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我花了大約2個小時試圖瞭解爲什麼我的代碼一直在拋出運行時錯誤。它不想接受用戶輸入...我很確定我的getext實現是正確的。你們可以看看我的代碼，並幫我看看我做錯了什麼嗎？Java getText NullPointerException
import java.util.*;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import javax.swing.border.*;
public class Mdt1 extends JFrame implements ActionListener{
/**
*
*/
private static final long serialVersionUID = 1L;
/**
* @param args
*/
JTextField twager, dcard1, dcard2, pcard1, pcard2;
public Mdt1() {
JFrame blackjack = new JFrame();
Border wwager = BorderFactory.createTitledBorder("Wager");
JPanel pwager = new JPanel();
pwager.setBorder(wwager);
JLabel lwager = new JLabel("Enter wager:");
JTextField twager = new JTextField(6);
twager.addActionListener(this);
pwager.add(lwager);
pwager.add(twager);
JPanel pplayer = new JPanel();
Border wayer = BorderFactory.createTitledBorder("Player");
pplayer.setLayout(new BoxLayout(pplayer, BoxLayout.Y_AXIS));
pplayer.setBorder(wayer);
pplayer.setSize(100, 100);
JTextField pcard1 = new JTextField(6);
pcard1.setEditable(false);
JTextField pcard2 = new JTextField(6);
pcard2.setEditable(false);
pplayer.add(pcard1);
pplayer.add(pcard2);
JPanel pdealer = new JPanel();
Border wealer = BorderFactory.createTitledBorder("Dealer");
pdealer.setLayout(new BoxLayout(pdealer, BoxLayout.Y_AXIS));
pdealer.setBorder(wealer);
pdealer.setSize(100, 100);
JTextField dcard1 = new JTextField(6);
dcard1.setEditable(false);
JTextField dcard2 = new JTextField(6);
dcard2.setEditable(false);
pdealer.add(dcard1);
pdealer.add(dcard2);
JPanel cards = new JPanel();
Border wards = BorderFactory.createTitledBorder("Cards");
cards.setBorder(wards);
cards.setSize(220, 80);
cards.add(pplayer);
cards.add(pdealer);
JPanel pendgame = new JPanel();
Border wesult = BorderFactory.createTitledBorder("Endgame");
pendgame.setBorder(wesult);
blackjack.setLayout(new BorderLayout());
blackjack.setVisible(true);
blackjack.setSize(200, 200);
blackjack.setTitle("♣ Blackjack ♠");
blackjack.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
blackjack.add(pwager, BorderLayout.NORTH);
blackjack.add(cards);
blackjack.pack();
blackjack.setResizable(false);
}
public void actionPerformed(ActionEvent e) {
String swager = twager.getText();
double wager;
int dealer1, dealer2, player1, player2;
int dealervalue1, dealervalue2, playervalue1, playervalue2;
int dealerTotal, playerTotal;
wager = Double.parseDouble(swager);
Random r=new Random();
// card faces
dealer1=r.nextInt(13) + 1;
String sdealer1 = Integer.toString(dealer1);
dealer2=r.nextInt(13) + 1;
String sdealer2 = Integer.toString(dealer2);
player1=r.nextInt(13) + 1;
String splayer1 = Integer.toString(player1);
player2=r.nextInt(13) + 1;
String splayer2 = Integer.toString(player2);
// Show dealer's card faces
switch(dealer1)
{
case 1: dcard1.setText("Ace "); break;
case 11: dcard1.setText("Jack"); break;
case 12: dcard1.setText("Queen"); break;
case 13: dcard1.setText("King"); break;
default: dcard1.setText(sdealer1); break;
}
switch(dealer2)
{
case 1: dcard2.setText("Ace"); break;
case 11: dcard2.setText("Jack"); break;
case 12: dcard2.setText("Queen"); break;
case 13: dcard2.setText("King"); break;
default: dcard2.setText(sdealer2); break;
}
// Show player's card faces
switch(player1)
{
case 1: System.out.print("Ace"); break;
case 11: System.out.print("Jack"); break;
case 12: System.out.print("Queen"); break;
case 13: System.out.print("King"); break;
default: System.out.print(splayer1); break;
}
switch(player2)
{
case 1: System.out.println("Ace"); break;
case 11: System.out.println("Jack"); break;
case 12: System.out.println("Queen"); break;
case 13: System.out.println("King"); break;
default: System.out.println(splayer2); break;
}
// Determine card values
dealervalue1 = dealer1;
switch(dealer1)
{
case 1: dealervalue1=11; break;
case 11: case 12: case 13:
dealervalue1=10; break;
} // switch
dealervalue2 = dealer2;
switch(dealer2)
{
case 1: dealervalue2=11; break;
case 11: case 12: case 13:
dealervalue2=10; break;
} // switch
dealerTotal = dealervalue1+dealervalue2;
if (dealerTotal == 22) dealerTotal = 12;
playervalue1 = player1;
switch(player1)
{
case 1: playervalue1=11; break;
case 11: case 12: case 13:
playervalue1=10; break;
} // switch
playervalue2 = player2;
switch(player2)
{
case 1: playervalue2=11; break;
case 11: case 12: case 13:
playervalue2=10; break;
} // switch
playerTotal = playervalue1+playervalue2;
if (playerTotal == 22)
playerTotal = 12;
if (playerTotal == 21)
{
wager = wager * 1.5;
JOptionPane.showMessageDialog(null, "You have a Blackjack!!! \n You won: $" + wager);
return;
}
if (playerTotal >= dealerTotal)
{
System.out.println("" + wager);
return;
}
JOptionPane.showMessageDialog(null, "You lost: $" + wager, "You lost!", JOptionPane.ERROR_MESSAGE);
System.out.println(swager);
}
public static void main(String[] args) {
// TODO Auto-generated method stub
/**
* 2
* 2-card Blackjack game
*/
Mdt1 black = new Mdt1();
}// main
}