如何在 Java Swing 应用程序中保留和删除多个图形对象

Question

我有一个图像，我在上面使用预定义的位置来创建带有颜色的图形对象。通过鼠标单击，我尝试在其上创建一些带有颜色的椭圆形。实际上我无法实现这个目标。因为，当我单击预定义的位置时，我可以在其上创建一个椭圆形，但是当我单击另一个预定义位置时，第一个椭圆形已经消失了。

椭圆可以通过单击两次来删除它。

看看这个，

public class PrintDialog extends javax.swing.JDialog{
private int count = 0;
private int count_1 = 0;
/**
 * Creates new form PrintFeetDialog
 */
public PrintDialog(java.awt.Frame parent, boolean modal)
{
    super(parent, modal);
    initComponents();
    ImagePanel panel = new ImagePanel("Areas.jpg");
    this.getContentPane().add(panel);
    this.setResizable(false);
    this.setLocationRelativeTo(panel);
    this.pack();
}
private void formMouseClicked(java.awt.event.MouseEvent evt)                                  
{                                      
    // TODO add your handling code here:
    System.out.println("Print y - " + evt.getY());
    System.out.println("Print x - " + evt.getX());
    if ((evt.getX() >= 68 && evt.getX() <= 84) && (evt.getY() >= 44 && evt.getY() <= 72))
    {
        Graphics g = getGraphics();
        count++;
        if (count == 1)
        {
            g.setColor(Color.red);
            g.fillOval(66, 52, 20, 20);
            //  repaint();
        } else if (count > 1)
        {
            g.setColor(new Color(-3692899));
            g.fillOval(66, 52, 20, 20);
            repaint();
            count = 0;
        }
        g.dispose();
    }
    if ((evt.getX() >= 137 && evt.getX() <= 157) && (evt.getY() >= 50 && evt.getY() <= 75))
    {
        Graphics g1 = getGraphics();
        count_1++;
        if (count_1 == 1)
        {
            g1.setColor(Color.RED);
            g1.fillOval(137, 54, 20, 20);
        } else if (count_1 > 1)
        {
            g1.setColor(new Color(-3692899));
            g1.fillOval(66, 52, 20, 20);
            repaint();
            count_1 = 0;
        }
        g1.dispose();
    }
}
}   

图像面板类

public class ImagePanel extends JPanel{
private Image img;
public ImagePanel(String img, String str)
{
    //this(new ImageIcon(img).getImage());    
}
public ImagePanel(String path)
{
    Image img = new ImageIcon(path).getImage();
    this.img = img;
    Dimension size = new Dimension(img.getWidth(null), img.getHeight(null));
    setPreferredSize(size);
    setMinimumSize(size);
    setMaximumSize(size);
    setSize(size);
    setLayout(null);
     try
    {
        BufferedImage image = ImageIO.read(new File(path));
        int rgb = image.getRGB(66, 52);
        System.out.println("Colour is: "+rgb);
    }
    catch(IOException e)
    {
        e.printStackTrace();
    }
}
public void paintComponent(Graphics g)
{
    super.paintComponent(g);
    g.drawImage(img, 0, 0, null);
}
}

有什么想法吗？

谢谢。

Answer 1

不要使用 getGraphics ，这不是自定义绘画的工作方式，请参阅 AWT 中的绘画和 摆动 和 执行自定义绘画 了解更多详情

基本思想是，您需要某种 List ，您将每个形状添加到其中。 发生mouseClicked时，您循环访问列表并检查鼠标单击是否出现了其中一个形状，如果是，则从List中删除该形状，如果没有，则在单击该形状的位置创建一个新形状并将其添加到List。

然后，在 paintComponent 方法中使用此List对形状进行物理绘制。

此示例扩展在自定义绘制中添加ImagePanel

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Shape;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.Ellipse2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class Test {
    public static void main(String[] args) {
        new Test();
    }
    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }
                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new DrawPane("/Volumes/Disk02/Dropbox/MegaTokyo/thumnails/0.jpg"));
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }
    public class ImagePanel extends JPanel {
        private Image img;
        public ImagePanel(String img, String str) {
            //this(new ImageIcon(img).getImage());    
        }
        public ImagePanel(String path) {
            Image img = new ImageIcon(path).getImage();
            this.img = img;
            try {
                BufferedImage image = ImageIO.read(new File(path));
                int rgb = image.getRGB(66, 52);
                System.out.println("Colour is: " + rgb);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        @Override
        public Dimension getPreferredSize() {
            return img == null ? new Dimension(200, 200) : new Dimension(img.getWidth(this), img.getHeight(this));          
        }
        @Override
        public void paintComponent(Graphics g) {
            super.paintComponent(g);
            g.drawImage(img, 0, 0, null);
        }
    }
    public class DrawPane extends ImagePanel {
        private List<Shape> shapes;
        public DrawPane(String img, String str) {
            super(img, str);
            init();
        }
        public DrawPane(String path) {
            super(path);
            init();
        }
        protected void init() {
            shapes = new ArrayList<>(25);
            addMouseListener(new MouseAdapter() {
                @Override
                public void mouseClicked(MouseEvent e) {
                    boolean clicked = false;
                    Iterator<Shape> it = shapes.iterator();
                    while (it.hasNext()) {
                        Shape shape = it.next();
                        if (shape.contains(e.getPoint())) {
                            it.remove();
                            clicked = true;
                            break;
                        }
                    }
                    if (!clicked) {
                        shapes.add(new Ellipse2D.Double(e.getX() - 10, e.getY() - 10, 20, 20));
                    }
                    repaint();
                }
            });
        }
        @Override
        public void paintComponent(Graphics g) {
            super.paintComponent(g); 
            Graphics2D g2d = (Graphics2D) g.create();
            g2d.setColor(Color.RED);
            for (Shape shape : shapes) {
                g2d.draw(shape);
            }
            g2d.dispose();
        }
    }
}