Use of JComboBox class

Hi All,

I need your help to get solution over my confusion. I am confused about the JComboBox class of java programming language. I am not getting how to use this 'JComboBox class' of java. I am not aware about it's constructors as well as it's method. If you have sound knowledge about the JComboBox class of java, then pleas try to share it with me. Your any help over JComboBox class would be greatly appreciable.

A JComboBox class component is used to combine a button or editable field and a drop-down list. The user can select a value from the drop-down list, which appears at the user's request. If you make the combo box editable, then the combo box includes an editable field into which the user can type a value. A JComboBox class is originally taken from the 'javax.swing.JComponent' of java programming.

Hi,

If you want to aware about the use of JComboBox class of java, then please go through the following example of JComboBox class:

Code:

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import javax.swing.JComboBox;
import javax.swing.JTextArea;

public class EditComboBoxDM {
  public static void main(String args[]) {
    String labels1[] = { "A", "B", "C", "D","E", "F", "G", "H","I", "J" };
    JFrame frame1 = new JFrame("Editable JComboBox");
    frame1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    Container contentPane = frame1.getContentPane();

    final JComboBox comboBox1 = new JComboBox(labels);
    comboBox1.setMaximumRowCount(5);
    comboBox1.setEditable(true);
    contentPane.add(comboBox1, BorderLayout.NORTH);

    final JTextArea textArea1 = new JTextArea();
    JScrollPane scrollPane = new JScrollPane(textArea1);
    contentPane.add(scrollPane, BorderLayout.CENTER);

    ActionListener actionListener = new ActionListener() {
      public void actionPerformed(ActionEvent actionEvent) {
        textArea1.append("Selected: " + comboBox1.getSelectedItem());
        textArea1.append(", Position: " + comboBox1.getSelectedIndex());
        textArea1.append(System.getProperty("line.separator"));
      }
    };
    comboBox1.addActionListener(actionListener);

    frame1.setSize(400, 200);
    frame1.setVisible(true);
  }
}

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Hi friend,

Please refer following methods of JComboBox class along with their different parameters:

• setSelectedIndex(int Index1)
• setRenderer(ListCellRenderer aRenderer1)
• setPrototypeDisplayValue(Object prototypeDisplayValue1)
• setPopupVisible(boolean bl1)
• setModel(ComboBoxModel aModel1)
• setMaximumRowCount(int cnt)

Below I have given the example JComboBox class, please study it carefully:

Code:

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import javax.swing.JComboBox;

public class JFontComboBox extends JFrame implements ActionListener {
  JLabel fontLabel = new JLabel("The fox jumps over the lazy dog.");

  private JComboBox fontComboBox01;

  public FontComboBox() {
    setTitle("ComboBoxTest");
    setSize(300, 300);
    addWindowListener(new WindowAdapter() {
      public void windowClosing(WindowEvent e) {
        System.exit(0);
      }    });

    fontComboBox01 = new JComboBox();
    fontComboBox01.setEditable(true);
    fontComboBox01.addItem("Serif");
    fontComboBox01.addItem("DialogInput");
    fontComboBox01.addActionListener(this);

    JPanel p1 = new JPanel();
    p1.add(fontComboBox01);
    getContentPane().add(p1, "North");
    getContentPane().add(fontLabel, "Center");
  }

  public void actionPerformed(ActionEvent evt) {
    JComboBox source = (JComboBox) evt.getSource();
    String item = (String) source.getSelectedItem();
    fontLabel.setFont(new Font(item, Font.PLAIN, 12));
  }

  public static void main(String[] args) {
    JFrame frame1 = new JFontComboBox();
    frame1.show();
  }
}

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Hello friend,

If you want to know about the constructors of JComboBox class, then refer following:

1. JComboBox(Vector itm) : It is used to for the creation of JComboBox with specified Vector.
2. JComboBox(): It is used to for the creation of JComboBox with a default data model.
3. JComboBox(Object[] itm): It is used to for the creation of JComboBox with specified arrar list.
4. JComboBox(ComboBoxModel aMdl): It is used to for the creation of JComboBox with specified ComboBoxModel.