java - Swing Graphics 对象未在 JLabel 中绘制图像

Question

我正在创建一个 Java 程序，它通过 TCP 套接字连接在 map 的二维图像上接收和绘制 GPS 坐标。构造函数创建 JFrame 和图形组件，然后启动一个 SwingWorker 线程来处理从套接字获取坐标，然后绘制一个椭圆来表示 map 上的修复。

我总是能够通过连接接收数据，但程序无法可靠地在图像上绘制点。

任何建议，谢谢!

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;
import java.io.File;
import java.util.List;

import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingWorker;

import connectivity.TelitSocketServer;
import calculations.PlottingMath;
import objects.ElephantFix;

@SuppressWarnings("serial")
public class Gui 
{
    protected JFrame mainWindow;

    protected JPanel mapArea = new JPanel();

    private ReceiveFix rfix;

    public Gui()
    {
        // TODO Auto-generated constructor stub

        mainWindow =  new JFrame();

        // Load map image
        Image map = null;
        try
        {
            File mapImage = new File("map_images/AWE_PLOT.JPG");
            map = ImageIO.read(mapImage);

        } catch (Exception e)
        {
            System.out.println(e.toString());
        }



        JLabel label = new JLabel(new ImageIcon(map));
        mapArea.add(label);


        // Map Image Dimensions

        mainWindow.getContentPane().add(mapArea, "Center");

        mainWindow.setSize(471, 670);
        mainWindow.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        mainWindow.setTitle("ElePlotter");
        mainWindow.setVisible(true);

        rfix = new ReceiveFix();
        rfix.execute();

}

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

}

private class ReceiveFix extends SwingWorker<Void, ElephantFix>
{

    @Override
    protected Void doInBackground()
    {
        // Start the server
        String fix = "";

        TelitSocketServer currentConnection = new TelitSocketServer();
        try
        {
            // Wait for client to connect
            currentConnection.intializeConnection();

            while (true)
            {
                // Parse and convert received GPS fix into arc radians  
                fix = currentConnection.readLine();

                String[] split = fix.split(" ");


                double latWholeDegrees = Double.parseDouble(split[0]
                        .substring(0, 3));
                double longWholeDegrees = Double.parseDouble(split[1]
                        .substring(0, 3));

                double latMinutes = Double.parseDouble(split[0]
                        .substring(3)) * .166667;
                double longMinutes = Double.parseDouble(split[1]
                        .substring(3)) * .166667;


                double lat = latWholeDegrees - latMinutes / 10;
                double lon = longWholeDegrees + longMinutes / 10;

                publish(new ElephantFix(lat, lon));
            }

        } catch (Exception e)
        {

            e.printStackTrace();
        }

        // Return null if somehow unable to publish node data
        return null;

    }


    @Override
    protected void process(List<ElephantFix> fixes)
    {
        int x, y;
        // Get the most recently published node
        ElephantFix aFix = fixes.get(fixes.size() - 1);



        // Translate lat/long into map X/Y pixel
        x = PlottingMath.getCurrentPixelX(aFix.getLatitude(),
                aFix.getLongitude());
        y = PlottingMath.getCurrentPixelY(aFix.getLatitude(),
                aFix.getLongitude());


        // Plot on image
        Graphics g = mapArea.getGraphics();

        g.setColor(Color.RED);

        g.fillOval(x, y, 15, 15);

        // mapArea.validate();
        //
        // mapArea.repaint();
        //
        // Gui.this.repaint();

    }
}

}

Answer 1

mapArea.getGraphics(); 并不是 Swing 中自定义绘画的完成方式。

先看看 Performing Custom Painting了解更多详情。

将组件添加到容器可确保子组件始终绘制在容器上...

JLabel label = new JLabel(new ImageIcon(map));
mapArea.add(label);

你把它倒过来了。将 label 和 mapArea 添加到同一个容器中可能会更好

您需要克服的下一个问题是您需要让绘画组件驻留在标签的顶部。

为此你可以...

• 使用 glass pane
• 使用 OverlayLayout
• 使用 GridBagLayout

用例子更新

有多种方法可以实现这一点，您可以使用多个组件作为图层，您可以在图层上添加其他组件或执行自定义绘画。

这并不像听起来那么容易。大多数布局管理器不考虑共享同一空间的两个组件。您还必须管理层之间的连接，因此如果 map 位于最低层的中心，但可用空间大于或小于 map ，偏移量开始漂移……困惑……

一个更简单的解决方案是使用单个组件并将所有内容渲染到它上面，例如......

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class TestMap {

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

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

                MapPane pane = new MapPane();
                pane.dropPinAt(174, 147);

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

    public class MapPane extends JPanel {

        private BufferedImage img;
        private BufferedImage pin;
        private List<Point> pins;

        public MapPane() {
            pins = new ArrayList<>(25);
            try {
                img = ImageIO.read(getClass().getResource("/Map.jpg"));
                pin = ImageIO.read(getClass().getResource("/Pin.png"));
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }

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

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            if (img != null) {
                Graphics2D g2d = (Graphics2D) g.create();

                int x = (getWidth() - img.getWidth()) / 2;
                int y = (getHeight() - img.getHeight()) / 2;

                g2d.drawImage(img, x, y, this);

                for (Point p : pins) {
                    // Offset the pin x/y
                    // to allow the point to land on the desired location
                    p.x -= 6;
                    p.y -= 64;
                    System.out.println(p);
                    g2d.drawImage(pin, p.x, p.y, this);

                }

                g2d.dispose();
            }
        }

        protected void dropPinAt(int x, int y) {
            pins.add(new Point(x, y));
        }
    }

}