CODEWITHSUNDEEP
javaswingevent-dispatch-threadconcurrency
Berek Bryan
Berek Bryan

Reputation: 14745

Swing - Update Label

I have a message label and a submit button. The submit button will be pressed multiple times, and the action for the each press can take up to a minute.

When the button is pressed, I want to set the message to empty, and after the task is complete, I want to set the message to "Complete".

private void submitActionPerformed(java.awt.event.ActionEvent evt) {
   message = "";
   updateMessageLabel();

   doTheTask();

   /* this update is apply to the label after completion */
   message = "Complete";
}

Is it possible to update that message label before the submitActionPerformed() method is run (or in the method), but after the the button is clicked?

Upvotes: 8

Views: 12234

Answers (2)

Robin
Robin

Reputation: 36621

Although the Swing concurrency tutorial already contains some very good samples on how to deal with concurrency in Swing, find below an example which

  • contains a checkbox to prove the UI is still alive
  • has a progress bar, which gets updated from the SwingWorker

  • has a label, which gets updated once the SwingWorker is finished

    import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JProgressBar;
import javax.swing.SwingWorker;
import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.lang.reflect.InvocationTargetException;
import java.util.List;
import java.util.concurrent.ExecutionException;

public class SwingWorkerExample {
  private static JProgressBar PROGRESS_BAR;
  private static JLabel OUTPUT_LABEL;
  private static JFrame createGUI(){
    JFrame testFrame = new JFrame( "TestFrame" );

    PROGRESS_BAR = new JProgressBar(  );
    PROGRESS_BAR.setMinimum( 0 );
    PROGRESS_BAR.setMaximum( 100 );

    OUTPUT_LABEL = new JLabel( "Processing" );

    testFrame.getContentPane().add( PROGRESS_BAR, BorderLayout.CENTER );
    testFrame.getContentPane().add( OUTPUT_LABEL, BorderLayout.SOUTH );

    //add a checkbox as well to proof the UI is still responsive
    testFrame.getContentPane().add( new JCheckBox( "Click me to proof UI is responsive" ), BorderLayout.NORTH );



    testFrame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
    return testFrame;
  }

  public static void main( String[] args ) throws InvocationTargetException, InterruptedException {
    EventQueue.invokeAndWait( new Runnable() {
      @Override
      public void run() {
        JFrame frame = createGUI();

        frame.pack();
        frame.setVisible( true );
      }
    } );
    //start the SwingWorker outside the EDT
    MySwingWorker worker = new MySwingWorker( PROGRESS_BAR, OUTPUT_LABEL );
    worker.execute();
  }
  private static class MySwingWorker extends SwingWorker<String, Double>{
    private final JProgressBar fProgressBar;
    private final JLabel fLabel;
    private MySwingWorker( JProgressBar aProgressBar, JLabel aLabel ) {
      fProgressBar = aProgressBar;
      fLabel = aLabel;
    }

    @Override
    protected String doInBackground() throws Exception {
      int maxNumber = 10;
      for( int i = 0; i < maxNumber; i++ ){
        Thread.sleep( 2000 );//simulate long running process
        double factor = ((double)(i+1) / maxNumber);
        System.out.println("Intermediate results ready");
        publish( factor );//publish the progress
      }
      return "Finished";
    }

    @Override
    protected void process( List<Double> aDoubles ) {
      //update the percentage of the progress bar that is done
      int amount = fProgressBar.getMaximum() - fProgressBar.getMinimum();
      fProgressBar.setValue( ( int ) (fProgressBar.getMinimum() + ( amount * aDoubles.get( aDoubles.size() - 1 ))) );
    }

    @Override
    protected void done() {
      try {
        fLabel.setText( get() );
      } catch ( InterruptedException e ) {
        e.printStackTrace();
      } catch ( ExecutionException e ) {
        e.printStackTrace();
      }
    }
  }
}

Upvotes: 13

Rajesh Pantula
Rajesh Pantula

Reputation: 10241

Yes you can do this using SwingWorker thread, do all the pre submitActionPerformed() activities like updating the label, in the execute() method of the currentThread and call doTheTask() as a background job using worker Thread.

I suggest you to go through this documentation for reference about SwingWorker Thread

Upvotes: 10

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