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How do I set the focus to a component ?

Posted on 1998-06-24
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Last Modified: 2010-05-18
I want to give the focus to a textfield. I tried using requestFocus method but didn't work. I am using JDK 1.1 and Swing 1.0.2.
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Question by:incah
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6 Comments
 
LVL 5

Accepted Solution

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fontaine earned 100 total points
ID: 1223748
requestFocus() set focus on the receiving component if isRequestFocusEnabled returns true.
Invoke setRequestFocusEnabled() to be sure that this condition is met. If this does not work
setCaretPosition(0) should give you what you want. If not again, please post a piece of code representative of the problem that we can recompile, test and make it work.


 
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Author Comment

by:incah
ID: 1223749
None of your proposals worked. Here is the code:

import java.awt.*;
import java.awt.event.*;
import java.sql.*;
import com.sun.java.swing.*;
import com.sun.java.swing.event.*;

public class SwingApp extends JFrame implements ActionListener,CaretListener {
  JPanel p1,p2;
  JLabel l1,l2;
  JButton b1,b2;
  JTextField tf1,tf2;
  FileJComboBox fcb1;
  Connection con;
  public SwingApp() {
    Container contentPane = getContentPane();
    p1=new JPanel();
    p2=new JPanel(new GridLayout(0,1));

    p1.add(l1=new JLabel("Database Name",SwingConstants.LEFT));
    p1.add(tf1=new JTextField(50));
    p1.add(b1=new JButton("Open"));
    p1.add(b2=new JButton("Close"));
    contentPane.add("Center",p1);

    p2.add(l2=new JLabel(" ",SwingConstants.CENTER));
    contentPane.add("South",p2);

    b1.setEnabled(false);
    b2.setEnabled(false);
    tf1.requestFocus();
    tf1.addCaretListener(this);
    tf1.addActionListener(this);
    b1.addActionListener(this);
    b2.addActionListener(this);
    addWindowListener(new WindowAdapter() {
      public void windowClosing(WindowEvent e) {
        dispose();
        System.exit(0);
      }
    });
  }

  public void actionPerformed(ActionEvent e) {
      if (e.getSource()==b1 || e.getSource()==tf1) {
      try {
         con=DriverManager.getConnection("jdbc:odbc:"+tf1.getText());
         l2.setText("SUCCESS!");
         tf1.setEnabled(false);
         b1.setEnabled(false);
         b2.setEnabled(true);
      } catch(SQLException sqle) {
        l2.setText("Could not open: "+tf1.getText());
        return;
      }
      } else if (e.getSource()==b2) {
      try {
        con.close();
      } catch(SQLException sqle) {
      }
      con=null;
      tf1.setEnabled(true);
      b1.setEnabled(true);
      b2.setEnabled(false);
      l2.setText("");
      }
  }

  public void caretUpdate(CaretEvent e) {
    if (tf1.getText().equals(""))
      b1.setEnabled(false);
    else
      b1.setEnabled(true);
  }

  public static void main(String[] args) {
    SwingApp window = new SwingApp();
   
    try {
      Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
      DriverManager.setLogStream(null);
    } catch(ClassNotFoundException cnfe) {
      System.err.println("Class not found");
      return;
    }

    window.setTitle("Java Application");
    window.pack();
    window.setVisible(true);
  }
}


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LVL 5

Expert Comment

by:fontaine
ID: 1223750
I have recompiled and run your code. The focus is OK when I start the app. When the database
does not exist, for example, the message appears and the focus is lost for the textfield. I
suppose that this is what annoy you. The following change fixes the "problem".

Before:

 } catch(SQLException sqle) {
      l2.setText("Could not open: "+tf1.getText());
      return;
}

After:

} catch(SQLException sqle) {
     l2.setText("Could not open: "+tf1.getText());
     tf1.requestFocus();
     return;
}

The caret position will be at the end of the text entered in the query. If you want to have it at
the beginning:

} catch(SQLException sqle) {
     l2.setText("Could not open: "+tf1.getText());
     tf1.requestFocus();
     tf1.setCaretPosition(0);
     return;
}
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LVL 5

Expert Comment

by:fontaine
ID: 1223751
I have recompiled and run your code. The focus is OK when I start the app. When the database
does not exist, for example, the message appears and the focus is lost for the textfield. I
suppose that this is what annoy you. The following change fixes the "problem".

Before:

 } catch(SQLException sqle) {
      l2.setText("Could not open: "+tf1.getText());
      return;
}

After:

} catch(SQLException sqle) {
     l2.setText("Could not open: "+tf1.getText());
     tf1.requestFocus();
     return;
}

The caret position will be at the end of the text entered in the query. If you want to have it at
the beginning:

} catch(SQLException sqle) {
     l2.setText("Could not open: "+tf1.getText());
     tf1.requestFocus();
     tf1.setCaretPosition(0);
     return;
}
0
 

Author Comment

by:incah
ID: 1223752
When I run this program the focus is not OK. It is not in the textfield as it should be.
0
 
LVL 5

Expert Comment

by:fontaine
ID: 1223753
Here is the full code I have tested. Try it on your system. The focus remains in textfield on
my system (Swing 1.0.2 & JDK 1.1.5 on Win NT 4.0).

import java.awt.*;
     import java.awt.event.*;
     import java.sql.*;
     import com.sun.java.swing.*;
     import com.sun.java.swing.event.*;

     public class SwingApp extends JFrame implements ActionListener,CaretListener {
       JPanel p1,p2;
       JLabel l1,l2;
       JButton b1,b2;
       JTextField tf1,tf2;
//       FileJComboBox fcb1;
//       Connection con;
       public SwingApp() {
         Container contentPane = getContentPane();
         p1=new JPanel();
         p2=new JPanel(new GridLayout(0,1));

         p1.add(l1=new JLabel("Database Name",SwingConstants.LEFT));
         p1.add(tf1=new JTextField(50));
         p1.add(b1=new JButton("Open"));
         p1.add(b2=new JButton("Close"));
         contentPane.add("Center",p1);

         p2.add(l2=new JLabel(" ",SwingConstants.CENTER));
         contentPane.add("South",p2);

         b1.setEnabled(false);
         b2.setEnabled(false);
         tf1.requestFocus();
         tf1.addCaretListener(this);
         tf1.addActionListener(this);
         b1.addActionListener(this);
         b2.addActionListener(this);
         addWindowListener(new WindowAdapter() {
           public void windowClosing(WindowEvent e) {
             dispose();
             System.exit(0);
           }
         });
       }

       public void actionPerformed(ActionEvent e) {
            java.sql.Connection con= null;

           if (e.getSource()==b1 || e.getSource()==tf1) {
           try {
               con=DriverManager.getConnection("jdbc:odbc:"+tf1.getText());
              l2.setText("SUCCESS!");
              tf1.setEnabled(false);
              b1.setEnabled(false);
              b2.setEnabled(true);
           } catch(SQLException sqle) {
             l2.setText("Could not open: "+tf1.getText());
tf1.requestFocus();
tf1.setCaretPosition(0);
             return;
           }
           } else if (e.getSource()==b2) {
           try {
             con.close();
           } catch(SQLException sqle) {
           }
           con=null;
           tf1.setEnabled(true);
           b1.setEnabled(true);
           b2.setEnabled(false);
           l2.setText("");
           }

       }

       public void caretUpdate(CaretEvent e) {
         if (tf1.getText().equals(""))
           b1.setEnabled(false);
         else
           b1.setEnabled(true);
       }

       public static void main(String[] args) {
         SwingApp window = new SwingApp();
         
         try {
           Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
           DriverManager.setLogStream(null);
         } catch(ClassNotFoundException cnfe) {
           System.err.println("Class not found");
           return;
         }

         window.setTitle("Java Application");
         window.pack();
         window.setVisible(true);
       }
     }
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