我有4个班级
UI / ProductUI
控制器/ ProductController的
project_package /产品
project_package / ProductRecords
UI：
package ui;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.GroupLayout.Alignment;
import javax.swing.LayoutStyle.ComponentPlacement;
import javax.swing.UnsupportedLookAndFeelException;
import controller.ProductController;
public class ProductUI {
private JFrame f;
private JPanel page1, page2;
private JTabbedPane tp;
private JTextField addProductTextFieldName;
private JTextField addProductTextFieldPrice;
private JTextField addProductTextFieldDescription;
private JTextField addProductTextFieldDiscount;
private JTextField addProductTextFieldQuantity;
private ProductController productCtrl;
public void display()
{
f.getContentPane().add(tp);
tp.add("Add product", page1);
tp.add("Edit product", page2);
f.setSize(510,450);
f.setVisible(true);
f.setResizable(false);
}
public ProductUI()
{
f = new JFrame("Product UI");
tp = new JTabbedPane();
//**********************************
// PAGE 1
//**********************************
page1 = new JPanel();
JLabel addProductLabelName = new JLabel("Product Name");
JLabel addProductLabelPrice = new JLabel("Product Price");
JLabel addProductLabelDescription = new JLabel("Product Description");
JLabel addProductLabelDiscount = new JLabel("Product Discount");
JLabel addProductLabelQuantity = new JLabel("Product Quantity");
JLabel addProductLabelLocation = new JLabel("Product Location");
JCheckBox addProductCheckBoxAalborg = new JCheckBox("Aalborg");
JCheckBox addProductCheckBoxOdense = new JCheckBox("Odense");
JCheckBox addProductCheckBoxCopenhagen = new JCheckBox("Copenhagen");
JButton addProductButtonReset = new JButton("Reset");
JButton addProductButtonAdd = new JButton("Add");
JButton addProductButtonClose = new JButton("Close window");
JButton addProductButtonExit = new JButton("Exit");
addProductTextFieldName = new JTextField(10);
addProductTextFieldPrice = new JTextField(10);
addProductTextFieldDescription = new JTextField(10);
addProductTextFieldDiscount = new JTextField(10);
addProductTextFieldQuantity = new JTextField(10);
addProductButtonAdd.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
/*double productPrice = Double.parseDouble(addProductTextFieldPrice.getText());
double productDiscount = Double.parseDouble(addProductTextFieldDiscount.getText());
int productQuantity = Integer.parseInt(addProductTextFieldQuantity.getText());
String productName = addProductTextFieldName.getText();
String productDescription = addProductTextFieldDescription.getText();
//productCtrl.createProduct(productName, productPrice, productDiscount, productDescription, productQuantity, "location");
*/
productCtrl.createProduct("Test", 20.0, 20.0, "haha", 20, "nqkude");
}
});
GroupLayout gl_page1 = new GroupLayout(page1);
gl_page1.setHorizontalGroup(
gl_page1.createParallelGroup(Alignment.LEADING)
.addGroup(gl_page1.createSequentialGroup()
.addGap(95)
.addGroup(gl_page1.createParallelGroup(Alignment.TRAILING)
.addGroup(gl_page1.createSequentialGroup()
.addGroup(gl_page1.createParallelGroup(Alignment.LEADING)
.addComponent(addProductLabelName)
.addComponent(addProductLabelPrice)
.addComponent(addProductLabelDescription)
.addComponent(addProductLabelDiscount)
.addComponent(addProductLabelQuantity)
.addComponent(addProductLabelLocation))
.addGap(82))
.addGroup(gl_page1.createSequentialGroup()
.addGap(34)
.addGroup(gl_page1.createParallelGroup(Alignment.TRAILING)
.addComponent(addProductButtonAdd, Alignment.LEADING, GroupLayout.DEFAULT_SIZE, 101, Short.MAX_VALUE)
.addComponent(addProductButtonClose, Alignment.LEADING, GroupLayout.DEFAULT_SIZE, 101, Short.MAX_VALUE))
.addGap(40)))
.addGroup(gl_page1.createParallelGroup(Alignment.LEADING, false)
.addComponent(addProductCheckBoxOdense)
.addComponent(addProductCheckBoxAalborg)
.addComponent(addProductTextFieldName, GroupLayout.DEFAULT_SIZE, 129, Short.MAX_VALUE)
.addComponent(addProductTextFieldPrice)
.addComponent(addProductTextFieldDescription)
.addComponent(addProductTextFieldDiscount)
.addComponent(addProductTextFieldQuantity)
.addGroup(gl_page1.createSequentialGroup()
.addPreferredGap(ComponentPlacement.RELATED)
.addGroup(gl_page1.createParallelGroup(Alignment.TRAILING, false)
.addComponent(addProductButtonExit, Alignment.LEADING, GroupLayout.DEFAULT_SIZE, GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
.addComponent(addProductCheckBoxCopenhagen, Alignment.LEADING, GroupLayout.DEFAULT_SIZE, GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
.addComponent(addProductButtonReset, Alignment.LEADING, GroupLayout.PREFERRED_SIZE, 96, GroupLayout.PREFERRED_SIZE))
.addGap(25)))
.addGap(100))
);
gl_page1.setVerticalGroup(
gl_page1.createParallelGroup(Alignment.LEADING)
.addGroup(gl_page1.createSequentialGroup()
.addGap(58)
.addGroup(gl_page1.createParallelGroup(Alignment.BASELINE)
.addComponent(addProductLabelName)
.addComponent(addProductTextFieldName, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE))
.addPreferredGap(ComponentPlacement.UNRELATED)
.addGroup(gl_page1.createParallelGroup(Alignment.BASELINE)
.addComponent(addProductLabelPrice)
.addComponent(addProductTextFieldPrice, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE))
.addPreferredGap(ComponentPlacement.UNRELATED)
.addGroup(gl_page1.createParallelGroup(Alignment.BASELINE)
.addComponent(addProductLabelDescription)
.addComponent(addProductTextFieldDescription, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE))
.addPreferredGap(ComponentPlacement.UNRELATED)
.addGroup(gl_page1.createParallelGroup(Alignment.BASELINE)
.addComponent(addProductLabelDiscount)
.addComponent(addProductTextFieldDiscount, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE))
.addPreferredGap(ComponentPlacement.UNRELATED)
.addGroup(gl_page1.createParallelGroup(Alignment.BASELINE)
.addComponent(addProductLabelQuantity)
.addComponent(addProductTextFieldQuantity, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE, GroupLayout.PREFERRED_SIZE))
.addPreferredGap(ComponentPlacement.UNRELATED)
.addGroup(gl_page1.createParallelGroup(Alignment.BASELINE)
.addComponent(addProductLabelLocation)
.addComponent(addProductCheckBoxAalborg))
.addPreferredGap(ComponentPlacement.RELATED)
.addGroup(gl_page1.createParallelGroup(Alignment.TRAILING)
.addGroup(gl_page1.createSequentialGroup()
.addComponent(addProductCheckBoxOdense)
.addPreferredGap(ComponentPlacement.RELATED)
.addComponent(addProductCheckBoxCopenhagen)
.addGap(7)
.addComponent(addProductButtonReset))
.addComponent(addProductButtonAdd))
.addPreferredGap(ComponentPlacement.RELATED)
.addGroup(gl_page1.createParallelGroup(Alignment.BASELINE)
.addComponent(addProductButtonClose)
.addComponent(addProductButtonExit))
.addContainerGap(57, Short.MAX_VALUE))
);
page1.setLayout(gl_page1);
//**********************************
// PAGE 2
//**********************************
page2 = new JPanel();
GroupLayout gl_page2 = new GroupLayout(page2);
gl_page2.setHorizontalGroup(
gl_page2.createParallelGroup(Alignment.LEADING)
.addGap(0, 499, Short.MAX_VALUE)
);
gl_page2.setVerticalGroup(
gl_page2.createParallelGroup(Alignment.LEADING)
.addGap(0, 394, Short.MAX_VALUE)
);
page2.setLayout(gl_page2);
}
public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException, UnsupportedLookAndFeelException
{
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
ProductUI productMenu = new ProductUI();
productMenu.display();
}
}
package controller;
import project_package.*;
public class ProductController {
ProductRecords productRecordsCtrl;
public ProductController()
{
productRecordsCtrl = ProductRecords.getInstance();
}
public void createProduct(String name, double price, double discount, String description, int quantity, String location)
{
productRecordsCtrl.createProduct(name, price, discount, description, quantity, location);
}
}
package project_package;
import java.util.ArrayList;
//import java.util.Arrays;
import java.util.List;
public class ProductRecords
{
private static ProductRecords instance = null;
ArrayList<Product> products = new ArrayList<Product>();
List<Integer> quantity = new ArrayList<Integer>();
List<String> location = new ArrayList<String>();
int productIndex = 0;
public static ProductRecords getInstance()
{
if(instance == null)
{
instance = new ProductRecords();
}
return instance;
}
// add a product to the list
public void addProduct(Product product, int quantity, String location)
{
products.add(product.getID(), product);
this.quantity.add(product.getID(), quantity);
this.location.add(product.getID(), location);
}
// create (add) a new product (to the shop list)
public void createProduct(String name, double price, double discount, String description, int quantity, String location)
{
Product newProduct = new Product(productIndex, price, discount, name, description);
addProduct(newProduct, quantity, location);
productIndex++;
}
}
package project_package;
public class Product {
int id;
double price;
double discount;
String name;
String description;
public Product(int id, double price, double discount, String name, String description)
{
this.id = id;
this.price = price;
this.discount = discount;
this.name = name;
this.description = description;
}
}
答案 0 :(得分：4)
完整的错误就是这个
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
抛出这一行
productCtrl.createProduct("Test", 20.0, 20.0, "haha", 20,"nqkude");
由于productCtrl尚未实例化的事实。你可以这样做：
productCtrl = new ProductController();