Question

I’m trying to get scrollbars to work.

The code displays the images I choose. And I’ve just read (on stackoverflow) about adding the image to a panel, then the panel to the scrollpane, and the scrollpane to the frame. So I tried doing that.

But I still can’t get the scrollbars to show. Even when the image is bigger than the JFrame window.

Can anyone help? I’ve tried revalidate, but it didn’t work so I took it out.

   import java.awt.*;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;
import javax.swing.*;
import javax.swing.filechooser.FileNameExtensionFilter;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

public class MakeResizedImage {
    private JFrame frame;
    private JFileChooser fc;
    private File file;
    private int r;
    private JTextField textField;
    private Image img;
    JScrollPane scrollPane;
    ImagePanel panel_2;

    public static void main(String[] args) {
        MakeResizedImage MRI = new MakeResizedImage();
        MRI.BuildJFrameGui();
    }

    private MakeResizedImage() {
    }

    private void BuildJFrameGui() {
        JPanel panel = new JPanel();
        panel.setLayout(null);

        frame = new JFrame("View/Resize a png, jpg or gif image");
        frame.setSize(400, 400);

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationRelativeTo(null);

        JPanel panel_1 = new JPanel();
        frame.getContentPane().add(panel_1, BorderLayout.NORTH);

        JLabel lblNewLabel = new JLabel("Image:");
        lblNewLabel.setHorizontalAlignment(SwingConstants.LEFT);
        panel_1.add(lblNewLabel);

        textField = new JTextField();
        panel_1.add(textField);
        textField.setColumns(10);

        JLabel lblNewLabel_1 = new JLabel("Width:");
        panel_1.add(lblNewLabel_1);

        Dimension Dim = new Dimension(45, 20);
        JSpinner spinner = new JSpinner();
        spinner.setModel(new SpinnerNumberModel(new Integer(0), new Integer(0),
                null, new Integer(1)));
        spinner.setPreferredSize(Dim);
        panel_1.add(spinner);

        JLabel lblHeight = new JLabel("Height:");
        panel_1.add(lblHeight);

        JSpinner spinner_1 = new JSpinner();
        spinner_1.setModel(new SpinnerNumberModel(new Integer(0),
                new Integer(0), null, new Integer(1)));
        spinner_1.setPreferredSize(Dim);
        panel_1.add(spinner_1);

        JPanel panel_3 = new JPanel();

        JButton btnNewButton = new JButton("Open");
        btnNewButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                chooseFile();
            }
        });

        panel_3.add(btnNewButton);

        JButton btnNewButton_1 = new JButton("Cancel");
        btnNewButton_1.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                System.exit(0);
            }
        });
        panel_3.add(btnNewButton_1);

        JButton btnSave = new JButton("Save");
        panel_3.add(btnSave);

        frame.getContentPane().add(panel_3, BorderLayout.SOUTH);

        scrollPane = new JScrollPane();
        frame.getContentPane().add(scrollPane, BorderLayout.CENTER);

        panel_2 = new ImagePanel();
        scrollPane.setViewportView(panel_2);

        frame.setVisible(true);
    }

    public void chooseFile() {
        if (aFileChosen()) {
            file = fc.getSelectedFile();
            if (file.exists()) {
                textField.setText(fc.getName());
                try {
                    img = ImageIO.read(file);
                    panel_2.setImg(img);
                } catch (IOException e) {
                }
            }
        } else
            JOptionPane.showMessageDialog(frame, "No file was chosen");
    }

    public boolean aFileChosen() {
        fc = new JFileChooser();
        FileNameExtensionFilter filter = new FileNameExtensionFilter(
                "PNG, JPG & GIF Images", "png", "jpg", "gif");
        fc.setFileFilter(filter);
        fc.setApproveButtonText("Choose");
        fc.setApproveButtonToolTipText("Selects the image you want to resize");
        r = fc.showOpenDialog(frame);
        if (r == JFileChooser.APPROVE_OPTION)
            return true;
        return false;
    }

    class ImagePanel extends JPanel {

        private static final long serialVersionUID = 1L;
        private Image img;

        ImagePanel() {
        };

        ImagePanel(Image img) {
            this.img = img;
        }

        public void setImg(Image img) {
            this.img = img;

            repaint();
        }

        @Override
        public Dimension getPreferredSize() {
            return (new Dimension(300, 300));
        }

        @Override
        public void paintComponent(Graphics g) {
            super.paintComponent(g);

            // Clears the previously drawn image.     
            g.clearRect(0, 0, getWidth(), getHeight());
            //and draws the new one...
            g.drawImage(img, 0, 0, this);
        }
    }
} 

Answer 1

Use the other constructor, the one that wraps another component: JScrollPane(Component).