Re: Display image selected from JFileChooser
In article
<c4d87166-e98d-4346-a119-290ddb26a24e@c33g2000yqm.googlegroups.com>,
jimmy <jimmy.cullen@gmail.com> wrote:
I am having big problems setting out my code and need help organising
it. I want to write a GUI that displays jpg images that are selected
by the user from a file chooser. I have written two classes: MyImage
does the painting to the screen and MyImageApp for drawing the
button, and then calls MyImage when it has returned an image selected
by the user. The problem is it doesn't work.
I am almost there, but I think I am causing problems with MyImageApp.
I need to be able to access the BufferedImage returned by the
JFileChooser and pass it as an argument to MyImage for painting. I
just can't figure it out though. Can someone show me the errors of my
ways?
In addition to Lew's compelling observations, each of which deserves
attention, I would like to address a few design problems.
First, your class MyImageApp extends Component, but it doesn't really
alter the behavior of Component; it just contains a JFrame holding two
JComponents (JPanel and JButton).
Second, your button handler needs to work in concert with your image
panel, but the button itself may be elsewhere. The Action interface is
intended "to separate functionality and state from a component." This
makes it east to add the "Open" functionality to a button or menu item.
<http://java.sun.com/docs/books/tutorial/uiswing/misc/action.html>
Compare this example with your own in light of Lew's comments. As a
convenience, ImageOpenAction uses pack() to adjust the parent Window to
the image's size:
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Window;
import java.awt.event.ActionEvent;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JPanel;
/** @author John B. Matthews */
public class ImageApp {
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
JFrame f = new JFrame();
f.setTitle("Title");
ImagePanel imagePanel = new ImagePanel(f);
f.add(imagePanel, BorderLayout.CENTER);
JButton open = new JButton(imagePanel.getAction());
f.add(open, BorderLayout.SOUTH);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.pack();
f.setVisible(true);
}
});
}
}
class ImagePanel extends JPanel {
private final Window parent;
private BufferedImage image;
private Action action = new ImageOpenAction();
public ImagePanel(JFrame parent) {
this.parent = parent;
this.setPreferredSize(new Dimension(320, 240));
}
@Override
public void paintComponent(Graphics g) {
g.drawImage(image, 0, 0, null);
}
public Action getAction() {
return action;
}
private class ImageOpenAction extends AbstractAction {
public ImageOpenAction() {
super("Open");
}
@Override
public void actionPerformed(ActionEvent e) {
JFileChooser chooser = new JFileChooser(
new File(System.getProperty("user.dir")));
int returnVal = chooser.showOpenDialog(chooser);
if (returnVal == JFileChooser.APPROVE_OPTION) {
File file = chooser.getSelectedFile();
try {
image = ImageIO.read(chooser.getSelectedFile());
ImagePanel.this.setPreferredSize(new Dimension(
image.getWidth(), image.getHeight()));
parent.pack();
} catch (IOException ex) {
Logger.getLogger(ImagePanel.class.getName())
.log(Level.SEVERE, null, ex);
}
}
}
}
}
--
John B. Matthews
trashgod at gmail dot com
<http://sites.google.com/site/drjohnbmatthews>