Java - 无法在Button内部访问我的JPanel

Question

我做了一些研究，但我无法找出问题所在，所以我希望有人可以帮助我。我想制作一个程序，当我点击不同的按钮时，会得到一个图像并改变它的长度，宽度和颜色。它工作到目前为止，但我有按钮的问题。首先，我想创建自己的Button类，但它们没有那么好用，所以我决定在测试类的主要方法中实现Buttons，如下所示：

        JButton test = new JButton("test");
    test.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            try {
                BufferedImage myPicture = ImageIO.read(new File("myImage.jpg"));
                JPanel p = new DrawNew(myPicture);
                center.removeAll();
                center.add(p);
            } catch (IOException ex) {
                System.out.println("didnt work");
                System.exit(0);
            }
        }
    });

问题是，当我按下按钮时，它会做任何事情。我只尝试了center.removeAll（）但它没有做任何事情。看起来Button中的中心似乎与主类中心不同。这是主要的课程：

package app.exercise.test;

import app.exercise.data.JButtonExit;
import app.exercise.data.JButtonOriginal;
import app.exercise.data.JButtonGrayscale;
import app.exercise.data.JButtonPattern;
import app.exercise.data.DrawNew;
import java.awt.BorderLayout;
import java.awt.*; 
import java.awt.event.*; 
import javax.swing.*;
import javax.imageio.ImageIO; 
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

public class AppTest {


public static void main(String[] args) {
    JFrame f = new JFrame("App");
    JPanel center = new JPanel();
    JPanel bottom = new JPanel();
    try {
        BufferedImage myPicture = ImageIO.read(new File("myImage.jpg"));
        JPanel p = new DrawNew(myPicture);
        center.add(p);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    } catch (IOException ex) {
        System.out.println("didnt work");
        System.exit(0);
    }

    JButton exitButton = new JButton("Exit");
    JButtonExit j = new JButtonExit();
    exitButton.addActionListener(j);

    int h =1;
    JButton test = new JButton("test");
    test.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            try {
                BufferedImage myPicture = ImageIO.read(new File("myImage.jpg"));
                JPanel p = new DrawNew(myPicture);
                center.removeAll();
                center.add(p);
            } catch (IOException ex) {
                System.out.println("didnt work");
                System.exit(0);
            }
        }
    });



    JButton originalButton = new JButton("Original");
    JButtonOriginal k = new JButtonOriginal();
    originalButton.addActionListener(k);

    JButton grayscaleButton = new JButton("Grayscale");
    JButtonGrayscale l = new JButtonGrayscale();
    grayscaleButton.addActionListener(l);

    JButton patternButton = new JButton("Pattern");
    JButtonPattern m = new JButtonPattern();
    patternButton.addActionListener(m);

    Box boxBottom = Box.createHorizontalBox();

    boxBottom.add(Box.createHorizontalGlue());
    boxBottom.add(exitButton);

    Box topBox = Box.createHorizontalBox();

    topBox.add(originalButton);
    topBox.add(grayscaleButton);
    topBox.add(patternButton);
    topBox.add(test);

    f.add(topBox, BorderLayout.NORTH);
    f.add(center, BorderLayout.CENTER);
    f.add(boxBottom, BorderLayout.SOUTH);

    f.pack();
    f.setVisible(true); 
}

}

DrawNew类看起来像这样：

package app.exercise.data;

import java.awt.BorderLayout; 
import java.awt.event.*;
import javax.swing.*;
import java.awt.*; 
import java.awt.event.*; 
import javax.swing.*;
import javax.imageio.ImageIO; 
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.awt.image.ColorModel;


public class DrawNew extends JPanel {

private int height;
private int width;
private BufferedImage myPic;

public DrawNew (BufferedImage myPicture) {
    height = myPicture.getHeight();
    width = myPicture.getWidth();
    myPic = myPicture;
}


    public Dimension getPreferredSize() {
        return new Dimension(width*2, height*2);
}
public void paintComponent(Graphics g) {
    super.paintComponent(g);

    int select = 1;

    switch(select) {
        case 1: select = 1;
            for (int i = 0; i < width; i++) {
                for (int k = 0; k<height;k++) {
                    Color mycolor = new Color(myPic.getRGB(i,k));
                    g.setColor(mycolor);
                    g.fillRect(2*i,2*k,2,2);
                }
            }
            break;

        case 2: select = 2;
            for (int i = 0; i < width; i++) {
                for (int k = 0; k<height;k++) {
                    Color mycolor = new Color(myPic.getRGB(i,k));
                    int h = mycolor.getRed();
                    int t = mycolor.getRed();
                    int f = mycolor.getRed();
                    int mittel = (h+f+t)/3;
                    Color newColor = new Color (mittel,mittel,mittel);
                    g.setColor(newColor);
                    g.fillRect(2*i,2*k,2,2);
                }
            }
            break;

        case 3: select = 3;
            for (int i = 0; i < width; i++) {
                for (int k = 0; k<height;k++) {
                    Color mycolor = new Color(myPic.getRGB(i,k));
                    int h = mycolor.getRed();
                    int t = mycolor.getRed();
                    int f = mycolor.getRed();
                    int mittel = (h+f+t)/3;
                    if (mittel <= 51) {
                        g.setColor(Color.BLACK);
                        g.fillRect(2*i,2*k,2,2);
                    } else if(mittel <=102) {
                        g.setColor(Color.WHITE);
                        g.drawLine(2*i,2*k,2*i,2*k); 
                        g.setColor(Color.BLACK);
                        g.drawLine(2*i+1,2*k+1,2*i+1,2*k+1); 
                        g.drawLine(2*i+1,2*k,2*i+1,2*k);
                        g.drawLine(2*i,2*k+1,2*i,2*k+1);
                    } else if(mittel <=153) {
                        g.setColor(Color.BLACK);
                        g.drawLine(2*i,2*k,2*i,2*k); 
                        g.drawLine(2*i+1,2*k+1,2*i+1,2*k+1); 
                        g.setColor(Color.WHITE);
                        g.drawLine(2*i+1,2*k,2*i+1,2*k);
                        g.drawLine(2*i,2*k+1,2*i,2*k+1);
                    } else if(mittel <=204) {
                        g.setColor(Color.BLACK);
                        g.drawLine(2*i,2*k,2*i,2*k); 
                        g.setColor(Color.WHITE);
                        g.drawLine(2*i+1,2*k,2*i+1,2*k);
                        g.drawLine(2*i,2*k+1,2*i,2*k+1);
                        g.drawLine(2*i+1,2*k+1,2*i+1,2*k+1);
                    } else if(mittel <=255) {
                        g.setColor(Color.WHITE);
                        g.fillRect(2*i,2*k,2,2);

                    }
                }
            }
            break;
    }
}

}

所以我的问题是：如何在我的Button中输入center.add（p）。它起初工作没有任何问题，但由于某些原因不在按钮中。

我感谢任何帮助。