单击JButton - Java Swing时椭圆形不会改变颜色

Question

我在JFrame里得到了 3 个JPanel .两个用于JButton，另一个用于绘图画布。我为每个JButton生成一个随机颜色，在JPanel中间画一个椭圆形，每次点击JButton时，我都会改变椭圆的颜色。问题是颜色没有改变。

圆面板.java：

public class CirclePanel extends JPanel
{
    private static final long serialVersionUID = 1L;
    private Color color;
    public Color getColor()
    {
        return this.color;
    }
    public void setColor(Color color)
    {
        this.color = color;
        repaint();
    }
    public CirclePanel()
    {
    }
    @Override
    protected void paintComponent(Graphics g) 
    {
        super.paintComponent(g);
        final int OVAL_WIDTH = this.getWidth() / 2;
        final int OVAL_HEIGHT = this.getHeight() / 2;
        final int xPosition =  OVAL_WIDTH / 2;
        final int yPosition =  OVAL_HEIGHT / 2;
        g.setColor(this.color);
        g.fillOval(xPosition,yPosition,OVAL_WIDTH,OVAL_WIDTH);
    }
}

RightPanel.java 和 LeftPanel.java：

public class RightPanel extends JPanel implements ActionListener
{
    private static final long serialVersionUID = 1L;
    private static final int BUTTONS = 6;
    private CirclePanel circlePanel;
    public RightPanel(CirclePanel circlePanel)
    {
        this.circlePanel = circlePanel;
        this.setLayout(new GridLayout(BUTTONS,0));
        // Adding buttons to the layout
        for (int i = 0;i < RightPanel.BUTTONS;i++)
        {
            JButton button = new JButton();
            button.setBackground(generateColor());
            button.addActionListener(this);
            this.add(button);
        }
        this.setVisible(true);
    }
    public Color generateColor()
    {
        Random random = new Random();
        // 255 - maximum value. 0 - minimum value
        int randomNumber1 = random.nextInt((255 - 0) + 1) + 0;
        int randomNumber2 = random.nextInt((255 - 0) + 1) + 0;
        int randomNumber3 = random.nextInt((255 - 0) + 1) + 0;
        Color color = new Color(randomNumber1,randomNumber2,randomNumber3);
        return color;
    }
    @Override
    public void actionPerformed(ActionEvent e)
    {
        Color color = ((JButton)e.getSource()).getBackground();
        this.circlePanel.setColor(color);
    }
}
public class LeftPanel extends JPanel implements ActionListener
{
    private static final long serialVersionUID = 1L;
    private static final int BUTTONS = 6;
    private CirclePanel circlePanel;
    public LeftPanel(CirclePanel circlePanel)
    {
        this.circlePanel = circlePanel;
        this.setLayout(new GridLayout(BUTTONS,0));
        // Adding buttons to the layout
        for (int i = 0;i < LeftPanel.BUTTONS;i++)
        {
            JButton button = new JButton();
            button.setBackground(generateColor());
            button.addActionListener(this);
            this.add(button);
        }
        this.setVisible(true);
    }
    public Color generateColor()
    {
        Random random = new Random();
        // 255 - maximum value. 0 - minimum value
        int randomNumber1 = random.nextInt((255 - 0) + 1) + 0;
        int randomNumber2 = random.nextInt((255 - 0) + 1) + 0;
        int randomNumber3 = random.nextInt((255 - 0) + 1) + 0;
        Color color = new Color(randomNumber1,randomNumber2,randomNumber3);
        return color;
    }
    @Override
    public void actionPerformed(ActionEvent e)
    {
        Color color = ((JButton)e.getSource()).getBackground();
        this.circlePanel.setColor(color);
    }
}

MyFrame.java：

public class MyFrame extends JFrame 
{
    private static final long serialVersionUID = 1L;
    private CirclePanel circlePanel;
    public MyFrame()
    {
        super("paintComponent");
        this.circlePanel = new CirclePanel();
        this.setLayout(new BorderLayout());
        this.setSize(400,400);
        this.setResizable(false);
        this.add(new LeftPanel(this.circlePanel),BorderLayout.WEST);
        this.add(new RightPanel(this.circlePanel),BorderLayout.EAST);
        this.add(new CirclePanel(),BorderLayout.CENTER);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setVisible(true);
    }
    public static void main(String[] args)
    {
        new MyFrame();
    }
}

我检查了程序是否适用于每个actionPerformed()方法，并且确实如此。

那么它有什么问题呢？

Answer 1

您显示的CirclePanel不是您传递给左/右面板的，请参阅：

this.add(new LeftPanel(this.circlePanel),BorderLayout.WEST);
this.add(new RightPanel(this.circlePanel),BorderLayout.EAST);
this.add(new CirclePanel(),BorderLayout.CENTER);

你可能想做：

this.add(new LeftPanel(this.circlePanel),BorderLayout.WEST);
this.add(new RightPanel(this.circlePanel),BorderLayout.EAST);
this.add(this.circlePanel,BorderLayout.CENTER);