Enable Jbutton from selection in Jtable and remove the initial focus from the table

Question

I have a window with a JTable, where only an entire row is valid, not just one field. The point is that the window already opens with the first line selected, and I’d like to disable that.

In that very window I have one JButton which is already disabled at the time of its creation, but I would like to activate it as soon as the user selects any line from JTable ...

Summarizing : How I disable automatic line selection JTable at the moment the window opens ? How to activate a button when the user selects any row from it JTable ?

Answer 1

To avoid automatic selection, you need to change the focus of the table when opening the window.

If your class has inherited from JFrame:

this.requestFocus();

If you have started a window from a variable:

meuFrame.requestFocus();

The requestFocus() will change the focus to your main window, thus preventing the JTable already appears with the first line selected.

To activate the button only when there is a selection, try the below:

this.tabela.getSelectionModel().addListSelectionListener(new ListSelectionListener() {
            @Override
            public void valueChanged(ListSelectionEvent e) {
                ListSelectionModel lsm = (ListSelectionModel) e.getSource();
                //altera os botoes para ativados somente se houver linha selecionada
                myButton.setEnabled(!lsm.isSelectionEmpty());
            }
        });

This way the activation of the button depends on whether or not there is a field/row selected in the table.

Answer 2

import java.awt.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.table.*;

class SelectTableExample
        extends     JFrame
        implements  ListSelectionListener
{
    // Instance attributes used in this example
   private  JPanel      topPanel;
   private  JTable      table;
   private  JScrollPane scrollPane;
   private  JButton     button;

    // Constructor of main frame
   public SelectTableExample()
   {
    // Set the frame characteristics
      setTitle( "Simple Table Application" );
      setSize( 300, 200 );
      setBackground( Color.gray );

    // Create a panel to hold all other components
      topPanel = new JPanel();
      topPanel.setLayout( new BorderLayout() );
      getContentPane().add( topPanel );

    // Create columns names
      String columnNames[] = { "Column 1", "Column 2", "Column 3" };

    // Create some data
      String dataValues[][] =
         {
         { "12", "234", "67" },
         { "-123", "43", "853" },
         { "93", "89.2", "109" },
         { "279", "9033", "3092" }
         };

    // Create a new table instance
      table = new JTable( dataValues, columnNames );

      // Block cell edition
      table.setModel(
            new DefaultTableModel(dataValues, columnNames) {
               public boolean isCellEditable(int row, int column) { 
                  return false;
               }
            });

        // Handle the listener
      ListSelectionModel selectionModel = table.getSelectionModel();
      selectionModel.addListSelectionListener( this );

    // Add the table to a scrolling pane
      scrollPane = new JScrollPane( table );
      topPanel.add( scrollPane, BorderLayout.CENTER );

      button = new JButton("continuar");
      button.setEnabled(false);
      topPanel.add( button, BorderLayout.SOUTH );
   }

    // Enable button for list selection changes
   public void valueChanged( ListSelectionEvent event )
   {
    // See if this is a valid table selection
      if( event.getSource() == table.getSelectionModel()
                    && event.getFirstIndex() >= 0 )
      {
         button.setEnabled(true);
      }
   }

    // Main entry point for this example
   public static void main( String args[] )
   {
    // Create an instance of the test application
      SelectTableExample mainFrame  = new SelectTableExample();
      mainFrame.setVisible( true );
   }
}