所以，我重新编写了你的部分代码。
如果您运行旧代码并添加了一些输出，那么在输出中您将看到实际问题所在：实际调整大小的次数。第二个问题是：如果你使用 getScaledInstance() 一起 new ImageIcon() ，imageicon初始化将等待图片完全创建/绘制完成。这将阻止所有其他ui操作，直到完成。
另一个小问题是您将控件重新添加到它们的父控件，这也可能会导致大量不必要的重新布局和重新绘制。
更简单的方法是使用/编写imagepanel。graphics.drawimage（）方法有一个imageobserver。无论何时调用drawimage（），都可以异步（非阻塞）绘制大型图像，因此不会有如此可怕的加载时间。另外，它将自己进行验证等，所以您不需要对此进行任何调用，这可能会导致不必要的布局和重新绘制。
在下面的示例中，我还包含了一些附加提示，如使用“final”、“early initialization”和“fail fast fail early”。
你看，解决办法是多么简单：
例子：

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Image;
import java.awt.Toolkit;
import java.awt.event.ComponentAdapter;
import java.awt.event.ComponentEvent;
import java.net.URL;

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

public class MunchkinLauncher extends JFrame {

    private static final long serialVersionUID = 1598309638008663371L;

    private final Toolkit       toolkit     = Toolkit.getDefaultToolkit();
    private final Dimension     screenDim   = toolkit.getScreenSize();
    private final JPanel        contentPane = new JPanel(null);
    private final JButton       btnHostGame = new JButton("Host Game");     // make as many 'final' as possible. earlier initialization saves you from a lot of problems when it comes to inheritance and events
    private final JButton       btnJoinGame = new JButton("Join Game");
    private final ImagePanel    imageLabel  = new ImagePanel();

    private final Image backgroundImageicon; // pardon my camelCase, imo composite logic is more important

    public static void main(final String[] args) {
        new MunchkinLauncher().setVisible(true);
    }

    public MunchkinLauncher() {
        setDefaultCloseOperation(EXIT_ON_CLOSE); // should always be first, you never know what exception happens next and this might keep a lot of JVMs running if due to exception a visual jframe is not disposed properly
        setTitle("Munchkin Launcher");
        setLocation(screenDim.width / 4, screenDim.height / 4);
        setSize(screenDim.width / 2, screenDim.height / 2);
        setMinimumSize(new Dimension(700, 387));
        setLayout(null);

        contentPane.setLayout(null);
        contentPane.setBackground(new Color(253, 205, 136));
        contentPane.add(imageLabel);
        contentPane.add(btnHostGame);
        contentPane.add(btnJoinGame);
        setContentPane(contentPane);

        loadComponents();

        backgroundImageicon = loadBgImage();
        imageLabel.setImage(backgroundImageicon);

        loadBounds();

        addActionListeners();

        //      setVisible(true); // should be last, unless you need something specific to happen durint init
        // and ACTUALLY it should be used outside the CTOR so caller has more control
    }

    private Image loadBgImage() {
        final long nowMs = System.currentTimeMillis();
        final URL res = this.getClass().getResource("/Munchkin_logo.jpg");

        // load Image
        //      final ImageIcon ret1 = new ImageIcon(res); // is not as good, we eventually only need an Image, we do not need the wrapper that ImageIcon provides
        //      final BufferedImage ret2 = ImageIO.read(res); // is better, but gives us BufferedImage, which is also more than we need. plus throws IOException
        final Image ret3 = Toolkit.getDefaultToolkit().getImage(res); // best way. If behaviour plays a role: Loads the image the same way that ImageIcon CTOR would.

        final long durMs = System.currentTimeMillis() - nowMs;
        System.out.println("Loading BG Image took " + durMs + "ms.");

        return ret3;
    }

    private void loadComponents() {}

    void loadBounds() {
        final int width = contentPane.getSize().width;
        final int height = contentPane.getSize().height;
        btnHostGame.setBounds(width / 2 - 300, height * 2 / 3, 250, 100);
        btnJoinGame.setBounds(width / 2 + 50, height * 2 / 3, 250, 100);
        imageLabel.setBounds(20, 0, width - 40, height * 2 / 3);
    }

    private void addActionListeners() {
        addComponentListener(new ComponentAdapter() {
            @Override public void componentResized(final ComponentEvent e) {
                super.componentResized(e);
                loadBounds(); // this access needs protected loadBounds() or synthetic accessor method
            }
        });
        btnHostGame.addActionListener(e -> {
            System.out.println("MunchkinLauncher.addActionListeners(1)");
            //          new MatchCreation();
            dispose();
        });
        btnJoinGame.addActionListener(e -> {
            System.out.println("MunchkinLauncher.addActionListeners(2)");
            //          new MatchJoin();
            dispose();
        });
    }
}

以及图像面板：

import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.RenderingHints;

import javax.swing.JPanel;

public class ImagePanel extends JPanel {

    private static final long serialVersionUID = 6196514831308649310L;

    private Image mImage;

    public ImagePanel(final Image pImage) {
        mImage = pImage;
    }
    public ImagePanel() {}

    public Image getImage() {
        return mImage;
    }
    public void setImage(final Image pImage) {
        mImage = pImage;
        repaint();
    }

    @Override protected void paintComponent(final Graphics pG) {
        if (mImage == null) return;

        final Graphics2D g = (Graphics2D) pG;
        g.setRenderingHint(RenderingHints.KEY_ALPHA_INTERPOLATION, RenderingHints.VALUE_ALPHA_INTERPOLATION_QUALITY);// can add more
        g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        g.drawImage(mImage, 0, 0, getWidth(), getHeight(), this);
    }
}

编辑：另一方面，您应该将嵌入的图像大小限制为合理的大小，例如，如果在全屏显示中使用4k。作为一个窗口控件显示，720p通常就足够了。其他的一切只会让你的软件膨胀，让它变慢。在很多情况下，建议使用矢量图形。