Column name not displayed!

[Fox Shen]

For display the Flight Info with JTable, I implemented the FlightModel as following:

     String[] columnNames = null;  //empty array of names
    Vector dataRows = new Vector();   //empty vector of rows
    public FlightModel(DataInfo[] dataInfo) {
        FieldInfo[] fields = dataInfo[0].getFields();
        columnNames = new String[fields.length];
        for (int i = 0; i < fields.length; i++) {
            columnNames[i] = fields[i].getName();
        }
        for (int i = 0; i < dataInfo.length; i++) {
            DataInfo data = dataInfo[i];
            dataRows.add(data.getValues());
        }
    }
    public int getColumnCount() {    //Return number of columns...
        return columnNames.length;
    }
    public int getRowCount() {    //Return number of rows...
        if (dataRows == null)
            return 0;
        else
            return dataRows.size();
    }
    public Object getValueAt(int row, int column) {    //Return the value at position row, column...
        return ((String[]) (dataRows.elementAt(row)))[column].trim();
    }
    public String getColumnName(int column) {    //Return the name for the column...
        System.out.println("Return the column name = " + columnNames[column]);
        return columnNames[column] == null?"No Name":columnNames[column];
    }
 

Now the JTable can display all the data info correctly, except for the column not found. According to the debug info, the columnNames are retrieved exactly, but just not displayed. Anyone know the reason, any comment would be appreciated!
-Fox

[Michael Morris]

Hi Fox (know any good vixens?):
I'm analyzing your code and so far have not figured out why the column head is not displyed but will keep looking.
If you don't already have it, you need to download
Code Conventions for the JavaTM Programming Language
A lot of this code does not comply with those conventions and you will lose points on general considerations for that. Also you need to use one of the newer Collections in place of Vector.
Michael Morris
[ August 29, 2002: Message edited by: Michael Morris ]

[Mark Spritzler]

"Fox"-
Welcome to the JavaRanch! Please adjust your displayed name to meet the
JavaRanch Naming Policy.
You can change it
here.
Thanks! and welcome to the JavaRanch!
Mark

[Michael Morris]

Hi Fox,
I ran a test using your table model and the table headers displayed fine in the frame I created. Here's the simple frame I used:

package suncertify.clientTest;
import java.awt.*;
import javax.swing.*;
import suncertify.db.*;
public class FBNClientTest extends JFrame {
    public FBNClientTest(DataInfo[] dataInfo) {
        getContentPane().add(new JScrollPane(new JTable(new FlightModel(dataInfo))), BorderLayout.CENTER);
    }
    public static void main(String[] args) {
        DataInfo[] dataInfo = null;
        try {
            Data data = new Data("db.db");
            dataInfo = new DataInfo[data.getRecordCount()];
            for (int i = 0; i < dataInfo.length; i++) {
                dataInfo[i] = data.getRecord(i + 1);
            }
        } catch (Exception e) {
            e.printStackTrace();
            System.exit(1);
        }
        FBNClientTest frame = new FBNClientTest(dataInfo);
        frame.pack();
        frame.show();
    }
}

There must be some other problem that you are missing.
Michael Morris

[George Lawniczak]

To display headers, you must decorate your JTable with a JScrollPanel, or else the headers will not display.

[Fox Shen]

Hi Michael
Thanks for your comments and code example. I think I now know the reason for that. Just as shown in your code and mentioned by George, the JTable must be decorated with a JScrollPane, or the header will not display. In my own code, I just put it into a JPanel, I think that's the problem.
Fox Shen

[ZhengQi Huang]

Hi,Michael:
I wrote code like Fox Shen too,why did you say

A lot of this code does not comply with those conventions and you will lose points on general considerations for that.

Could you please tell me how to modify this code to comply with java code conventions???
And another question:why can't use Vector here?Which Collections should I take???
[ August 30, 2002: Message edited by: ZhengQi Huang ]
[ August 30, 2002: Message edited by: ZhengQi Huang ]

[Michael Morris]

Hi ZhengQi,
There are many code conventions that you should be aware of for this assignment. To view those conventions, click on the link of my first post.
To download the HTML version click the following link:
Java Code Conventions (Download HTML)
Here are some examples:
Don't do this:

    for (int i = 0; i < 10; i++) j += i;

Do this instead:

    for (int i = 0; i < 10; i++) {
        j += i;
    }

Don't do this:

    if (a == b && c == d)
    {
        e = f;
    }
    else
    {
        if (a == b && c != d)
        {
            e = g;
        }
        else
        {
            e = h;
        }
    }

Do this instead:

    if (a == b && c == d) {
        e = f;
    } else if (a == b && c != d) {
        e = g;
    } else {
        e = h;
    }

Never have lines over 80 characters. If you have to break up a long line of code, there are guidelines to where to break the line and many other items to make code very easy to read.

And another question:why can't use Vector here?Which Collections should I take???

Vector is one of the old Collections objects and the newer ones are now preferred. A good choice for a table model would be an ArrayList which has both the functionality of a dynamic array like Vector and implements the List interface. You could also use a HashMap by mapping a row to a record.
Hope this helps,
Michael Morris