CODEWITHSUNDEEP
javaconcurrencysplash-screen
Berry
Berry

Reputation: 23

Threads and a splash screen

I have an application that relies on the creation of certain objects from N files before a GUI should be presented to the user. I have decided to create a splash screen and want to show a progress bar giving an estimate of how far the app has progressed with its initial tasks.

I have just started studying the java.util.concurrent API and am thinking of solving this by using CountDownLatch and FutureTask: Create a FutureTask for each of the files needed to be read and get the constructed objects; use the CountDownLatch to both ensure the GUI is not presented until preliminary tasks are done and to register how far in the process we are (by querying getCount() and redraw a status bar over the image of the splash screen accordingly.

Is this overkill ?

Upvotes: 0

Views: 253

Answers (2)

Kaj
Kaj

Reputation: 10949

I would create a CountDownLatch that is initialized with the number of tasks that you need to execute before you can display the UI.

I would then use e.g a fixed thread pool to which I post tasks similar to:

public class Task implements Runnable {
   CountDownLatch latch;
   public Task(CountDownLatch latch) {
      this.latch = latch;
   }

   public void run() {
      //First perform some business logic... then
      latch.countDown();
   }
}

The monitoring thread (note this should not be executed by the UI thread) should do something like this:

public void monitorProgress(final CountDownLatch latch) {
   while (latch.await(5, TimeUnit.SECONDS) == false) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            // update the progress, latch.getCount() tasks are remaining
         }
      });
   }
   //Execution has been completed once you reach this line..
}

Note, the code isn't tested, and might not compile, but it illustrates what you want to do.

Upvotes: 0

ratchet freak
ratchet freak

Reputation: 48206

a semaphore is better as you can allow the threads of the tasks to be reused during startup

create the semaphore with s = new Semaphore(-nbFiles+1) and have each task call s.release() when they are done with a file

the splash screen can know how far everything is progressed with nbFiles+s.availablePermits()

Upvotes: 1

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