当选择JMenuItem时，更改JPanel中的图像

我在使用JMenu时遇到了问题，我怀疑这是因为我误解了Jframe在实时更新方面的工作方式。提前为草率地把代码放在一起作为我想法的测试场地而道歉。

目前，这段代码生成了一个JFrame，它有一个名为High Slot的JMenu，有3个子菜单，每个子菜单有5个选项。目前只有rail子菜单的前两个选项具有动作侦听器。在它下面，我有一个JPanel和一个自动缩放到JPanel大小的图像。

问题是，当我点击其中一个选项时，它并没有像我认为的那样更新图片。我知道Action监听器正在工作，因为每当它启动时，我都会让它打印出一份声明。

我做错了什么？

import java.awt.*;
import java.awt.image.*;
import java.awt.event.*;
import java.io.*;
import javax.swing.*;
import javax.swing.JLabel;
import javax.swing.ImageIcon;
import javax.imageio.*;
class Tests {
JMenu w, Rail, Cann, Miss;
JMenuItem r1,r3,r5,r7,r9,c1,c3,c5,c7,c9,m1,m3,m5,m7,m9;
private static BufferedImage h_empty, t1, t2, placeholder;
private boolean br1 = false, br3 = false, br5 = false, br7 = false, br9 = false, bc1 = false, bc3 = false, bc5 = false, bc7 = false, bc9 = false, 
bm1 = false, bm3 = false, bm5 = false, bm7 = false, bm9 = false;
JFrame f= new JFrame("EveSim");
JPanel panel=new JPanel();
Tests(){
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
JPanel panel=new JPanel();  
panel.setBounds(0,0,48,48);    
panel.setBackground(Color.black);
try { 
h_empty = ImageIO.read(new File("Icon_fit_high.png"));
} catch(IOException ex) {
System.out.println("Error: Image Failed to Load!");
}
try { 
t1 = ImageIO.read(new File("index.png"));
} catch(IOException ex) {
System.out.println("Error: Image Failed to Load!");
}
try { 
t2 = ImageIO.read(new File("index1.png"));
} catch(IOException ex) {
System.out.println("Error: Image Failed to Load!");
}
placeholder = h_empty;
ImageIcon imageIcon = new ImageIcon(fitimage(placeholder, panel.getWidth(), panel.getHeight()));
JLabel jl = new JLabel(imageIcon);
panel.add(jl);
JMenuBar mb=new JMenuBar();  
w=new JMenu("High Slot");  
Rail=new JMenu("Railguns");  
Cann=new JMenu("Cannons");
Miss=new JMenu("Missiles");
r1=new JMenuItem("Tech 1");
r1.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ev) {
Reset();
br1 = !br1;
System.out.println("rail-tech1");
placeholder = t1;
p_add();
}
});
r3=new JMenuItem("Tech 3");
r3.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ev) {
Reset();
br3 = !br3;
System.out.println("rail-tech3");
placeholder =t2;
p_add();
}
});  
r5=new JMenuItem("Tech 5");  
r7=new JMenuItem("Tech 7");  
r9=new JMenuItem("Tech 8");
c1=new JMenuItem("Tech 1");  
c3=new JMenuItem("Tech 3");  
c5=new JMenuItem("Tech 5");  
c7=new JMenuItem("Tech 7");  
c9=new JMenuItem("Tech 8");
m1=new JMenuItem("Tech 1");  
m3=new JMenuItem("Tech 3");  
m5=new JMenuItem("Tech 5");  
m7=new JMenuItem("Tech 7");  
m9=new JMenuItem("Tech 8"); 

Rail.add(r1); Rail.add(r3); Rail.add(r5); Rail.add(r7); Rail.add(r9); 
Cann.add(c1); Cann.add(c3); Cann.add(c5); Cann.add(c7); Cann.add(c9); 
Miss.add(m1); Miss.add(m3); Miss.add(m5); Miss.add(m7); Miss.add(m9); 
w.add(Rail); w.add(Cann); w.add(Miss);
mb.add(w);  
f.setJMenuBar(mb);  
f.add(panel);
f.setSize(400,400);  
f.setLayout(null);  
f.setVisible(true);
}
private Image fitimage(Image img , int w , int h) {
BufferedImage resizedimage = new BufferedImage(w,h,BufferedImage.TYPE_INT_RGB);
Graphics2D g2 = resizedimage.createGraphics();
g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
g2.drawImage(img, 0, 0,w,h,null);
g2.dispose();
return resizedimage;
}
private void p_add() {
panel.setBounds(0,0,48,48);    
panel.setBackground(Color.black);
ImageIcon imageIcon = new ImageIcon(fitimage(placeholder, panel.getWidth(), panel.getHeight()));
JLabel jl = new JLabel(imageIcon);
panel.add(jl);
f.add(panel);
}
private void Reset() {
br1 = false;
br3 = false;
br5 = false; 
br7 = false; 
br9 = false; 
bc1 = false; 
bc3 = false; 
bc5 = false; 
bc7 = false; 
bc9 = false; 
bm1 = false; 
bm3 = false; 
bm5 = false; 
bm7 = false;
bm9 = false;
}
public static void main(String args[]){
new Tests();
}
}