Java JTable列标题不显示-JScrollPane？

Question

New to GUIs in Java. I have been looking through stackoverflow and still don't understand how JTables work. I can get data in perfectly fine but I can't figure out why the column headers are not showing up and also how to re-size/position the table to another spot in the frame. I keep reading about using JScrollPane which I'm probably using incorrectly.. Thanks for any help.

        String[] columnNames = {"Date","Field", "Home Team","Visitor Team", "Score"};
        JFrame guiFrame = new JFrame();
        guiFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        guiFrame.setTitle("Soccer Schedule");
        guiFrame.setSize(500,500);
        guiFrame.setLocationRelativeTo(null);

        JPanel panel = new JPanel();
        panel.setSize(450, 450);
        JLabel titleLabel = new JLabel("Real Tired");
        String[][] data = createTableContents(scheduleCsv);
        JTable scheduleTable = new JTable(data,columnNames);
        JScrollPane scrollPane = new JScrollPane(scheduleTable);
        panel.add(scrollPane);
        panel.add(titleLabel);
        panel.add(scheduleTable);

        guiFrame.add(panel);
        guiFrame.setVisible(true);

Answer 1

The problem is not the table or the jscrollpane but how you put them in the panel:

panel.add(scrollPane);
panel.add(titleLabel);
panel.add(scheduleTable);

First of all the scheduleTable is (visually) inside the scrollPane, so you only need to put the scrollPane, not the table again. So we want:

panel.add(titleLabel); //first put the title
panel.add(scrollPane);

this works nicely:

And when I say it works nicely I mean it works nicely... by chance. The real layout of the elements is discovered when you make the window bigger:

The problem is in this code again:

panel.add(titleLabel); //first put the title
panel.add(scrollPane);

This surely adds the components (label and scrollpane) to the panel, however the obvious question is "Where in the panel adds them?".

Then answer is that the panel has a LayoutManager that decides the position of its components. There are several of them, you have to pick one, learn how it works and use it, look at this visual guide .

Because you didn't specify a layout, the panel is using the default layout for panels FlowLayout , that puts the components one after the other, side by side.

Pick a layout look at the tutorial and then use it. For example I could use a BorderLayout like this:

JPanel panel = new JPanel(new BorderLayout());
...
panel.add(titleLabel, BorderLayout.NORTH);
panel.add(scrollPane, BorderLayout.CENTER);

Gives:

Full code:

String[] columnNames = {"Date","Field", "Home Team","Visitor Team", "Score"};
JFrame guiFrame = new JFrame(); //no layout specified, frames use BorderLayout by default
guiFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
guiFrame.setTitle("Soccer Schedule");
guiFrame.setSize(500,500);
guiFrame.setLocationRelativeTo(null);

JPanel panel = new JPanel(new BorderLayout());
panel.setSize(450, 450);
JLabel titleLabel = new JLabel("Real Tired");

//String[][] data = createTableContents(scheduleCsv);

//my test data
String[][] data = new String[1][5];
for (int i = 0; i < 5; ++i)
{
    data[0][i] = "cell " + i;
}

JTable scheduleTable = new JTable(data,columnNames);
JScrollPane scrollPane = new JScrollPane(scheduleTable);
panel.add(titleLabel, BorderLayout.NORTH);
panel.add(scrollPane, BorderLayout.CENTER);

guiFrame.add(panel); //this is actually  guiFrame.add(panel, BorderLayout.CENTER);
guiFrame.setVisible(true);

Answer 2

You only need to add scrollpane to panel and not scheduleTable as scrollpane already  contain scheduleTable. see below code. Hope it helps.

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;


public class Test extends JFrame {

    public static void main(String args[]){
        String[] columnNames = {"Date","Field", "Home Team","Visitor Team", "Score"};
        JFrame guiFrame = new JFrame();
        guiFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        guiFrame.setTitle("Soccer Schedule");
        guiFrame.setSize(500,500);
        guiFrame.setLocationRelativeTo(null);

        JPanel panel = new JPanel();
        panel.setSize(450, 450);
        JLabel titleLabel = new JLabel("Real Tired");
        String[][] data = new String[0][0];
        JTable scheduleTable = new JTable(data,columnNames);
        JScrollPane scrollPane = new JScrollPane(scheduleTable);
        panel.add(scrollPane);
        panel.add(titleLabel);

        guiFrame.add(panel);
        guiFrame.setVisible(true);
    }
}