Running another thread not to block UI

Question

I do some heavy operation inside the actionPerformed (load images from File Chooser, resize it for display and populate it in the ScrollPane etc) and I realize that the windows freezes until the whole operation is finished. And it doesn't really help that I do repaint() or validate(). I make some research and some of the books and people from forums say that I actually needed to dispatch another thread to run the heavy operation. So that I won't block the UI interface and can update things accordingly. But the problem is, I don't have any clear example to understand this concept. How to clean up the thread after operation finished. How can a thread notify the progress back and etc. I need to know how much images has been loaded so that I can update the progress bar and so on. Can anyone help me point out a good example? :D

Answer 1

Think I should show my code snippet to you
public void actionPerformed(ActionEvent e) {
        if (e.getSource() == BtnBrowse) {
            int returnVal = fcSelectFile.showDialog(this,"Select");
            if (returnVal == JFileChooser.APPROVE_OPTION) {
                file= fcSelectFile.getSelectedFiles();
                //This is where a real application would open the file.
                Thread worker=new Thread(){
                        public void run(){
                            int count=0;
                            selectedFile=new JLabel[file.length]; 
                            while(count<file.length)
                            {   final int index=count;
                                String actualFile=file[count].toString();
                                String fileName= file[count].getName();
                                selectedFile[count]=new JLabel(createImageIcon(actualFile,fileName));
                                SwingUtilities.invokeLater(new Runnable(){
                                public void run(){
                                PnlImageHolder.add(selectedFile[index]);
                                PnlImageHolder.repaint();
                                PnlImageHolder.validate();
                                count++;
                worker.start();
                ScpImageScroller.getViewport().add(PnlImageHolder);
}