为什么java swing不允许从ExecutorService Thread进行更改

Question

I have a problem about my java GUI management. I'm making an updater but when i'm trying to edit some JText or JProgressbar from an ExecutorService Thread, nothing..

Why is it broken ? This is my ControllerManager:

public class UpdateManager extends AppManager {
    private final List<Controller> controllers;
    @Getter private final ExecutorService worker;
    @Getter private final UserInterface form;
    private boolean isEnd;

    public UpdateManager() {
        this.controllers = new ArrayList<>();
        this.form = new Form(this);
        this.worker = Executors.newCachedThreadPool();
    }

    @Override
    public void start(Controller... controllers) {
        form.initialize();

        this.controllers.addAll(Arrays.asList(controllers));

        for(Controller controller: controllers)
            controller.start();
    }

    @Override
    public void end(boolean dispose) {
        if(isEnd) return;

        for(Controller controller: controllers)
            controller.end();

        if(dispose) form.dispose();
        isEnd = true;
    }
}

And here is an example when i'm trying to change some labels:

/**
 * Created by romain on 17/05/2015.
 */
public class ReleaseController implements Controller {
    private final AppManager manager;
    @Getter private final LinkedBlockingDeque<URL> files;
    private Future<?> future;
    private final SerializedObject<SerializedReleases> serializedReleases;
    private final SerializedObject<Integer> serializedRelease, serializedTimestamp;

    public ReleaseController(AppManager manager) {
        this.manager = manager;
        this.files = new LinkedBlockingDeque<>();
        this.serializedReleases = SerializedObjectImpl.create(FileUtils.path("releases", "releases.dat"), true, null);
        this.serializedRelease = SerializedObjectImpl.create(FileUtils.path("swtour", "release.int"), false, 0);
        this.serializedTimestamp = SerializedObjectImpl.create(FileUtils.path("swtour", "timestamp.int"), false, 0);
    }

    /**
     * TODO: checking local files
     */
    @Override
    public void start() {
        this.future = manager.getWorker().submit(new Runnable() {
            @Override
            public void run() {
                int release = serializedRelease.get();
                int serverRelease = serializedReleases.get().lastRelease(AppUtils.OS);
                int result = serverRelease - release;

                if(result == 0 || result < 0) {
                    manager.getForm().alreadyUpdated(); //HERE
                    return;
                }

                for(int i=release+1;i<serverRelease;i++) {
                    try {
                        files.addLast(new URL(
                                FileUtils.path(Main.SERVER, "releases", AppUtils.OS.toString(), i + ".zip")));
                    } catch(Exception e) {
                        System.out.println(e.getMessage());
                    }
                }

                serializedRelease.setObject(serverRelease).write();
                serializedTimestamp.setObject((int)System.currentTimeMillis()).write();
            }
        });
    }

    @Override
    public void end() {
        if(future != null && !future.isCancelled())
            future.cancel(true);
    }

}

If you saw correctly, it:

manager.getForm().alreadyUpdated();

Modifies my GUI :

public void alreadyUpdated() {
        content.getFirstLine().setText("");
        content.getSecondLine().setText("Your client is already up-to-date!");
        content.getPlayButton().setEnabled(true);
}

but nothing.. My gui is not changed ! Thank you

Answer 1

There are two problems with attempting to update a Swing data structure from another thread:

1. Swing is not designed to be multi-thread safe. You could corrupt its data structures.
2. There is nothing forcing it to see changes made in another thread. It can be running with values in registers or caches that are not affected by changes to memory.

As already noted in a comment, you need to use invokeAndWait or invokeLater to make your changes in the Swing event handling thread.