Java JTextField 在内部类的方法调用中不起作用

Question

我正在构建一个GUI，并试图实现一个非常简单的搜索-当您输入一个SSN时，它会检查是否有客户使用该SSN。我有一个JTextField，其中输入了SSN，当您单击submit时，它会调用searchBySSNString方法并返回true或false。问题是，每当我从JTextField中提取文本时，它都会返回false。

为了解决这个问题，我试图将其归结为尽可能少的代码，这样就不必有人费力地阅读我的所有代码。我在问题部分包含了额外的代码，以显示我一直在处理的内容。如果我在中硬编码一个字符串并搜索它，它会返回true，如果我将该硬编码字符串与JTextField中的文本进行比较，如果键入了相同的文本，它就会返回0。

一些杂项注释：我使用SSN作为字符串，因为我认为我永远不需要像处理数字一样处理它。如果这是个坏主意，我想知道为什么。创建的帐户上的SSN为222222222。我还没有实现任何东西来验证输入或解释破折号或任何东西。

如果你真的仔细阅读我的代码，你会发现，我是一个初学者，所以我总是愿意听取任何人的建议，但现在的紧迫问题是弄清楚为什么JTextField的输入在搜索中不起作用。

import java.util.ArrayList;
import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.JTextPane;
public class Bank {
    private JFrame frame;
    private JTextField txtSearchBySSN;
    private JTextField txtTestMessage;
    static ConnectionFactory connectionFactory = ConnectionFactory.getConnectionFactory();
    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        connectionFactory.newAccountAndCustomer("Mike", "222222222");
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    Bank window = new Bank();
                    window.frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }
    /**
     * Create the application.
     */
    public Bank() {
        initialize();
    }
    /**
     * Initialize the contents of the frame.
     */
    private void initialize() {
        frame = new JFrame();
        frame.setBounds(100, 100, 607, 429);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().setLayout(null);
        JLabel lblSearchBySSN = new JLabel("Search for customer by SSN");
        lblSearchBySSN.setBounds(6, 38, 190, 16);
        frame.getContentPane().add(lblSearchBySSN);
        txtSearchBySSN = new JTextField();
        txtSearchBySSN.setBounds(208, 32, 134, 28);
        frame.getContentPane().add(txtSearchBySSN);
        txtSearchBySSN.setColumns(10);
        //here's the problem portion
        JButton btnSearchBySSN = new JButton("Search");
        btnSearchBySSN.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                //get text from the textbox
                String testString = txtSearchBySSN.getText();
                //print out the text from the textbox to see if it looks the same
                System.out.println(testString);
                //call the search method using the string from the textbox
                System.out.println(connectionFactory.searchBySSNString(testString));
                //call the search method using two hard-coded string to see if the method works
                //one that does match and one that doesnt
                System.out.println(connectionFactory.searchBySSNString("222222222"));
                System.out.println(connectionFactory.searchBySSNString("333333333"));
                //compare the text from the textbox to a hard-coded string - this returns 0
                System.out.println(testString.compareTo("222222222"));
            }
        });
        btnSearchBySSN.setBounds(355, 33, 117, 29);
        frame.getContentPane().add(btnSearchBySSN);
        txtTestMessage = new JTextField();
        txtTestMessage.setBounds(117, 83, 134, 28);
        frame.getContentPane().add(txtTestMessage);
        txtTestMessage.setColumns(10);
    }
}
class ConnectionFactory {
    private ArrayList<Customer> customers;
    private ArrayList<Account> accounts;
    private ArrayList<Connection> connections;
    private static ConnectionFactory connectionFactory;
    private ConnectionFactory() {
        customers = new ArrayList<Customer>();
        accounts = new ArrayList<Account>();
        connections = new ArrayList<Connection>();
    }
    //creates a ConnectionFactory if one doesn't already exist
    public static ConnectionFactory getConnectionFactory() {
        if (connectionFactory == null) {
            connectionFactory = new ConnectionFactory();
        }
        return connectionFactory;
    }
    //create new account and new customer
    public void newAccountAndCustomer(String customerName, String ssn) {
        Customer customer = new Customer(customerName, ssn);
        Account account = new CheckingAccount();
        //create the connection object, add all of the items to their respective arrays
        Connection connection = new Connection(customer, account);
        customers.add(customer);
        accounts.add(account);
        connections.add(connection);
    }
    //check to see if customer exists
    public String searchBySSNString(String ssn) {
        boolean customerExists = false;
        for(int i = 0; i < customers.size(); i++) {
            if(customers.get(i).getSSN() == ssn) {
                customerExists = true;
                break;
            }
        }
        if (customerExists) {
            return "true";
        }
        else {
            return "false";
        }
    }
}
abstract class Account {
    private long accountNumber;
    private double currentBalance;
    protected Account() {
        //
    }
    protected Account(double currentBalance) {
        this.currentBalance = currentBalance;
    }
    public void withdraw(double withdrawalAmount) {
        currentBalance -= withdrawalAmount;
    }
    public void deposit(double depositAmount) {
        currentBalance += depositAmount;
    }
    public double getCurrentBalance() {
        return currentBalance;
    }
    public void setCurrentBalance(double newBalance) {
        this.currentBalance = newBalance;
    }
    public long getAccountNumber() {
        return accountNumber;
    }
    public void setAccountNumber(long accountNumber) {
        this.accountNumber = accountNumber;
    }
}
class CheckingAccount extends Account {
    private double overdraftAmount;
    private static long nextAccountNumber = 10000000;
    private long accountNumber;
    public CheckingAccount() {
        accountNumber = nextAccountNumber;
        nextAccountNumber++;
    }
    public void setOverdraftAmount(double overdraftAmount) {
        this.overdraftAmount = overdraftAmount;
    }
    public double getOverdraftAmount() {
        return overdraftAmount;
    }
    public long getAccountNumber() {
        return accountNumber;
    }
    @Override
    public String toString() {
        return String.valueOf(accountNumber);
    }
}
class Connection {
    private Customer customer;
    private Account account;
    public Connection(Customer customer, Account account) {
        this.customer = customer;
        this.account = account;
    }
    public void setCustomer(Customer customer) {
        this.customer = customer;
    }
    public Customer getCustomer() {
        return customer;
    }
    public void setAccount(Account account) {
        this.account = account;
    }
    public Account getAccount() {
        return account;
    }   
}
class Customer {
    private String name;
    private String ssn;
    public Customer(String name, String ssn) {
        this.name = name;
        this.ssn = ssn;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getName() {
        return name;
    }
    public void setSSN(String ssn) {
        this.ssn = ssn;
    }
    public String getSSN() {
        return ssn;
    }
    @Override
    public String toString() {
        return name;
    }
}

Answer 1

实际上，我并没有阅读您的所有代码，但在Java中比较对象之间的观测等式的方法是使用equals方法，==只是引用等式。所以

更改：

if(customers.get(i).getSSN() == ssn)

至

if(customers.get(i).getSSN().equals(ssn))

也不要使用null布局。Swing设计用于布局管理器。

阅读更多：

如何比较java 中的字符串

使用布局管理器

Answer 2

if(customers.get(i).getSSN() == ssn)

这行有问题。使用equals（）方法进行字符串比较，而不是==。

如果使用==比较字符串，则如果两个String对象在内存中的位置相同，则返回true。但equals（）方法将检查这些String对象的值。因此，使用改变以上线路

if(customers.get(i).getSSN().equals(ssn))

将解决您的问题。