在GUI线程中的繁重工作期间显示ProgressIndicator必须完成

import javafx.application.Application;
import javafx.concurrent.Task;
import javafx.scene.Scene;
import javafx.scene.control.ProgressIndicator;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

public class Main extends Application {

    @Override
    public void start(Stage primaryStage) {
        ProgressIndicator progressIndicator = new ProgressIndicator();

        Task<Void> task = new Task<Void>() {
            @Override
            protected Void call() throws Exception {
                // 执行繁重工作的代码
                // ...

                return null;
            }
        };

        progressIndicator.progressProperty().bind(task.progressProperty());

        Thread thread = new Thread(task);
        thread.start();

        StackPane root = new StackPane();
        root.getChildren().add(progressIndicator);

        Scene scene = new Scene(root, 200, 200);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

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