JMenuBar重新绘制我的JPanel

Question

我正在编程一个小的绘画应用程序，问题是，当我在菜单上点击，然后将鼠标移出并在面板上点击以继续绘画时，面板会擦除我画的所有内容，并更改背景。。。这是我的代码：

帧的代码：

public class Ardoise extends JFrame {
private JMenuBar menu = new JMenuBar();
private JToolBar toolbar = new JToolBar();
private JMenu file = new JMenu("Fichier");
private JMenu edit = new JMenu("Edition");
private JMenu about = new JMenu("About");
private JMenu shape = new JMenu("Forme du curseur");
private JMenu color = new JMenu("Couleur du curseur");
private JMenuItem clear = new JMenuItem("Effacer");
private JMenuItem quit = new JMenuItem("Quitter");
private JMenuItem rond = new JMenuItem("Rond");
private JMenuItem carre = new JMenuItem("Carre");
private JMenuItem rouge = new JMenuItem("Rouge");
private JMenuItem bleu = new JMenuItem("Bleu");
private JMenuItem noir = new JMenuItem("Noir");
private JButton rougeButton = new JButton(new ImageIcon("rouge.jpg"));
private JButton bleuButton = new JButton(new ImageIcon("bleu.jpg"));
private JButton noirButton = new JButton(new ImageIcon("noir.jpg"));
private JButton formecarreeButton = new JButton(new ImageIcon("formecarree.png"));
private JButton formerondeButton = new JButton(new ImageIcon("formeronde.png"));
private JPanel container = new JPanel();
private Panneau pan = new Panneau();
private ColorListener cListener = new ColorListener();
public Ardoise(){
    this.setTitle("Paint");
    this.setSize(700,500);
    this.setDefaultCloseOperation(EXIT_ON_CLOSE);
    this.setLocationRelativeTo(null);
    initComposants();
    this.setVisible(true);
}
private void initComposants(){
    file.add(clear);
    file.addSeparator();
    file.add(quit);
    file.setMnemonic('F');
        clear.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_N,KeyEvent.CTRL_DOWN_MASK));
        quit.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_W,KeyEvent.CTRL_DOWN_MASK));
    shape.add(rond);
    shape.add(carre);
    color.add(rouge);
    color.add(bleu);
    color.add(noir);
    edit.add(shape);
    edit.add(color);
    edit.setMnemonic('E');
    menu.add(file);
    menu.add(edit);

    toolbar.add(formecarreeButton);
    toolbar.add(formerondeButton);
    toolbar.addSeparator();
    toolbar.add(noirButton);
    toolbar.add(rougeButton);
    toolbar.add(bleuButton);
    pan.addMouseMotionListener(new PaintListener1());
    pan.addMouseListener(new PaintListener2());
    clear.addActionListener(new ClearListener());
    rougeButton.addActionListener(cListener);
    bleuButton.addActionListener(cListener);
    noirButton.addActionListener(cListener);
    container.setLayout(new BorderLayout());
    container.add(toolbar,BorderLayout.NORTH);
    container.add(pan,BorderLayout.CENTER);
    this.setContentPane(container);
    this.setJMenuBar(menu);
}

class PaintListener1 implements MouseMotionListener{
    public void mouseDragged(MouseEvent e) {
        pan.setx(e.getX());
        pan.sety(e.getY());
        pan.repaint();
    }
    @Override
    public void mouseMoved(MouseEvent arg0) {
        // TODO Auto-generated method stub
    }       
}
class PaintListener2 implements MouseListener{
    @Override
    public void mouseClicked(MouseEvent e) {
        // TODO Auto-generated method stub
    }
    @Override
    public void mouseEntered(MouseEvent e) {
        // TODO Auto-generated method stub
    }
    @Override
    public void mouseExited(MouseEvent e) {
        // TODO Auto-generated method stub
    }
    @Override
    public void mousePressed(MouseEvent e) {
        pan.setx(e.getX());
        pan.sety(e.getY());
        pan.repaint();
    }
    @Override
    public void mouseReleased(MouseEvent e) {
        // TODO Auto-generated method stub
    }
}
class ClearListener implements ActionListener{
    public void actionPerformed(ActionEvent e) {
        pan.setClean(true);
        pan.repaint();
    }
}
class ColorListener implements ActionListener{
    public void actionPerformed(ActionEvent e) {
        if(e.getSource() == rougeButton)
            pan.setColor(Color.red);
        if(e.getSource() == bleuButton)
            pan.setColor(Color.blue);
        if(e.getSource() == noirButton)
            pan.setColor(Color.black);
    }
}

}

面板代码：

public class Panneau extends JPanel{
private int mousex=0,mousey=0;
private boolean clean=true;;
private Color color= Color.black;
public void paintComponent(Graphics g){
    g.setColor(color);
    draw(g);
    if(clean){
        g.setColor(Color.white);
        g.fillRect(0, 0, this.getWidth(), this.getHeight());
        clean=false;
    }
}
private void draw(Graphics g){
    g.fillOval(mousex, mousey, 10, 10);
}
public void setx(int x){
    this.mousex=x;
}
public void sety(int y){
    this.mousey=y;
}
public void setClean(boolean c){
    this.clean = c;
}
public void setColor(Color c){
    this.color=c;
}
}

Answer 1

面板擦除了我画的所有东西，还改变了背景。。。这是我的代码：

你需要跟踪所有已绘制的内容，然后重新绘制所有内容。

请参阅自定义绘画方法，了解两种常见的方法：

1. 使用ArrayList跟踪绘制的对象
2. 使用缓冲图像