how can I use JTextField and JLabel together?

Question

I need a text field on a label but when i run this code there is no text field on the screen. How can i fix it.

JFrame jf = new JFrame() ;

JPanel panel = new JPanel() ;

JLabel label = new JLabel() ;

JTextField tField = new JTextField("asd" , 10) ;

label.add( tField ) ;
panel.add( label ) ;

jf.setSize( 500,400 ) ;
jf.add( panel ) ;
jf.setVisible(true) ;

Answer 1

JLabel's have no default layout manager, and so while your JTextField is being added tot he JLabel, it's not showing because the label has no idea how to show it.

There can be several ways to solve this depending on what you're trying to achieve:

• Give the JLabel a layout manager, and then add the JTextField to it: but then the JTextField covers the JLabel, its text (if it has any) and its icon (if it has one), not good.
• Create a JPanel to hold both, and give it an appropriate layout manager: probably a good bet.
• Add them both to the same JPanel, using a layout manager that can easily place them in association: another good bet. GridBagLayout works well for this.

Don't forget to also call the JLabel's setLabelFor(...) method to associate it tightly with the JTextField, as per the JLabel Tutorial

For example:

import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.KeyEvent;
import java.util.HashMap;
import java.util.Map;
import javax.swing.*;

public class GridBagEg {
    private static void createAndShowGui() {
        PlayerEditorPanel playerEditorPane = new PlayerEditorPanel();

        int result = JOptionPane.showConfirmDialog(null, playerEditorPane, "Edit Player",
                JOptionPane.OK_CANCEL_OPTION, JOptionPane.PLAIN_MESSAGE);
        if (result == JOptionPane.OK_OPTION) {
            // TODO: do something with info

            for (PlayerEditorPanel.FieldTitle fieldTitle : PlayerEditorPanel.FieldTitle.values()) {
                System.out.printf("%10s: %s%n", fieldTitle.getTitle(),
                        playerEditorPane.getFieldText(fieldTitle));
            }
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGui();
            }
        });
    }
}

@SuppressWarnings("serial")
class PlayerEditorPanel extends JPanel {
    enum FieldTitle {
        NAME("Name", KeyEvent.VK_N), SPEED("Speed", KeyEvent.VK_P), STRENGTH("Strength", KeyEvent.VK_T);
        private String title;
        private int mnemonic;

        private FieldTitle(String title, int mnemonic) {
            this.title = title;
            this.mnemonic = mnemonic;
        }

        public String getTitle() {
            return title;
        }

        public int getMnemonic() {
            return mnemonic;
        }
    };

    private static final Insets WEST_INSETS = new Insets(5, 0, 5, 5);
    private static final Insets EAST_INSETS = new Insets(5, 5, 5, 0);
    private Map<FieldTitle, JTextField> fieldMap = new HashMap<FieldTitle, JTextField>();

    public PlayerEditorPanel() {
        setLayout(new GridBagLayout());
        setBorder(BorderFactory.createCompoundBorder(
                BorderFactory.createTitledBorder("Player Editor"),
                BorderFactory.createEmptyBorder(5, 5, 5, 5)));
        GridBagConstraints gbc;
        for (int i = 0; i < FieldTitle.values().length; i++) {
            FieldTitle fieldTitle = FieldTitle.values()[i];
            JLabel label = new JLabel(fieldTitle.getTitle() + ":", JLabel.LEFT);
            JTextField textField = new JTextField(10);
            label.setDisplayedMnemonic(fieldTitle.getMnemonic());
            label.setLabelFor(textField);
            gbc = createGbc(0, i);
            add(label, gbc);
            gbc = createGbc(1, i);
            add(textField, gbc);

            fieldMap.put(fieldTitle, textField);
        }
    }

    private GridBagConstraints createGbc(int x, int y) {
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.gridx = x;
        gbc.gridy = y;
        gbc.gridwidth = 1;
        gbc.gridheight = 1;

        gbc.anchor = (x == 0) ? GridBagConstraints.WEST : GridBagConstraints.EAST;
        gbc.fill = (x == 0) ? GridBagConstraints.BOTH : GridBagConstraints.HORIZONTAL;

        gbc.insets = (x == 0) ? WEST_INSETS : EAST_INSETS;
        gbc.weightx = (x == 0) ? 0.1 : 1.0;
        gbc.weighty = 1.0;
        return gbc;
    }

    public String getFieldText(FieldTitle fieldTitle) {
        return fieldMap.get(fieldTitle).getText();
    }

}

Which displays as

Note that the JLabels have underlines on mnemonic chars, chars that when pressed in alt-key combination will bring the focus to the JTextField that the JLabel was linked to via, setLabelFor(...), and is caused by this code:

FieldTitle fieldTitle = FieldTitle.values()[i]; // an enum that holds label texts
JLabel label = new JLabel(fieldTitle.getTitle() + ":", JLabel.LEFT); // create JLabel
JTextField textField = new JTextField(10);  // create JTextField

// set the label's mnemonic -- brings focus to the linked text field
label.setDisplayedMnemonic(fieldTitle.getMnemonic());   

// *** here we *link* the JLabel with the JTextField
label.setLabelFor(textField);