在Swing里面的BufferedImage中绘画

Im working on a paint application written in java and running into a few (more) problems. I have a gui and a working program(kinda), my only problem is that the lines and graphics that the user draws are not saved(disappear after next one is drawn).

我正在研究用java编写的绘图应用程序并遇到一些(更多)问题。我有一个gui和一个工作程序(有点),我唯一的问题是用户绘制的线条和图形没有保存(在绘制下一个之后消失)。

From a past question i learned that i will need to use a BufferedImage to store the drawings then paint that inside my paint class.

从过去的问题我了解到我将需要使用BufferedImage来存储绘图然后在我的绘画类中绘制它。

My questions are, Can anyone provide a basic explanation/example of how to use a bufferedimage to store and paint the drawing and if i need to, how will i pass the color and thickness of the drawn line into a stored array.

我的问题是,任何人都可以提供如何使用bufferedimage来存储和绘制绘图的基本解释/示例,如果需要,我将如何将绘制线的颜色和粗细传递到存储的数组中。

thats my whole class.

那就是全班同学。

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));        }    }}}

Thanks ahead!

2 个解决方案

#1

OK - here are a ..few changes.

好的 - 这里有一些改动。

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 modifyprivate 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}

Screen shot

#2

Drawing into a buffer is just like drawing in a paintComponent(Graphics g). The difference is that you:

绘制到缓冲区就像在paintComponent(Graphics g)中绘制一样。不同的是你:

1) first create the buffer from any component (e.g. a Panel):

1)首先从任何组件(例如Panel)创建缓冲区:

Image image = panel.createImage(width, height);

2) get the graphics context for the image:

2)获取图像的图形上下文:

Graphics g = image.getGraphics();

3) finally when done drawing into the buffer:

3)最后完成绘制到缓冲区时:

g.dispose();

Later, to draw the image onto your component:

稍后,将图像绘制到组件上:

void paintComponent(Graphics g) {  g.drawImage(image, x_offset, y_offset, null);}