Develop Reference

Java Swing one-row scrollable container?

I'm writing an app, that needs some kind of one-row JList to store formula objects. I first tried with just buttons as objects with text on them, but it was not good. Then I made one-row JList but all it's cells have the same width, and it looks like this
(a scrollable area). So "<" will have the same width as others and it looks bad.
Is there a way to force list cells to use their real width? Or there is any cool container that just can store objects(just text) with scrolling over them?
With buttons it looks like

How about you use the JTable which you can configure it to have a single row?
Example Code:
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTable;
public class JTableTest {
JFrame f;
JTable j;
JTableTest()
{
f = new JFrame();
f.setTitle("JTable Example");
String[][] data = {
{ "F=ma", "e=mc^2", "a^2=b^2+c^2" }
};
String[] columnNames = { "Newton", "Einstein", "Pythagoras" };
j = new JTable(data, columnNames);
j.setBounds(30, 40, 200, 300); //Position x,y & Size of JTable height,width
JScrollPane sp = new JScrollPane(j);
f.add(sp);
f.setSize(500, 200);
f.setVisible(true);
}
public static void main(String[] args)
{
new JTableTest();
}
}
By default, the width of JTable cells are fixed. You can change them, however, using:
j.getColumnModel().getColumn(0).setPreferredWidth(5); //Set Width=5 for first column

How to refresh JTable with always-changing tableModel?

2015.5.5 22:11 updated. I found that, when I create a sorter and call setRowSorter() method in the MyTable's construction, afterwards, it
will keep the original line number(in which the data still refresh
correctly but not easy to discover)even though the dataModel inside is
already changed many times which can be proven as
printf(getModel().getRowCount()). What's more,
MyTable.getAutoCreateRowSorter() always return true. I must explicitly
call setAutoCreateRowSorter(true) to fix the issue it if I called
setRowSorter(). I am happy but this is still wierd.
[2015.5.5 6:19 updated] I have found a way to access: make a "setRow" with the combination of insertRow() and removeRow() and everytime I
update, I setrRow all the rows in the table. It reflect immediately in
the UI. BUT there will be a series of error begin with "AWT-EventQueue-0" java.lang.IndexOutOfBoundsException: Invalid index" and I　guess it's about some kiind of swing thread problem because I can see "RepaintManager" or "paint" in the error. It occurs especially when I move the scrollbar when it's running.(but it still occur if I don't move it)
I have a JTable in a JScrollPane in a JFrame. I initial a MyTableModel with a data and use it to Create a JTable.Like this
MyTableModel extends DefaultTableModel{
Data data;
//object
MyTableModel (Data a){
data = a;
// do something to initial the table model,like build object[][] and add rows.
}
}
class main{
MyTableModel tm = new MyTableModel(data);
Jtable table = new JTable(tm);
JScrollpane jsp = new JScrollpane(table);
JFrame window = new JFrame();
window.getxxxpane().add(jsp);
}
So, as my data is always changing/updating and the changed row is plural and impossible to caculate.
while(true){
data.change();
refreshing the table to display the data immediately;
}
my idea is to simply build a new MyTableModel object and set it as the table's model like:
table.setModel(new MyTableModel(data)); //data had been changed.
which doesn't work.
and I tried this:
tm = MyTableModel(data);
tm.fireTableDataChanged();
which doesn't work either.
and the combination as well:
MyTableModol nm = new MyTableModel(data); //data had been changed
table.setModel(nm);
nm.fireTableDataChanged();
Could someone please give me some clue to change the TableModel object in an unchangable Jtable and update everytime.I dont want to change the tableModel Object because the calculation is huge, instead ,i Want to always create a new object with the construction method's parameter(changed data).
the most worst method is to remove the JScrollpane and rebuild one table/tablemodel/jscrollpane and re-add it, in which I have to call window.setVisible(true). window.repait() doesn't work,either,unless I move it.
I create a space-wasting but runnable program for demostration ,which most of them are nonsense.
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Formatter;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTabbedPane;
import javax.swing.JTable;
import javax.swing.table.DefaultTableModel;
class TM extends DefaultTableModel {
int[] inside;
static String[] columnNames = { "Hellium", "Radon",
};
TM(int[] data) {
super(columnNames, 0);
this.inside = data;
update();
}
void update() {
Object[][] data = new Object[2][columnNames.length];
for (int i = 0; i < 2; ++i) {
data[i][0] = inside[0];
data[i][1] = inside[1];
// setValueAt(aValue, row, column);
addRow(data[i]);
}
fireTableDataChanged();
}
}
class idkName {
TM tm;
JButton jb, jb2;
int data[] = { 1, 2 };
int data2[] = { 9, 10 };
JTable table;
JScrollPane jsp;
JFrame twindow;
idkName() {
JFrame window = new JFrame();
window.setSize(400, 400);
window.setLayout(new BorderLayout());
jb = new JButton("show");
jb2 = new JButton("change model");
window.add(jb, BorderLayout.EAST);
window.add(jb2, BorderLayout.WEST);
twindow = new JFrame();
jb.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent arg0) {
tm = new TM(data);
table = new JTable(tm);
jsp = new JScrollPane(table);
twindow.getContentPane().add(jsp);
twindow.setSize(500, 500);
twindow.setVisible(true);
}
});
window.setVisible(true);
jb2.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
// tm = new TM(data2);
tm = new TM(data2);
System.out.println(""+tm.getValueAt(0,0));
tm.fireTableDataChanged();
twindow.setVisible(true);
}
});
}
}
public class main2 {
TM tm;
public static void main(String[] args) {
idkName i = new idkName();
}
}

If you're going to extend DefaultTableModel, then when the data is changed, you need to update it in DefaultTableModel's internal representation using the setValueAt or setDataVector methods. If you have extensive changes (which it sounds like you do), use the setDataVector method to change all the cells and the table structure at once. Your example code looks like it's missing some updates because it's not pushing the new values in to the DefaultTableModel's data vectors.
But since you have a lot of updates, you're probably better off avoiding DefaultTableModel and just extending AbstractTableModel, using your own custom data storage, and calling the appropriate fireXxx() methods whenever your data changes. This will probably be more efficient in terms of both data conversion and number of events raised.
And then make sure all the event and value change work is done on the AWT event thread, using SwingWorkers or other threading support.

How do I remove the A on the top of the JTable inside a JScrollPane?

Why is there an A on the top of the table?
I placed a JTable inside a JScrollPane to make it scrollable.
Are there methods that I need to place?
I did not place a letter A though so I cant track.
import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.BorderLayout;
import javax.swing.BoxLayout;
import javax.swing.JTable;
import javax.swing.border.LineBorder;
import java.awt.Color;
import javax.swing.JScrollPane;
import javax.swing.ScrollPaneConstants;
public class Rawr {
private JFrame frame;
private JScrollPane scrollPane;
private JTable table;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
Rawr window = new Rawr();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the application.
*/
public Rawr() {
initialize();
}
/**
* Initialize the contents of the frame.
*/
private void initialize() {
frame = new JFrame();
frame.setBounds(100, 100, 450, 300);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel panel = new JPanel();
frame.getContentPane().add(panel, BorderLayout.CENTER);
panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));
scrollPane = new JScrollPane();
scrollPane.setToolTipText("");
scrollPane.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
panel.add(scrollPane);
table = new JTable(100, 1);
table.setBorder(new LineBorder(new Color(0, 0, 0)));
scrollPane.setViewportView(table);
}
}
How do I remove it? Thanks!

Set the column name explicitly using:
String[] colNames = new String[]{"Your Column Name"};
DefaultTableModel defaultTableModel = new DefaultTableModel(colNames, 100);
table = new JTable(defaultTableModel);
If you create a table using new JTable(100, 1) you will see the A, B and so on column headers because the constructor javadoc says:
Constructs a JTable with numRows and numColumns of empty cells using DefaultTableModel.
Since the JTable constructor does not have any information about the column headers. It can only create a DefaultTableModel that does not know any column header names.
The DefaultTableModel extends AbstractTableModel and the javadoc of AbstractTableModel.getColumnName() says
Returns a default name for the column using spreadsheet conventions: A, B, C, ... Z, AA, AB, etc. If column cannot be found, returns an empty string.

Add the following code after the creation of your table.
String[] columns = new String[]{"Column Name"};
((DefaultTableModel)table.getModel()).setColumnIdentifiers(columns);

How do I remove it?
A JTable is designed to display data with a header to describe the data in the column.
Since you only have a single column of data, if you don't want the header then don't use a JTable. Instead you can use a JList.
Read the section from the Swing tutorial on How to Use Lists for more information and examples.

JTable won't refresh

Why won't table cell 0,1 change from aaa to XXXX?
import java.awt.*;
import javax.swing.*;
import javax.swing.table.DefaultTableModel;
class MainFrame {
public static void main(String[] args) {
JFrame f = new JFrame("Refreshing JTable");
JPanel p = new JPanel(new GridBagLayout());
DefaultTableModel productsModel;
JTable productsTable;
f.setSize(800, 600);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
String[] tableTitle = new String[] {"ID", "Name"};
String[][] tableData = {{"1", "AAA"},{"2", "BBB"}};
productsModel = new DefaultTableModel(tableData, tableTitle);
productsTable = new JTable(productsModel) {
public boolean isCellEditable(int r, int c) {
return false;
}
};
JScrollPane scrollpane = new JScrollPane(productsTable);
tableData[0][1] = "XXXX";
f.add(p);
p.add(scrollpane);
f.validate();
f.setVisible(true);
}
}
REASON:
Apparently trying to update the array where data is stored will result in JTable not changing. Either DefaultTableModel needs to be updated or the whole table needs to be redrawn.
EDIT (possible Solution) One way is using Timer:
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
import javax.swing.table.DefaultTableModel;
class MainFrame {
static JFrame f = new JFrame("Refreshing JTable");
static JPanel p = new JPanel(new GridBagLayout());
static DefaultTableModel productsModel;
static JTable productsTable;
public static void main(String[] args) {
runGui();
}
#SuppressWarnings("serial")
public static void runGui() {
f.setSize(800, 600);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
String[] tableTitle = new String[] {"ID", "Name"};
String[][] tableData = {{"1", "AAA"},{"2", "BBB"}};
productsModel = new DefaultTableModel(tableData, tableTitle);
productsTable = new JTable(productsModel) {
public boolean isCellEditable(int r, int c) {
return false;
}
};
JScrollPane scrollpane = new JScrollPane(productsTable);
tableData[0][1] = "XXXX";
Timer t = new Timer(2000, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
addColumns();
remakeData();
productsTable.setModel(productsModel);
}
});
t.start();
f.add(p);
p.add(scrollpane);
f.validate();
f.setVisible(true);
}
private static void addColumns() {
productsModel.setColumnCount(0);
productsModel.addColumn("ID");
productsModel.addColumn("Name");
}
private static void remakeData() {
productsModel.setRowCount(0);
productsModel.insertRow(productsModel.getRowCount(), new Object[] {"1", "Dummy item 1"});
productsModel.insertRow(productsModel.getRowCount(), new Object[] {"2", "Dummy itme 2"});
productsModel.insertRow(productsModel.getRowCount(), new Object[] {"3", "Dummy item 3"});
productsModel.insertRow(productsModel.getRowCount(), new Object[] {"4", "Dummy item 4"});
productsModel.insertRow(productsModel.getRowCount(), new Object[] {"5", "Dummy item 5"});
}
}
EDIT(much better solution, the way it worked for me flawlessly) Using a static method. Since I'm adding new data in array through another Frame, I created a static method in MainFrame, which I call every time I add/update/delete Object in array. This method will redo the whole model after update and will therefore refresh table.

One problem with the SSCCE posted on your related thread is that the code changes the array which originally formed the table model, whereas it should be changing the table model itself.

The solution to your problem (and the previous one) is rather simple, but unfortunately a bit too long to post it in a comment
You make sure you do some reading on how a JTable actually works. A good starting point is the Swing tutorial and perhaps even the class javadoc of the most important classes JTable and TableModel. Another good read about Swing and the use of MVC is this document. It is much broader then only JTables but will provide you with more insight in how all Swing components are designed, and how you should use them.
After reading that tutorial, you should understand that if you want to update the data which is shown in the table, you update the model of your table. The model will fire events which are received by the table, and the table will make sure it updates itself. After all, the table is only a view on the data (=the TableModel) so updates on the take should take place on the model side. If this is not clear, go back to step 1
Now take a look at your code and remove the listener. Instead, update the model on the table and see how the table updates itself.
If this does not work, you come back to this site with an SSCCE which you post. That way we can see that you tried something, what you tried and most likely what is wrong in your code. This SSCCE should include your code of the TableModel you use and the code that updates your TableModel since that is the most likely location for your problem.

Add a title to a JTable

I have a JTable which is created using a TableModel JTable t = new JTable(tableModel) I want to add a title to it. I was hoping for something like t.setTitle(graphTitle); but i cant find anything on that lines. I dont mind if the title is on top or below the table.
I was using JLabels but it just looks messy.
Can anyone help?
Cheers in advance

Another option you could consider is enclosing the JTable in a JPanel and setting a TitledBorder to that JPanel.
Like this:
import javax.swing.*;
import javax.swing.border.TitledBorder;
public class TableTitle
{
public TableTitle ()
{
JFrame frame = new JFrame ();
frame.setDefaultCloseOperation (JFrame.DISPOSE_ON_CLOSE);
JPanel panel = new JPanel ();
panel.setBorder (BorderFactory.createTitledBorder (BorderFactory.createEtchedBorder (),
"Table Title",
TitledBorder.CENTER,
TitledBorder.TOP));
JTable table = new JTable (3, 3);
panel.add (table);
frame.add (panel);
frame.setLocationRelativeTo (null);
frame.pack ();
frame.setVisible (true);
}
public static void main (String[] args)
{
SwingUtilities.invokeLater (new Runnable ()
{
#Override public void run ()
{
TableTitle t = new TableTitle ();
}
});
}
}
It looks like this:

You would have to add it when you instantiate your DefaultTableModel:
String data[][] = {{"Vinod","MCA","Computer"},
{"Deepak","PGDCA","History"},
{"Ranjan","M.SC.","Biology"},
{"Radha","BCA","Computer"}};
String col[] = {"Name","Course","Subject"};
DefaultTableModel model = new DefaultTableModel(data,col);
table = new JTable(model);
If it already exists, you can do something like this:
ChangeName(table,0,"Stu_name");
ChangeName(table,2,"Paper");
public void ChangeName(JTable table, int col_index, String col_name){
table.getColumnModel().getColumn(col_index).setHeaderValue(col_name);
}
Courtesy of RoseIndia.net
Hope that helps.

You can also add your title the JScrollPane which inscribes jtable in it.
Code:
JScrollPane scrollPane = new JScrollPane(table);
scrollPane.setBorder(BorderFactory.createTitledBorder ("Table Title"));

I don't think you have much options here. JTable has no functionality to add a titlebar.
So using JLabel or other components is your only option.
Try putting the JTable in a JTabbedPane.