java - 为什么当我调用 repaint() 时我的 JPanel 没有改变？

Question

我有以下代码需要帮助...

public class Nodes extends JPanel implements ActionListener, MouseListener, MouseMotionListener {

    private static JPanel p1;
    private static JPanel p2;
    private JButton linkButton, nodeButton;
    private Vector nodeVector, linkVector;
    private Vector<Integer> data;
    private String s1,s2;
    public int x;
    int pt1;
    public int pt2;
    private Rectangle Node;
    private boolean f1, f2 = false;

    Nodes () {
        JFrame F = new JFrame ("Add Node / Add Link");
        nodeVector = new Vector ();
        linkVector = new Vector ();
        data = new Vector <Integer> ();
        F.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
        F.setVisible (true);
        F.setSize (500, 500);
        p1 = new JPanel ();
        p2 = new JPanel ();
        linkButton = new JButton ("Add Link");
        nodeButton = new JButton ("Add Node");
        linkButton.addActionListener (this);
        nodeButton.addActionListener (this);
        p2.addMouseListener (this);
        p2.addMouseMotionListener (this);
        p1.add (linkButton);
        p1.add (nodeButton);
        F.add (p1,BorderLayout.SOUTH);
        F.add (p2,BorderLayout.CENTER);
        p2.setBackground (Color.WHITE);
    }

    public void paintComponent (Graphics g) {
        super.paintComponent (g);
        Graphics2D g2d = (Graphics2D)(g);
        BufferedImage buffImage = new BufferedImage (25,25,BufferedImage.TYPE_INT_RGB);
        Graphics2D gg = buffImage.createGraphics ();
        gg.setColor (Color.GRAY);
        gg.fillRect (0, 0, 25, 25);
        gg.setStroke (new BasicStroke (12.0f));
        gg.setColor (Color.BLUE);
        gg.drawString ("" + data, 10, 10);
        g2d.setPaint (new TexturePaint (buffImage, new Rectangle (25,25)));
        g.drawRect (pt1, pt2, 10, 10);
        repaint ();
    }

    public void actionPerformed(ActionEvent e){                   
        if(e.getSource()==linkButton){
        s1 = JOptionPane.showInputDialog (null, "Insert the first Node Number");
            s2 = JOptionPane.showInputDialog (null, "Insert the second Node Number");
        }
        if (e.getSource () == nodeButton){
            x = Integer.parseInt ((JOptionPane.showInputDialog (null, "Insert the Node Number")));
            for (int i = 0 ; i < data.size (); i++){ 
                if (x == (int) data.get (i))
                    x = Integer.parseInt (JOptionPane.showInputDialog (null, "Used before insert another number"));
            }
            data.add (x);
            f1 = true; 
        }
    }

    public void mouseClicked (MouseEvent e){
           f2 = true;
           if (f1){ 
               JOptionPane.showMessageDialog (null, "you clicked at" + e.getPoint ());
               pt1 = e.getX ();
               pt2 = e.getY ();
               f1 = !f1;
               repaint ();
           }
    }

    public static void main (String[] args) {
        new Nodes();
    }   
}

我尝试通过调用 repaint() 来更新显示，但是 paintComponent() 方法不起作用，并且实际上没有任何变化。在正确的行为中，当我按下“添加节点”按钮然后单击面板上的任意位置时，应绘制一个带有用户输入的数字的矩形。

有人可以帮忙解释一下我的代码有什么问题吗？

Answer 1

您的主类是 JPanel，但它没有添加到 JFrame 及其面板/按钮/诸如此类的内容中。

尝试这样:

private Vector<Integer> data;
public int x;
int pt1;
public int pt2;
private Rectangle Node;
private boolean f1, f2 = false;
private JButton linkButton, nodeButton;

Nodes ()
{
    JFrame F = new JFrame ("Add Node / Add Link");
    Vector nodeVector, linkVector;
    nodeVector = new Vector ();
    linkVector = new Vector ();
    data = new Vector <Integer> ();
    F.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
    F.setVisible (true);
    F.setSize (500, 500);

    JPanel p1 = new JPanel ();
    linkButton = new JButton ("Add Link");
    nodeButton = new JButton ("Add Node");
    linkButton.addActionListener (this);
    nodeButton.addActionListener (this);
    addMouseListener (this);
    addMouseMotionListener (this);
    p1.add (linkButton);
    p1.add (nodeButton);
    F.add (p1, BorderLayout.SOUTH);
    F.add (this, BorderLayout.CENTER);
    setBackground (Color.WHITE);
}

许多属性可以是局部变量。 JPanel p2 被删除并被 this 的 JPanel 取代，它允许使用 PaintComponent 方法。