How to terminate a scheduled thread when JavaFX Runtime exits?

Question

I'm looking over similar examples to this problem. We have a JavaFX app which runs some GUI updates via thread running from: ScheduledExecutorService::scheduleAtFixedRate.

This is similar to a couple of other questions. The two I recognised as most like my situation are these:

• JavaFX Task threads not terminating
• how to stop "JavaFX Application Thread"

The question I need to resolve, however, is about the next step. My target is for an embedded application and there's no opportunity to manually kill the JVM-task, or the other easy answers, etc. I'm afraid a reboot is reserved for something critically-serious.

We need to ensure that all threads are closed off in an orderly way. What I'm looking for is some kind of call back or event that lets me register a clean-up routine to close-down my stuff?

I was thinking that there ought to be 'something' in the base class, JavaFX javafx.application.Application to do the deed.

• http://docs.oracle.com/javafx/2/api/javafx/application/Application.html

Is the Stop method something I might use or can I register to be called when there is a stop from my FXMLController?

At present when I run my JavaFX app from Netbeans, the JVM process persists. This stops any further build scripts and locks the JAR file. Netbeans gives you an option to kill the task. The true solution means that the application/JVM closes-down orderly and neatly.

(update) ... I looked into the javafx.Application class that you use to launch the JavaFX app. I implemented a Stop() method. Here I make sure that I've called Platform.exit() ...

/////
//  @see
//    -- http://docs.oracle.com/javafx/2/api/javafx/application/Application.html#stop%28%29
//
public void stop()
{
    Platform.exit();
}

This doesn't cure the problem when running from NetBeans. Sometimes you need to click the stop [X] button two times, but the process does stop when you use the kill button. If you are interested in progress this is reported as bug: [Bug 245284], there's a small clock example to demonstrate the problem. When you close the window, the NetBeans process running panel is still 'running'. You can't build because the JAR file is locked. At least we know to manually kill the development program.

• Suggestions welcome . . .

Answer 1

I have a partial solution to cover fellow developers who get caught in this situation. Declare a stop() method in in your JavaFX app (called "MainApp" by the Netbeans Maven JavaFX template). There are questions of course, but first the method.

• See: JavaFX Application

Stop is called at the end of your program. I had the call to call Platform.exit() to close-down JavaFX runtime. I've added a call to shutdown other active Executor threads, which I kept in an list for now, to test the solution.

 public class MainApp extends Application
 {

     @Override
     public void start(Stage stage) throws Exception
     { 
        .....
     }

         /**
          *  Close down the application
          *  @see
          *   -- http://docs.oracle.com/javafx/2/api/javafx/application/Application.html#stop%28%29
          **/
      @Override
      public void stop()
      {
          Platform.exit();
          for( ScheduledExecutorService sched : activeExecutorServices )
          {
              sched.shutdown();
          }
      }

}//MainAppl class

So by commenting-out the call to shutdown and running my JavaFX program, the application finishes but won't exit, and Netbeans show a running task. You need to manually click on the kill-button in Netbeans.

Uncomment the shutdown() call. When the JavaFX application exits, it also dissappears from the Netbeans running jobs. That appears to be a resolotion.

The remaining questions:

1. What is the correct order between Platform.exit() and shutdown()?
2. With more than one ScheduledExecutorService does it matter which order is used to shut them-off? LIFO or FIFO?
3. Is there a better way?
4. Ought Netbeans be able to detect the 'process overrun' and report this as a problem. That at least leave you and I with the option to ignore it or fix the program.

Hopefyully that will assist the next someone who faces a similar problem :-)

Answer 2

you can use setOnCloseRequest

@Override
public void start(Stage primaryStage) {
    primaryStage.setOnCloseRequest(new EventHandler<WindowEvent>() {
        @Override
        public void handle(WindowEvent event) {
            ThreadPool.shutdown();
        }
    });

    initGui(primaryStage);
    initData();
}