Simple example for 'ScheduledService' in Javafx

问题

I am a student and learning JavaFX since a month. I am developing a application where I want a service to repeatedly start again after its execution of the task. For this I have come to know that 'ScheduledService' is used. So can anybody please explain the use of scheduledservice with simple example and also how it differs from the 'Service' in JavaFX. Thanks ;)

EDIT : How can I define that this ScheduledService named DataThread should be restarted every 5 seconds ?

public class DataThread extends ScheduledService<Void>
{
    @Override
    public Task<Void> createTask() {
        return new Task<Void>() {
            @Override
            public Void call() throws Exception {
             for(i=0;i<10;i++)
             {
                 System.out.println(""+i);
             }
              return null;
            }
        };
    }
}

回答1:

Considering you have a sound knowledge of Service class. ScheduledService is just a Service with a Scheduling functionality.

From the docs

The ScheduledService is a Service which will automatically restart itself after a successful execution, and under some conditions will restart even in case of failure

So we can say it as,

Service -> Execute One Task
ScheduledService -> Execute Same Task at regular intervals

A very simple example of Scheduled Service is the TimerService, which counts the number of times the Service Task has been called. It is scheduled to call it every 1 second

import java.util.concurrent.atomic.AtomicInteger;

import javafx.application.Application;
import javafx.beans.property.IntegerProperty;
import javafx.beans.property.SimpleIntegerProperty;
import javafx.concurrent.ScheduledService;
import javafx.concurrent.Task;
import javafx.concurrent.WorkerStateEvent;
import javafx.event.EventHandler;
import javafx.stage.Stage;
import javafx.util.Duration;

public class TimerServiceApp extends Application {

    @Override
    public void start(Stage stage) throws Exception {
        TimerService service = new TimerService();
        AtomicInteger count = new AtomicInteger(0);
        service.setCount(count.get());
        service.setPeriod(Duration.seconds(1));
        service.setOnSucceeded(new EventHandler<WorkerStateEvent>() {

            @Override
            public void handle(WorkerStateEvent t) {
                System.out.println("Called : " + t.getSource().getValue()
                        + " time(s)");
                count.set((int) t.getSource().getValue());
            }
        });
        service.start();
    }

    public static void main(String[] args) {
        launch();
    }

    private static class TimerService extends ScheduledService<Integer> {
        private IntegerProperty count = new SimpleIntegerProperty();

        public final void setCount(Integer value) {
            count.set(value);
        }

        public final Integer getCount() {
            return count.get();
        }

        public final IntegerProperty countProperty() {
            return count;
        }

        protected Task<Integer> createTask() {
            return new Task<Integer>() {
                protected Integer call() {
                    //Adds 1 to the count
                    count.set(getCount() + 1);
                    return getCount();
                }
            };
        }
    }
}

来源：https://stackoverflow.com/questions/27853735/simple-example-for-scheduledservice-in-javafx

标签

javafx

scheduled-tasks