0

编辑

我做了一些更正，现在可以编译了。尝试将联系人添加到文件时，我在 ContactsCollection 类的第 13 行收到空指针异常：

for (int i = 0; i < contactList.size(); i++)

和 Contacts (GUI) 类的第 93 行：

contactList.add(contact);

联系人类：

import java.util.*;
import java.io.*;

public class Contact implements Serializable
{
public static final long serialVersionUID = 42L;
public String name, number;

Contact()
{
    name = "No name";
    number = "No number";
}

Contact (String theName, String theNumber)
{
    this.name = theName;
    this.number = theNumber;
}

public void setName(String aName)
{
    this.name = aName;
}

public void setNumber(String aNumber)
{
    this.number =aNumber;
}

public String getName()
{
    return name;
}

public String getNumber()
{
    return number;
}

public String toString()
{
    return name + ": " + number;
}

public boolean equals(Contact other)
{
   if (name.equals(other.getName()) && number.equals(other.getNumber()))
   {
      return(true);
   }
   else
   {
      return(false);
   }
}   
}

联系人集合类

import java.io.*;
import java.util.*;

class ContactsCollection
{
public static ArrayList<Contact> contactList;

public static void write()
{
    try 
    {
        ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("contactList.dat"));
        for (int i = 0; i < contactList.size(); i++)
        {
            out.writeObject(contactList.get(i));
        }
        out.close();
    } 
    catch(IOException e)
    {
        e.printStackTrace();
    }
}

public static void read()
{
contactList = new ArrayList<Contact>();
try
{
    ObjectInputStream in = new ObjectInputStream(new FileInputStream("contactList.dat"));
    Contact temp;
    while (in.available()!=0)
    {
        temp = (Contact)in.readObject();
        contactList.add(temp);
    }
    in.close();
}
catch(FileNotFoundException e)
{
    e.printStackTrace();
}
catch(IOException e)
{
    e.printStackTrace();
}
catch(ClassNotFoundException e)
{
    e.printStackTrace();
}       

}
}

联系人 (GUI) 类

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import javax.swing.Timer;
import java.util.*;

class Contacts extends JFrame implements ActionListener, WindowListener
{
public static final int WIDTH = 400;
    public static final int HEIGHT = 600;
    public static final int SMALL_WIDTH = 200;
    public static final int SMALL_HEIGHT = 100;

private static final Dimension stdBtn = new Dimension(150, 50);    

    JPanel centerPanel, northPanel, southPanel;
ImageIcon icon;
JLabel picture;
JButton addContact, displayContacts;
JScrollPane scroll;
JTextArea textArea;
Clock clock;
Background background;
Contact contact;
ArrayList<Contact> contactList;


public Contacts()
{
    super("Contacts");
    this.setLayout(new BorderLayout());
    this.setSize(WIDTH, HEIGHT);
    this.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
    addWindowListener(this);
    this.setLocationRelativeTo(null);

    centerPanel = new JPanel();
    northPanel = new JPanel();
    southPanel = new JPanel();

    centerPanel.setBackground(Color.BLACK);
    southPanel.setBackground(Color.BLACK);      

    clock = new Clock();
    northPanel.add(clock);

    icon = new ImageIcon("ContactsBackground.jpg");
    picture = new JLabel(icon);
    centerPanel.add(picture);

    textArea = new JTextArea("", 10, 30);
    textArea.setEditable(false);
    JScrollPane scroll = new JScrollPane(textArea, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
            JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);    
    centerPanel.add(scroll);    

    JButton displayContacts = new JButton("Display contacts");
    displayContacts.addActionListener(this);
    southPanel.add(displayContacts);

    JButton addContact = new JButton("Add contact");
    addContact.addActionListener(this);
    southPanel.add(addContact);

    this.add(northPanel, BorderLayout.NORTH);
    this.add(centerPanel, BorderLayout.CENTER);
    this.add(southPanel, BorderLayout.SOUTH);       

    setResizable(false);        
}

public void actionPerformed(ActionEvent e)
{
    contactList = new ArrayList<Contact>();
    JButton source = (JButton)e.getSource();
    String contactInput = source.getText();

    if (contactInput == "Display contacts")
    {
        ContactsCollection.read();
        for (int i = 0; i < contactList.size(); i++)
        {
            contact = (Contact)contactList.get(i);
            textArea.setText(contact.getName() + "," + contact.getNumber() + "\n");
        }
    }
    if (contactInput == "Add contact")
    {
        String name = JOptionPane.showInputDialog(null, "Enter Name");
        String number = JOptionPane.showInputDialog(null, "Enter Number");
        contact = new Contact(name, number);
        contactList.add(contact);
        ContactsCollection.write();
    }
}

public void windowOpened(WindowEvent e)
{}

public void windowClosing(WindowEvent e)
{
    this.setVisible(false);
    background = new Background();
    background.setVisible(true);        
}

public void windowClosed(WindowEvent e)
{}

public void windowIconified(WindowEvent e)
{}

public void windowDeiconified(WindowEvent e)
{}

public void windowActivated(WindowEvent e)
{}

public void windowDeactivated(WindowEvent e)
{}      
}
4

1 回答 1

0

关于

我遇到的第一个错误是“找不到符号方法 read()”和“找不到符号方法 write()”。

您正在调用 ArrayList 上的一个方法，该方法read()不存在。您需要对 ArrayList 的内容之一调用此方法，而不是 ArrayList 本身。这就像试图用一个鸡蛋箱做煎蛋 - 是行不通的。你需要用一两个鸡蛋代替。同样的事情write()。

关于

第二个错误是在显示联系人的操作侦听器中，指出“需要一个数组，但找到了一个联系人”。

你应该告诉我们是哪一行导致了这个错误。

编辑
你显示：

for (int i = 0; i < contactList.size(); i++)
{
    textArea.setText(contact[i].getName() + "," + contact [i].getNumber() + "\n");
}

该代码没有任何意义。您需要使用列表变量 contactList 并通过 ArrayListget(...)方法获取其项目。

您的代码表明您正在盲目地添加一堆代码，而不管错误如何，这是行不通的。如果你不能使用 IDE，你应该经常编译，在每 1-3 行之后，并在尝试添加更多代码之前修复所有编译错误。否则，您最终会遇到一堆错误。另外，请阅读手册/书籍。不要猜测这些东西。

于 2013-05-15T02:56:52.143 回答