Java Swing multi threads and ui freezes

Question

Can't figure this one out. Using worker or invokeLater, the UI still freeze. After each file is downloaded, I want a JList to be updated. But the JList will only update after the tread returns.

Here is the code:

public class MyUi extends javax.swing.JFrame{
    ...

   private void jButton2ActionPerformed(java.awt.event.ActionEvent evt){

      SwingUtilities.invokeLater(new Runnable() {
         //To get out of the event tread
         public void run() {
            dl(); 
         }
       });
   }

   private void dl(){
      ...
      //ini and run the download class
      Download myDownload = new Download();
      myDownload.doDownload(myDlList);
   }

   public void updateJlist(String myString){

       myModel.addElement(myString);
       jList1.repaint();
   }

}

public class Download{
...

  public void doDownload(String[] fileName){
      for(int i=0; i<fileName.length; i++){
         ...//download action...
         //for my jList1 to be updated after each file.
         MyUi.updateJlist(fileName[i]);
      }
   }

}

Any example would help.

Answer 1

invokeLater does exactly the opposite of what you expect it to do - it runs operations on the EDT, which explains the behaviour.

Answer 2

Download the file on a background thread and wrap just updateJlist() in a Runnable.

SwingWorker would be more reliable.

Addendum: As @mre notes, SwingWorker also makes it easy to report interim results, as shown here.