    {
        this.repaint();
        draw = true;
    }

    @Override
    public void run()
    {
        draw = true;

        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        frame.add(this);
        frame.setMinimumSize(new Dimension(518, 540));
        frame.setResizable(false);
        frame.setLocationRelativeTo(null);
        frame.addKeyListener(this);
        frame.addMouseListener(this);
        frame.setFocusable(true);
        frame.setVisible(true);
        frame.pack();
        timer.start();
    }
}

其他两个类当前都有空实体。我只是不知道怎么做。

我希望当玩家在游戏中时，InWorldHandler类在面板上绘制，当玩家在主菜单中时，OutWorldHandler类在game类中调用。我该怎么做？

Answer 1

与其使用一个JPanel，不如尝试使用CardLayout，并根据确定您在程序中的位置的标志来切换是显示内部世界还是显示外部世界。

当您实现KeyListener时，我认为这是为了让您能够移动您的角色，请查看这个问题的公认答案：Keylistener不适用于JPanel，并使用KeyBindings代替。

还要避免使用setMimimum/max/PreferredSize（）并替代这些方法：我应该避免在JavaSwing中使用set（Preferred | max | Minimum）Size方法吗？

以该代码为例：

import java.awt.BorderLayout;
import java.awt.CardLayout;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class Game {
    private JFrame frame;
    private JButton button;
    private boolean status;
    private JPanel[] cards;
    private CardLayout cl;
    private JPanel gamePane;

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> new Game().createAndShowGUI());
    }

    private void createAndShowGUI() {
        frame = new JFrame(getClass().getSimpleName());
        button = new JButton("Switch Worlds");
        status = true; //True = Inner / False = Outer

        cl = new CardLayout();

        gamePane = new JPanel(cl);
        cards = new JPanel[2];

        cards[0] = new InnerWorld();
        cards[1] = new OuterWorld();

        gamePane.add(cards[0], "innerWorld");
        gamePane.add(cards[1], "outerWorld");

        button.addActionListener(e -> {
            status = !status;
            if (status) {
                cl.show(gamePane, "innerWorld");
            } else {
                cl.show(gamePane, "outerWorld");
            }
        });

        frame.add(gamePane);
        frame.add(button, BorderLayout.SOUTH);

        frame.pack();
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}

@SuppressWarnings("serial")
class InnerWorld extends JPanel {
    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);

        Graphics2D g2d = (Graphics2D) g;

        g2d.drawString("Inner World", 50, 50);
    }

    @Override
    public Dimension getPreferredSize() {
        return new Dimension(200, 200);
    }
}

@SuppressWarnings("serial")
class OuterWorld extends JPanel {
    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);

        Graphics2D g2d = (Graphics2D) g;

        g2d.drawString("Outer World", 50, 50);
    }

    @Override
    public Dimension getPreferredSize() {
        return new Dimension(200, 200);
    }
}