Building a simple GUI using the Swing library in Java 1.6

I'm trying to build a simple GUI using the Swing library. I don't understand why my table is erasing everything that previously was added to the GUI and only then creates the table. I'm assuming it's a certain command in addMainPanel, but I'm not sure which. Your advice would be much appreciated.

package fuelConsumption;

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.*;

public class LogView implements ActionListener {

    private Log myLog;
    private JFrame frame;

    public LogView (String frameName) {
        this.frame = new JFrame(frameName);
        this.frame.setPreferredSize(new Dimension(500,500));
        this.frame.getContentPane().setLayout(new BorderLayout());

        this.addMainPanel(frame);
        this.addTable(frame);
        //addMenu(frame);
        //addToolBar(frame);

        this.frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.frame.pack();
        this.frame.setVisible(true);
    }

    private void addTable(JFrame frame2) {
        String[] columnNames = {"date",
                               "station",
                               "fuel grade",
                               "fuel amount",
                               "fuel unit cost",
                               "fuel cost",
                               "trip distance"};
        Object[][] data = {
            {"Shell", 89, 40, 109.5, "bla", 100, 123}
        };

        JTable table = new JTable(data, columnNames);
        table.setPreferredScrollableViewportSize(new Dimension(500, 70));
        //table.setFillsViewportHeight(true);

        //Create the scroll pane and add the table to it.
        JScrollPane scrollPane = new JScrollPane(table);

        //Add the scroll pane to this panel.
        //this.frame.setContentPane(scrollPane);
        frame2.getContentPane().add(scrollPane);
    }

    private void addMainPanel(JFrame frame2) {
        // TODO Auto-generated method stub

        JPanel panel = new JPanel(new GridBagLayout());

        GridBagConstraints c = new GridBagConstraints();
        c.gridx = 0;
        c.gridy = 0;
        c.gridwidth = 5;
        c.ipady = 50;
        c.anchor = GridBagConstraints.LINE_START;
        c.weightx = 0.5;
        c.weighty = 0.5;
        JLabel label = new JLabel("");
        panel.add(label,c);

        label = new JLabel("Info");
        c = new GridBagConstraints();
        c.gridx = 0;
        c.gridy = 1;
        c.anchor = GridBagConstraints.LINE_START;
        c.weightx = 0.5;
        c.weighty = 0.5;
        panel.add(label,c);

        label = new JLabel("Label");
        c = new GridBagConstraints();
        c.gridx = 2;
        c.gridy = 1;
        c.anchor = GridBagConstraints.LINE_START;
        c.weightx = 0.5;
        c.weighty = 0.5;
        panel.add(label,c);

        label = new JLabel("Comments");
        c = new GridBagConstraints();
        c.gridx = 0;
        c.gridy = 2;
        c.anchor = GridBagConstraints.FIRST_LINE_START;
        c.weightx = 0.5;
        c.weighty = 0.5;
        panel.add(label,c);

        JTextArea textArea = new JTextArea(4,30);
        JScrollPane textScroll = new JScrollPane(textArea);
        c = new GridBagConstraints();
        c.gridx = 1;
        c.gridy = 2;
        c.gridwidth = 4;
        c.ipadx = 30;
        c.ipady = 50;
        c.anchor = GridBagConstraints.FIRST_LINE_START;
        c.fill = GridBagConstraints.HORIZONTAL;
        c.weightx = 0.5;
        c.weighty = 0.5;
        panel.add(textScroll,c);

        JButton button = new JButton("Edit");
        button.addActionListener(this);
        button.setActionCommand("Edit");
        c = new GridBagConstraints();
        c.gridx = 1;
        c.gridy = 3;
        c.fill = GridBagConstraints.HORIZONTAL;
        c.weightx = 0.5;
        c.weighty = 0.5;
        panel.add(button,c);

        button = new JButton("Previous");
        button.addActionListener(this);
        button.setActionCommand("Pre开发者_如何学运维vious");
        c = new GridBagConstraints();
        c.gridx = 2;
        c.gridy = 3;
        c.weightx = 0.5;
        c.weighty = 0.5;
        panel.add(button,c);

        button = new JButton("Next");
        button.addActionListener(this);
        button.setActionCommand("Next");
        c = new GridBagConstraints();
        c.gridx = 3;
        c.gridy = 3;
        //        c.weightx = 0.5;
        //        c.weighty = 0.5;
        panel.add(button,c);

        frame2.getContentPane().add(panel);
    }

    public static void main(String [] args){
        new LogView("Fuel Consumption");
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        // TODO Auto-generated method stub

    }
}

Your GUI could be:

If you change

private void addTable(JFrame frame2) { to private void addTable() {

and

frame2.getContentPane().add(scrollPane); to frame.add(scrollPane, BorderLayout.CENTER);

to:

private void addMainPanel(JFrame frame2) { to private void addMainPanel() {

and

frame2.getContentPane().add(panel); to frame.add(panel, BorderLayout.SOUTH);

Because in BorderLayout only one JComponent can be placed in one of the areas, as there aren't definitions for BorderLayout constants, then JComponent would be placed in the BorderLayout.CENTER area.

3)

Then you have to change

this.addMainPanel(frame);
this.addTable(frame);

to

this.addMainPanel();
this.addTable();

The default layout of JFrame is BorderLayout, so you need something like these in your addTable and addMainPanel methods, respectively:

frame2.add(scrollPane, BorderLayout.CENTER);
frame2.add(panel, BorderLayout.SOUTH);

Note that getContentPane() is not required.

You are mixing layouts, components...

If want to add the panel and the table to the frame as two separate components (not the table inside the panel), should take care about the layout of the frame, BorderLayout. You should add the panel and the table to the frame using indications to the layout to place the components, like:

 frame2.getContentPane().add(scrollPane, BorderLayout.SOUTH);

and

frame2.getContentPane().add(panel, BorderLayout.NORTH);