通过选择JComboBox选项动态添加JTextField和JLabel

Question

I want to write a program that allows user to connect,view and add or delete values from database. I'm stuck with the swing part. When i select a combobox option nothing happens but i want to create a view like mysql workbench. It suppose to be like that; user picks a table name from combobox and can see column names from that table and textfields to add new values or existing values above column names.

My code is this so far:

public class DBC extends JFrame{

static String tablo;
static JTextField tf = new JTextField(20);
static int columnCount;
static JPanel tfPanel = new JPanel();
static JLabel depName = new JLabel("Name");
static JLabel depLocation = new JLabel("Location");
static Box box = new Box(BoxLayout.Y_AXIS);

public static void main(String[] args) throws Exception {

    Class.forName("com.mysql.jdbc.Driver");
    Connection connect = DriverManager.getConnection("jdbc:mysql://localhost:3306/project"
              ,"root","123456789");

    final Statement statement = connect.createStatement();

    JLabel tabloSec = new JLabel("Tablo Seçin:");
    final JComboBox<String> tablolar = new JComboBox<String>();
    DatabaseMetaData md = connect.getMetaData();
    final ResultSet rs = md.getTables(null, null, "%", null);
    while (rs.next()) {
        tablolar.addItem(rs.getString(3));
    }

    tablolar.addActionListener(new ActionListener(){

        @Override
        public void actionPerformed(ActionEvent arg0) {

            tablo = tablolar.getSelectedItem().toString();

            try {
                 columnCount = rs.getMetaData().getColumnCount();
                 for(int i=0;i<=columnCount;i++ ){

                        box.add(tf);
                    }
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    });

    JButton ekle = new JButton("Ekle");
    ekle.addActionListener(new ActionListener(){

        @Override
        public void actionPerformed(ActionEvent e) {

            try {
                switch(tablo){
                case "department":

                    statement.executeUpdate("INSERT INTO department(Name,Location) VALUES('"+tf.getText()+"')");
                case "employee":

                    statement.executeUpdate("INSERT INTO employee(Id,FirstName,LastName,Sex,Address,Email,Salary,BirthDate,JoinDate) VALUES('"+tf.getText()+"')");
                case "engineer":

                    statement.executeUpdate("INSERT INTO engineer(EngineerType) VALUES('"+tf.getText()+"')");
                case "manager":

                    statement.executeUpdate("INSERT INTO manager(Department) VALUES('"+tf.getText()+"')");
                case "project":

                    statement.executeUpdate("INSERT INTO project(Name,Number,Value) VALUES('"+tf.getText()+"')");
                case "secretary":

                    statement.executeUpdate("INSERT INTO secretary(TypingSpeed) VALUES('"+tf.getText()+"')");
                }

            } catch (SQLException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }
        }
    });

    JButton cik = new JButton("Çık");
    cik.addActionListener(new ActionListener() {

        @Override
        public void actionPerformed(ActionEvent e) {

            System.exit(0);
        }
    });

    JPanel panel = new JPanel(new GridLayout(4,3));

    panel.add(tabloSec);
    panel.add(tablolar);
    panel.add(box);
    panel.revalidate();
    panel.add(ekle);
    panel.add(cik);

    JFrame frame = new JFrame("Deneme");
    frame.setSize(600,600);
    frame.setLocationRelativeTo(null);
    frame.add(panel);
    frame.pack();
    frame.setVisible(true);
  }
}

Answer 1

Looks like you're adding the same text field when iterating over the metadata of the result set: box.add(tf); . This will add the same text field only once. You also need to validate() and repaint() the box container after adding new controls to it. Note that you also need to remove all controls from the box container when selecting new table. You may need to introduce scroll pane. In addition, SQL statement execution refers to the same text field. Unless of course there is only one column and one value that is always should be updated.

All in all, unless this is a very specific solution for a very specific set of tables, you may consider using friendlier controls for this, perhaps a list or a table. Maybe something similar to a properties table where first column specifies the name of the property, and the second column the value of that property. The value column is editable. You can repopulate the properties table once new SQL table is selected. Then on statement execution, just collect all the necessary values. As an alternative, you can also show the relevant view of a SQL table and let user tweak whatever values and then update SQL once done. Look at Table From Database by @camickr.

Also note that you should not execute SQL statements on Event Dispatch Thread , this may freeze your UI as long operations will block EDT. These operations should be handled on an auxiliary worker thread. See Event Dispatch Thread . It is common to use SwingWorker to handle such lengthy tasks.