我正在为我的大学的一个问答比赛写一个程序，类似于＆＃34;谁想成为百万富翁＆＃34;或者＆＃34; Kaun Banega Crorepati＆＃34;。 我正在从总共有6列的数据库中检索问题; 1表示问题，4表示选项，1表示正确答案。问题是JLabel的形式和JButton形式的选项。另外，我有Check和Next JButtons。 但是当我尝试从数据库中检索数据时，我得到一个NullPointerException。我在这里发布了代码。
我希望你们能帮助我解决这个问题，这样我就能在学院里为学生成功举办问答比赛。
import java.util.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.filechooser.*;
import java.io.*;
import java.sql.*;
public class KBP{
public static void main(String[] argv){
JFrame jf = new Frames();
jf.pack();
jf.setExtendedState(JFrame.MAXIMIZED_BOTH);
jf.setForeground(Color.WHITE);
jf.setVisible(true);
}
}
class Frames extends JFrame implements ActionListener{
Toolkit tk = Toolkit.getDefaultToolkit();
ImageIcon logo = new ImageIcon("logo.jpg");
JLabel questions;
JButton option1;
JButton option2;
JButton option3;
JButton option4;
JButton check = new JButton("Check");
JButton next = new JButton("Next");
Statement st = null;
Connection con = null;
ResultSet rs = null;
public Frames(){
super();
setDefaultCloseOperation(3);
// System.out.println(" "+number());
setSize(((int) tk.getScreenSize().getWidth()),((int) tk.getScreenSize().getHeight()));
System.out.println("width is "+getWidth());
System.out.println("height is "+getHeight());
setIconImage(logo.getImage());
setTitle("Kaun Banega PhysicsPati");
getContentPane().add(questions);
questions = new JLabel("Question "+number()+": "+question(), SwingConstants.CENTER);
questions.setBounds(0,(int)(getHeight()/5), getWidth(),60);
System.out.println("bounds of question is "+questions.getBounds().toString());
questions.setFont(new Font("ARIAL",1,20));
questions.setForeground(Color.RED);
getContentPane().add(option1);
option1 = new JButton(first());
option1.setBounds(100,(int)(2*getHeight()/5),500,40);
System.out.println("bounds of option 1 is "+option1.getBounds().toString());
// option1.setBounds((int)(getWidth()/100),(int)(2*getHeight()/5),(int)(2*getWidth()/5)-(int)(getWidth()/100),40);
option1.setBackground(Color.CYAN);
option1.addActionListener(this);
getContentPane().add(option2);
option2 = new JButton(second());
option2.setBounds(750,(int)(2*getHeight()/5),500,40);
System.out.println("bounds of option 2 is "+option2.getBounds().toString());
// option2.setBounds((int)(getWidth()/100)+(int)(getWidth()/2),(int)(2*getHeight()/5),(int)(2*getWidth()/5)-(int)(getWidth()/100),40);
option2.setBackground(Color.CYAN);
option2.addActionListener(this);
getContentPane().add(option3);
option3 = new JButton(third());
option3.setBounds(100,(int)(3*getHeight()/5),500,40);
System.out.println("bounds of option 3 is "+option3.getBounds().toString());
// option3.setBounds((int)(getWidth()/100),(int)(3*getHeight()/5),(int)(2*getWidth()/2)-(int)(getWidth()/100),40);
option3.setBackground(Color.CYAN);
option3.addActionListener(this);
getContentPane().add(option4);
option4 = new JButton(fourth());
option4.setBounds(750,(int)(3*getHeight()/5),500,40);
System.out.println("bounds of option 4 is "+option4.getBounds().toString());
// option4.setBounds((int)(getWidth()/100)+(int)(getWidth()/2),(int)(3*getHeight()/5),(int)(getWidth()/2)-(int)(getWidth()/100),40);
option4.setBackground(Color.CYAN);
option4.addActionListener(this);
getContentPane().add(check);
check.setBounds((int)(getWidth()/2),(int)(4*getHeight()/5),100,40);
System.out.println("bounds of check is "+check.getBounds().toString());
// check.setSize(100,40);
check.addActionListener(this);
check.setVisible(false);
getContentPane().add(next);
next.setBounds((int)(getWidth()/2),(int)(4*getHeight()/5),100,40);
System.out.println("bounds of next is "+next.getBounds().toString());
// next.setBounds(683,614,100,40);
next.addActionListener(this);
// next.addActionListener(this);
next.setVisible(false);
next.setBackground(Color.PINK);
}
public void connect(){
try{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
System.out.println("after classforname");
con = DriverManager.getConnection("jdbc:odbc:quiz","","");
System.out.println("after drivermanager");
st = con.createStatement();
rs = st.executeQuery("SELECT * FROM Questions");
}catch(Exception e){
// System.out.println("Exception caught : " + e.toString());
}finally{
try{
if(con!=null){
con.close();
}
}catch (Exception e2){
// System.out.println("Exceptions caught : " + e2.toString());
}
try{
if(rs!=null){
rs.close();
}
}catch (Exception e3){
// System.out.println("Exceptions caught : " + e2.toString());
}
try{
if(st!=null){
st.close();
}
}catch (Exception e2){
// System.out.println("Exceptions caught : " + e2.toString());
}
}
}
public int number(){
int n =0;
connect();
try{
if (rs.next()){
n = rs.getInt(1)-1;
}
}catch(Exception e){
// System.out.println("Exception caught : " + e.toString());
}finally{
try{
if(con!=null){
con.close();
}
}catch (Exception e2){
// System.out.println("Exceptions caught : " + e2.toString());
}
try{
if(rs!=null){
rs.close();
}
}catch (Exception e3){
// System.out.println("Exceptions caught : " + e2.toString());
}
try{
if(st!=null){
st.close();
}
}catch (Exception e2){
// System.out.println("Exceptions caught : " + e2.toString());
}
}
return n;
}
public String question(){
String q = "";
connect();
try{
if (rs.next()){
q = rs.getString(2);
}
}catch(Exception e){
// System.out.println("Exception caught : " + e.toString());
}finally{
try{
if(con!=null){
con.close();
}
}catch (Exception e2){
// System.out.println("Exceptions caught : " + e2.toString());
}
try{
if(rs!=null){
rs.close();
}
}catch (Exception e3){
// System.out.println("Exceptions caught : " + e2.toString());
}
try{
if(st!=null){
st.close();
}
}catch (Exception e2){
// System.out.println("Exceptions caught : " + e2.toString());
}
}
return q;
}
public String first(){
String f = "";
connect();
try{
if (rs.next()){
f = "A "+rs.getString(3);
}
}catch(Exception e){
// System.out.println("Exception caught : " + e.toString());
}finally{
try{
if(con!=null){
con.close();
}
}catch (Exception e2){
// System.out.println("Exceptions caught : " + e2.toString());
}
try{
if(rs!=null){
rs.close();
}
}catch (Exception e3){
// System.out.println("Exceptions caught : " + e2.toString());
}
try{
if(st!=null){
st.close();
}
}catch (Exception e4){
// System.out.println("Exceptions caught : " + e4.toString());
}
}
return f;
}
public String second(){
String s = "";
connect();
try{
if (rs.next()){
s = "B "+rs.getString(4);
}
}catch(Exception e){
// System.out.println("Exception caught : " + e.toString());
}finally{
try{
if(con!=null){
con.close();
}
}catch (Exception e2){
// System.out.println("Exceptions caught : " + e2.toString());
}
try{
if(rs!=null){
rs.close();
}
}catch (Exception e3){
// System.out.println("Exceptions caught : " + e2.toString());
}
try{
if(st!=null){
st.close();
}
}catch (Exception e4){
// System.out.println("Exceptions caught : " + e4.toString());
}
}
return s;
}
public String third(){
String t = "";
connect();
try{
if (rs.next()){
t = "C "+rs.getString(5);
}
}catch(Exception e){
// System.out.println("Exception caught : " + e.toString());
}finally{
try{
if(con!=null){
con.close();
}
}catch (Exception e2){
// System.out.println("Exceptions caught : " + e2.toString());
}
try{
if(rs!=null){
rs.close();
}
}catch (Exception e3){
// System.out.println("Exceptions caught : " + e2.toString());
}
try{
if(st!=null){
st.close();
}
}catch (Exception e4){
// System.out.println("Exceptions caught : " + e4.toString());
}
}
return t;
}
public String fourth(){
String f = "";
connect();
try{
if (rs.next()){
f = "D "+rs.getString(6);
}
}catch(Exception e){
// System.out.println("Exception caught : " + e.toString());
}finally{
try{
if(con!=null){
con.close();
}
}catch (Exception e2){
// System.out.println("Exceptions caught : " + e2.toString());
}
try{
if(rs!=null){
rs.close();
}
}catch (Exception e3){
// System.out.println("Exceptions caught : " + e2.toString());
}
try{
if(st!=null){
st.close();
}
}catch (Exception e4){
// System.out.println("Exceptions caught : " + e4.toString());
}
}
return f;
}
public String correct(){
String c = "";
connect();
try{
if (rs.next()){
c = rs.getString(7);
}
}catch(Exception e){
// System.out.println("Exception caught : " + e.toString());
}finally{
try{
if(con!=null){
con.close();
}
}catch (Exception e2){
// System.out.println("Exceptions caught : " + e2.toString());
}
try{
if(rs!=null){
rs.close();
}
}catch (Exception e3){
// System.out.println("Exceptions caught : " + e2.toString());
}
try{
if(st!=null){
st.close();
}
}catch (Exception e4){
// System.out.println("Exceptions caught : " + e4.toString());
}
}
return c;
}
public void actionPerformed(ActionEvent ae){
if (ae.getSource()==option1){
option1.setBackground(Color.YELLOW);
option1.removeActionListener(this);
option2.removeActionListener(this);
option3.removeActionListener(this);
option4.removeActionListener(this);
check.setVisible(true);
System.out.println("bound of check is "+check.getBounds().toString());
System.out.println(option1.getText());
}else if (ae.getSource()==option2){
option2.setBackground(Color.YELLOW);
option1.removeActionListener(this);
option2.removeActionListener(this);
option3.removeActionListener(this);
option4.removeActionListener(this);
check.setVisible(true);
System.out.println("bound of check is "+check.getBounds().toString());
}else if (ae.getSource()==option3){
option3.setBackground(Color.YELLOW);
option1.removeActionListener(this);
option2.removeActionListener(this);
option3.removeActionListener(this);
option4.removeActionListener(this);
check.setVisible(true);
System.out.println("bound of check is "+check.getBounds().toString());
}else if (ae.getSource()==option4){
option4.setBackground(Color.YELLOW);
option1.removeActionListener(this);
option2.removeActionListener(this);
option3.removeActionListener(this);
option4.removeActionListener(this);
check.setVisible(true);
System.out.println("bound of check is "+check.getBounds().toString());
}else if (ae.getSource()==check){
option1.removeActionListener(this);
option2.removeActionListener(this);
option3.removeActionListener(this);
option4.removeActionListener(this);
check.setVisible(false);
System.out.println("bounds of check is "+check.getBounds().toString());
System.out.println("Checked");
System.out.println("bound of next is "+next.getBounds().toString());
next.setVisible(true);
connect();
if (option1.getText().contains(correct())){
option1.setBackground(Color.GREEN);
}else if (option2.getText().contains(correct())){
option2.setBackground(Color.GREEN);
}else if (option3.getText().contains(correct())){
option3.setBackground(Color.GREEN);
}else if (option4.getText().contains(correct())){
option4.setBackground(Color.GREEN);
}
}else if (ae.getSource()==next){
System.out.println("Next");
System.out.println("bounds of next is "+next.getBounds().toString());
}
}
}
答案 0 :(得分：0)
我正在粘贴新代码。除了JButton＆＃34; Next＆＃34;以外，一切正常。即使我评论除了这个JButton之外的所有行。
String format with [INFO] color = rgba(102, 0, 255, 0.506)