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java - TableModel，导致 Java JFrame 中出现重复的数据库信息

转载 作者：行者123 更新时间：2023-12-01 23:56:59 26 4
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我在 JFrame 中设置了此方法，当用户按下“加载文件”按钮时将调用该方法；但是，当用户第二次按下按钮时。 。 。他们在第一个表格下面得到了另一个表格，因此所有信息都会被复制，并且它会扩展到我的“不可调整大小”框架之外。

如何让它无论用户按下按钮多少次都只加载一张表？

    JButton btnLoad = new JButton("Load File")

private void GetAction()
{
    ActionHandler handler = new ActionHandler();
    btnLoad.addActionListener(handler);
}

    private class ActionHandler implements ActionListener
{       
    public void actionPerformed(ActionEvent evt) 
    {
        String incmd = evt.getActionCommand();
        if (incmd.equals("Load File")) // If Load File button is pressed
            DatabaseLoad();
        else if (incmd.equals("Exit")) // If Exit button is pressed
            System.exit(0);  
    }
}
    private void DatabaseLoad()
    {
        try 
        {
            // The driver allows you to query the database with Java
            // forName dynamically loads the class for you           
            Class.forName("com.mysql.jdbc.Driver");

            // DriverManager is used to handle a set of JDBC drivers
            // getConnection establishes a connection to the database
            // You must also pass the userid and password for the database            
            String url = "jdbc:mysql://localhost:3306/charity";
            conn = DriverManager.getConnection (url,"root","password");

            // Statement objects executes a SQL query
            // createStatement returns a Statement object            
            Statement sqlState = conn.createStatement();

            // This is the query I'm sending to the database
            String selectStuff = "SELECT `name`, `charity`, `amount` FROM `charity`.`donations` ";                  

            // A ResultSet contains a table of data representing the
            // results of the query. It can not be changed and can 
            // only be read in one direction            
            rows = sqlState.executeQuery(selectStuff);

            // Temporarily holds the row results            
            Object[] tempRow;

            // next is used to iterate through the results of a query            
            while(rows.next()){

            // Gets the column values based on class type expected
            tempRow = new Object[]{rows.getString(1), rows.getString(2), rows.getDouble(3) };

            // Adds the row of data to the end of the model             
            dTableModel.addRow(tempRow);                

        }
            // Successfully loaded, message the user
            message1.setText("<html><font color='red'>Database Info Loaded</font>");
            message2.setText("");
    } 
        catch (SQLException ex) 
        {            
            // String describing the error          
            System.out.println("SQLException: " + ex.getMessage());

            // Vendor specific error code            
            System.out.println("VendorError: " + ex.getErrorCode());
        } 
        catch (ClassNotFoundException e) 
        {
            // Executes if the driver can't be found
            System.out.println("Driver Cannot be found");
            e.printStackTrace();
        }

        // Create a JTable using the custom DefaultTableModel       
        JTable table = new JTable(dTableModel);

        // Increase the font size for the cells in the table        
        table.setFont(new Font("Serif", Font.PLAIN, 16));

        // Increase the size of the cells to allow for bigger fonts        
        table.setRowHeight(table.getRowHeight()+5);

        // Allows the user to sort the data     
        table.setAutoCreateRowSorter(true);

        // right justify amount column
        TableColumn tc = table.getColumn("amount");
        RightTableCellRenderer rightRenderer = new RightTableCellRenderer();
        tc.setCellRenderer(rightRenderer);      

        // Disable auto resizing
        table.setAutoResizeMode(JTable.AUTO_RESIZE_OFF);

        // Set the width for the columns        
        TableColumn col1 = table.getColumnModel().getColumn(0);
        col1.setPreferredWidth(200);

        TableColumn col2 = table.getColumnModel().getColumn(1);
        col2.setPreferredWidth(275);

        TableColumn col3 = table.getColumnModel().getColumn(2);
        col3.setPreferredWidth(75);     

        // Put the table in a scrollpane and add scrollpane to the frame          
        JScrollPane scrollPane = new JScrollPane(table);
        scrollPane.setPreferredSize(new Dimension(552, 400));
        this.add(scrollPane, BorderLayout.CENTER);
    }   

    // To change justification to the right
    class RightTableCellRenderer extends DefaultTableCellRenderer {   
          public RightTableCellRenderer() {  
            setHorizontalAlignment(JLabel.RIGHT);  
        }           
    }

最佳答案

How can I get it to only load the one table no matter how many times the user presses the button?

当您构建 GUI 组件时，表格和滚动 Pane 只能创建一次。然后，当您想要更改数据时，只需更改现有表的模型即可:

table.setModel( updatedModel );

关于java - TableModel，导致 Java JFrame 中出现重复的数据库信息，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/15437355/

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