CODEWITHSUNDEEP
javamultithreadingswingconcurrencyevent-dispatch-thread
nask00s
nask00s

Reputation: 97

4 threads adds to one jlist

In my program there are 4 threads that addElemets to a model of a jlist at the same time. This causes jlist to blink, throw excpetions or even crash, because of the too many updates or repaints.

I tried to put some delay that fixed my problem but I was losing to much precious time.

What can I do?

this code simulates my problem:

new Thread(new Runnable() {
    @Override
    public void run() {
        for(int i=0; i<4; i++){
            new Thread(new Runnable() {
                @Override
                public void run() {
                    for(int o=0; o<2000; o++){
                        model.addElement("add");
                        try {
                            Thread.sleep(100);
                        } catch (InterruptedException ex) {
                            Logger.getLogger(NewJFrame.class.getName()).log(Level.SEVERE, null, ex);
                        }
                    }
                }
            }).start();
        }
   }
}).start();

Upvotes: 1

Views: 121

Answers (3)

Aubin
Aubin

Reputation: 14863

To avoid too many refresh/repaint you have to do the model updates in the background threads and to copy once into the swing model in the EDT with the technique previously exposed. I suggest to do not use the DefaultListModel but a custom made to dispose of addAll().

SwingUtilities.invokeLater(new Runnable() {
    public void run() {
        listModel.addAll( backgroundModel ); // only one fireDataChanged() fired
    }
});

Upvotes: 1

Dan D.
Dan D.

Reputation: 32391

The model.addElement("add"); should be something like this:

SwingUtilities.invokeLater(new Runnable() {
    public void run() {
        listModel.addElement("add");
    }
});

This way you make sure that the elements are added under the EDT and not in some random thread.

Upvotes: 2

Vedant Agarwala
Vedant Agarwala

Reputation: 18819

GUI manipulations should only be performed on the event dispatch thread. Even if you have created many threads, do your non-GUI work on them n fire an actionCommand (or something similar) to manipulate GUI aspects.

You will get to read this warning many times in the Java Docs: Swing components are not thread safe

Upvotes: 1

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