Apply keyEvent to a method

Question

I created this method:

public void comboS() {

    ResultSet rset = null;
    String sch = ((JTextField) ComboItemName.getEditor().getEditorComponent()).getText();
    try {
        rset = new JDBC.DB().getData("SELECT * FROM item_reg WHERE id LIKE '" + sch + "%';");
    } catch (Exception e) {
        System.out.println(e);
    }
    ComboItemName.removeAllItems();
    try {
        while (rset.next()) {
            String item = rset.getString("id");
            ComboItemName.addItem(item);
        }
    } catch (SQLException ex) {
        Logger.getLogger(jfilechooser.class.getName()).log(Level.SEVERE, null, ex);
    }
    System.out.println(sch);
    ComboItemName.setSelectedItem(null);
    ComboItemName.setPopupVisible(true);
    ((JTextField) ComboItemName.getEditor().getEditorComponent()).setText(sch);

}

I call this method in actionPerformed of the JComboBox(ComboItemName)..When I type HDD and hit enter it shows all the ids of hard disks in database..But I want this to be appear while I typing HDD.I think for that a keyEvent should be apply to the method like this.

public void comboS(java.awt.event.KeyEvent evt)

But I don't know how to call this method and where in combo box.give me some help for this.thanks. Like this

Answer 1

Use DocumentListener on your editor component for that purposes, here is example with that:

import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.SwingUtilities;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
import javax.swing.text.BadLocationException;
import javax.swing.text.JTextComponent;

public class Example extends JFrame {


    public Example() {
        JComboBox comboBox = new JComboBox(new String[]{"1","2"});
        comboBox.setEditable(true);
        ((JTextComponent)comboBox.getEditor().getEditorComponent()).getDocument().addDocumentListener(new DocumentListener() {

            @Override
            public void removeUpdate(DocumentEvent arg0) {
                validateHDD(arg0);
            }

            @Override
            public void insertUpdate(DocumentEvent arg0) {
                validateHDD(arg0);
            }

            @Override
            public void changedUpdate(DocumentEvent arg0) {
                validateHDD(arg0);
            }

            private void validateHDD(DocumentEvent arg0) {
                try {
                    String text = arg0.getDocument().getText(0, arg0.getDocument().getLength());
                    if(text.equals("HDD")){
                        System.out.println("HDD entered");
                        //call your method here
                    }
                } catch (BadLocationException e) {
                    e.printStackTrace();
                }
            }

        });
        add(comboBox);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                Example frame = new Example();
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }
}

validateHDD validate if you entered HDD into editor of JComboBox, and then executes some logic if it is true.

Answer 2

To attach a KeyListener on a ComboBox, first of all your Combo must be editable.

    jComboBox1.setEditable(true);

Then just attach the KeyListener like this:

    jComboBox1.getEditor().getEditorComponent().addKeyListener(new KeyListener() {
        @Override
        public void keyTyped(KeyEvent e) {
            System.out.println(e.getKeyChar() + " KEY_TYPED DETECTED. \n");
        }
        @Override
        public void keyPressed(KeyEvent e) {
            System.out.println(e.getKeyChar() + " KEY_PRESS DETECTED. \n");
        }
        @Override
        public void keyReleased(KeyEvent e) {
            System.out.println(e.getKeyChar() + " KEY_RELEASE DETECTED. \n");
        }
    });

As simple as that :)

UPDATE

As @alex2410 spotted, it would be best to implement this with DocumentListener instead. Here is how to:

    final JTextComponent tc = (JTextComponent) jComboBox1.getEditor().getEditorComponent();
    tc.getDocument().addDocumentListener(new DocumentListener() {
        @Override
        public void insertUpdate(DocumentEvent e) {
            System.out.println("Combo Value is: " + tc.getText() + " . \n");
        }

        @Override
        public void removeUpdate(DocumentEvent e) {
            System.out.println("Combo Value is: " + tc.getText() + " . \n");
        }

        @Override
        public void changedUpdate(DocumentEvent e) {
            System.out.println("Combo Value is: " + tc.getText() + " . \n");
        }
    });

As a side note, please stick to Java code Conventions