CODEWITHSUNDEEP
javamultithreadinguser-interface
hat_to_the_back
hat_to_the_back

Reputation: 99

How to know when a thread has completed its task

As I am using gui and I need to create a thread to complete a task. See I want to display a dialog letting the user know the task has been completed I have tried

if(!thread.isAlive()) {
    JOptionPane.showMessageDialog(null, "Done");
}

But that doesnt work.

Can anyone help me

Thanks

Upvotes: 0

Views: 168

Answers (4)

SANN3
SANN3

Reputation: 10119

Use Callable thread. It will return value,So we can identify that it completed its task.

Upvotes: 0

droidchef
droidchef

Reputation: 2307

create a listener in your main Thread, and then program your Thread to tell the listener that it has completed.

public interface ThreadCompleteListener {
    void notifyOfThreadComplete(final Thread thread);
}

then create the following class:

public abstract class NotifyingThread extends Thread {
  private final Set<ThreadCompleteListener> listeners
                   = new CopyOnWriteArraySet<ThreadCompleteListener>();
  public final void addListener(final ThreadCompleteListener listener) {
    listeners.add(listener);
  }
  public final void removeListener(final ThreadCompleteListener listener) {
    listeners.remove(listener);
  }
  private final void notifyListeners() {
    for (ThreadCompleteListener listener : listeners) {
      listener.notifyOfThreadComplete(this);
    }
  }
  @Override
  public final void run() {
    try {
      doRun();
    } finally {
      notifyListeners();
    }
  }
  public abstract void doRun();
}

NotifyingThread thread1 = new OneOfYourThreads();
thread1.addListener(this); // add ourselves as a listener
thread1.start();           // Start the Thread

then, as each Thread exits, your notifyOfThreadComplete method will be invoked with the Thread instance that just completed. So now you can run any of your code in this method.

Upvotes: 0

Duncan Jones
Duncan Jones

Reputation: 69410

One option is to do your work using a SwingWorker. Override the done() method and have it notify your GUI that work is complete.

A simple example that nearly matches your use case is shown in the Javadocs at the top of the page:

final JLabel label;
class MeaningOfLifeFinder extends SwingWorker<String, Object> {
  @Override
  public String doInBackground() {
    // Here you do the work of your thread
    return findTheMeaningOfLife();
  }

  @Override
  protected void done() {
    // Here you notify the GUI
    try {
      label.setText(get());
    } catch (Exception ignore) {
    }
  }
}

Upvotes: 2

elias-berg
elias-berg

Reputation: 559

You could just have the thread print a message as it's last line of code in it's run method:

Thread thread = new Thread() {
  @Override
  public void run() {
      //whatever you want this thread to do

      //as the last line of code = the thread is going to terminate
      JOptionPane.showMessageDialog(null, "Done"); 
  }
}
thread.start();

If you want the main thread to wait for the thread to finish, in the main thread's code you'd use:

thread.join();

Upvotes: 0

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