java - .drawLine() 问题和缓冲图像

Question

我有一个绘画程序，并且我已经完成了所有按钮和 slider ，但是我在实际绘画本身方面遇到了问题。当我将光标拖过屏幕而不是一条不间断的线时，我几乎得到了一条我不想要的虚线。以下是 JPanel 和 BufferedImage 中 MouseListener 的代码:

      public void mouseDragged(MouseEvent e) {
          Graphics g=buffered.getGraphics();
          g.setColor(mycol);
              Graphics2D graph=(Graphics2D)g;
          BasicStroke stroke=new BasicStroke(30);
          graph.setStroke(stroke);
              //  g.fillRect(xcor, ycor, 20, 20);
          /  /varx=e.getX();
            ycor=e.getY();
             xcor=e.getX();
            int bad=xcor;
            int good=ycor;
            graph.drawLine(xcor, ycor, bad, good);
           // buffered.setRGB(xcor, ycor, mycol.getRGB());
            repaint();
            // g.drawLine(xcor, ycor, x, x)
             repaint();


        }

Answer 1

• 只是为了证明我的评论是正确的，我添加了这个答案，尽管有点轻微评论的更改在这里，这是使用mousePressed(...) 而不是 mouseClicked(...)。

• 还有一个补充，因为您想要的 Graphics2D 对象BufferedImage 因此不要使用 getGraphics() 而是始终使用createGraphics() 返回 Graphics2D 对象，因此您真的不必担心 Actor 阵容的问题。

  请看一下下面的示例:

======================

import java.awt.*;
import java.awt.image.BufferedImage;
import java.awt.event.*;
import java.net.URL;
import javax.swing.*;
import javax.imageio.ImageIO;

public class PaintingExample {

    private BufferedImage bImage;
    private ImageIcon image;
    private JLabel imageLabel;
    private int xClicked = 0;
    private int yClicked = 0;
    private int xDragged = 0;
    private int yDragged = 0;

    private MouseAdapter mouseListener = new MouseAdapter() {
        @Override
        public void mousePressed(MouseEvent me) {
            xClicked = me.getX();
            yClicked = me.getY();
        }

        @Override
        public void mouseDragged(MouseEvent me) {
            xDragged = me.getX();
            yDragged = me.getY();

            Graphics2D g2 = bImage.createGraphics();
            g2.setColor(Color.WHITE);
            BasicStroke stroke=new BasicStroke(30);
            g2.setStroke(stroke);
            g2.drawLine(xClicked, yClicked, xDragged, yDragged);
            g2.dispose();
            imageLabel.setIcon(new ImageIcon(bImage));
        }
    };

    public PaintingExample() {
        try {
            bImage = ImageIO.read(new URL(
                    "http://i.imgur.com/fHiBMwI.jpg"));
            image = new ImageIcon(bImage);          
        } catch(Exception e) {
            e.printStackTrace();
        }
    }

    private void displayGUI() {
        JFrame frame = new JFrame("Painting on Image");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel contentPane = new JPanel();
        imageLabel = new JLabel(image);
        imageLabel.addMouseListener(mouseListener);
        imageLabel.addMouseMotionListener(mouseListener);

        contentPane.add(imageLabel);

        frame.setContentPane(contentPane);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    public static void main(String... args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new PaintingExample().displayGUI();
            }
        });
    }
}