Javafx service to update GUI objects status - javafx

Question

I'm trying to update the GUI status based on a time consuming task. When I push on a button, I want the button to be inactive and the cursor to change until the job is completed. I've come up with this code that mostly works as needed.
import javafx.application.Application;
import javafx.beans.binding.Bindings;
import javafx.concurrent.Service;
import javafx.concurrent.Task;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Cursor;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.FlowPane;
import javafx.stage.Stage;
public class TestWait2 extends Application {
#Override
public void start(Stage primaryStage) {
FlowPane root = new FlowPane();
primaryStage.setScene(new Scene(root));
MyService myService = new MyService();
primaryStage.getScene().getRoot().cursorProperty()
.bind(Bindings.when(myService.runningProperty())
.then(Cursor.WAIT).otherwise(Cursor.DEFAULT));
Button startButton = new Button();
startButton.setText("Button");
startButton.disableProperty().bind(myService.runningProperty());
root.getChildren().add(startButton);
startButton.setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent event) {
myService.start();
}
});
primaryStage.show();
}
private class MyService extends Service<Void> {
#Override
protected Task<Void> createTask() {
return new Task<Void>() {
#Override
protected Void call() throws Exception {
Thread.sleep(5000);
return null;
}
};
}
}
public static void main(String[] args) {
launch(args);
}
}
When I launch it works great the first time. The problem is that if I click on the button a second time it get an error.
Exception in thread "JavaFX Application Thread" java.lang.IllegalStateException: Can only start a Service in the READY state. Was in state SUCCEEDED
Any thoughts on how to get around that issue?
I'm running on Java 8u5.

Answer 1

The problem with your code that you try to call myService.start(); when its on SUCCEEDED state(since you started it already once).
this is according to javadoc of Service start method
Starts this Service. The Service must be in the READY state to succeed in * *this call.
This method should only be called on the FX application thread.
to make your code work, you need to you call myService.restart().
since you are planning to use your service over and over you can do the following:
startButton.setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent event) {
//replace this line
// myService.start();
//with this
myService.restart();
}
});

Answer 2

Adding this to the program seemed to solve this.
myService.setOnSucceeded(new EventHandler<WorkerStateEvent>() {
#Override
public void handle(WorkerStateEvent t) {
myService.reset();
}
});
I also found I can add the following directly to the MyService class.
#Override
protected void succeeded() {
reset();
}
There doesn't seem to be any other way to have it go to the ready state after completing it's work.