我用 Java 为使用 2D 图形的吉他和弦查找器应用程序编写了一个 GUI。程序在画布上打开一个 .jpg 图像。然后它将每个单独的音符（音品之间的空间）绘制为带有音符名称的椭圆。该程序允许用户通过更改和弦各个音符的颜色从工具栏中选择和弦，这些和弦显示在指板上。然而，每当用户选择一个新的和弦时，之前的和弦都不会被删除。我怎样才能解决这个问题？这是我的一些代码（该程序超过 1000 行代码）。
public class Fretboard extends JFrame implements ActionListener{
public static void main(String[] args) {
JFrame frame = new Fretboard();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setVisible(true);
}
// Variables to be used throughout the program
ImagePanel imageSrc;
// Declare fonts to be used
Font font1 = new Font("SansSerif", Font.BOLD, 18); // Font to be used for notes with # or b
Font chordFont = new Font("SansSerif", Font.BOLD, 50); // Font for the name of the chord displayed
Font font = new Font("SansSerif", Font.BOLD, 20); // Font to be used for whole note
int h = 40, w = 26, x = 695, y = 254;
// Declare the note variables
// First string
Ellipse2D E1 = new Ellipse2D.Double(x, y-110, w, h); // E note, open 1st string
Ellipse2D F1 = new Ellipse2D.Double(x, y, w, h); // F note, 1st string, 1st fret
Ellipse2D fSharp1 = new Ellipse2D.Double(x, y+125, w, h); // F#/Gb note, 1st string, 2nd fret
Ellipse2D G1 = new Ellipse2D.Double(x+2, y+240, w, h); // G note, 1st string, 3rd fret
/**
* Create the menu bar and set title
*/
public Fretboard() {
// Change the title of the window
setTitle("Fretboard Chord Finder");
// Create a menu bar where user will be given choice of chords
JMenuBar mb = new JMenuBar();
setJMenuBar(mb);
JMenu menu = new JMenu("Chords");
// Add names of chords to the menu
JMenuItem mi = new JMenuItem("A Major");
mi.addActionListener(this);
menu.add(mi);
mi = new JMenuItem("A Minor");
mi.addActionListener(this);
menu.add(mi);
Container cp = this.getContentPane();
cp.setLayout(new FlowLayout());
imageSrc = new ImagePanel();
cp.add(imageSrc);
}
/**
* Obtain the user's chord selection from the chord menu
*/
public void actionPerformed(ActionEvent e) {
String command = e.getActionCommand();
if("A Major".equals(command))
paintAMajor();
if("A Minor".equals(command))
paintAMinor();
}
/**
* Displays the notes for the A Major chord when the user selects
* "A Major" from the toolbar.
*/
public void paintAMajor() {
// Declare local variables
Graphics g = getGraphics();
Graphics2D g2 = (Graphics2D) g;
// Display the name of the chord
g2.drawString("A Major Chord", 40, 150);
g2.drawString("Notes: A, C#, E", 40, 180);
// Display notes for the A Major chord
// Draw the E note on the open 1st string
// Change color to blue
g2.setColor(Color.red);
g2.draw(E1);
g2.fill(E1);
g2.setColor(Color.white);
g2.setFont(font);
g2.drawString("E", x+7, y-82);
// Change color back to red
g2.setColor(Color.red);
}
class ImagePanel extends JPanel {
BufferedImage image = null;
public ImagePanel() {
File fretBoardFile = new File("/Users/macbook/documents/workspace/Fretboard App/Gibson_Fretboard.jpg"); // The location of the fretboard image
// Open the image
try {
image = ImageIO.read(fretBoardFile);
}
catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
setPreferredSize(new Dimension(1280, 960));
}
/**
*
* @param bi
*/
public ImagePanel(BufferedImage bi) {
image = bi;
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
// Draw the image of the fretboard on the canvas.
// Check to see if the image is available
if(image != null) {
g2.drawImage(image, 25, 0, null);
}
else
g2.drawRect(0, 0, getWidth()-1, getHeight()-1);
// Draw notes
// Draw the E note on the open 1st string
// Change color to blue
g2.setColor(Color.blue);
g2.draw(E1);
g2.fill(E1);
g2.setColor(Color.white);
g2.setFont(font);
g2.drawString("E", x+7, y-82);
// Change color back to blue
g2.setColor(Color.blue);
}
这是该计划的要点。其他一切基本上是每个单独音符的位置或显示和弦的类似方法。我被卡住了，不知道如何修复这个程序。这也是我编写的第一个 GUI。请帮忙。谢谢！
