我尝试以多种方式修复此问题，并尝试在各处搜索答案，我的颜色按钮正常工作，但内置数字按钮无法正常工作。

   package tralala;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.*;

import java.awt.*;

public class DugmiciKojiMenjajuBoju extends JFrame implements ActionListener {

/**
 * 
 */
private static final long serialVersionUID = 4317497849622426733L;
private JButton dugme1;
private JButton dugme2;
private JButton dugme3;
private JPanel panel;
private JOptionPane a;
private JPanel panel1;
private JButton dugmeBroja0;
private JButton dugmeBroja1;
private JButton dugmeBroja2;
private JButton dugmeBroja3;
private JButton dugmeBroja4;
private JButton dugmeBroja5;
private JButton dugmeBroja6;
private JButton dugmeBroja7;
private JButton dugmeBroja8;
private JButton dugmeBroja9;
private JButton dugmeZaPlus;
private JButton dugmeZaMinus;
private JButton dugmeZaPuta;
private JButton dugmeZaPodeljeno;
private JButton dugmeZaJednako;
private JTextField polje;

DugmiciKojiMenjajuBoju(){
    getContentPane().setBackground(Color.white);
    this.setLayout(new FlowLayout());
    a = new JOptionPane("");
    dugme1 = new JButton("zuta");
    dugme2 = new JButton("plava");
    dugme3 = new JButton("crvena");

    dugmeBroja0 = new JButton("0");
    dugmeBroja1 = new JButton("1");
    dugmeBroja2 = new JButton("2");
    dugmeBroja3 = new JButton("3");
    dugmeBroja4 = new JButton("4");
    dugmeBroja5 = new JButton("5");
    dugmeBroja6 = new JButton("6");
    dugmeBroja7 = new JButton("7");
    dugmeBroja8 = new JButton("8");
    dugmeBroja9 = new JButton("9");
    dugmeZaPlus = new JButton("+");
    dugmeZaMinus = new JButton("-");
    dugmeZaPuta = new JButton("*");
    dugmeZaPodeljeno = new JButton("/");
    dugmeZaJednako = new JButton("=");
    polje = new JTextField("", 20);

    panel = new JPanel();
    panel1 = new JPanel();
    dugmeBroja0.setSize(50,50);
    dugmeBroja1.setSize(50,50);
    dugmeBroja2.setSize(50,50);
    dugmeBroja3.setSize(50,50);
    dugmeBroja4.setSize(50,50);
    dugmeBroja5.setSize(50,50);
    dugmeBroja6.setSize(50,50);
    dugmeBroja7.setSize(50,50);
    dugmeBroja8.setSize(50,50);
    dugmeBroja9.setSize(50,50);


    panel1.add(dugmeBroja0);
    panel1.add(dugmeBroja1);
    panel1.add(dugmeBroja2);
    panel1.add(dugmeBroja3);
    panel1.add(dugmeBroja4);
    panel1.add(dugmeBroja5);
    panel1.add(dugmeBroja6);
    panel1.add(dugmeBroja7);
    panel1.add(dugmeBroja8);
    panel1.add(dugmeBroja9);
    panel1.add(dugmeZaPlus);
    panel1.add(dugmeZaMinus);
    panel1.add(dugmeZaPuta);
    panel1.add(dugmeZaPodeljeno);
    panel1.add(dugmeZaJednako);
    panel1.add(polje);


    panel1.setLayout(new FlowLayout(50, 0 ,0));
    FlowLayout mojLayout = new FlowLayout(FlowLayout.CENTER , 20 , 20);
    panel.setLayout(mojLayout);
    panel.add(dugme1);
    panel.add(dugme2);
    panel.add(dugme3);

    this.setTitle("Kalkulator Koji Menja Boju Pozadine");
    this.setSize(500,500);
    this.setDefaultCloseOperation(EXIT_ON_CLOSE);
    this.setLocationRelativeTo(null);
    this.add(panel1);
    this.add(panel);
    dugme1.addActionListener(this);
    dugme2.addActionListener(this);
    dugme3.addActionListener(this);
    polje.addActionListener(this);
    panel.setBackground(Color.white);
    panel1.setBackground(Color.white);
}
public static void main(String[] args) {
     DugmiciKojiMenjajuBoju  a = new  DugmiciKojiMenjajuBoju();
     a.setVisible(true);

}

@Override
public void actionPerformed(ActionEvent arg0) {
    if( arg0.getSource() == dugme1){
        panel.setBackground(Color.yellow);
        panel1.setBackground(Color.yellow);
        getContentPane().setBackground(Color.yellow);
        a.setSize(200,200);
        a.showMessageDialog(this, "Klikcite dalje :D" ,"Postavili ste zutu",JOptionPane.INFORMATION_MESSAGE);
    }
    else if(arg0.getSource() == dugme2){
        panel.setBackground(Color.blue);
        panel1.setBackground(Color.blue);
        getContentPane().setBackground(Color.blue);
        a.setSize(200,200);
        a.showMessageDialog(this, "Klikcite dalje :D","Postavili ste plavu", JOptionPane.INFORMATION_MESSAGE);
    }
    else if(arg0.getSource() == dugme3){
        panel.setBackground(Color.red);
        panel1.setBackground(Color.red);
        getContentPane().setBackground(Color.red);
        a.setSize(200,200);
        a.showMessageDialog(this,  "Klikcite dalje :D","Postavili ste crvenu",JOptionPane.INFORMATION_MESSAGE);
    }
    else if(arg0.getSource() == dugmeBroja0){
        polje.setText("0");
        System.out.println("blabla");
    }

}
}

我的按钮0不起作用…所以我无法继续编写代码。