如何停止JPanel上的JTextField和JTextLabel被截断

Question

I have JTextFields and JLabels added to my JPanel (from left to right) every time the JButton is pressed. However, every new JTextField and JLabel that is added becomes smaller and smaller. How do I fix this?

Also I would like to add a JScrollPane to the JPanel but having problems doing so.

     public class MyExample 
{
    // Field members
    static JPanel panel = new JPanel();
    static Integer indexer = 1;
    static List<JLabel> listOfLabels = new ArrayList<JLabel>();
    static List<JTextField> listOfTextFields = new ArrayList<JTextField>();
    static JScrollPane scrollPane = new JScrollPane( panel );

    public static void main(String[] args)
    {       
        // Construct frame
        JFrame frame = new JFrame();
        frame.setLayout(new GridBagLayout());
        frame.setPreferredSize(new Dimension(2000, 2000));
        frame.setTitle("My Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        frame.getContentPane().add(scrollPane);

        // Frame constraints
        GridBagConstraints frameConstraints = new GridBagConstraints();

        // Construct button
        JButton addButton = new JButton("Add");
        addButton.addActionListener(new ButtonListener());

        // Add button to frame
        frameConstraints.gridx = 0;
        frameConstraints.gridy = 0;
        frame.add(addButton, frameConstraints);

        // Construct panel
        panel.setPreferredSize(new Dimension(1000, 1000));
        panel.setLayout(new GridBagLayout());
        panel.setBorder(LineBorder.createBlackLineBorder());

        // Add panel to frame
        frameConstraints.gridx = 0;
        frameConstraints.gridy = 1;
        frameConstraints.weighty = 1;
        frame.add(panel, frameConstraints);

        // Pack frame
        frame.pack();

        // Make frame visible
        frame.setVisible(true);
    }

    static class ButtonListener implements ActionListener
    {
        @Override
        public void actionPerformed(ActionEvent arg0) 
        {       
            // Clear panel
            panel.removeAll();

            // Create label and text field
            JTextField jTextField = new JTextField();
            jTextField.setSize(100, 200);
            listOfTextFields.add(jTextField);
            listOfLabels.add(new JLabel("Label " + indexer));

            // Create constraints
            GridBagConstraints textFieldConstraints = new GridBagConstraints();
            GridBagConstraints labelConstraints = new GridBagConstraints();

            // Add labels and text fields
            for(int i = 0; i < indexer; i++)
            {
                // Text field constraints
                textFieldConstraints.gridx = i;
                textFieldConstraints.fill = GridBagConstraints.HORIZONTAL;
                textFieldConstraints.weightx = 0.5;
                textFieldConstraints.insets = new Insets(10, 10, 10, 10);
                textFieldConstraints.gridy = 1;

                // Label constraints
                labelConstraints.gridx = i;
                labelConstraints.gridy = 0;
                labelConstraints.insets = new Insets(10, 10, 10, 10);

                // Add them to panel
                panel.add(listOfLabels.get(i), labelConstraints);
                panel.add(listOfTextFields.get(i), textFieldConstraints);
            }

            // Align components
            GridBagConstraints c = new GridBagConstraints();
            c.gridx = 0;
            c.gridy = indexer;
            c.weighty = 1;
            panel.add(new JLabel(), c);

            // Increment indexer
            indexer++;
            panel.updateUI();
        }
    }
}

Answer 1

However, every new JTextField and JLabelthat is added becomes smaller and smaller. How do I fix this?

panel.setPreferredSize(new Dimension(1000, 1000));

Don't set the preferred size. If the size is fixed then as you add more components they need to shrink to fit in the allowed space.

Don't attempt to set the size of any component. Let the layout manager do its job and determine the preferred size of the panel.

When creating a JTextField the code should be something like:

//JTextField jTextField = new JTextField();
JTextField jTextField = new JTextField(10);

This will allow the text field to determine its own preferred size to dispaly about 10 characters.

panel.updateUI();

Don't use updateUI(). That is used internally by Swing when you change the LAF. When you remove/add components you should be using:

panel.revalidate();
panel.repaint();

Answer 2

As for the JScrollPane with panel as a viewport, you should not be adding the panel to the frame at all - setting it as the viewport (like you're doing in the JScrollPane constructor) and adding the JScrollPane is sufficient. Adding the panel itself may be the cause of your problem.

As for the shrinking problem, I am still trying to understand your layout code - your use of GridBagLayout seems a tad overcomplicated to me. Maybe you can draw a simple sketch of how you would like the layout look?