CODEWITHSUNDEEP
javaswingmultithreading
nevets1219
nevets1219

Reputation: 7706

Java's Swing Threading

My understanding is that if I start up another thread to perform some actions, I would need to SwingUtilities.invokeAndWait or SwingUtilities.invokeLater to update the GUI while I'm in said thread. Please correct me if I'm wrong.

What I'm trying to accomplish is relatively straightforward: when the user clicks submit, I want to (before performing any actions) disable the submit button, perform the action, and at the end of the action re-enable the button. My method to perform the action updates the GUI directly (displays results) when it gets the results back.

This action basically queries a server and gets some results back.

What I have so far is:

boolean isRunning = false;

synchronized handleButtonClick() {
  if ( isRunning == false ) {
    button.setEnabled( false );
    isRunning = true;
    doAction();
  }
}

doAction() {
  new Thread() {
    try {
      performAction(); // Concern A
    } catch ( ... ) {
      displayStackTrace( ... ); // Concern B
    } finally {
      SwingUtilities.invokeLater ( /* simple Runnable to enable button */ );
      isRunning = false;
    }
  }
}

For both of my concerns above, do I would have to use SwingUtilities.invokeAndWait since they both will update the GUI? All GUI updates revolve around updating JTextPane. Do I need to in my thread check if I'm on EDT and if so I can call my code (regardless of whether it updates the GUI or not) and NOT use SwingUtilities.invokeAndWait?

EDIT: Here is what I am doing now:

handleButtonClick() {
  if ( isRunning == true )
     return;
  disable button;
  SwingWorker task = new MyTask();
  task.execute();
}

...inside MyTask
doInBackground() {
  return performAction();
}

done() {
  result = get();
  enable button;
  isRunning = false;
  interpret result (do most of the GUI updates here);
}

While performAction() does some GUI updates, I have wrapped those in:

if ( SwingUtil.isEDT() )
  doGUIupdate()
else
  SwingUtil.invokeLater( new Runnable() {
    run() {
      doGUIupdate();
    }
  } );

Hopefully this is a step in the right direction, please comment if you believe there are better ways to handle my situation.

Upvotes: 13

Views: 7876

Answers (3)

ArifMustafa
ArifMustafa

Reputation: 4965

I keep the simple Thread inside EventQueue.invokeLater(...) and that worked smoothly...

java.awt.EventQueue.invokeLater(new Runnable() {
    public void run(){

        new Thread(new Runnable(){
            public void run(){

                try{
                    EdgeProgress progress = EdgeProgress.getEdgeProgress();
                    System.out.println("now in traceProgressMonitor...");
                    while(true){
                        // here the swing update
                        if(monitor.getState() == ProgressMonitor.STATE_BUSY){
                            System.out.println(monitor.getPercentDone()/2);
                            progress.setProgress(monitor.getPercentDone()/2);
                        }else{
                            break;
                        }
                        Thread.sleep(5);
                    }
                }catch(InterruptedException ie){}

            }
        }).start();

    }
});

Upvotes: 0

cletus
cletus

Reputation: 625347

In my opinion you should almost never use invokeAndWait(). If something is going to take awhile that will lock your UI.

Use a SwingWorker for this kind of thing. Take a look at Improve Application Performance With SwingWorker in Java SE 6.

Upvotes: 18

Justin Ethier
Justin Ethier

Reputation: 134255

You should consider using SwingWorker since it will not block the UI thread, whereas both SwingUtilities methods will execute on the EDT thread, thus blocking the UI.

Upvotes: 5

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