Question

I encountered a problem while I am trying to display an image after I clicked a button and chose image file within the “Choose File Dialog”.

Initially, I was managed to display the chosen image in JLabel, but later I created a separate ActionListener, I think it started to go wrong since then. Whatever image I choose, the JLabel won’t display it.

I debugged it, and sure that the file chooser does pass the image to ImageIcon, JLabel does get the value from ImageIcon, but it doesn’t display the image even after revalidate() and repaint().

Here I attached my code for your kind reference!

(I trimmed the code for a clean look, so there might be some brackets left not useful)

package com.xxx.LoyalCardManager;

import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.sql.SQLException;
import java.util.ArrayList;

import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JSeparator;
import javax.swing.JTextField;
import javax.swing.filechooser.FileFilter;

public class LoyalCardManagerMain implements ActionListener{

private JFrame frame;
private DatabaseHandler db = new DatabaseHandler();


private JLabel labelPic;

private JButton buttonPic;

private File picFile = new File("");
private BufferedImage image;


/**
 * Launch the application.
 * @throws SQLException 
 * @throws ClassNotFoundException 
 */
public static void main(String[] args) throws SQLException, ClassNotFoundException {
    EventQueue.invokeLater(new Runnable() {
        public void run() {
            try {
                LoyalCardManagerMain window = new LoyalCardManagerMain();
                window.frame.setVisible(true);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    });


}



}

/**
 * Create the application.
 */
public LoyalCardManagerMain() {

    // Database initialisation
    initDatabase();

    // Draw GUI
    frame = new JFrame();
    frame.setBounds(100, 100, 619, 487);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.getContentPane().setLayout(null);

    buttonPic = new JButton("Click to Choose Pic");
    buttonPic.setBounds(415, 252, 166, 29);
    frame.getContentPane().add(buttonPic);
    buttonPic.setEnabled(false);
    buttonPic.setActionCommand("ChoosePic");
    buttonPic.addActionListener(this);

    labelPic = new JLabel();
    labelPic.setBounds(415, 30, 167, 210);
    frame.getContentPane().add(labelPic);




}



public void actionPerformed(ActionEvent event) {
    String command = event.getActionCommand();

     if (command.equals("ChoosePic")) {
        //TODO Label now cannot display images.
        JFileChooser chooser = new JFileChooser();
        chooser.setFileSelectionMode(JFileChooser.FILES_AND_DIRECTORIES);
        chooser.setAcceptAllFileFilterUsed(false);
        chooser.setFileFilter(new FileFilter() {
            public boolean accept (File f) {
                String extension = Utils.getExtension(f);
                if(extension != null) {
                    if (extension.equals(Utils.gif) ||
                        extension.equals(Utils.jpeg) ||
                        extension.equals(Utils.jpg) ||
                        extension.equals(Utils.png) ||
                        extension.equals(Utils.tif) ||
                        extension.equals(Utils.tiff)) {
                        return true;
                    }else{
                        return false;
                    }
                }
                return false;
            }

            public String getDescription() {
                return "Image File (*.gif, *.jpeg, *.jpg, *.png, *.tif, *.tiff)";
            }

        });

        int retVal = chooser.showOpenDialog(frame);
        if (retVal == JFileChooser.APPROVE_OPTION) {
            picFile = chooser.getSelectedFile();
            try {
                image = ImageIO.read(picFile);
            } catch (IOException e) {

                e.printStackTrace();
            }

            // Calculate the pic's ratio and do re-scale

            double ratio = (double) labelPic.getWidth() / (double) labelPic.getHeight();
            // Do image scale, scaledW is the new Width, and LabelPic.getHeight is the new Height.
            int scaledW = (int) (image.getHeight() * ratio);
            image = new BufferedImage(scaledW, labelPic.getHeight(), BufferedImage.SCALE_FAST);
            ImageIcon icon = new ImageIcon(image);

            labelPic.setVisible(true);
            labelPic.setIcon(icon);
            labelPic.revalidate();
            labelPic.repaint();

        }


    }
}
}

I also referenced other similar questions:

image loading using a JFileChooser into a JFrame

Image won't display in JLabel

Updating an image contained in a JLabel – problems

External Site: JFIleChooser opening image to JLabel

As well as Java Tutorial Docs
How to Use Buttons, Check Boxes, and Radio Buttons

But I still can’t figure it out why the JLabel not display the chosen image.

Thanks for your kind help mates!

Answer 1

Ok, I finally figured out what’s wrong with the code:

If I intend to use BufferedImage to resize (sorry, in my question I mis-understanding the method scale with resize), I need to use drawImage method to “redraw” the image. Otherwise the image will not be shown.

I made modification here:

double ratio = (double) labelPic.getWidth() / (double) labelPic.getHeight();
        // Do image scale, scaledW is the new Width, and LabelPic.getHeight is the new Height.
        int scaledW = (int) (image.getHeight() * ratio);
        image = new BufferedImage(scaledW, labelPic.getHeight(), BufferedImage.SCALE_FAST);// Edit here
        ImageIcon icon = new ImageIcon(image);

        labelPic.setVisible(true);
        labelPic.setIcon(icon);
        labelPic.revalidate();
        labelPic.repaint();

From the “Edit Here” mark, I use the following code:

BufferedImage imageTemp = new BufferedImage(resizedW, resizedH, BufferedImage.TYPE_INT_RGB);
            imageTemp.getGraphics().drawImage(image,0,0, scaledW, scaledH, null);
            image = imageTemp;

And there’s difference between first pass the value to imageTemp then pass to image and directly pass the value to image. If I pass the new BufferedImage directly to image, it will display a pure black colour instead of the image you choose.