无法访问 JPanel 的公共方法/变量，也无法从 Jpanel 访问其他公共方法/变量

Question

package client;

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import javax.swing.ImageIcon;
import javax.swing.JPanel;
import javax.swing.JTextArea;

public class YootPanel extends JPanel
{

    private ImageIcon bgIcon;
    public JTextArea textBox;
    public ClientUI clientUI;
    public static final int HORSE_HEIGHT = 25;
    public static final int HORSE_WIDTH = 40;
    public int r1,r2,r3,r4;
    public int b1,b2,b3,b4;
    YootPanelPlot plot;

    public YootPanel(ClientUI clientUI)
    {
        super();    
        init_rest();
        init_bg();
            plot =  = new YootPanelPlot();
        this.setVisible(true);
        this.clientUI = clientUI;
    }

    private void init_bg()
    {
        java.net.URL imgUrl = ClientUI.class.getResource("../images/images/background.png");
        bgIcon = new ImageIcon(imgUrl);
    }

    protected void paintComponent(Graphics g)
    {
        try
        {
            g.drawImage(bgIcon.getImage(), -20, 0, null);
            super.paintComponent(g);
        } catch (Exception e)
        {


        set_Loc();


        g.setColor(Color.RED);
        g.fillOval(plot.plot[0][r1], plot.plot[1][r1], HORSE_WIDTH, HORSE_HEIGHT);
        g.fillOval(plot.plot[0][r2], plot.plot[1][r2], HORSE_WIDTH, HORSE_HEIGHT);
        g.fillOval(plot.plot[0][r3], plot.plot[1][r3], HORSE_WIDTH, HORSE_HEIGHT);
        g.fillOval(plot.plot[0][r4], plot.plot[1][r4], HORSE_WIDTH, HORSE_HEIGHT);
        g.setColor(Color.BLUE);
        g.fillOval(plot.plot[0][b1], plot.plot[1][b1], HORSE_WIDTH, HORSE_HEIGHT);
        g.fillOval(plot.plot[0][b2], plot.plot[1][b2], HORSE_WIDTH, HORSE_HEIGHT);
        g.fillOval(plot.plot[0][b3], plot.plot[1][b3], HORSE_WIDTH, HORSE_HEIGHT);
        g.fillOval(plot.plot[0][b4], plot.plot[1][b4], HORSE_WIDTH, HORSE_HEIGHT);
        System.err.println("Paint");
        }
    }

    public void paint(Graphics g)
    {
        super.paint(g);

    }

private void init_rest()
{
        this.setBorder(javax.swing.BorderFactory.createTitledBorder("Yoot Map"));
        this.setFocusable(false);
        this.setMinimumSize(new java.awt.Dimension(670, 400));
        this.setName("map"); // NOI18N
        this.setOpaque(false);
        this.setPreferredSize(new java.awt.Dimension(630, 400));
        this.setSize(new java.awt.Dimension(630, 400));
        this.setVerifyInputWhenFocusTarget(false);

        org.jdesktop.layout.GroupLayout yootMapLayout = new org.jdesktop.layout.GroupLayout(this);
        this.setLayout(yootMapLayout);
        yootMapLayout.setHorizontalGroup(
        yootMapLayout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING).add(0, 658, Short.MAX_VALUE));
yootMapLayout.setVerticalGroup(
        yootMapLayout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING).add(0, 442, Short.MAX_VALUE));
}

    public void set_Loc()
    {
        try
        {
            System.err.println("......"+clientUI.client.c2.blueHorseLocation[0]);
            r1 = clientUI.client.c2.getRed(0);
            r2 = clientUI.client.c2.getRed(1);
            r3 = clientUI.client.c2.getRed(2);
            r4 = clientUI.client.c2.getRed(3);
            b1 = clientUI.client.c2.blueHorseLocation[0];
            b2 = clientUI.client.c2.blueHorseLocation[1];
            b3 = clientUI.client.c2.blueHorseLocation[2];
            b4 = clientUI.client.c2.blueHorseLocation[3];
        } catch (NullPointerException e)
        {
             e.printStackTrace();
        }
    }
}

What I'm trying to do is get updates for where to put draw the ovals. However the last part's r1 = clientUI.client.c2.getRed(1); throws an NullPointerException

So I tried accessing this Classes public variables r1, r2... etc however, I couldn't reach these public variables either....

Is there a way I can modify these variables so that I cam move the ovals around as I get new coordinate updates?

Answer 1

Don't use public variables.

Define methods to udate the values of any property that you want to change.

Also, custom painting is done by overriding the paintComponent() method. You should not be overriding the paint() method.

Answer 2

Okay, I was being stupid and did a wrong job when creating the object... I should have used

YootPanel object = new YootPanel();

but I used

JPanel object = new YootPanel();

instead.... No wonder I couldn't access the methods that I created in the YootPanel class....

Thank you all for all your Answers!