java - 多个 JPanel 完全重叠

Question

我正在创建一个程序，我可以在其中绘制地图并向其添加不同的道路等。我计划在一个 jpanel 上添加地图地形，在另一个 jpanel 上添加道路等，彼此叠加。但我不能让他们工作。我不知道如何将多个 jpanel 完全叠加在一起并让它们都能够绘制。

Answer 1

解决这个问题的基本方法是使用 aJLayeredPane和类似的东西GridBagLayout。

这JLayeredPane将使您更好地控制各个层的 z 深度，并GridBagLayout允许您根据需要将组件相互叠加。

你也可以看看OverlayoutLayout，但从未使用过，我无法评论。

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Image;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLayeredPane;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class MapLayers {

    public static void main(String[] args) {
        new MapLayers();
    }

    public MapLayers() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                MapPane mapPane = new MapPane();
                try {
                    mapPane.addLayer(new ImageLayer(ImageIO.read(new File("Ponie.png")), 360, 10));
                    mapPane.addLayer(new ImageLayer(ImageIO.read(new File("Layer01.png")), 0, 0));
                } catch (IOException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(mapPane);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class ImageLayer extends JComponent {

        private Image bg;
        private int xOffset;
        private int yOffset;

        public ImageLayer(Image image, int x, int y) {
            bg = image;
            xOffset = x;
            yOffset = y;
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            if (bg != null) {
                Graphics2D g2d = (Graphics2D) g.create();
                g2d.drawImage(bg, xOffset, yOffset, this);
                g2d.dispose();
            }
        }

    }

    public class MapPane extends JLayeredPane {

        private BufferedImage bg;

        public MapPane() {
            try {
                bg = ImageIO.read(new File("PirateMap.jpg"));
            } catch (IOException exp) {
                exp.printStackTrace();
            }
            setLayout(new GridBagLayout());
        }

        public void addLayer(JComponent layer) {

            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridx = 0;
            gbc.gridy = 0;
            gbc.weightx = 1;
            gbc.weighty = 1;
            gbc.fill = GridBagConstraints.BOTH;

            add(layer, gbc);

        }

        @Override
        public Dimension getPreferredSize() {
            return bg == null ? new Dimension(200, 200) : new Dimension(bg.getWidth(), bg.getHeight());
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            if (bg != null) {
                Graphics2D g2d = (Graphics2D) g.create();
                int x = (getWidth() - bg.getWidth()) / 2;
                int y = (getHeight()- bg.getHeight()) / 2;
                g2d.drawImage(bg, x, y, this);
                g2d.dispose();
            }
        }
    }
}

查看如何使用 LayeredPanes了解更多详细信息

Answer 2

您是否打算使JPanels 透明？您可以调用setOpaque(false)，这将防止面板淹没背景矩形。Swing 教程中有一些关于堆叠窗格的有用信息。