.drawLine()问题和缓冲图像

Question

我有一个绘画程序,我已经完成了所有按钮和滑块,但是我对实际绘画本身有问题.当我将光标拖过屏幕而不是一条连续线时,我几乎得到了一条我不想要的虚线.下面是该代码MouseListener中JPanel和BufferedImage:

      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

• 为了证明我的评论是正确的,我正在添加这个答案,虽然这里的评论略有改变,mousePressed(...)而不是使用 mouseClicked(...).

• 还有一个补充,因为你想要的Graphics2D是BufferedImageso 的对象,而不是getGraphics()总是使用 createGraphics()返回Graphics2D对象,因此你不必担心这里的Cast thingy.

  请看下面的例子:

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

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();
            }
        });
    }
}