在Swing内部的BufferedImage中绘画

| 我正在用Java编写的Paint应用程序上工作,并遇到了一些(更多)问题。我有一个gui和一个工作程序(kinda),我唯一的问题是用户绘制的线条和图形没有保存(在绘制下一个图形后消失)。 从过去的问题中,我了解到我将需要使用BufferedImage来存储图形,然后在我的绘画类中绘画它。 我的问题是,任何人都可以提供有关如何使用缓冲图像来存储和绘制图形的基本解释/示例,以及如果需要的话,如何将绘制的线条的颜色和粗细传递到存储的数组中。 多数民众赞成在我全班。
package javapaint;

import java.awt.*;
import javax.swing.*;

public class JavaPaintUI extends javax.swing.JFrame {

/** Creates new form JavaPaintUI */
public JavaPaintUI() {
    initComponents();
}

// <editor-fold defaultstate=\"collapsed\" desc=\"Generated Code\">                          
private void initComponents() {

    buttonGroup1 = new javax.swing.ButtonGroup();
    buttonGroup2 = new javax.swing.ButtonGroup();
    jPanel4 = new javax.swing.JPanel();
    jRadioButton9 = new javax.swing.JRadioButton();
    jRadioButton10 = new javax.swing.JRadioButton();
    jSlider2 = new javax.swing.JSlider();
    jLabel1 = new javax.swing.JLabel();
    jPanel2 = new Panel2();
    jPanel3 = new javax.swing.JPanel();
    jRadioButton3 = new javax.swing.JRadioButton();
    jRadioButton4 = new javax.swing.JRadioButton();
    jRadioButton5 = new javax.swing.JRadioButton();
    jRadioButton6 = new javax.swing.JRadioButton();
    jRadioButton7 = new javax.swing.JRadioButton();
    jRadioButton8 = new javax.swing.JRadioButton();
    jButton1 = new javax.swing.JButton();
    jButton2 = new javax.swing.JButton();

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
    setTitle(\"JavaPaint ~ Nick R\");

    jPanel4.setBorder(javax.swing.BorderFactory.createTitledBorder(\"Tool\"));

    buttonGroup1.add(jRadioButton9);
    jRadioButton9.setText(\"Pen\");
    jRadioButton9.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jRadioButton9ActionPerformed(evt);
        }
    });

    buttonGroup1.add(jRadioButton10);
    jRadioButton10.setText(\"Line\");
    jRadioButton10.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jRadioButton10ActionPerformed(evt);
        }
    });

    jSlider2.setMajorTickSpacing(10);
    jSlider2.setMaximum(51);
    jSlider2.setMinimum(1);
    jSlider2.setMinorTickSpacing(5);
    jSlider2.setPaintTicks(true);
    jSlider2.addChangeListener(new javax.swing.event.ChangeListener() {
        public void stateChanged(javax.swing.event.ChangeEvent evt) {
            jSlider2StateChanged(evt);
        }
    });

    jLabel1.setText(\"Stroke Size (Radius)\");

    javax.swing.GroupLayout jPanel4Layout = new javax.swing.GroupLayout(jPanel4);
    jPanel4.setLayout(jPanel4Layout);
    jPanel4Layout.setHorizontalGroup(
        jPanel4Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(jPanel4Layout.createSequentialGroup()
            .addContainerGap()
            .addGroup(jPanel4Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addComponent(jRadioButton9)
                .addComponent(jRadioButton10))
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 51, Short.MAX_VALUE)
            .addGroup(jPanel4Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                .addComponent(jLabel1)
                .addComponent(jSlider2, javax.swing.GroupLayout.PREFERRED_SIZE, 150, javax.swing.GroupLayout.PREFERRED_SIZE))
            .addContainerGap())
    );
    jPanel4Layout.setVerticalGroup(
        jPanel4Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(jPanel4Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
            .addComponent(jSlider2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addGroup(jPanel4Layout.createSequentialGroup()
                .addGroup(jPanel4Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jRadioButton9)
                    .addComponent(jLabel1))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                .addComponent(jRadioButton10)))
    );

    jPanel2.setBackground(new java.awt.Color(255, 255, 255));
    jPanel2.setBorder(javax.swing.BorderFactory.createBevelBorder(javax.swing.border.BevelBorder.RAISED));
    jPanel2.addMouseListener(new java.awt.event.MouseAdapter() {
        public void mousePressed(java.awt.event.MouseEvent evt) {
            jPanel2MousePressed(evt);
        }
        public void mouseReleased(java.awt.event.MouseEvent evt) {
            jPanel2MouseReleased(evt);
        }
    });
    jPanel2.addMouseMotionListener(new java.awt.event.MouseMotionAdapter() {
        public void mouseDragged(java.awt.event.MouseEvent evt) {
            jPanel2MouseDragged(evt);
        }
    });

    javax.swing.GroupLayout jPanel2Layout = new javax.swing.GroupLayout(jPanel2);
    jPanel2.setLayout(jPanel2Layout);
    jPanel2Layout.setHorizontalGroup(
        jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 596, Short.MAX_VALUE)
    );
    jPanel2Layout.setVerticalGroup(
        jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 357, Short.MAX_VALUE)
    );

    jPanel3.setBorder(javax.swing.BorderFactory.createTitledBorder(\"Color\"));

    buttonGroup2.add(jRadioButton3);
    jRadioButton3.setText(\"Red\");
    jRadioButton3.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jRadioButton3ActionPerformed(evt);
        }
    });

    buttonGroup2.add(jRadioButton4);
    jRadioButton4.setText(\"Black\");
    jRadioButton4.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jRadioButton4ActionPerformed(evt);
        }
    });

    buttonGroup2.add(jRadioButton5);
    jRadioButton5.setText(\"Gray\");
    jRadioButton5.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jRadioButton5ActionPerformed(evt);
        }
    });

    buttonGroup2.add(jRadioButton6);
    jRadioButton6.setText(\"Green\");
    jRadioButton6.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jRadioButton6ActionPerformed(evt);
        }
    });

    buttonGroup2.add(jRadioButton7);
    jRadioButton7.setText(\"White\");
    jRadioButton7.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jRadioButton7ActionPerformed(evt);
        }
    });

    buttonGroup2.add(jRadioButton8);
    jRadioButton8.setText(\"Blue\");
    jRadioButton8.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jRadioButton8ActionPerformed(evt);
        }
    });

    javax.swing.GroupLayout jPanel3Layout = new javax.swing.GroupLayout(jPanel3);
    jPanel3.setLayout(jPanel3Layout);
    jPanel3Layout.setHorizontalGroup(
        jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(jPanel3Layout.createSequentialGroup()
            .addContainerGap()
            .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                .addComponent(jRadioButton3, javax.swing.GroupLayout.Alignment.TRAILING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addComponent(jRadioButton4, javax.swing.GroupLayout.Alignment.TRAILING, javax.swing.GroupLayout.DEFAULT_SIZE, 66, Short.MAX_VALUE))
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
            .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addComponent(jRadioButton5, javax.swing.GroupLayout.DEFAULT_SIZE, 55, Short.MAX_VALUE)
                .addComponent(jRadioButton6, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
            .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)
                .addComponent(jRadioButton8, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addComponent(jRadioButton7, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
            .addContainerGap())
    );
    jPanel3Layout.setVerticalGroup(
        jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel3Layout.createSequentialGroup()
            .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(jRadioButton4)
                .addComponent(jRadioButton5)
                .addComponent(jRadioButton7))
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 3, Short.MAX_VALUE)
            .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(jRadioButton3)
                .addComponent(jRadioButton6)
                .addComponent(jRadioButton8)))
    );

    jButton1.setText(\"Clear\");
    jButton1.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jButton1ActionPerformed(evt);
        }
    });

    jButton2.setText(\"About\");
    jButton2.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jButton2ActionPerformed(evt);
        }
    });

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addContainerGap()
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addComponent(jPanel2, javax.swing.GroupLayout.Alignment.TRAILING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addGroup(layout.createSequentialGroup()
                    .addComponent(jPanel4, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                    .addComponent(jPanel3, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                        .addComponent(jButton2, javax.swing.GroupLayout.DEFAULT_SIZE, 112, Short.MAX_VALUE)
                        .addComponent(jButton1, javax.swing.GroupLayout.DEFAULT_SIZE, 112, Short.MAX_VALUE))))
            .addContainerGap())
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                .addGroup(layout.createSequentialGroup()
                    .addGap(4, 4, 4)
                    .addComponent(jButton1, javax.swing.GroupLayout.PREFERRED_SIZE, 30, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                    .addComponent(jButton2, javax.swing.GroupLayout.PREFERRED_SIZE, 28, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addComponent(jPanel4, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addComponent(jPanel3, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
            .addComponent(jPanel2, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
            .addContainerGap())
    );

    pack();
}// </editor-fold>                        

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
    System.out.println(\"You cleared the canvas.\");
}                                        

private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {                                         

    JOptionPane.showMessageDialog(null, \"JavaPaint is a simple java based painting application.\"
            + \"  Nick R 5/22/2011\", \"About\", JOptionPane.INFORMATION_MESSAGE);
}                                        
int currentX, currentY, oldX, oldY;

private void jPanel2MouseDragged(java.awt.event.MouseEvent evt) {                                     
    currentX = evt.getX();
    currentY = evt.getY();
    repaint();
    if (tool == 1) {
        oldX = currentX;
        oldY = currentY;
        System.out.println(\"Using pen at \" + currentX + \", \" + currentY);
    }

}                                    

private void jPanel2MousePressed(java.awt.event.MouseEvent evt) {                                     

    oldX = evt.getX();
    oldY = evt.getY();
    if (tool == 2) {
        currentX = oldX;
        currentY = oldY;
    } 


}                                    
//Tool Selection//
int tool = 0;
private void jRadioButton9ActionPerformed(java.awt.event.ActionEvent evt) {                                              
    tool = 1;
    System.out.println(\"Using the pen tool.\");
}                                             

private void jRadioButton10ActionPerformed(java.awt.event.ActionEvent evt) {                                               
    tool = 2;
    System.out.println(\"Using the line tool.\");
}                                              
//Slider Properties//
double value = 5;
private void jSlider2StateChanged(javax.swing.event.ChangeEvent evt) {                                      
    value = jSlider2.getValue();
    System.out.println(value);
}                                     
//COLOR CODE//
int color = 1;
private void jRadioButton4ActionPerformed(java.awt.event.ActionEvent evt) {                                              
    color = 1;        // Black
}                                             

private void jRadioButton5ActionPerformed(java.awt.event.ActionEvent evt) {                                              
    color = 2;        // Grey
}                                             

private void jRadioButton7ActionPerformed(java.awt.event.ActionEvent evt) {                                              
    color = 3;        // White
}                                             

private void jRadioButton3ActionPerformed(java.awt.event.ActionEvent evt) {                                              
    color = 4;    // Red
}                                             

private void jRadioButton6ActionPerformed(java.awt.event.ActionEvent evt) {                                              
    color = 5;        // Green
}                                             

private void jRadioButton8ActionPerformed(java.awt.event.ActionEvent evt) {                                              
    color = 6;        // Blue
}                                             

//mouse released//
private void jPanel2MouseReleased(java.awt.event.MouseEvent evt) {                                      

    currentX = evt.getX();
    currentY = evt.getY();
    if (tool == 2) {
        System.out.println(\"line from \" + oldX +\", \"+ oldY + \" to \" + currentX + \", \" + currentY);
    }
}                                     

//set ui visible//
public static void main(String args[]) {
    java.awt.EventQueue.invokeLater(new Runnable() {

        public void run() {
            new JavaPaintUI().setVisible(true);
        }
    });
}
// Variables declaration - do not modify                     
private javax.swing.ButtonGroup buttonGroup1;
private javax.swing.ButtonGroup buttonGroup2;
private javax.swing.JButton jButton1;
private javax.swing.JButton jButton2;
private javax.swing.JLabel jLabel1;
public javax.swing.JPanel jPanel2;
private javax.swing.JPanel jPanel3;
private javax.swing.JPanel jPanel4;
private javax.swing.JRadioButton jRadioButton10;
private javax.swing.JRadioButton jRadioButton3;
private javax.swing.JRadioButton jRadioButton4;
private javax.swing.JRadioButton jRadioButton5;
private javax.swing.JRadioButton jRadioButton6;
private javax.swing.JRadioButton jRadioButton7;
private javax.swing.JRadioButton jRadioButton8;
private javax.swing.JRadioButton jRadioButton9;
public javax.swing.JSlider jSlider2;
// End of variables declaration                   
class Panel2 extends JPanel {

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);

       if(color==1)
        g2.setPaint( Color.black );
        else if(color==2)
        g2.setPaint( Color.gray);
        else if(color==3)
        g2.setPaint( Color.white );
        else if(color==4)
        g2.setPaint( Color.red );
        else if(color==5)
        g2.setPaint( Color.green );
        else if(color==6)
        g2.setPaint( Color.blue );

        if (tool == 1) {

            g2.fillOval(currentX - ((int) value / 2), currentY - ((int) value / 2), (int) value, (int) value);
        } else if (tool == 2) {
            g2.setStroke(new BasicStroke((float) value, BasicStroke.CAP_ROUND,BasicStroke.JOIN_ROUND));
            g2.drawLine(oldX, oldY, currentX, currentY);
            g2.setStroke(new BasicStroke(1.0f));
        }


    }
}
}
谢谢你!     
已邀请:
好的-这是一个..少量更改。
import java.awt.*;
import java.awt.image.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
import javax.swing.event.*;

public class JavaPaintUI extends JFrame {

    private BufferedImage canvas;

/** Creates new form JavaPaintUI */
public JavaPaintUI() {
    initComponents();
}

    //this was moved from the overriden paintComponent()
    // instead it update the canvas BufferedImage and calls repaint()
    public void updateCanvas() {
        Graphics2D g2d = canvas.createGraphics();
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);

        g2d.setPaint( getColor() );

        if (tool == 1) {

            g2d.fillOval(currentX - ((int) value / 2), currentY - ((int) value / 2), (int) value, (int) value);
        } else if (tool == 2) {
            g2d.setStroke(new BasicStroke((float) value, BasicStroke.CAP_ROUND,BasicStroke.JOIN_ROUND));
            g2d.drawLine(oldX, oldY, currentX, currentY);
            g2d.setStroke(new BasicStroke(1.0f));
        }
        repaint();
    }

    // used in both the updateCanvas and \'clear\' method.
    private Color getColor() {
        Color c = null;
       if(color==1)
        c = Color.black;
        else if(color==2)
        c = Color.gray;
        else if(color==3)
        c = Color.white;
        else if(color==4)
        c = Color.red;
        else if(color==5)
        c = Color.green;
        else if(color==6)
        c = Color.blue;

        return c;
    }

// <editor-fold defaultstate=\"collapsed\" desc=\"Generated Code\">
private void initComponents() {

    canvas = new BufferedImage(600,400,BufferedImage.TYPE_INT_RGB);

    buttonGroup1 = new ButtonGroup();
    buttonGroup2 = new ButtonGroup();
    jPanel4 = new JPanel();
    jRadioButton9 = new JRadioButton();
    jRadioButton10 = new JRadioButton();
    jSlider2 = new JSlider();
    jLabel1 = new JLabel();
    jPanel2 = new JPanel(new GridBagLayout());
    JLabel canvasLabel = new JLabel(new ImageIcon(canvas));
    jPanel2.add(canvasLabel, null);

    jPanel3 = new JPanel();
    jRadioButton3 = new JRadioButton();
    jRadioButton4 = new JRadioButton();
    jRadioButton5 = new JRadioButton();
    jRadioButton6 = new JRadioButton();
    jRadioButton7 = new JRadioButton();
    jRadioButton8 = new JRadioButton();
    jButton1 = new JButton();
    jButton2 = new JButton();

    setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    setTitle(\"JavaPaint ~ Nick R\");

    jPanel4.setBorder(BorderFactory.createTitledBorder(\"Tool\"));

    buttonGroup1.add(jRadioButton9);
    jRadioButton9.setText(\"Pen\");
    jRadioButton9.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent evt) {
            jRadioButton9ActionPerformed(evt);
        }
    });

    buttonGroup1.add(jRadioButton10);
    jRadioButton10.setText(\"Line\");
    jRadioButton10.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent evt) {
            jRadioButton10ActionPerformed(evt);
        }
    });

    jSlider2.setMajorTickSpacing(10);
    jSlider2.setMaximum(51);
    jSlider2.setMinimum(1);
    jSlider2.setMinorTickSpacing(5);
    jSlider2.setPaintTicks(true);
    jSlider2.addChangeListener(new ChangeListener() {
        public void stateChanged(ChangeEvent evt) {
            jSlider2StateChanged(evt);
        }
    });

    jLabel1.setText(\"Stroke Size (Radius)\");

    GroupLayout jPanel4Layout = new GroupLayout(jPanel4);
    jPanel4.setLayout(jPanel4Layout);
    jPanel4Layout.setHorizontalGroup(
        jPanel4Layout.createParallelGroup(GroupLayout.Alignment.LEADING)
        .addGroup(jPanel4Layout.createSequentialGroup()
            .addContainerGap()
            .addGroup(jPanel4Layout.createParallelGroup(GroupLayout.Alignment.LEADING)
                .addComponent(jRadioButton9)
                .addComponent(jRadioButton10))
            .addPreferredGap(LayoutStyle.ComponentPlacement.RELATED, 51, Short.MAX_VALUE)
            .addGroup(jPanel4Layout.createParallelGroup(GroupLayout.Alignment.TRAILING)
                .addComponent(jLabel1)
                .addComponent(jSlider2, GroupLayout.PREFERRED_SIZE, 150, GroupLayout.PREFERRED_SIZE))
            .addContainerGap())
    );
    jPanel4Layout.setVerticalGroup(
        jPanel4Layout.createParallelGroup(GroupLayout.Alignment.LEADING)
        .addGroup(jPanel4Layout.createParallelGroup(GroupLayout.Alignment.TRAILING)
            .addComponent(jSlider2, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE)
            .addGroup(jPanel4Layout.createSequentialGroup()
                .addGroup(jPanel4Layout.createParallelGroup(GroupLayout.Alignment.BASELINE)
                    .addComponent(jRadioButton9)
                    .addComponent(jLabel1))
                .addPreferredGap(LayoutStyle.ComponentPlacement.UNRELATED)
                .addComponent(jRadioButton10)))
    );

    jPanel2.setBackground(new Color(128, 40, 128));
    jPanel2.setBorder(BorderFactory.createBevelBorder(BevelBorder.RAISED));
    // add the listeners to the label that contains the canvas buffered image
    canvasLabel.addMouseListener(new MouseAdapter() {
        public void mousePressed(MouseEvent evt) {
            jPanel2MousePressed(evt);
        }
        public void mouseReleased(MouseEvent evt) {
            jPanel2MouseReleased(evt);
        }
    });
    canvasLabel.addMouseMotionListener(new MouseMotionAdapter() {
        public void mouseDragged(MouseEvent evt) {
            jPanel2MouseDragged(evt);
        }
    });

    // this part of the code was not helping.
    // either layout a container or custom paint it.
    // only attempt both if you are very confident of what you are doing.
/*
    GroupLayout jPanel2Layout = new GroupLayout(jPanel2);
    jPanel2.setLayout(jPanel2Layout);
    jPanel2Layout.setHorizontalGroup(
        jPanel2Layout.createParallelGroup(GroupLayout.Alignment.LEADING)
        .addGap(0, 596, Short.MAX_VALUE)
    );
    jPanel2Layout.setVerticalGroup(
        jPanel2Layout.createParallelGroup(GroupLayout.Alignment.LEADING)
        .addGap(0, 357, Short.MAX_VALUE)
    );
*/
    jPanel3.setBorder(BorderFactory.createTitledBorder(\"Color\"));

    buttonGroup2.add(jRadioButton3);
    jRadioButton3.setText(\"Red\");
    jRadioButton3.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent evt) {
            jRadioButton3ActionPerformed(evt);
        }
    });

    buttonGroup2.add(jRadioButton4);
    jRadioButton4.setText(\"Black\");
    jRadioButton4.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent evt) {
            jRadioButton4ActionPerformed(evt);
        }
    });

    buttonGroup2.add(jRadioButton5);
    jRadioButton5.setText(\"Gray\");
    jRadioButton5.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent evt) {
            jRadioButton5ActionPerformed(evt);
        }
    });

    buttonGroup2.add(jRadioButton6);
    jRadioButton6.setText(\"Green\");
    jRadioButton6.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent evt) {
            jRadioButton6ActionPerformed(evt);
        }
    });

    buttonGroup2.add(jRadioButton7);
    jRadioButton7.setText(\"White\");
    jRadioButton7.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent evt) {
            jRadioButton7ActionPerformed(evt);
        }
    });

    buttonGroup2.add(jRadioButton8);
    jRadioButton8.setText(\"Blue\");
    jRadioButton8.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent evt) {
            jRadioButton8ActionPerformed(evt);
        }
    });

    GroupLayout jPanel3Layout = new GroupLayout(jPanel3);
    jPanel3.setLayout(jPanel3Layout);
    jPanel3Layout.setHorizontalGroup(
        jPanel3Layout.createParallelGroup(GroupLayout.Alignment.LEADING)
        .addGroup(jPanel3Layout.createSequentialGroup()
            .addContainerGap()
            .addGroup(jPanel3Layout.createParallelGroup(GroupLayout.Alignment.LEADING, false)
                .addComponent(jRadioButton3, GroupLayout.Alignment.TRAILING, GroupLayout.DEFAULT_SIZE, GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addComponent(jRadioButton4, GroupLayout.Alignment.TRAILING, GroupLayout.DEFAULT_SIZE, 66, Short.MAX_VALUE))
            .addPreferredGap(LayoutStyle.ComponentPlacement.RELATED)
            .addGroup(jPanel3Layout.createParallelGroup(GroupLayout.Alignment.LEADING)
                .addComponent(jRadioButton5, GroupLayout.DEFAULT_SIZE, 55, Short.MAX_VALUE)
                .addComponent(jRadioButton6, GroupLayout.DEFAULT_SIZE, GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
            .addPreferredGap(LayoutStyle.ComponentPlacement.RELATED)
            .addGroup(jPanel3Layout.createParallelGroup(GroupLayout.Alignment.TRAILING, false)
                .addComponent(jRadioButton8, GroupLayout.DEFAULT_SIZE, GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addComponent(jRadioButton7, GroupLayout.DEFAULT_SIZE, GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
            .addContainerGap())
    );
    jPanel3Layout.setVerticalGroup(
        jPanel3Layout.createParallelGroup(GroupLayout.Alignment.LEADING)
        .addGroup(GroupLayout.Alignment.TRAILING, jPanel3Layout.createSequentialGroup()
            .addGroup(jPanel3Layout.createParallelGroup(GroupLayout.Alignment.BASELINE)
                .addComponent(jRadioButton4)
                .addComponent(jRadioButton5)
                .addComponent(jRadioButton7))
            .addPreferredGap(LayoutStyle.ComponentPlacement.RELATED, 3, Short.MAX_VALUE)
            .addGroup(jPanel3Layout.createParallelGroup(GroupLayout.Alignment.BASELINE)
                .addComponent(jRadioButton3)
                .addComponent(jRadioButton6)
                .addComponent(jRadioButton8)))
    );

    jButton1.setText(\"Clear\");
    jButton1.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent evt) {
            jButton1ActionPerformed(evt);
        }
    });

    jButton2.setText(\"About\");
    jButton2.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent evt) {
            jButton2ActionPerformed(evt);
        }
    });

    GroupLayout layout = new GroupLayout(getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addContainerGap()
            .addGroup(layout.createParallelGroup(GroupLayout.Alignment.LEADING)
                .addComponent(jPanel2, GroupLayout.Alignment.TRAILING, GroupLayout.DEFAULT_SIZE, GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addGroup(layout.createSequentialGroup()
                    .addComponent(jPanel4, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE)
                    .addPreferredGap(LayoutStyle.ComponentPlacement.UNRELATED)
                    .addComponent(jPanel3, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE)
                    .addPreferredGap(LayoutStyle.ComponentPlacement.RELATED)
                    .addGroup(layout.createParallelGroup(GroupLayout.Alignment.LEADING)
                        .addComponent(jButton2, GroupLayout.DEFAULT_SIZE, 112, Short.MAX_VALUE)
                        .addComponent(jButton1, GroupLayout.DEFAULT_SIZE, 112, Short.MAX_VALUE))))
            .addContainerGap())
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addGroup(layout.createParallelGroup(GroupLayout.Alignment.LEADING, false)
                .addGroup(layout.createSequentialGroup()
                    .addGap(4, 4, 4)
                    .addComponent(jButton1, GroupLayout.PREFERRED_SIZE, 30, GroupLayout.PREFERRED_SIZE)
                    .addPreferredGap(LayoutStyle.ComponentPlacement.RELATED)
                    .addComponent(jButton2, GroupLayout.PREFERRED_SIZE, 28, GroupLayout.PREFERRED_SIZE))
                .addComponent(jPanel4, GroupLayout.DEFAULT_SIZE, GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addComponent(jPanel3, GroupLayout.DEFAULT_SIZE, GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
            .addPreferredGap(LayoutStyle.ComponentPlacement.RELATED)
            .addComponent(jPanel2, GroupLayout.DEFAULT_SIZE, GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
            .addContainerGap())
    );

    pack();
}// </editor-fold>

// clear the canvas using the currently selected color.
private void jButton1ActionPerformed(ActionEvent evt) {
    System.out.println(\"You cleared the canvas.\");
    Graphics g = canvas.getGraphics();    
    g.setColor( getColor() );
    g.fillRect(0,0,canvas.getWidth(),canvas.getHeight());
    repaint();
}

private void jButton2ActionPerformed(ActionEvent evt) {

    JOptionPane.showMessageDialog(null, \"JavaPaint is a simple java based painting application.\"
            + \"  Nick R 5/22/2011\", \"About\", JOptionPane.INFORMATION_MESSAGE);
}
int currentX, currentY, oldX, oldY;

private void jPanel2MouseDragged(MouseEvent evt) {
    currentX = evt.getX();
    currentY = evt.getY();
    updateCanvas();
    if (tool == 1) {
        oldX = currentX;
        oldY = currentY;
        System.out.println(\"Using pen at \" + currentX + \", \" + currentY);
    }

}

private void jPanel2MousePressed(MouseEvent evt) {

    oldX = evt.getX();
    oldY = evt.getY();
    if (tool == 2) {
        currentX = oldX;
        currentY = oldY;
    }


}
//Tool Selection//
int tool = 0;
private void jRadioButton9ActionPerformed(ActionEvent evt) {
    tool = 1;
    System.out.println(\"Using the pen tool.\");
}

private void jRadioButton10ActionPerformed(ActionEvent evt) {
    tool = 2;
    System.out.println(\"Using the line tool.\");
}
//Slider Properties//
double value = 5;
private void jSlider2StateChanged(ChangeEvent evt) {
    value = jSlider2.getValue();
    System.out.println(value);
}
//COLOR CODE//
int color = 1;
private void jRadioButton4ActionPerformed(ActionEvent evt) {
    color = 1;        // Black
}

private void jRadioButton5ActionPerformed(ActionEvent evt) {
    color = 2;        // Grey
}

private void jRadioButton7ActionPerformed(ActionEvent evt) {
    color = 3;        // White
}

private void jRadioButton3ActionPerformed(ActionEvent evt) {
    color = 4;    // Red
}

private void jRadioButton6ActionPerformed(ActionEvent evt) {
    color = 5;        // Green
}

private void jRadioButton8ActionPerformed(ActionEvent evt) {
    color = 6;        // Blue
}

//mouse released//
private void jPanel2MouseReleased(MouseEvent evt) {

    currentX = evt.getX();
    currentY = evt.getY();
    if (tool == 2) {
        System.out.println(\"line from \" + oldX +\", \"+ oldY + \" to \" + currentX + \", \" + currentY);
    }
}

//set ui visible//
public static void main(String args[]) {
    EventQueue.invokeLater(new Runnable() {

        public void run() {
            new JavaPaintUI().setVisible(true);
        }
    });
}
// Variables declaration - do not modify
private ButtonGroup buttonGroup1;
private ButtonGroup buttonGroup2;
private JButton jButton1;
private JButton jButton2;
private JLabel jLabel1;
public JPanel jPanel2;
private JPanel jPanel3;
private JPanel jPanel4;
private JRadioButton jRadioButton10;
private JRadioButton jRadioButton3;
private JRadioButton jRadioButton4;
private JRadioButton jRadioButton5;
private JRadioButton jRadioButton6;
private JRadioButton jRadioButton7;
private JRadioButton jRadioButton8;
private JRadioButton jRadioButton9;
public JSlider jSlider2;
// End of variables declaration
}
屏幕截图     
绘制到缓冲区就像在paintComponent(Graphics g)中绘制一样。区别在于您: 1)首先从任何组件(例如面板)创建缓冲区:
Image image = panel.createImage(width, height);
2)获取图像的图形上下文:
Graphics g = image.getGraphics();
3)最后当完成绘制到缓冲区中时:
g.dispose();
稍后,将图像绘制到组件上:
void paintComponent(Graphics g) {
  g.drawImage(image, x_offset, y_offset, null);
}
    

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