类型字符串[closed]的getText（）方法未定义

Question

我发现这个错误：类型字符串的getText（）方法未定义

怎么了？

这是代码：

try {
            Connection connection = (Connection) DriverManager.getConnection("jdbc:postgresql://localhost:5432/Banca2", "postgres", "postgres");
                
                

PreparedStatement st = (PreparedStatement) connection;
                            
                    
                    ResultSet rs = st.executeQuery();
                    if (rs.next()) {
                        String test = test.getText();
                        test.setText("Succes");

我在最后2次对齐时得到错误。

以下是JtextArea的代码

JTextArea test = new JTextArea();
test.setBounds(286, 10, 127, 31);
frame.getContentPane().add(test);

以下是完整的代码：

public class Login {

    private static final long serialVersionUID = 1L;
    private static JFrame frame;
    private JPasswordField txtPassword;
    private JTextField txtUsername;
    

    


    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        //invokeLater Causes runnable to have its run method
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                //The try statement allows you to define a block of code to be tested for errors while it is being executed.
                try {
                    Login window = new Login();
                    window.frame.setVisible(true);
                    //The catch statement allows you to define a block of code to be executed, if an error occurs in the try block.
                } catch (Exception e) {
                    // is a tool used to handle exceptions and errors
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the application.
     */
    public Login() {
        // give a correct initial value
        initialize();
    }

    /**
     * Initialize the contents of the frame.
     */
    private void initialize() {
        //Here we create the panel, what color and size to have.
        frame = new JFrame();
        frame.getContentPane().setBackground(new Color(51, 204, 204));
        frame.setBounds(200, 200, 450, 300);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().setLayout(null);
        frame.setResizable(false);
        //We create a text and set it's properties
        JLabel lblNewLabel = new JLabel("Welcome");
        lblNewLabel.setFont(new Font("Tahoma", Font.BOLD | Font.ITALIC, 13));
        lblNewLabel.setBounds(200, 25, 80, 15);
        //getContentPane() method retrieves the content pane layer so that you can add an object to it
        frame.getContentPane().add(lblNewLabel);
        
        JLabel lblNewLabel_1 = new JLabel("Password:");
        lblNewLabel_1.setBounds(70, 120, 66, 13);
        frame.getContentPane().add(lblNewLabel_1);
        
        JLabel lblNewLabel_2 = new JLabel("Display");
        lblNewLabel_1.setBounds(70, 120, 66, 13);
        frame.getContentPane().add(lblNewLabel_1);
        
        
        
        txtPassword = new JPasswordField();
        txtPassword.setBounds(130, 117, 90, 20);
        frame.getContentPane().add(txtPassword);
        //Create a button 
        JButton btnNewButton = new JButton("Confirm");
        btnNewButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                
                String password = txtPassword.getText();
                String username = txtUsername.getText();
                
                try {
                    Connection connection = (Connection) DriverManager.getConnection("jdbc:postgresql://localhost:5432/Banca2", "postgres", "postgres");
                    
                    PreparedStatement st = (PreparedStatement) connection;
                            
                    
                    ResultSet rs = st.executeQuery();
                    if (rs.next()) {
                        String test = test.getText();
                        test.setText("Succes");

                    } else {
                        JOptionPane.showMessageDialog(btnNewButton, "Wrong Username & Password");
                    }
                    
                    }catch (SQLException sqlException) {
                        sqlException.printStackTrace();
                        }

JTextArea test = new JTextArea();
test.setBounds(286, 10, 127, 31);
frame.getContentPane().add(test);

    }
}

Answer 1

您有两个不同的test对象。

在您的代码块中，而不是这样：

if(rs.next(){
    String test = test.getText();
    ...
}

使用这个：

if(rs.next(){
    String differentName = test.getText();
    ...
}

使用的测试对象是字符串对象。然而，你想要的是文本区域。所以你应该给它们取不同的名字。

它之所以采用字符串1，是因为范围界定。这是最近的一个。请通过你最喜欢的搜索引擎搜索范围，我认为这将非常有用。