我目前正在订购系统上，遇到一些问题，例如在面板上显示总价
public class SummaryPanel extends MasterPanel {
private JTable table;
public JTable tblList3;
protected ArrayList<Food>foodList;
protected JComboBox category_CB;
protected JComboBox cb_FoodItem;
private JComboBox combo;
private JTextField ImagePath_TF;
private double total;
private String totalPrice;
private Orders orders;
private JComboBox comboBox;
private JComboBox cb;
private JComboBox cb_tableno;
private double totalAmount;
private ComboBoxModel cb_nopax1;
private JComboBox cbNoPax;
private String numPax;
private String tableNo;
private JLabel txtPrice;
private Double s;
/**
* Create the panel.
*/
public SummaryPanel(JFrame myFrame, ArrayList<Food> listSelected) {
super(myFrame);
this.foodList =listSelected;
setBackground(Color.WHITE);
setForeground(Color.WHITE);;
JLabel lblConfirmOrder = new JLabel("Confirm Order");
lblConfirmOrder.setFont(new Font("Tw Cen MT", Font.PLAIN, 26));
lblConfirmOrder.setBounds(52, 105, 173, 49);
add(lblConfirmOrder);
JScrollPane scrollPane = new JScrollPane();
scrollPane.setBounds(27, 342,568, 204);
add(scrollPane);
tblList3 = new JTable();
setTableModel();
scrollPane.setViewportView(tblList3);
JButton btnHome = new JButton("Cancle Order");
btnHome.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
actionPerformedCancleOrder();
}
});
btnHome.setBounds(93, 554, 119, 43);
add(btnHome);
JLabel lblTableNo = new JLabel("Table No");
lblTableNo.setBounds(337, 241, 67, 39);
add(lblTableNo);
JButton btnOrder = new JButton("Order");
btnOrder.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
actionPerformedOrder();
}
});
btnOrder.setBounds(297, 554, 151, 43);
add(btnOrder);
JLabel lblNumberOfPax = new JLabel("Number Of Pax");
lblNumberOfPax.setBounds(337, 174, 106, 27);
add(lblNumberOfPax);
/*JButton btnPrice = new JButton("Price");
btnPrice.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
actionPerformedTotalPrice();
}
});
btnPrice.setBounds(71, 176, 89, 23);
add(btnPrice); */
JLabel label = new JLabel("")label.setIcon(newImageIcon(SummaryPanel.class.getResource("/fourFinger/
images/Wall-E6.jpg")));
label.setBounds(636, 327, 253, 258);
add(label);
JLabel lblPleaseIndicateThe = new JLabel("Please indicate the ");
lblPleaseIndicateThe.setFont(new Font("Tw Cen MT", Font.BOLD, 19));
lblPleaseIndicateThe.setBounds(561, 174, 173, 55);
add(lblPleaseIndicateThe);
JLabel lblTheSelectedFood = new JLabel("quantity of the");
lblTheSelectedFood.setFont(new Font("Tw Cen MT", Font.BOLD, 19));
lblTheSelectedFood.setBounds(561, 209, 173, 31);
add(lblTheSelectedFood);
JLabel lblFoodSelected = new JLabel("food selected");
lblFoodSelected.setFont(new Font("Tw Cen MT", Font.BOLD, 19));
lblFoodSelected.setBounds(561, 251, 119, 14);
add(lblFoodSelected);
JLabel lblDsdsds = new JLabel("");
lblDsdsds.setIcon(new ImageIcon(SummaryPanel.class.getResource("/fourFinger/images/chatbox.png")));
lblDsdsds.setBounds(527, 151, 237, 176);
add(lblDsdsds);
txtPrice = new JLabel("");
txtPrice.setBounds(113, 177, 74, 21);
add(txtPrice);
cb_tableno = new JComboBox();
cb_tableno.setBounds(424, 250, 93, 20);
cb_tableno.setModel(new DefaultComboBoxModel(new String[]{ "1","2","3","4","5","6","7","8","9","10"}));
add(cb_tableno);
cbNoPax = new JComboBox();
cbNoPax.setBounds(424, 177, 93, 20);
cbNoPax .setModel(new DefaultComboBoxModel(new String[]{ "1","2","3","4","5","6","7","8","9","10"}));
add(cbNoPax);
}
private void actionPerformedOrder() {
//retrieve user input
String numPax = (String) cbNoPax.getSelectedItem();
String tableNo= (String)cb_tableno.getSelectedItem();
Date orderDate = new Date();
orders=newOrders(Integer.parseInt(tableNo),Integer.parseInt(numPax),orderDate, totalAmount);
int orderID = OrdersDA.createOrders(orders);
}
private double getTotalPrice(){
total = 0;
for(Food fd:foodList){
total += fd.getFoodPrice()*Food.getQuantity();
System.out.printf("Total:$%.2f ", total);
}
return total;
}
private void actionPerformedCancleOrder() {
int resp = JOptionPane.showConfirmDialog(myFrame, "Confirm Cancle Order \n\n Note : Selected food items will be discarded" , "Confirmation", JOptionPane.YES_NO_OPTION);
if(resp == JOptionPane.NO_OPTION){
}
else {
MasterPanel contentPane = new MasterPanel(myFrame);
myFrame.setContentPane(contentPane);
myFrame.setVisible(true);
}
}
private void setTableModel() {
FoodTableModel model = new FoodTableModel(foodList);
totalAmount = getTotalPrice();
s = String.valueOf(totalAmount);
txtPrice.setText(s);
tblList3.setModel(model);
tblList3.removeColumn(tblList3.getColumnModel().getColumn(0));
}
}
当我运行问题时，该错误发生在：txtPrice.setText（s）并说明为NullPointerexception。有人知道哪里出了问题吗？
最佳答案
您正在指令setTableModel()之前调用方法txtPrice = new JLabel("");。如果需要更精确的答案，请发布所有代码。