如何在JavaFX中增加进度条的大小

Question

1. 我在Javafx中设计UI有一些进度条组件的问题。      我希望进度条的大小适合下面示例中的窗口大小。任何一个帮助都可以对齐它。

Click her for UI

import java.util.Random;

    import javafx.application.Application;
    import javafx.scene.Group;
    import javafx.scene.Scene;
    import javafx.scene.control.*;
    import javafx.scene.image.Image;
    import javafx.scene.layout.GridPane;
    import javafx.scene.text.Font;
    import javafx.stage.Stage;

    public class SampleCode extends Application {

        Label l1 = new Label("Loading channel(s) details from NE... ");
        Label l2 = new Label("Please wait...");
        public final static String cssFilePath = "MainPage.css";

        @Override
        public void start(Stage stage) {
            Group root = new Group();
            Scene scene = new Scene(root, 350, 50);
            stage.setScene(scene);
            stage.setTitle("1830 PSS-APA");
            scene.getStylesheets().add(getClass().getResource(cssFilePath).toExternalForm());
            GridPane grid = new GridPane();

            scene.setRoot(grid);

            Image nokiaIconImg = new Image(SampleCode.class.getResource("nokiaicon.jpg").toExternalForm());

            grid.getChildren().add(l1);
            GridPane.setConstraints(l2, 0, 2);
            GridPane.setColumnSpan(l2, 3);
            grid.getChildren().add(l2);

            ProgressBar p2 = new ProgressBar();

            grid.getChildren().add(p2);
            GridPane.setConstraints(p2, 0, 4);
            GridPane.setColumnSpan(p2, 4);

            stage.getIcons().add(nokiaIconImg);

            stage.show();

        }

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